Table of contents

The first Nordic Conference on Zero Emission and Plus Energy Buildings (ZEB+) was arranged in Trondheim, Norway, on November 6-7 2019. The conference presented state-of-the art within research and practical solutions that pave the way towards a low carbon built environment, with a focus on Nordic countries. The proceedings include 69 papers addressing the following main topics:

• Lessons learnt from design, construction and use of ZEB+

• Planning and procurement strategies

• Energy supply systems

• Energy flexibility

• Policy and business models

• Life cycle analysis and carbon footprint

• Scenarios and potential studies

• Energy performance simulation

• Method and tools for design

• Existing buildings: renovation and management

• Performance criteria and certification

• Building physics

• Indoor environment

• Heating, cooling and ventilation

• Carbon footprint

All papers published in this volume of IOP Conference Series: Earth and Environmental Science have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Energy efficiency policy forces architects to design buildings with increasingly well-sealed building skin. With the minimized outdoor connection, the indoor environment factors depend strongly on technical systems and control. In these scenarios, occupant dissatisfaction indicates a need for improvements of indoor environment and the way it is controlled. The aim of the article is to contribute to the discussion about the user perspective of indoor environmental quality in ZEB in the Nordic region. The focus on daylight as a factor for visual comfort, and on low outside temperature as an aspect of thermal comfort was dictated by this choice. An experimental study was conducted with 75 participants, in which the thermal, acoustic and visual conditions (controlled factors) together with a view out, humidity and CO2 level (monitored factors) were assessed by them and quantified via sensors. In most studied settings, the thermal comfort was the most determinant factor, followed by the acoustic and visual comfort. Other significant factors were mean illuminance in the room, mean temperature at the participants' desks and a mode value of the noise level. The daylight levels much lower than recommended in regulations were accepted by participants as comfortable if they were sitting by the window. Also, participants preferred a higher indoor temperature than the recommended in Norway.

The future low-carbon emission societies rely on energy systems bearing an increasing share of renewable energy sources (RES). Consequently, demand-side management and energy flexibility become a key solution to compensate for the intermittent nature of RES. District heating systems hold a large potential for energy flexibility if households are actively integrated. While previous research and local policies have applied demand-side management such as smart meters, new smart home technology envisions full employment of the flexibility potential of the building stock. Morning energy demand peak is a major concern for district heating systems in Nordic countries. Demand-side management for district heating has thus mainly focused on morning hours peak-shaving. While integrating smart home technology as a demand-side management solution, the household becomes a flexible energy hub for thermal energy storage. While the technical potential of achieving such flexibility has been investigated, less research has been carried out concerning how users engage with smart home technology and how this influences the possibilities for load-shifting of the indoor space-heating demand. By conducting qualitative studies (interviews and 'show and tell' home tours) in 16 Danish households, this paper explores how users engage with smart home technology and how this influences the possibilities for load-shifting in a district heating system. The study provides insight into how the occupants interact with different smart technologies providing space-heating control. Results show that engagement with smart home technology must be understood as part of people's everyday practices. The flexibility in energy demand must be generated by understanding and changing practices to make them more flexible during peak hours. While smart home technology holds the potential for adding flexibility within the district heating system, the technology is rarely used as intended by occupants. Smart home technology is disrupting, and users rapidly create workarounds in order to perform everyday practices. Load-shifting during morning hours is thus a technical possibility, but the dominant techno-economic paradigm embedded in smart home technologies remains a barrier, as the latter must adapt to the everyday practices.

The town-hall building (Rathaus im Stühlinger: RIS) of the city of Freiburg (D) has been designed and built with the objective of a plus-energy balance and has been handed over to the city in November 2017. With a net floor area (NFA) of 22.650 m², it is to date one of the largest designed and built plus-energy building in Europe. The boundaries considered in the annual energy balance are limited to the loads of the heating, ventilation and cooling systems (HVAC), of the domestic hot water (DHW) and of the lighting; user-dependent energy demands are not considered. To achieve a positive primary energy balance, the building envelope is highly insulated, the energy supply is based on a low-exergy concept and onsite energy is generated by a large Building Integrated Photovoltaic (BIPV) plant combined with photovoltaic-thermal combined collectors (PVT). The central component of the heat generation is a ground-water coupled heat pump system supplying thermal activated concrete slabs, heating ceilings and air handling units (AHUs). Cooling is ensured over the geothermal well. To the date of this publication, the building has been intensively monitored for one-and-a-half year. Here, we present the energy concept as well as the results of the first monitoring period and provide an assessment of the energy balance in comparison to the plus-energy objective as well as an initial analysis of the load curves and of the heating and cooling systems.

The Research Centre for Zero Emission Neighbourhoods in Smart cities has established a concept for living labs. Central to the concept is an experimental format that offers some control over the social and physical environment, as well as opportunities to observe and engage during a limited period. According to Bulkeley et al. 2018, an experiment offers a means to make sense of the present whilst also providing a vision of the future [1]. The paper asks, what are the implications for users when engaging with experiments and presents results from a ZEN living lab experiment that took place at Campus Evenstad in Hedmark, Norway.

Technical management at Evenstad proposed the experiment, they wanted to test if it was possible to reduce campus energy consumption and the starting point was the old administration building, which has the highest energy consumption on campus. The energy use reduction was to be achieved by turning off the building's heating and ventilation systems during a limited four-week period. This took place in July 2018, when the building users were expected to be on holiday or doing fieldwork. A workshop to anchor the experiment among building users took place a month before the experiment started. During the workshop challenges associated with the experiment and with the building, for users, became apparent. However, building users agreed to participation in the experiment because they saw it as an opportunity to highlight what they understood as necessary changes to the building. The experiment achieved the energy saving potential that the building managers envisioned, but the results for the building users are less tangible.

From a pragmatist approach, living labs and their experiments are about providing solutions, but the Evenstad example highlights the challenge of providing tangible solutions and how we engage users with more intangible future solutions. We discuss therefore the limitations and potentials associated with the experimental format. Moving beyond demonstrating what a sustainable future should look like and include [1p.1], and instead noting opportunities for the translation of societal learning into concrete actions that serve the user groups engaged as well as demonstrating, the potential to influence wider sustainable transitions.

This paper documents research conducted in the Norwegian FLEXNETT project. It describes a new tool that was developed to study the future impact of prosumers with PV panels on the grid in Norway and the potential energy flexibility that lies with residential prosumers. Systematic use of energy flexibility can be an important instrument for managing peak loads and voltage problems in weak power grids. The influx of distributed energy resources can amplify this problem, but also help to resolve it. Self-balancing neighborhoods can be very attractive. This implies that loads related to energy demands can be curtailed and leveled out by different controllable devices or managed by using local energy production in the area to reduce the impact on the general distribution grid. The simulation tool is GIS based and can be applied to study the situation related to a single household, a neighborhood or in a specific transformer area. Unlike similar tools that address production yields over a period, the FLEXNETT Simulator addresses production and energy dynamics down to every 10 minutes. Due to the relatively low solar angle in Norway and rapidly changing weather these dynamics can be very prominent and induce local impact that is specific to a house or a neighborhood. The paper further describes how a recurrent neural network has been used as an engine to produce realistic values for the simulator.

Buildings are becoming an increasingly active part of the power system due to the ongoing deployment of decentralized energy resources. To reap the added value that may be realized by zero emission neighbourhoods, it is important that the regulatory framework promotes an efficient development with buildings as an integrated and active part of the power system. When considering energy resources at the neighbourhood level and energy flows within neighbourhoods in Norway, the regulatory framework is challenged by innovative technical solutions. Therefore, it is necessary to explore how deployment of energy resources in neighbourhoods fit together with existing regulations and market mechanisms. Challenges concerning decentralized energy resources are identified based on discussions with stakeholders in Norway and a review of relevant literature in the scientific and regulatory domain. Key challenges for the deployment of energy resources in ZEN are identified, explained through examples, and related to ongoing projects in Norway. It is found that incentives regarding decentralized energy resources are highly dependent on the ownership structure, and therefore a distinction between two major classes of ZEN is made.

An energy management system can be introduced on a neighbourhood level, to achieve energy goals such as increased self-consumption of locally produced energy. In this case-study, electricity generation from photovoltaic (PV) systems is simulated at Risvollan housing cooperative, a large housing cooperative in Norway. The electricity generation from PV systems of different orientations and capacities are analysed with the electricity load. Key performance indicators (KPIs) such as self-generation, self-consumption and generation multiple are described, based on hourly values. The electricity generation from the south-oriented building façade PV systems are about 5-6% higher than for the east-west oriented rooftop PV systems on an annual basis, since the façade PV systems generate more electricity in the spring and autumn. The self-consumption factor is the most important KPI in Norway, due to the national tariff structure. For the total housing cooperative, a PV capacity of about 1,000 kW_p seem suitable, giving a self-consumption factor of 97% for a rooftop system, based on 2018 electricity and climate data. From the perspective of the housing cooperative, it is financial beneficial to aggregate electricity loads for common areas and apartments, since a higher share of the electricity can be used by the cooperative. For this to be possible, also housing cooperatives with PV must be facilitated for in the prosumer agreement. Comparing a single 1,100 kW_p PV system providing electricity to the total cooperative with 22 PV systems of 50 kW_p behind 22 garage meters, the self-consumption factor decreases from 95% to average 14%, resulting in a 41% lower financial value for the PV electricity.

Buildings represent a critical piece of a low-carbon future and their long lifetime necessitates urgent adoption of state-of-the-art performance standards. So far, LCA studies have assessed buildings, mobility and energy systems mainly individually. Zero Emission Neighbourhoods (ZEN) give a unique chance to combine these elements. In Norway, the Research Centre on ZEN has as a goal to enable the transition to a low carbon society by developing sustainable ZENs.

In this study, a LCA model for neighbourhood based on a modular structure with five physical elements; buildings, mobility, infrastructure, networks and on-site energy was applied on Ydalir, a pilot project of the ZEN Centre. Revealing that regardless of which scenario considered, the ZEN Ydalir does not achieve their ambitious goal of zero emissions. Further, the results show that the operation of mobility is a major source of the total greenhouse gas (GHG) emissions, accounting for 21-46%. Considering the life cycle stage materials, buildings are the largest contributor representing 24% of all GHG emissions. Thus, these two areas have been highlighted as the best options for improvement. Parameters related to uncertainties or are large contributors to the environmental impact are included in a sensitivity analysis.

Denmark's first energy neutral multi-family house, BOLIG+, is constructed at Søborg near Copenhagen and consists of 10 flats divided on 4 floors. BOLIG+ was the first attempt to construct a multi-family block of flats that complies with a set of criteria and dogmas that defines the BOLIG+ concept. Energy production on the building needed e.g. to meet not only the buildings energy demand, but also the residents' electricity energy use for light and appliances. Additionally when exchanging energy with the grid, energy "sold" should have at least the same exergy level as energy "bought". Building multi-family houses that are energy neutral on annual basis, is, therefore, much more difficult than for a single-family house. One of the reasons for this is the small amount of roof area available (per. dwelling) for local electricity production compared to the roof area of a single-family house. Last, but not least, the buildings was constructed under normal economical market conditions, i.e. without any subsidies for the construction.

When designing the building, the normal standard conditions for calculating the buildings energy performance was offset in order to ensure better coherence between the design energy demand and the following energy measurements. The indoor temperature was set higher, and so was the domestic hot water demand. Additionally, free loads (gains) from persons, light and appliances was set lower than the standard.

To meet the goal of being energy neutral, several low-energy solutions are used e.g. compact thermal envelope; highly insulated constructions; highly insulating windows; hybrid decentral ventilation; heat recovery on grey wastewater; PV on facades and roof; buffer zones. Additionally, an electric battery was installed to improve the economy of the PV installation by optimizing the amount of electricity used inside the meter (tackling the feed-in tariff issue).

This paper presents results from 1½ year of measurements of energy performance and indoor climate carried out in the building during the period 2017-2018.

Measurements of energy consumption showed that if the PV installation has produced as expected and the residents had used electricity as expected, the building would have been only 11% from being energy neutral.

Indoor climate measurements show high temperatures in a large share of the period.

Geothermal energy constitutes an important renewable resource that will become increasingly prominent in future constructions. A common method of extraction and usage consists of installing, inside the foundation piles of buildings, U-shaped heat exchangers called "energy piles".

In this paper such installations are addressed by means of a full parametric study, performed for a hall-type commercial building in a cold climate. By computing the transient heat transfer between energy piles and ground for a period of 20 years, guidelines for a preliminary sizing of the geothermal system as a whole are provided. These are valid for this specific building and climate, for a clay-type soil and without assuming thermal storage.

A highly nonlinear behaviour of the expected yield in relation to pile separation and evaporator extraction power is observed. Furthermore, 15m-long piles are found to be more efficient than those with double length, a smaller extraction power seems to be more favourable and differences in the pile diameter have little impact for heat transfer.

A geothermal system sizing guide, which is useful for a preliminary quantitative test prior to any installation, is introduced. Even though our specific results are valid only for a commercial hall-type building in Finland, our procedure is qualitatively general and can be utilized for any given building type and climate zone.

Present day European legislation focuses upon the reduction of greenhouse gas (GHG) emissions in buildings through better design and technological solutions, with a view to reduce operational energy use and embodied GHG emissions. Currently, environmental performance assessment tools for buildings lack in assessing these parameters over the entire lifecycle of a building. Life cycle assessment (LCA) is a well-established methodology that gives a clear insight into the potential environmental impacts during the service life of a building. However, architect, engineer and constructor (AEC) professionals consider LCA as complex and time consuming. This paper builds upon a methodology for the development of a parametric analysis tool (PAT), which comprehensively assesses operational energy use and embodied GHG emissions during the lifecycle of a building. In this phase of the PAT's development, the complexity of the tool has been increased by expanding the number of parameters from four (i.e. insulation thickness, window types, North façade glazing area and South façade glazing area) to seven (i.e. climatic zones, solar shading and electricity emission factors). This has increased the amount of parametric permutations from 1,372 to 12,348. The PAT has been applied to a conceptual two-storey single-family house, developed by the Norwegian ZEB Research Centre, which is assumed to be in either Oslo (Norway) or Lecce (Italy). The results show that the choice of insulation thickness influences total energy use less than the selection of shading types or glazing areas. The results also show the parametric selection with the least amount of operational energy use (34kWh/m²/yr) in the Lecce climate consists of triple-glazed windows (0.5W/m²k), 10m² of glazing on the north façade, 20m² of glazing on the south facade. The results show the parametric selection with the lowest total GHG emissions in the Oslo climate (7.8kgCO_2eq/m²/yr) consists of triple glazing (0.5W/m²k), 10m² of glazing on the north facade and 20m² glazing on the south facade. This is because a lower electricity emission factor (132gCO_2eq/kWh for Norway and 290gCO_2eq/kWh for Italy) was used for converting operational energy use to GHG emissions, even though the Oslo climate has a higher heating demand compared to Lecce. In conclusion, this paper shows how complex design options can be evaluated in a holistic way through PAT to ascertain the best selection of design criteria for low GHG emissions and low operational energy use.

As a component of the urban fabric system, zero-emission neighborhood (ZEN) projects represent an opportunity to boost the sustainable performance of cities. However, overlooking the potential of different actors or underestimating the complexity of interactions among them may threaten the projects themselves. Public procurement is a powerful tool that potentially enables national and local authorities to achieve sustainable development goals while procuring necessary products and services. This paper aims to understand the potential of innovative public procurement (IPP) to reduce some of the project complexity in ZEN. Besides literature on sustainable neighborhoods (SN), empirical insights are drawn from an ongoing ZEN project to map the primary sources of complexity in such projects. Afterward, the potential for dialogue with suppliers is mainly discussed in light of these sources. Our findings suggest that using IPP may assist in reducing the complexity imposed on ZEN projects.

Flexibility in Buildings is an integral part of the solution to address the electrical grid's challenges of grid balancing and renewable generation hosting capacity. One of the main barriers to greater participation of commercial and residential buildings in demand response schemes is the complexity and cost associated with assessing the flexibility of buildings. To overcome these barriers, an early stage flexibility assessment methodology was developed to provide stakeholders with actionable information in a concise and relevant way, so they can effectively evaluate the flexibility of their building and negotiate with aggregators for demand response participation. This paper validates the early stage flexibility assessment methodology in multiple buildings, demonstrating its ease of implementation and scalability. The validation was conducted at five pilot sites, in different geographical regions, activating a range of flexible sources through experiments on site.

Climate responsive urban design that makes use of passive heating and cooling strategies and enhances pedestrian comfort is a key element to a sustainable society. Knowing the impact of different materials, building typologies and arrangements and a building's sensitivity to microclimatic conditions, the energy balance can be enhanced. This study aims to evaluate the microclimatic conditions at the campus of the Norwegian University of Science and Technology, located in Trondheim, Norway. A numerical model was used and validated with punctual measurements on site. The results for air temperature showed a considerable seasonal variation with highest spatial temperature differences in summer and lowest in winter. Regarding the analysis of the wind field, east-west passages were identified as problematic. The influence of the seasonal changing leaf area density of the vegetation had a visible but minor influence on the wind field. The calibrated model will be used for further research on the influence of new building bodies on microclimate and thus building energy demand and pedestrian comfort.

One of the design principles for future sustainable towns is compactness. The densification of cities is very much needed, but it usually compromises the access of daylight. Densification is especially challenging in the Nordic region characterized by low angled sunlight, something that also limits daylight distribution and restricts its intensity. The higher the latitude, the greater is the difficulty in the distribution. Perimeter blocks give shelter from wind and often create semi-public courtyards which have been seen to be attractive in many Nordic settlements during history. In the present study, alternative design to the conventional perimeter blocks are explored and geometric options such as chamfered corners, strategically varied building heights and differently positioned openings in a broken perimeter block are analyzed. The yearly simulations as well as simulations for May 1^st have been carried out for the same perimeter blocks located at four different latitudes (decimal coordinates):

1. 65.0 Oulu (similar to Mo i Rana 66.3, Jokkmokk 66.6 and Rovaniemi 66.5)

2. 63.4 Trondheim (similar to Reykjavik 64.1, Östersund 63.2 and Vaasa 63.1)

3. 59.3 Stockholm (similar to Oslo 59.9, Helsinki 60,2, Tallinn 59.4, Saint Petersburg 59.9 and Anchorage 61.2)

4. 55.7 Copenhagen (similar to Malmö 55.6, Glasgow 55.9 and Moscow 55.8)

The choice of evaluation criteria is based on scientific discourse in the field of daylighting. According to the new European standard, solar radiation is included. Computer-based daylighting simulations are performed for different designs of the perimeter blocks with equal density, FAR = 1.33. The further north a city is located, the lower the houses in a perimeter block must be to maintain a certain level of daylight. The study confirms that latitude affects daylighting and that geometrical change can improve the conditions for daylight in the perimeter blocks.

As energy standards focus on reducing energy use in new buildings, attention is drawn to the gap between the expected and actual building operation and energy performance. This performance gap can be associated with the building construction, its systems, its unbalanced operation, the assumptions on occupancy profiles during the design phase, or the users' interaction with the systems' operation and control. This work focuses on a nearly zero-energy (nZEB) single-family house located in central Denmark. The analysis of indoor environment and energy use is based on year-long data monitoring. The reasons for the deviation between the expected and actual energy use are suggested. The indoor environmental quality is analyzed to verify the compliance with the standards. The European recommendation for the yearly primary energy use of new single-family houses is 50 – 65 kWh/m². For the current case, the simulation tool Be18 gives a result of 30.8 kWh/m² for the design phase. However, the actual energy use is measured to be 58.2 kWh/m². The sensibility of nZEBs to such imbalances can lead to houses that do not function as intended. It is thus crucial to investigate further the causes of these disparities in order to bridge the gap between expected and final energy use in dwellings.

To achieve a sustainable building stock, it is necessary to focus on existing as well as new buildings. New houses built according to the Norwegian building code are close to nZEB (near Zero-Energy Building) level, but existing buildings contribute a significant share of the energy consumption, and the difference between new and older houses is increasing. As the renovation rate is low, it is important to include ambitious energy upgrading once a renovation project is undertaken. So far, however, there is almost no market for nZEB renovation of small wooden buildings. These buildings are challenging to renovate, and even more challenging to do so with ambitious climate targets. In effect, only half of the renovations in Norway include energy renovation. The demand for ambitious renovation depends on a value proposition that is understood by the customer. Novel and well-designed business models can be central tools for achieving this. In this paper, existing and potential business models for renovation of wooden housing are identified and analysed.

This paper is based on the "Energy upgrading of wooden dwellings to nearly zero energy level" (OPPTRE) project. One of the activities for researchers, industry and public partners in OPPTRE is to identify, analyse and assess current business models, and develop novel approaches through collaborative workshops and interviews. The results are documented and elaborated upon by the research team before the next step, which is to test the most promising models.

Previous research indicates that only a small share of Norwegian enterprises have changed their business model over time. Two of the reasons for this are lack of critical reflection on existing business models and fear of changing the status quo. A third reason is lack of knowledge of how to manage the transformation process. In the process of identifying existing and developing novel business models, the partners in OPPTRE explore new opportunities to promote ambitious energy upgrading. Their commercial performance is likely to increase through the focus on business model design. New business models may also help increase the uptake of innovative energy solutions in the renovation market for small wooden buildings.

The paper explains the major steps in Energy Master Planning process. It proposes a definition of target goals. Then, a number of constraints have to be analyzed in order to be able to define site specific framing goals and associated limitations. This process will narrow the numerous design options down to those that offer an optimized fit to the local conditions and the objectives for the building or community. Based on the target definition a Baseline can then be developed. This consists of a snapshot of the current energy use situation. The baseline is one reference point used to evaluate alternative futures. Then Base Cases will be developed that extends the baseline into the future and includes already-funded renovation as well as planned construction and demolition activities. The base case is a future reference point for "business as usual." Different alternatives – A selected set of scenarios that include different energy measures related to buildings, distribution systems, and generation systems will then developed. These scenarios are compared to the baseline for energy use change and to the Base Case for investment and operational costs.

This paper compares and estimates cost-optimal means to increase the potential of reducing the carbon footprint of future rental houses. As a case study we present a comparison between four rental apartment houses, where one house has achieved the Nordic Swan ecolabel. The carbon footprints of these buildings have been calculated for the building lifetime. According to the results, the effects of single measures are quite small in reducing the carbon footprint, but larger effects can be obtained by combining several measures together. It is essential to minimize the amount of used materials by paying attention to material efficiency under both design and construction phase. The paper also discusses the role of the voluntary ecolabelling of buildings as a tool to reduce the carbon footprint of the building sector.

Over the last couple of years, research related to fossil free and emission free construction sites has developed rapidly in Norway, with an ambition to contribute towards global, national and regional emission reduction targets. Major public players are already demanding fossil free construction sites through public procurement, whilst requirements for emission free construction sites are on the way. Even though the Norwegian construction industry is a forerunner, there is a lack of knowledge or common understanding among different stakeholders on the definition, scope and strategies needed for fossil free and emission free construction sites. The aim of this paper is to present the main challenges and opportunities from the construction phase of two Norwegian zero emission construction sites, namely Campus Evenstad in Hedmark and Lia nursery school in Oslo. Construction activities considered include transportation and installation of building materials, construction machinery, temporary works, energy use, waste management and person transport. This paper presents and discusses the lessons learnt from the design, ambition levels, inputs from stakeholders, emission reduction solutions of these two construction sites, and evaluates methods considered to address conceptual and practical issues. In conclusion, this paper suggests lessons learnt for reducing GHG emissions from Norwegian zero emission construction sites.

Using firewood as a space heating source is a popular solution in Norwegian housing and can significantly reduce the electrical energy demand of houses. This study analysed habits and reasons for using a wood stove from survey data. From this, typical behaviour patterns were defined. These patterns were imported into a building performance simulation model of a typical Norwegian single-family detached house to evaluate the impact of the stove user behaviour on the electrical energy demand and on the overheating risk. Results showed that up to 32% of the electrical energy demand for space heating can be saved using a wood stove. The number of overheating hours increased when the wood stove was used more frequently. However, it decreased after full renovation because the stove is used less often, as the total space heating demand decreases and the indoor temperature drops less often below the temperature set-point when the stove is started. Active use of the wood stove is effective as retrofitting measure when the aim is to save electricity or fossil fuels. Nevertheless, if the stove power is not adapted to the building, it can be challenging to maintain a comfortable temperature in the room.

The historic buildings have a significant value in providing a sense of identity to the cities and the community. On the other hand, due to their age, they show the highest ratio of living discomfort and energy consumption. Therefore, their refurbishment is a very important process because, if done right, it will not only reduce their energy demand and increase the living comfort but will also strengthen the social and cultural benefits through leisure and tourism.

In the city of Trondheim, as in many other European cities, the historic buildings have been erected in different architectural periods, which manifest diverse historic and technical features. A categorisation of the wall sections of historic buildings has been done for each city's development period regarding their construction material and technique, building functionality and protection status.

The scope of the article is to estimate the potential for reduction of greenhouse gas emissions at a street/neighbourhood/city level prior to applying large-scale intervention measures. This can be achieved by proposing refurbishment alternatives for wall and window sections that preserve the historic value and at the same time, approach or even meet the actual technical standards. Afterwards, the carbon footprint of the refurbishment action itself and the environmental benefits after the refurbishment (operational phase) is estimated for each category of wall sections. The environmental results, multiplied with the total surface of sections carrying the same attributes, give the overall potential of reduction for the entire group of buildings. Based on this, the on-site renewable energy that would lead to achieving zero-emission targets can be calculated. The framework is also important because it does not treat each building separately, but it suggests refurbishment scenarios for specific categories of buildings built in different historical periods.

Energy requirements for buildings are continually tightened, as seen in the ambitions to introduce near zero-energy building (nZEB) requirements in Norwegian and European building codes from 2020. One consequence of this is an increased use of insulation. However, standard insulation may cause challenges in many circumstances, for example where increased wall dimensions lead to reduced daylight levels or where increased insulation leads to increased floor height. Super-insulation materials are a possible solution to these challenges. Although several super-insulation products exist on the market, there is still a need for proven system solutions that provide the required level of insulation, along with reduced thickness in the constructions. An additional challenge is that these solutions should also be cost-effective and carbon-effective. The economic benefits should outweigh the costs and the carbon footprint should ideally be reduced, but at least not significantly increased.

To analyse the potential of super-insulation, we have performed a parametric case study of terrace constructions based on super-insulation and compared these with a baseline solution. The terrace construction uses vacuum insulation panels (VIP) as the main insulation. The top plate insulation is tapered mineral wool, aerogel is used in the edges and on top of the construction there are wood tiles. The parameters that have been varied are i) terrace dimensions, ii) width of the edge with non-combustible aerogel, iii) the thickness of the VIP layer, iii) the slope of the tapering, and iv) the heat conductivity of the VIP panels.

To evaluate the benefits of the super-insulation an analysis of energy performance in the use phase has been done. As the energy efficiency of the super-insulation solution is improved, this gain can be used either to reduce thickness or to increase energy performance. Both these will have an impact on the costs. To evaluate the environmental performance of the solution a screening LCA has been performed, with focus on the carbon footprint. The results of the case study show under which circumstances the super-insulation solution has better performance than the baseline, and vice versa. Key parameters that drive energy performance and carbon footprint are identified, providing suggestions for further research.

The Norwegian University of Science and Technology (NTNU) is gathering from dispersed locations to one central campus at Gløshaugen, requiring an estimated 92 000 m² new buildings and upgrading 45 000 m² of existing buildings. NTNU has high environmental ambitions for the new campus, including zero-emission ambitions. This paper explores system boundary definitions and ambition levels in a Zero Emission Neighbourhood (ZEN) context. A key element is a plus energy campus that provides a surplus of renewable energy in the operational phase, that can compensate the carbon footprint of buildings, infrastructure and mobility. Preliminary energy and carbon analyses of the campus have been performed A key result is an overview of design choices and methodology choices for concept stage calculations for a zero-emission campus. Six system boundaries have been defined, with the production to consumption ratio varying from 19 % to 132 %. The lowest includes all buildings, the highest includes production from all buildings, but consumption only from new and renovated buildings. The main finding is that it is possible to realise a plus energy campus for new and renovated buildings, but not including non-renovated buildings. A plus energy campus requires a combination of PV and seasonal energy storage.

In the frame of the Norwegian Research Centre on Zero Emission Buildings, nine real-life zero emission pilot building projects were initiated during the period of 2009 to 2017. Eight of the pilot building projects have been constructed and are currently in use, whilst one of them is still in the planning phase. All the pilot projects have been followed up by researchers during the design, construction, and operation phases, by e.g. analyses of construction documents, and post-occupancy surveys. The main lessons learnt from this work are presented in this paper. They include the importance of an integrated design process, having clear goals and associated assessment methods, following a strategy based on 'trias energetica', as well as choosing locally sourced materials with low embodied carbon and long service lives, and increasing the focus on the users.

The installation of technical solutions for heat recovery from the ventilation air is a very important step, both with respect to improving the indoor climate and as an energy-saving measure. Ventilation without heat recovery use a substantial part of an entire building's heating use, especially if the building is a low energy building. To realize a large implementation of heat recovery property owners must increase their knowledge about how these systems work and they must be able to rely on them functioning properly. The function and performance of a ventilation system when it comes to heat recovery can be a problem as soon as temperatures drop far below zero. When freezing occurs some form of defrosting is required and this can lead to indoor climate problems and to little or no heat recovery being obtained, which will reduce the energy efficiency and, at the same time, may compromise moisture safety. The goal of this project is to increase knowledge about how heat recovery systems for residential buildings with respect to defrosting and frost protection measures in heat exchangers. The knowledge can thereafter be used to develop effective defrosting strategies and frost protection measures so that the energy use and power requirements are minimized. Measurements were performed for heat recovery systems placed in dwellings in north Sweden to investigate occurrence of frost formation. The paper will present these measurements and some comparing simulations which can serve as a basis for further development of good defrosting strategies.

Green Bonds are an instrument for driving the environmentally friendly and low-carbon economy. Green Bonds are bonds whose proceeds are earmarked for and transparently channelled to environmentally-friendly projects and activities. The real estate industry has a multi-decade track record of addressing environmental impacts through the use of rating systems certified by independent third parties. Green building certification systems address multiple environmental impacts and measure outcomes across all asset lifecycle phases. Using bonds for such investments is not new but in an effort to improve transparency and increase opportunities both for issuers and investors it can take a more active role in combating climate change. The goal of this paper is to describe how property developer can use Green Bond as one instrument in sustainable life cycle management and continuous development of properties. The method used is a case study of Finnish property owner company, which commits to invest the funds raised in certified, environmentally responsible and energy-efficient projects. The single case study method employed in this study captured the process of case organization towards Green Bond initiative. More precisely the data was gathered by qualitative document analysis (QDA). The results show that company begin the process with focusing on environmental sustainability especially putting the effort in the first phase to energy efficiency. The Green Bond initiative provided a new avenue towards economic sustainability. Additionally, issues like shared use of facilities was discussed from social sustainability perspective. The results are interesting for property owners who are interested in systematic development towards regenerative built environment.

This study is part of the EU funded project RiBuild and aims to create a web tool for supporting decisions relating to energy retrofits of historic buildings. The web tool provides a quantitative sustainability evaluation of hygro-thermally optimized insulation solutions through a greenhouse gas (GHG) emissions indicator. The study presents LCAs of five insulation systems for installation in historic buildings. The web tool accommodates 160 locations in seven countries and generates 210,180 impact profiles by combining insulation system, installation location, and heating systems. In 2 % of the scenarios, the induced impacts exceed the avoided impacts. Across all analyses, the mineral wool insulation system is the least GHG intensive solution. This study illuminates that the environmental justification of internal insulation depends on the geographical location of installation and the installed heating system in the retrofitted building. To further improve the sustainability performance of energy retrofits in historic buildings, the implementation of insulation recycling solutions and measures for reducing production impacts of insulation systems are needed.

Within the Norwegian Research Centre for Zero Emission Neighbourhoods (ZEN) in smart cities, a definition for achieving zero emission neighbourhoods will be developed and tested against nine pilot areas. The ZEN definition considers a series of assessment criteria and key performance indicators (KPI) under seven categories; GHG emissions, energy, power/load, mobility, economy, spatial qualities and innovation. This paper presents the first draft of the ZEN definition, and discusses some of the opportunities and challenges in implementing assessment criteria and KPIs (ZEN metrics) into a ZEN KPI tool. This paper briefly presents the ZEN pilot areas and maps out existing tools used by ZEN stakeholders for the documentation of ZEN metrics. The paper goes further by presenting a ZEN KPI tool conceptual framework for the implementation of the ZEN definition in ZEN pilot areas and outlines a specification for the future development of a ZEN KPI tool. Finally, the paper presents further work for the development of a ZEN KPI tool.

The aim of the study was to utilize different building data for prediction of development in energy use of a typical building type. In this study, energy use and its future development for kindergartens in Trondheim, Norway, were analyzed. The energy use data were retrieved from the energy monitoring platform of Trondheim Municipality. The total area of all the kindergartens was about 76 000 m², where the area of each kindergarten was ranging from 100 – 4 471 m². Firstly, typical heat and electricity duration curves per m² of kindergartens in Trondheim within six years were identified. Secondly, the kindergartens were divided into two cohorts based on their connection to district heating (DH). The average total annual energy use was 177 kWh/m² for kindergartens without DH, and 168 kWh/m² for kindergartens connected to DH. The peak load values were similar for both cohorts, about 140 W/m². Analysis of the duration curves showed a bigger electricity load variation for the kindergartens without DH connection. Within the building cohort with DH, three cases were found depending on the energy share from DH; i.e. DH high share, DH average share, and DH low share. By following different background data for CO² factors of electricity and local DH, the kindergarten with DH high share had almost the lowest annual CO² emission. Contrarily, the annual CO² emission of a kindergarten with lower share of DH, or without DH, usually had a wider range of emissions due to its dependence of the electricity production mix. Finally, a prediction was made by assuming 14.2 % growth rate of kindergartens on the ground of the average six-year total kindergarten area. The result showed that if more than 50-67 % of the new building area would be connected to DH, a smaller increase of CO² emission from the projected area could be achieved, depending on the relevant CO² factors. This proved that buildings with DH were more robust than the one without DH concerning CO² emission. The suggested analysis method and identified duration curves could be used to as a reference example for defining energy profiles of other building types. These profiles are necessary for diversifying and upgrading local energy supply pathways, infrastructure sizing, and improving urban energy planning.

Intermittent energy resources challenge the ways in which the existing energy system operates. Studies suggest that residential buildings can provide a flexibility service for district heating (DH) systems. This technique involves load shifting by heating buildings to higher temperatures at times when energy is more readily available, thus diminishing heating needs at times of peak demand or when energy is scarce. Based on three Future Workshops (FWs) where DH professionals and other relevant DH stakeholders participated and discussed this topic, this paper reports on the extent to which these actors see energy flexibility as a realistic future development, and on what they see as key potentials and challenges in that regard. Preliminary results indicate that the mix of the actors and the specific local context greatly influence how this topic is understood, emphasizing the importance of including local context in investigations of energy flexibility. FW participants included representatives from DH companies, municipalities, building associations, technology developers, etc. The FWs were conducted at three different localities of Denmark: Copenhagen, Aalborg and Sønderborg, i.e. the national capital, a regional capital and a smaller city, respectively.

Use of solar cells (PV) and solar collectors are key remedies in buildings where a large part of the energy supply should be based on renewable energy. The aim of this work has been to evaluate calculated and measured solar production of two identical BIPV roofs located at the ZEB Living Laboratory situated at NTNU-campus in Trondheim. Temperature, irradiance and wind speed and direction at the rooftop of the building have been monitored since the construction of the house. There was found a large difference in energy production of the northern roof section and the southern. One possible explanation is shading of the northern roof because of low solar azimuth during the measuring period. In order to avoid such disadvantages, design of the PV-roofs should be considered early in the design phase of the building project. A small difference was found between the hourly measured and the calculated values of the PV performance based on the monitored local climate data. Use of generic climate data expect to cause a larger difference between measured and simulated energy performance due to lack of consideration to local conditions.

Daylight availability is an important aspect that can potentially improve both the quality and the energy performance of buildings. However, it is not always straightforward easy to assure that an increase in the daylight availability leads to a reduction of electric energy use for artificial lighting. In this study, experimental measurements and numerical simulations were conducted to analyse the relation between the uses of artificial light and the daylighting availability for different groups of users who lived for one month each in a Zero Emission Building single-family house located in Trondheim, Norway. The use of electric lighting and the outdoor environment conditions (irradiance and illuminance on the horizontal plan) were recorded through advanced daylighting simulations, carried out with DIVA-for-Rhino, the daylighting availability during the periods of occupancy was then reconstructed, using as input data the outdoor environmental variable recorded during the experimental analysis. The results show that the coefficient of correlation between daylight availability and the artificial light is in general low and the use of artificial lighting seems to be largely independent from the availability of natural light.

A wide variety of disciplines engage in Smart Cities as the scope and breadth of it is broad. Within the built environment, there is much discussion on how planning and construction phases influence Smart Cities. There is little discussion on the role of Facilities Management (FM). However, there has been much work on the influence FM has on design phases to ensure functional and usable buildings. Neglecting to scale up the influence of FM from individual buildings to city scale may have long term consequences on sustainability of cities. Taking a mindset of including an FM perspective early in the development of a Smart City is considered here in terms of social aspects of required services. The work draws on ideas of Urban FM to operationalize local needs which also responds to the need to link to broader city sustainable strategies. The starting point is from the development of two districts in Trondheim, Norway. In a three-day workshop, students interpret the needs of the area based on their own knowledge-based perspective, guidance from tutors of Urban FM and through engagement with local users of the area. The work highlights the potential of including an FM perspective in the development of cities.

With increasing share of distributed renewable energy resources in the grid and arising energy consumer awareness on environmental challenges new market models are sought where energy can be traded in an efficient and end-user centric way. This trend, together with the increasing consciousness on the benefits of local consumption and production has given rise to an increased focus on local energy market structures. Within the E-REGIO project, funded through the ERA-Net Smart Grid Plus initiative, local energy markets have been paid particular attention. This paper discusses opportunities associated with local energy trading, as verified through the E-REGIO local energy system pilot - Skagerak EnergiLab in Norway. Embracing, among others, local loads, energy storage system, PV generation and a large consumer (stadium facility), the pilot-based simulations have produced some useful insides on the implementation of local energy markets and have helped collect learnings that can be of benefit for future local energy market establishments.

The study aimed to show in a systematic way possible energy efficiency measures that would decrease the total energy use at the university campus in Trondheim, Norway. The entire study was developed in close collaboration with the NTNU Property and Technical Management divisions, meaning that suggested energy efficiency scenarios and other assumptions were highly relevant. Currently, the campus floor area is about 300 000 m² and consists of buildings combining offices, lecturing halls, study halls, and laboratories. The campus building stock has been built from 1910 to 2002. To perform this study, building performance simulation and the dynamic segmented modeling were combined. A dynamic neighborhood building stock model was utilized to aggregate the outputs from the building simulation and evaluate global effects of energy efficiency measures. Reference building models for each university cohort were developed based on the methodology for defining the reference buildings. The results of the single reference building analyses showed that a decrease of up to 50% in heating energy use might be achieved by increasing efficiency of the ventilation system and by decreasing the temperature of the heating system. The results showed that in spite of building stock growth, the estimated energy use would decrease from 2017 to 2050 by 10% for the standard renovation, and by 26% for the combination of ambitious renovation and technical improvements.

High penetration rates of novel building energy technologies has prompted a growing concern about their microeconomic effect and grid influence. Deployment of photovoltaic (PV), solar water heating (SWH) systems and energy storage solutions, in addition to the growth of electric vehicles (EV) fleet, are reshaping the structure of built stock and lead to the changes in its electric energy demand profile. Long-term forecasting of such structural changes is necessary to guide the decision-making process that would satisfy the needs of both, energy consumers and the suppliers. Whereas electric energy price model is one of the key influencing factors of technologies acceptance for households, peak loads and grid feed-in determine the needed capacity of power grids. The objective of this study was to assess both, the aggregated cost of energy and the changes in cumulative load profiles that are excepted by 2050 for one of residential building typologies in Norway. Methodologically, it was achieved with descriptive statistics, stochastic forecasting and detailed energy performance simulation. Annual electric energy cost for consumers were evaluated under six pricing models. The results suggested that time-of-use and variable maximum power extraction models represent the lowest and the highest extremes in energy cost. At the aggregated level, peak load will decrease in range 1% to 13% compared to current level. Peak PV feed-in will reach up to 40% of peak load by 2050.

Neighbourhoods can contribute to climate change mitigation by supplying and/or facilitating renewable energy sources (RES). In this context, we evaluate opportunities related to the energy system of a Norwegian university campus, Campus Evenstad, by quantifying monetary value of local energy resources like solar photovoltaics (PV) and a bio-based combined heat and power (CHP) plant in a cost analysis. Environmental value is discussed regarding operational control of energy units to minimize emissions. Using mixed integer linear programming (MILP), we also present results from an investment analysis for local thermal and electric energy system to achieve different levels of emission compensation. Results show that local electricity supply generates most monetary value through saved costs related to reduced power grid import, and that solar PV is the most cost-efficient resource to achieve compensation of GHG emissions.

For the new housing area with approx. 130 low energy residential houses, located in Kassel, Germany, various supply concepts are investigated. Main objective of the project is the development of an innovative and optimised heat supply concept based on renewable energies and a low temperature district heating for later realisation.

During the course of the project several heat supply concepts have been investigated and compared to give an input to the decision and realisation process. A promising heat supply concept is based on a central ground source heat pump in combination with a low temperature district heating (40°C supply temperature) for space heating and decentralised solar thermal systems for domestic hot water preparation. The advantages of this supply variant are comparable low annual heating costs and about 60% lower CO²-emissions in comparison to the reference system (decentralized air / water heat pump with solar thermal system).

Due to time constrains it was decided not to realise the above mentioned energy concept. However, the research project took up the task to investigate the transferability of the concept in technological and economical perspectives to other locations and boundary conditions. From the results of the study the importance of a very high connection rate can be highlighted. Also the question of the particular business models for such capital demanding projects (high investment costs for the heating grid vs. low energy demand/sales) has been regarded.

The built environment is a major contributor to global greenhouse gas (GHG) emissions. There is a growing need to quantifying GHG emissions, and LCA tools can be used to help address them and find the key contributors. In order to compare different solutions of development of the built environment in the early stage planning process, the OmrådeLCA tool has been developed. OmrådeLCA has the unique advantage, compared to other similar tools, of using the system expansion approach, which allows for comparing different scenarios based on the same functional unit. We applied OmrådeLCA on Ydalir (Norway), a zero emission neighbourhood in an early stage planning process. The results show how significant the share of emissions from transportation are, contributing to more than 60 % to the total GHG emissions. Sensitivity analysis shows that choices made, and data used in modelling transportation significantly impact resulting GHG emissions. Thus, conducting a thorough analysis of factors affecting transportation is important for obtaining representative results when using OmrådeLCA. The results from the assessment of Ydalir with OmrådeLCA have been compared with results from the same case assessed with a tool developed by NTNU. The comparison shows relatively small differences in calculated results. This small degree of variation between the two tools in calculated results, demonstrates that OmrådeLCA can provide good estimates even at an early stage. This gives the tool great utility value because it is in the early stages of a project major actions can be performed and decisions made that will affect the emissions the most.

The ZEB Lab project, coordinated by SINTEF and NTNU, aims at building a ZEB (Zero Emission Building) in Trondheim (Norway) in 2019, to be used both as office building and living laboratory. An innovative latent heat storage (LHS) unit using phase change material (PCM) will be integrated in the centralized heating system. The LHS unit will be able to store excess heat from various heat sources connected to the heating system, when they are not required for space heating. One challenge is to make use of the full potential of the PCM latent heat to have a compact and effective unit, while the unit itself should have a low associated CO₂-footprint. The LHS system consists of two units designed for a total heat storage capacity of 0.6 MWh, corresponding to the heat needed on top of the heat pump to cover for up to 3 consecutive days in the coldest period of the year, with a maximum combined effect of 26 kW. A bio-based wax is used as PCM with melting temperature 37 °C and measured latent heat 198 kJ/kg. Dynamic system modelling is used to support the design of the LHS unit and ensure sufficiently high heat transfer rates.

LED lighting and smart controlling can decrease the consumption of electric power in zero or positive energy buildings. This study demonstrates that cyclic dimming, which appears in smart controlling, e.g. through occupancy sensing, might have an effect on the luminaire lifetimes and failure rates. Two different types of LED luminaires were aged in 30-s cycled dimming and undimmed modes. The manufacturer-specified lifetimes for both luminaire types were 100 000 hours. For one of the luminaire types, four out of five cycled units failed before 30 000 operating hours. For the uncycled luminaires, the lifetimes estimated from the measurements were over 100 000 hours. For the other type, the estimated lifetimes were 75 000 hours and 64 000 hours for uncycled and cycled luminaires, respectively.

One of the key elements in driving the energy performance of buildings has been recognized as occupant behavior (OB). However, available tools for assessing and simulating occupant behavior are based on fixed schedules and aggregated profiles, which fail to capture the diversity of OB. A significant aspect of OB is its relation to social groups and their influence and interdependence on each other. The data regarding the influence of social groups is important to achieve an effective model of OB as it accentuates the individual OB profile based on the influences it can have from the social groups they belong to. This added module is not present in traditional building simulation tools. This study aims to explore the tools and methods to evaluate the factors that are responsible for the influence of social groups on individuals' energy-related behavior. The paper investigates the kind of data sets needed for understanding this interdependence, including the occupant's social group, their standing in the group, and the intent behind different actions and its comparison to the actions the individual would take without any external influence. The results will be used to construct questionnaires, which can prove beneficial in developing social group profiles in OB models.

In 2015-2016, a six-month long experiment was carried out in the ZEB Living Lab, one of the first houses in Norway planned to reach net zero emission throughout its lifetime. By means of qualitative experiments, social scientists evaluated how six groups of occupants impacted the zero emission building, and how the zero emission building impacted its occupants in different ways. Data were collected through direct observation, diaries and interviews before, during and after the stay. In this paper, we take a closer look at the sensor data from the detailed monitoring system, generated during each group's 25-day long residing's. We find that despite the experiment being a controlled environment with many shared household characteristics, occupancy is determined by diverse factors, and the users' preferences and attitudes influence energy consumption. All major household appliances were the same, but the time of use, frequency, duration and type of use differed. The study contributes to increasing understanding of user behaviour and energy use in low energy houses. Providing occupancy profiles is valuable, in light of the increasing amount of local renewable energy production. These datasets can be used as input in energy simulation and planning of zero-emission neighbourhoods.

Aerogel insulation blankets could be the solution to some of the challenges encountered when designing (energy efficient) buildings. However, uncertainties regarding performance in different applications and environments may limit their use in cases where they could otherwise be employed to advantage. The purpose of this study was to examine how to best adapt European standards for the measurement of thermal insulation properties to aerogel insulation and highlight important aspects to be aware of when evaluating material parameters. We have systematically varied measurement parameters for thermal conductivity and compressive strength to map the impacts on reported material properties. Furthermore, we have compared the measurement conditions to actual conditions in selected building applications. In conclusion we propose that the European (EN) standard for measuring compression behavior for insulation materials should be revised and clarified with regards to materials that do not exhibit a clear elastic domain. We also suggest that the thermal conductivity of aerogel insulation blankets should be measured with a slight compressive load on the material, but that the calculation of the thermal conductivity should nevertheless be based on the measured sample thickness.

Prefabricated façade elements with integrated technical infrastructure is an attractive technology for refurbishment of existing dwellings. Heating and cooling demand can be reduced, local energy production introduced, and indoor air quality be improved, with disturbance to the tenants and building site being small and of short duration compared to more traditional building processes. On the other hand, unexpected events could largely reduce these benefits. Thus, risk management of the building process is of great importance. Focus group interviews and workshops were arranged before and after the building phase in a pilot project using such elements in Oslo, Norway. Representatives of building owner, design team and contractor contributed actively at the workshop. In a pre-building phase workshop, a range of hazards were identified and prioritized using a participative process facilitated by a neutral moderator. A large proportion of the prioritized risks in the building phase were connected to the renovated flats being occupied during the renovation. Other significant identified risks related to transport and logistics, and undetected challenges in the existing construction. Mitigation included prioritizing tenant information, including direct dialog, and increasing the presence of on-site workforce both for coordination with tenants and in order to respond quickly to unforeseen events. The participants emphasized that an open, cooperative processes with a high degree of trust and sense of a common goal had been important for the robust design that was developed prior to the workshop. During the retrospective evaluation, the participants concluded that the risk mitigation procedures had been successful in preventing some events as well as reducing the consequences of others. However, some of the measures to mitigate an identified risk of rain intrusion were inadequate, and it was acknowledged that the combination of bad weather and long working days could have identified this as preventable.

This paper provides a review of heat and ventilation measures that can be applied to ambitious energy renovation of detached houses in Nordic countries. In this review, requirements for solutions are defined. Key technologies are described and analysed in the context of renovation. The review focuses on strategies that are simple, cost-effective and robust, and can be transposed to the Norwegian context. The review revealed that a wider range of concepts and strategies than commonly used in Norway seem to be relevant. No solution or system appears to be an obvious and universal choice. A number of very different system solutions, with their pros and cons, are relevant, depending on the individual house and situation. Some combined heat and ventilation systems include hydronic space heating. This is however not common in Norwegian houses, and installing this is a major cost and intervention. Wood stoves, on the other hand, are regular, and can be used for peak heating. These factors seem to be crucial for the choice of system. Improved airtightness after renovation makes systematic ventilation measures necessary. Assumptions for occupant preferences and behaviour also seem to be important for choice of system. There are also differences in the commonly used HVAC concepts and strategies for renovation between the Nordic countries. These differences do not seem to be explained by climate only, and differences in building code may be part of the reason. A number of demonstration projects on ambitious energy upgrading are completed, but few of them have been systematically monitored and evaluated.

Recent research results from different countries show that although energy efficiency measures in buildings indeed led to lower energy use in buildings, there is a performance gap between the calculated energy use and the actual measured energy use in energy-efficient houses, leading to a higher energy use than predicted. Thermal comfort related behaviour is one out of manifold reasons contributing to this performance gap. Thermal comfort requirements are based on objectively measurable parameters. A number of contextual factors impact an individual's thermal comfort perception and preference. Technological opportunities and material arrangements offer several ways to conditioning indoor environments. Research shows that they shape the occupants' thermal comfort attitudes. Over time, technology as conditioning practice and insulation has led to different thermal comfort practice in buildings contributing to this performance gap. As humans show an excellent adaptation potential towards a wide range of temperature, enabling them to adapt to diverse climates but also seasonally, it follows also the adaptation process can work in the opposite direction. Hence, that with reduced exposure to outdoor weather and more narrow temperature ranges inside building humans might also adapt to indoor thermal conditions and get more sensitive to small indoor temperature changes, leading probably to higher indoor temperature over time ("indoor exposure rebound"). As our energy conservation efforts of the recent years show less effects than expected, it seems that the two mainly applied sustainability strategies efficiency and consistency have limited effects as they are affected by rebound phenomena. Sufficiency, as the third sustainability strategy, is not yet a generally accepted strategy. It refers to what has been described as "the right measure". The question of what would be "the right measure" of indoor thermal comfort, meaning what thermal conditions would be sufficient, can be raised. Based on a discussion of findings from literature, it will be concluded that there is a need for a new thermal comfort thinking in climates which have the need for seasonal or all year round active conditioning leading to a more sufficient conditioning practice.

Buildings with renewable energy systems and sizeable energy storage capacity can provide significant energy flexibility. Defining appropriate load management strategies requires estimating this flexibility accurately. However, this is no easy task, since the energy flexibility depends on the building structure, heating/cooling system, meteorological conditions, occupant activities, demand response strategy, among other factors. This paper focuses on the thermal storage flexibility of a building component: a concrete floor with an embedded radiant hydronic system. An approach based on a combined adaptive Auto Regressive model with exogenous inputs (ARX) is used to quantify the thermal energy available in the concrete slab. The model describes the relationship between: (a) the geothermal pump system and weather variables and (b) the temperatures of the indoor air and the concrete surface slab. These temperatures are then used to assess the state of charge (SOC) of the slab. The SOC indicator is critical to reducing heating energy use during peak periods. Results show that the proposed model can accurately quantify the energy flexibility of the building through performance indicators. Finally, tests using real data confirm the validity of the model as a tool to estimate energy flexibility.

Personal Comfort Systems (PCS) for heating, such as foot warmers, heated chairs and infrared heaters, can compensate for a lowering of up to 10°C in ambient temperatures in a heating situation. They are found to lead to a significant increase in occupant satisfaction with the thermal environment, as they enable for a personalized thermal environment. In this way, the use of PCS systems can ensure occupant satisfaction while widening the temperature dead-band, or difference between heating and cooling set-points in buildings. Several field studies from North America have indicated that the average dead-band between heating and cooling set-points is between 1 and 2 °C, leading to considerable amounts of energy used for over-heating and overcooling. This kind of systems may therefore be an important contributor towards Plus energy buildings, but they are seldom used. The objectives of this study were (1) to test PCS heaters in a modern Norwegian office environment and see how they are appreciated by office workers and (2) to investigate how large energy savings such systems can contribute to in a Plus energy building. Powerhouse Kjørbo was selected as a case building for the study. Potential energy savings were calculated using energy simulations. The results in this case study were not able to confirm an increase in occupant thermal acceptability rate due to the use of a PCS heater. Interviews of occupants however suggest that PCS heaters are a good solution for improving the satisfaction of the limited number of occupants who have special needs, preferences or are located in a place with lower temperature. In buildings with an effective heating source, such as ground source heat pumps, PCS solutions are not likely to contribute to notable energy savings. In an indirect way, they may however still contribute toward realizing Plus energy buildings as PCS systems can help relax the demands set to other climate installations in the building. This again can allow the use of more environmentally friendly solutions such as utilization of thermal mass, temperature stratification and natural ventilation. They can also reduce installation costs by eliminating the need for more complicated and costly HVAC systems.

Buildings are responsible for a large portion of the energy consumption and harmful emissions to the environment. To change this situation, the European Performance of Buildings Directive requires new buildings to be nearly Zero Energy Buildings. To achieve this goal, energy saving measures combined with large use of renewables on-site must be applied. In this paper, a reliable and cost-effective polygeneration system for an existing test building, able to provide electricity, cooling and heating needs is presented, modelled and assessed. The system relies on solar energy as the primary source (PV and solar thermal collectors). Building heat and cooling demand is achieved with a variable geometry ejector heat pump. To reduce the mismatches between generation and consumption, it includes different types of storage (electrical and thermal). For the test building energy needs assessment, the electricity consumption of all test building consumers was measured. Thermal energy demand evaluation required the development of a dynamic numerical model using TRNSYS software. The building thermal performance was validated using experimental data. The numerical model also includes the solar field, thermal energy storage, ejector cycle subjected to know meteorological conditions and operation control. To model and simulate yearly electricity production PVSyst commercial software was applied. Regarding the thermal energy, it was found that on a yearly basis the energy supplied by the thermal collectors about six times the demand. Nevertheless, on the hourly and daily levels, there are thermal energy shortages, due to the lack of solar radiation or mismatch between production and demand. Regarding the electric energy consumption, the potential electric energy production is about 1.6 times the demand. Like for the thermal energy, on the hourly and daily levels, there are energy deficits mostly in winter, for which an electrical energy storage unit will be used. Additionally, the highest peak occurs in summer because of low solar radiation at the end of the day and high demand due to the high cooling load of the test room.

ZEB Laboratory is a full-scale office building with a ZEB-COM ambition, searching a high degree of flexibility and where components and technical systems can be modified for research purposes. Project delivery of a living laboratory with a ZEB standard is not an easy task. The implementation of the ZEB method in a partnering contract as a project delivery model has been developed. This paper describes and elaborate the development of the project delivery and design process for ZEB Laboratory seen by the client. The ZEB Laboratory design and procurement process has given valuable insight and experience into the use of partnering and collaborative elements for planning and production of ZEB buildings.

Current regulations to reduce energy consumption, and GHG emissions from buildings have focused on reducing operational impacts [1] This paper addresses the specific challenge of increasing complexity and decreasing usability when dealing with the level of detail required when modelling life cycle assessment (LCA) and integrating embodied emission calculations in the design process of a ZEB. It is well known that architectural design processes inherently have high degrees of complexity, and this paper investigates how the use of information and communication technology (ICT) in the design process can have a great impact on reducing GHG emissions and increasing sustainability in ZEBs. Visualisation is an invaluable tool to communicate complex data in an interactive way that makes it easier for non-expert users to integrate LCA thinking early and throughout the design process.

The paper presents a chronology in the development of a more visual, integrated and dynamic approach involving the use of parametric LCA models for decision-support purposes. Such an approach provides the designer with a direct link between the 3D digital model and embodied emissions data contained in the ZEB Tool to perform life cycle GHG emission calculations of buildings. Integrating LCA in a more visual and easily understood way in the holistic design process can also influence more tangible material choices in terms of, for example, architectural tectonics or cultural heritage. This allows designers the possibility to choose, for example, durable or natural materials with the lowest environmental impact or innovative materials with high or low associated emissions and consider these holistically early in the design phase when the level of design freedom is greater. The extent to which existing ICT tools and User Interfaces (UI), such as dashboards, can provide dynamic visual feedback on selected parameters, including LCA, in the design process of zero emission buildings, is discussed. The paper presents two 'proof of concept' dashboards to visualise LCAs at the building (ZEB) and neighbourhood (ZEN) scale. Both approaches are currently being further developed in The ZEN research centre to visualise, analyse and model the data at different scales for different ZEN Key Performance Indicators (KPIs) using visualisation and immersive technologies, such as Extended Reality (XR) technologies including Virtual Reality (VR) and Augmented Reality (AR).

In recent years, several systems and tools to assess energy consumption and carbon emissions at scales beyond that of merely buildings, such as LEED, CASBEE and BREEAM communities have been development. However, reviews reveal a lack of robustness in these methods both in terms of an unstructured mix of qualitative and quantitative criteria and lack of focus on urban form parameters found to influence energy consumption and carbon emissions. A promising quantitative assessment system including various urban form indicators is developed by the Urban Morphology Institute (UMI) in Paris. Within the research centre on zero emission neighbourhoods in smart cities (ZEN), a GIS-based method is applied to analyze conditions of urban form known to contribute to carbon emissions. In this paper we demonstrate how a selection of the UMI indicators describing proximity can be further specified applying GIS-based methods. The potential of applicability of urban assessment system in planning as well as design processes will increase when linked to tools that are already implemented, and map visualizations as well as data provided by these methods are highly applicable in planning and urban design. As further research, methods described in recent research within ZEN and specified measures for calculating UMI indicators, will be tested in analyses of urban development areas in Norway.

Powerhouse Telemark (PHT) is an eleven stories high office building in Telemark in Norway, built to plus energy standard. A plus energy building that is built according to the Powerhouse definition prior to 2019 must produce more renewable, locally produced energy during the lifetime of the building, and must produce enough renewable energy to cover the total embodied energy used for the production and transportation of the building materials used in the building. The local renewable energy production must also cover the yearly net energy needs for operations, renovations and demolition of the building. The local production of renewable energy on the building is not required to cover the energy needed for plug loads in the building.

The building will have a unique diamond shape, and the roof of the building is oriented towards the south, and slopes at an angle of 24 degrees from the horizontal. The building will be a net supplier of electricity when seen over a whole year.

In addition to other "normal" measures to achieve a plus energy building, like a high performance building envelope, and an extremely efficient ventilation system, energy efficient lighting and equipment and a solar PV system, a new low exergy heating and cooling system has been implemented in the building. This low exergy system (called Lowex) is based on low temperature heating and high temperature cooling, which together with an optimized energy well design will give extremely low demand for delivered energy (electricity). To design this Lowex system, a lot of different calculations and simulations had to be done, both with commercial software packages, but also with new develop dynamic simulation models. These design procedures and models are described in this paper. This paper also describes how these results will be used for the operation of the building.

The building is currently under construction and will be commissioned in late 2019/early 2020. The main experience from the design phase and early construction phase is that the Lowex system sets strict demands on both façade design and the interior design. Transparent vs. opaque area ratios, solar shading and glazing solutions set boundaries for the architectural concept, and must be taken into account early in the design process. Flooring materials, ratio of landscape vs. office cells, and thermal zoning of the building affects the interior design. The acoustic concept and the carbon footprint of the building as well as the design of the supplementary HVAC-system are also important factors that need to be taken into account at an early stage in the design phase. To solve these interdisciplinary problems it requires a design team that can work together closely. The architect, and the engineer that is responsible for the energy performance of the building, have a central role to play at the very beginning of the design phase when the geometry and the general parameters of the building is still in flux.

To reduce the space-heating needs, balanced mechanical ventilation equipped with a heat recovery is frequently implemented in highly-insulated residential buildings. This standard ventilation strategy tends to homogenize temperature inside the building, in other words, to reduce temperature zoning. In some countries, such as Norway, many users would like colder bedrooms. It has been proved that a significant part of the occupants in Norwegian passive houses opens bedroom windows during several hours every night during winter. Dynamic simulations have shown that it strongly increases the space-heating needs and that control only is unable to create temperature zoning in an energy-efficient way. The building concept should be changed. In the present contribution, the physical processes during temperature zoning are further explained. Detailed dynamic simulations of a detached single-family house are performed using the simulation software IDA ICE for different insulation levels, construction modes (which also influence the thermal insulation in partition walls) and control strategies. Alternative mechanical ventilation strategies are compared. They manage to reduce the influence of mechanical ventilation on the increased space-heating needs due to window opening but they cannot improve the large contribution of heat conduction through partition walls between heated areas and unheated bedrooms. Among the investigated ventilation strategies, decentralized ventilation has intrinsically the best performance.

The building sector is of major concern when seeking to reduce the environmental impact of our society. A common tool often used in certification systems for quantification of environmental impacts is Life Cycle Assessments (LCAs). LCAs are traditionally used for relative comparisons, i.e. to assess whether one product or service performs better than another. Recently, a method for absolute evaluations based on the Planetary Boundaries, was coupled with LCA in order to define the boundary between environmental sustainability and unsustainability. In this study Planetary Boundaries-based Life Cycle Impact Assessment method has been applied to a case study of six single family stand-alone dwellings to assess whether these buildings can be considered absolute sustainable relative to the Planetary Boundaries. The results from the assessment indicate that irrespective of the design strategy used for the six houses and future increase in the use of renewables for electricity and heat production, it is unlikely that any of these houses can be regarded as sustainable in absolute terms. This underlines that more radical changes are needed in the way buildings are constructed and used in order for buildings to become environmentally sustainable.

Learning performance is strongly related to thermal comfort and lighting conditions of classrooms. Poor facade design can result in high indoor temperatures or insufficient access to natural light. To maintain the required temperatures and illuminance levels in such rooms may require intensive use of artificial lighting and active cooling systems, which are energy-intensive, costly to install, operate and maintain. The purpose of this study was to determine essential parameters and facade design options that ensure overheating prevention and fulfil daylight requirements in classrooms without mechanical cooling. The present study is based on simulations of a parametric room model with variable dimensions and orientations. Facade glazing solutions with optimal combination of solar factor and visible light transmittance were used to minimize overheating risk and maximize natural lighting impact. For east, south and west oriented facades, the effect of horizontal shading was also analysed. Overheating assessment through indoor temperature simulations was conducted with dynamic simulation software IDA ICE, daylighting was simulated with DIVA4 coupled with Grasshopper software. Results show that classrooms without mechanical cooling require in depth analysis to determine satisfying solutions for both overheating and daylighting criteria. The results of this paper can be used for early stage facade design guide for school buildings or similar use free-running buildings.

A main challenge in building carbon-neutral built environments is the ability to scale and replicate solutions. We examine how to develop low-carbon neighbourhoods and districts, while aiming at climate-friendly and sustainable livable urban environments. We take a view that not only scales up individual building solutions, but embraces the added complexities arising from the scale change and utilizes them for a novel approach. It includes a strong focus on co-creation and open innovation to develop sustainable solutions.

In this contribution, we present the approach of the +CityxChange project in implementing Positive Energy Blocks (PEB) through a European H2020 project from the topic of Smart Cities and Communities. A PEB comprises several connected buildings that have a averaged yearly positive energy balance between them. This definition excludes embodied emissions, but allows to focus on the infrastructure and systems between buildings as part of the built environment, and ways to implement and incorporate them within existing cities. The +CityxChange approach relies on co-creating Europe-wide deployment of Positive Energy Districts, with Integrated Planning and Design, Creation of a Common Energy Market, and CommunityxChange with all stakeholders of the city.

Lia kindergarten is designed to be a plus energy building. The kindergarten was opened in January 2018, and the first year has been a tune-in phase for the technical systems. The plus energy concept consist of a well insulated building envelope, a highly efficient ventilation system, a lighting system with LED-fixtures and advanced control system and a low exergy thermal energy supply based on geothermal wells and a small inverter heat pump. The energy demand is balanced with a solar PV-system on the roof to achieve the plus energy definition. A lithium-ion battery package of approximately 40 kWh has been installed for peak shaving and to utilize more of the solar energy produced on the building (reducing mismatch).

A lot of research, calculations and simulations has been done in the design phase for the low exergy system. The floor concrete slab with embedded heating (pex pipes) is designed for very low temperature heating (22-28 °C). The floor system is reversed in the summer providing high temperature cooling (18-19 °C) which also charge the geothermal wells for the heating season. The calculations and simulations has also been used to make control strategies based on model predictive control (MPC) methodology, also taking in on-line weather forecast.

The concept of Building-integrated Photovoltaics (BIPV) is one of the most promising strategies to employ clean energy in the built environment. Up to now, the PVs have been applied mostly on roofs, but since the total roof area is insufficient, there is a need to integrate photovoltaics on building façades as well. This challenges not only the architectural design of a single building but also the visual image of urban environment, as photovoltaics have to harmonize with conventional building materials used on building facades as brick, concrete, wood, etc. Aiming to provide a foundation for research exploring facade-integration methods that will ensure successful architectural result, the paper presents a state of the art on façade integrated photovoltaics (FIPV) with focus on the experimental research methodology. It embraces both, theoretical research and PVs applications in building projects. As pure computer simulations are not recognized as an experimental methodology, papers conveying such generated results have not been included. In addition, the research that deals exclusively with energy aspects is omitted. The study is based on a comprehensive literature review. Advanced experimental methodologies from selected literature are described and categorized according to the scale (building or urban) and the transparency of the PVs (opaque or translucent). Then detailed features of PV experimental methods are demonstrated in structured tables for analysis and discussion. The study shows that even though solid scientific methods are used to evaluate single features of PVs, e.g. colour or reflectance, there is an obvious lack of methodology providing holistic assessment of Façade-integrated Photovoltaics, especially at the urban scale. The further research will lead toward developing of evaluation criteria framework (in interdisciplinary cooperation) and then provide a holistic methodology combining qualitative and quantitative methods for a successful FIPVs in urban context.

The 6Zs target refers to the concept of a minus carbon and plus energy eco-cycle refugee house. A 37 m² house was designed and constructed in a participatory manner in the City of Lund, Sweden. The 6Zs include: zero emissions, zero energy, zero waste, zero cost, zero indoor air pollutants and zero impact on the environment after the shelter is demolished. The key idea of this eco-cycle house is to reach net 6Zs during all stages—material extraction, building construction, operation and maintenance—until the shelter's end of life. The main construction material is plant-based raw fibers (mainly straw and reed), which are available around the building site. This house is designed to accommodate the needs of two adults and one child. It was built with the help of 7 refugees in 11 working days through an experimental participatory urban living lab methodology. The paper discusses the 6Z design concepts and draws conclusions on the preliminary assessment of the house prototype that was built as a proof of concept. The beneficiaries of this project are not restricted to refugees but also include the majority of individuals and families seeking affordable ways of living with a low impact on the environment. The house is designed for the cold Swedish climate, but the design concept and methodological approach can be adjusted to other climates or geographical contexts.

Globally, there has been a rising focus on improving the sustainability of buildings. Reaching zero net greenhouse gas emissions or producing excess renewable energy throughout the entire lifetime of a building is now clearly possible and certainly worth aiming for. However, in remote Nordic regions like Greenland, current building practices are so far away from these targets that setting intermediary goals is the only option for moving forward in the construction industry. Besides, remote Nordic regions are facing different challenges that are not considered into current building certification schemes, making some practices that can be highly sustainable in some regions inapplicable or even detrimental there. It would be highly desirable to have a certification scheme more accessible for improving current building practices in remote Nordic regions. For a sustainability index to be widely adopted in such a context, it should be relatively simple and straightforward to implement. This contribution presents the Greenlandic Sustainable Index (GSI) for residential buildings, which was developed with the goal to be simple to implement while being ambitious in terms of level of performance. This index is composed of three main categories: Economical, Social and Environmental sustainability.

As circular economy (CE) is becoming a growing focus in the building industry due to the industries large resource consumption, waste production and environmental impacts a better understanding of buildings material composition, resource consumption and resulting environmental performance becomes increasingly important in order to support the transition towards CE. The research presented here is a stepping stone in order to investigating the existing building portfolio and the conducted analysis. It is used to get further information on what is included and where there is lack of information, in order to understand what is missing or what is needed to develop CE design strategies. Although, life cycle assessment (LCA) is increasingly used by the industry to assess these aspects, the lack of a systematic analytical approach as well as the high building complexity and diversity between buildings limits generalised knowledge from these studies. However, it is assumed that there are certain commonalities between the existing portfolio of prevailing building typologies which can be deducted. The study at hand is a part of a larger research project that aims at developing industry specific tools to support designers and decision makers select CE design strategies that improve the environmental performance and resource consumption of buildings. On the basis of a comprehensive systematic literature review (SLR) of whole building LCAs the paper at hand aims at tracing the environmental impact origin within the existing building portfolio of prevailing building typologies. To identify potentially important building parameters relevant to the resulting environmental impact performance and resource consumption of different building typologies. Based on 39 building LCA case studies that matched the specific inclusion and exclusion criteria of the SLR a focus on global warming and climate change was detected. It was found that even though buildings have different characteristics (size, typology, storeys, reference study period and location), for most of the buildings' environmental impacts were predominantly related to the production of structurally important concrete components e.g. the structural frame, the external envelope, floor slabs and walls. To point towards which CE design strategies should be used to improve the environmental performance of buildings; the environmental information from the studies was insufficient due to lack of detailed information.

Building Bioclimatic Design (BBCD) understands architecture as a filter between outdoor climate and indoor comfort. This way, it encourages the exploitation of freely available climatic resources, before adding any HVAC system. Therefore, BBCD represents a fundamental strategy for improving energy efficiency in buildings. The climate / comfort comparison in building design determines the passive strategies that are most suitable for a specific climatic context, as well as the level of architectural complexity. In cold climates, it would suggest the use of compact shapes and extremely airtight and insulating envelopes, in order to minimize heat losses while maximizing solar heat gains. However, when combined with high internal gains, these measures might cause overheating problems in the warm seasons. That is the case of office buildings, where cooling equipment is included as default even in cold climates, drastically increasing their energy consumption. It is therefore becoming a necessity to consider here the adoption of passive cooling strategies once identified with warmer climates. The aim of this research is to explore how the theories and tools for BBCD could be applied to cold climate office buildings. In order to study the effect of the different climatic contributors, we will use Building Performance Simulation to analyse relevant cases with EnergyPlus (in combination with DesignBuilder). This will in turn help drawing suggestions on how to adapt the Building Bioclimatic Chart (BBCC) for its application to cold climate office buildings in practice. It is well known that the earlier we apply the measures for energy efficiency, the greater their effect and with higher degree of integration. The BBCC is used in the pre-design phase to determine the most suitable passive strategies for climate adaptation and control, informing the design as early as possible along the process. This study can contribute to the development of zero emission neighbourhoods in cold climates, by improving the energy efficiency of their buildings. Additionally, it complements the existing research in BBCD by extending its application to cold climates and office buildings.

Recent reports from UN International Resource Panel call for double decoupling – decoupling of material use and related environmental impacts from economic growth. The construction and use of buildings constitute a significant portion of energy use, GHG emissions and extraction of materials in Europe. One of the central strategies addressing double decoupling in the construction industry is reuse and recycling of building materials and components that would limit raw material extraction and embodied emissions related to new products. A recent IPCC report states the urgency of limiting GHG emissions already by 2030 to remain below the 1.5-degree target. Given this timeframe, reducing emissions in the early stages of a buildings lifetime appears worth considering, meaning prioritizing embodied over operational emissions. The case study used for this article is an ongoing building project "Selbukassa" ("the Selbu box") situated in Svartlamon – an experimental neighbourhood for urban ecology in Trondheim, Norway. It is a bottom-up, self-build project with a strong focus on reuse of materials. The 300 m² building will house 4 families and is built reusing an old log house, as well as CLT-elements from a former pavilion used for exhibiting an art piece by the local artist Killi Olsen. Other salvaged materials and components include windows, doors, roof slate and most of the internal and external finishes. Due to the experimental status of the area and to allow for reuse of building components with lower energy performance, the fulfilment of energy requirements in the building code TEK 17 was not required by the local building authorities. The article examines the embodied and operational emissions of Selbukassa, and compares it with a reference building with no reused components and complying with energy requirements in the building code TEK17. Simien v.6.009 is used for energy simulations of the two cases, and LCA tool One Click LCA Norge for NS 3720:2018 with data sourced from Norwegian and other European EPDs is used for estimating embodied emissions. The article investigates the possible savings in emissions linked to reuse of materials, as well as the trade-offs between reused components with worse energy performance and the consequential higher energy demand. The article contributes to the discussion about the various implications of reuse of materials and more generally on how the built environment could respond more optimally to a combined emission and resource use reduction challenge.

Heat recovery in ventilation is essential to reduce energy use and thus mitigate greenhouse gas emissions from the building sector. Heat recovery efficiency of at least 80 % in new buildings is required according to Norwegian standards. However, measurements show that the real heat recovery efficiency during operation is commonly 10-20 % lower. Measuring heat recovery efficiency in buildings is challenging, mainly due to difficulties measuring airflow rates close to the air handling unit (AHU). This study assesses the following duct airflow measurement techniques and equipment: pressure differential, velocity traversal technique, ultrasound and tracer gas. The pressure differential method can provide accurate flow rates and thus it is used as the reference measurement. However, it is not suitable for duct flow measurements due to its high pressure penalty and long straight duct requirement. Velocity traverse and tracer gas methods introduce less disturbance to the flow. Nevertheless, both methods require intensive labour work and cannot track quick changes of the airflow with time. The application of ultrasound to measure airflow is relatively novel and it can automatically measure constant and fluctuating airflows with low pressure drop and acceptable accuracy when the proper installation and minimum straight duct are provided.

This paper presents a simulation study on the use of shading devices in highly glazed facades in the context of zero emission buildings (ZEB) located in a Nordic climatic context. Shading devices have the task to control different uses of solar energy (solar gain for passive solar heating and daylighting) and to avoid cooling load, and to find the best strategy (i.e. to optimize the overall performance) for controlling shading devices is not trivial.

Different control strategies for the activation of the shading devices (venetian blinds) are simulated, and their performance calculated in this study through a dynamic whole-building simulation tool (EnergyPlus). The results of the simulation studies show that it is possible to achieve very high performance and balanced use of solar energy (for passive solar heating, daylighting), without occurring in too high cooling load, even in the case of fully glazed facades. The optimal strategy for shading activation is not straightforward, and different strategies should be recommended during the year to assure an overall optimal performance.