Energy efficiency through façade design model of Nobel house building

One of the triggers to global warming is the increase of CO2 trace caused by fossil energy consumption. The escalation of fossil energy consumption in urban area comes from industrial sector, housing sector, and commercial sector. Commercial buildings in urban area play a major contribution in CO2 production level. That is why, electricity efficiency efforts are needed. The high energy consumption in commercial buildings are commonly caused by less precise façade construction, either on its design, material, and orientation. The objective of this research is to evaluate the effect of façade design on energy efficiency level at Nobel House Building. The participation of Nobel House to lower CO2 is actually an effort to improve GBCI green building certification valuation result, from Gold to Platinum. Energy aspect is a priority in certification valuation to improve their rank. The research method utilized in this research is a descriptive qualitative method with OTTV analysis on 15 Nobel House Building façade models. The research is further narrating the initial 15 models with gold certifications. The result of this research is used to determine 4 façade model with energy efficiency below the base line. (SNI 6389-2011, GBCI,2013) with two main considerations which are easy in construction and maintenance work.


Introduction
At this moment, energy consumption level has reached 60% and is predicted to reach 80% on 2040. If the consumed energy comes from fossil energy, the unavoidable impact would be the increase of carbon dioxide/CO2 production as pollutant that would leads to global warming which will endanger the lives all over the world [1]. Indonesian energy consumption on industrial sector is at 36%, on housing sector is at 31%, on transportation system at 28%, meanwhile the commerce and service sectors are at 5% [2]. Energy consumption level of buildings in urban area contribute up to 43%, industrial at 25%, and transportation at 32%. Whereas, these buildings are categorized into 5% of industrial building, 17% of commercial building (one of them is rented office), and 21% of residential buildings [3].
Urban building performance evaluation must be conducted with reference of: Year 2012 on Green Building [7]. For the area of Jakarta, all of these four regulations are mandatories for new building design with certain area and function. To complete the government regulation on new building construction, Green Building Council Indonesia (GBCI) will provide Green Building Certification. on the design after conducting an evaluation on the design based on 6 criteria. These 6 criteria are shown in Table 1. Table 1. Six criteria of green building evaluation rank [8].

Criteria
Total The main requirement of energy efficiency valuation by GBCI is the external heat load on the building façade which is measured with Overall Therman Transfer Value (OTTV) method. OTTV is a evaluation of external thermal/heat transmission on building façade surface influenced by façade design (W/m²). The submission of green building certification, OTTV analysis has become a perquisite for valuation of energy efficiency. When the original façade design is unable to fulfill the minimum/base line requirement (the required minimum OTTV value according to GBCI is at 35° Watt/m² of façade area and according to Indonesian National Standard is at 45 Watt/m²). That is why façade design that would fulfill evaluation level ≤ the baseline is required [8].
The effort to improve energy efficiency is conducted by air conditioning with the right passive façade design (the right material usage, orientation, and shading application on building façade, color and tecture). This research is focused on energy efficiency through façade design accuracy. We can see that the energy efficiency aspect is a prioritized scale.
This research is aimed to evaluate Nobel House Building façade design based on its energy consumption efficiency. Nobel House Building involvement to lower CO2 level is aimed to improve its certification level on GBCI green building certification valuation. The initial design with gold certificate is aimed to be improved into platinum by analyzing 15 façade design models through OTTV method. Based on the OTTV analysis on the 15 façade models, we are hoping to obtain: (1) heat transmission value that would represent energy consumption level, while also considering the comfort temperature of 24-25°C with humidity level of (RH) 60-70% [9]; (2) determine several models that appropriate with the baseline; (3) determine 4 models with the highest energy efficiency level out of the available 15 models. Four façade models are chosen with analysis consideration of the ability to minimize OTTV value based on the utilized baseline, with two main considerations which are easy in construction and maintenance work.

Methods
The method utilized in this research is a descriptive qualitative method through 2 phases of activities which is divided into; (1) Phase 1 which includes; (a) conducting data compilation of micro climate characteristic of the building to obtain output of average temperature on the hottest months and the coldest months (draught and rainy seasons); (b) average humidity level, vegetation element on the footprint according to its outer design;

Results and discussion
Nobel House Building is a commercial office building which is located in Lingkar Mega Kuningan Street at South Jakarta. The building is fitted with 32 main floors, and 4 floors of basements used as parking areas and utility rooms. The orientation and building height data can be seen in the following figure 2: The details of processed data based on field physical and initial design measurements is as follow:

Façade model to be analyzed with OTTV measurement
Determining 15 façade models as negotiated by the architect and Nobel House Building owner with the following criteria; (1) modern façade looks; (2) determining façade orientation/direction according to its environmental potential and building visualization based on urban view with sun heat as consideration factor. Orientation or direction with lower heat factor is preferable. The data is presented in table 3 below.

Obtaining minimum OTTV value on the façade
(a) choosing low value U façade wall material; (c) material with low absorption coefficient value; (c) shading utilization; (d) double wall/glass utilization [10]; (4) categorizing the façade models into two groups which are; (a) curtain wall looks façade design combined with 80 cm parapet and 140 cm spandrel, (b) façade design group that utilizes a combination of 80 cm parapet, 70 cm horizontal shading made of aluminum material as penetration, glass and 140 cm spandrel. By replacing several materials, we were able to determine 15 façade models, one of them is an initial gold ranked façade design.
Out of the produced 15 models, either by replacing or stimulating several types of glass with certain characteristic with low energy glasses such as Stopsol glass, Double glass T sun, Double glass Stopray with several level of thickness as shown in Table 4.  The 15 façade models that has been analyzed with OTTV calculation is compared to obtain 4 models (with criteria of low OTTV value, fulfill GBCI Standard and National Indonesian Standard 6398, 2011; with consideration of construction and maintenance facilitations and efficient Life Cycle Cost). The results of comparation analysis on 15 façades are as follows.    Based on the analysis above, the alternative design that categorized as preferable designs are; (a) alternative 6: façade design alternative with building cover materials of pure glass with glass type of Low e (Stopray Ace 52/26) Neutral Bluish Silver; (b) alternative 7: façade design alternative with building cover materials of pandrel, 12 mm stopsol super silver glass, and plastered brick parapet; (c) alternative 8: façade design alternative with building cover materials of pandrel, 12 mm T-Sunflux glass and plastered brick parapet; and (d) alternative 9: façade design alternative with building cover materials of pandrels, 12 mm Stopray AC clear glass, and plastered brick parapet.