The Building Energy Code (BEC) provides standards and specifications for: building envelope, lighting system, air conditioning (AC) system, hot water generating system and renewable energy performance. The BEC allows for either conformity on system standards on building envelope, lighting system and air conditioning systems, or alternatively on whole-of-building energy performance. For whole building, compliance designed buildings must be lower or equal to a reference building for the category. In case the building uses renewable energy, this is taken into consideration for the calculation of the energy performance of the building.
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Annex D. Building Energy Code standards
Building Envelope
The BEC evaluates the building envelope by assessing the overall thermal transfer value (OTTV) and roof thermal transfer value (RTTV) of the enveloped area in a building with air conditioning. This value depends on the thermal properties of the material and the envelope composition, both opaque and transparent. The standard sets the calculation methodology based on factors such as the heat transfer coefficient value, window-to-wall ratio and equivalent temperature. For transparent materials, the solar heat gain, shading coefficient and solar radiation are also considered (Ananwattanaporn et al., 2021[1]).
Table A D.1. Building envelope
Note: Overall Thermal Transfer Value (OTTV), Roof Thermal Transfer Value (RTTV)
Source: Ministry of Energy (2022[2]), Building Energy Code, https://bec.dede.go.th/wp-content/uploads/2022/05/ebook.pdf
Air conditioning systems in the BEC are evaluated through the energy performance for each individual unit for both split types and packaged air conditioning units using the seasonal energy efficiency ratio as an index. In the case of central systems, the evaluation is separated into chiller and other components. The chiller needs to have a coefficient of performance according to the standard, while other equipment in the system needs to have a total power consumption below 0.5 kW per refrigerator tonnes. Other considerations on space cooling system performance (for example shorter ducts on an AC unit can improve its efficiency) are not considered.
Under the BEC, for air conditioners with a capacity of less than 12 000 watts, the Seasonal Energy Efficiency Ratio must be under the current EGAT Label No. 5 Certification Criteria. The water cooler of a vapor-compression air conditioning system must have an electric power per Ton of Refrigeration no greater than the value specified in the notification.
Whole-of-building energy consumption
In cases where one or more systems do not meet minimum efficiency requirements, then the building may be evaluated according to overall building energy consumption criteria. This is done by calculating the building’s overall annual energy consumption and comparing to the overall energy consumption of the reference building.
If the building’s overall energy consumption value is lower than that of the reference building, then the building is compliant with the BEC. To evaluate this criterion, the reference building must have the same usage area, direction for the building perimeter system on each side as the evaluated new building or renovate building (Table A D.2). In addition, the reference building must have the minimum requirements for the building envelope system, lighting system and air conditioning systems according to the requirements for each system.
The whole of building approach aimed to allow more flexibility regarding the building design but can mean that individual standards particularly for building envelope are not met.
Table A D.2. Efficiency coefficient of cooling load in building energy code
Source: Ananwattanaporn et al (2021[1]), Retrofitted Existing Residential Building Design in Energy and Economic Aspect According to Thailand Building Energy Code, 10.3390/app11041398
Renewable energy
Under the BEC, in case the building consumes energy from a renewable source the power generation from the renewable system can be deducted from the whole building energy performance value.
In case there is a renewable power generation in the building (e.g. a solar PV system), it is possible to deduct the amount of renewable electricity power generated from the overall building energy consumption of the building, prior to comparing to the reference building energy consumption value. The renewable energy of solar power generation is to be calculated from the average annual electricity produced by the solar PV system. The use of renewable energy heat for buildings can be calculated equivalent to the heat to electrical energy, in kWh/y. Buildings can take the amount of equivalent electrical energy to deduct from the overall energy consumption of the buildings.
Procedure for construction permit under BEC compliance
Following the BEC compliance regulation, building owners must apply for building permits by preparing an application document with a building design that is compliant with the BEC standards detailed in Ministerial Regulation B.E. 2563. This permit must be approved by an authorised person holding BEC-certified professional license (for professional engineer/architect) before being submitted to the local building administration. To support this process in 2018, DEDE launched a training programme to certify over 2 500 BEC auditors (DEDE, 2018[3]) (Figure A D.1).
Figure A D.1. Owner approval under BEC standards
Source: Ananwattanaporn et al (2021[1]), Retrofitted Existing Residential Building Design in Energy and Economic Aspect According to Thailand Building Energy Code, 10.3390/app11041398
References
[1] Ananwattanaporn, S. et al. (2021), “Retrofitted Existing Residential Building Design in Energy and Economic Aspect According to Thailand Building Energy Code”, Applied Sciences, Vol. 11/4, p. 1398, https://doi.org/10.3390/app11041398.
[3] DEDE (2018), Building Energy Code (BEC), https://seforallateccj.org/wpdata/wp-content/uploads/ecap17-thailand.pdf.
[2] Ministry of Energy (2022), Building Energy Code, https://bec.dede.go.th/wp-content/uploads/2022/05/ebook.pdf.