Code on Envelope Thermal Performance for Buildings

Background

Since 1979, the Building Control Regulations had prescribed an envelope thermal performance standard know as Overall Thermal Transfer Value (OTTV). The OTTV standard applied only to air-conditioned non-residential buildings.

A major review of the OTTV formula was carried out in the early 2000 to provide a more accurate measure of the thermal performance of building envelope. The new formula is given the name ‘Envelope Thermal Transfer Value’ (ETTV) to differentiate it from the original OTTV formula.

A similar review of the OTTV formula for roof was also conducted and a new formula, known as ‘Roof Thermal Transfer Value’ (RTTV), replaces the Roof OTTV formula.

The ETTV requirement does not apply to non air-conditioned buildings such as residential buildings that are designed to be naturally ventilated. However, as it becomes increasingly common for residential buildings to be air-conditioned, there is a need to regulate the design of their envelopes so that heat gain into the interior spaces and hence air-conditioning energy used can be minimised.

Based on the results of a NUS study commissioned by BCA, the ETTV concept was extended in 2008 to cover residential buildings. As the air-conditioners in residential buildings are usually turned on in the night, the envelope thermal performance standard for residential buildings is given the name Residential Envelope Transmittance Value (RETV) so as to differentiate it from ETTV, which is meant for buildings that operate the air-conditioning system during the day.

Code on Envelope Thermal Performance for Buildings

This code aims to assist architects and professional engineers to comply with the envelope thermal performance standards prescribed in the Building Regulations.

The Code covers the following Envelope Thermal Performance Standards:

i. Envelope Thermal Transfer Value (ETTV) for air-conditioned non-residential buildings

ii. Roof Thermal Transfer Value (RTTV) for air-conditioned non-residential buildings (with skylight)

iii. Residential Envelope Transmittance Value (RETV) for residential buildings

iv. Roof insulation for air-conditioned non-residential buildings (without skylight) and residential buildings

Pls click here to download the Code on Envelope Thermal Performance for Buildings.

Computation Tools

1. Building Energy Standards X (BEST Ver.X)

"BEST is capable of computing ETTV and RETV, the annual energy consumption and energy efficiency index, the building lighting power allowance and receptacle power density, and performing parametric calculations in support of prescriptive and performance standards."

To purchase this software, contact: rosa@energyventures.biz

2. Helios

A 3D modeling tool that automatically computes ETTV/RETV upon the completion of the 3D design of the building and selection of the materials for the facade.

BCA invites you to take part in the beta testing of Project Helios (Designed and developed by Dr. Uma Maheswaran). The testing will last till 15 July 08

Pls click here http://www.bca.gov.sg/helios/helios.htm