For certification under the Singapore Green Mark Scheme, envelopes of non- residential and residential buildings are required to comply with the following criteria: For non-residential buildings: ETTV = 12(1 - WWR)(Uw) + 3.4(WWR)(Uf) + 211(WWR)(CF)(SC) For residential buildings: - RETV = 3.4(1 - WWR)(Uw) + 1.3 (WWR) (Uf) + 58.6(WWR)(CF)(SC) where (ii) (iii) RETV/ETTV WWR Uw Uf CF SC = = || || || = = = respective envelope transmittance value (W/m) window-to-wall ratio (fenestration area/gross area of exterior wall) thermal transmittance of opaque wall (W/m K) thermal transmittance of fenestration (W/m K) correction factor for solar heat gain through fenestration shading coefficient of fenestration Briefly state the relative significance of the heat gain streams across the building envelope. (3 marks) Explain briefly the basis for using a much reduced solar factor in the RETV. (2 marks) Explain briefly how one might obtain the overall envelope thermal transfer value for a building with multiple facades. (2 marks)