KC-84-12-1 -- Analysis of Overall Thermal Transfer Value (OTTV) Energy Conservation Standard for Singapore Office Buildings

The present Singapore OTTV Standard requires that air-conditioned buildings have an OTTV less than 45 W/m2. The OTTV concept takes into account the three basic heat gains through the external walls of a building: heat conduction through opaque walls, heat conduction through windows and solar radiation through windows. An analysis indicates that, for Singapore, the term for radiation through windows, understates the contribution of this type of heat transfer, and the first two heat conduction terms overpredict conductive heat transfer. Thus, the present OTTV standard underestimates the energy savings that can be achieved by various measures to reduce solar gains and overestimates the energy savings that would result from measures that reduce conductive heat gains through the building envelope. The authors recommend that Singapore replace the existing Singapore MTV formulation with only one term, a solar gain term. In locations where heating is not required, such as Honolulu or Miami, a comparable analysis may result in similar conclusions.