COOLING EFFECT COMPARISON OF COOL ROOF AND GREEN ROOF

Abstract

As part of its commitment to reducing the carbon footprint of Singapore, the Singaporean government has the ambitious aim of bringing at least 80% of buildings in Singapore up to the government green building standard, “Green Mark”, by 2030, which would involve reducing the thermal transmittance (U-value) of the roof in every building. The Housing and Development Board (HDB) of Singapore has conducted pilot projects to reduce the U-value of roofs in HDB estates using an extensive green roof system. HDB estates house more than 80% of people living in Singapore and represent a significant portion of building stock in Singapore. If every roof in HDB estates is covered with an extensive green roof, the area covered by green roofs in Singapore will grow dramatically. Although extensive green roofs usually require little maintenance, they still generate waste biomass and need to be irrigated in times of drought. Current anthropogenic climate change models predict that global warming may make droughts more likely around the world and, as Singapore is already a water-poor country, maintenance of future green roofs may become unsustainable. Cool roof technologies offer an alternative solution to reducing the U-value of roofs which does not depend on water. It is essential that research be conducted to ascertain whether cool roof technologies can compete with extensive green roofs in terms of cooling effect in a Singaporean context so that the use of green and cool roofs can be correctly prioritized. Therefore, a comparative study of the cooling effect of a cool roof and an extensive green roof was conducted in Singapore.