Topic 2 Taxonomies of green roofs based on climate conditions

Some studies have examined how different climates influence the performance of green roofs, as well as which type of green roof is best suited for specific climates…

Study 1: Presented evidence regarding thermal insulation per type of green roof in a humid-tropical climate (Maiolo et al., 2020).

The reported energy use reduction was as follows:

  • With an intensive green roof, energy use was reduced between 45-60%.
  • With a semi-intensive green roof, energy use was reduced between 60-70%.
  • With an extensive green roof, energy use was reduced by around 20%.

This suggests that a semi-intensive green roof has the maximum energy use reduction in humid tropical climates.

Study 2 presented findings from various studies conducted during wintertime in a sub-tropical climate concerning the ability of green roofs to create stable internal temperatures (Collins et al., 2017).

  • Extensive green roofs were proven to have positive results: the roofing material acted as a heat sink that released heat into the building during cooler nights.
  • Intensive green roofs were proven to have negative results: heat was lost from the substrate to the air, drawing indoor warmer air outwards.

This suggests that an extensive green roof is more able in creating stable internal temperatures in sub-tropical climates during wintertime.

In studies conducted in the French temperate climate however, green roofs were shown to have very little impact on overall heating demands.

This was mainly due to reduced heat losses during cold winter days along with a reduction in positive solar gains during sunny winter days.

This suggests that green roofs have little impact in the thermal conductivity of buildings in temperate climate.

Study 3 examined the thermal effectiveness of an extensive green roof and how it varies according to climate (Bau-Show et al., 2013).

They measured the cooling effectiveness of extensive green roofs in a sub-tropical climate and a tropical island climate. They found that:

  • Maximum cooling effectiveness up to 22.5 °C in the summer in the sub-tropical climate.
  • Maximum cooling effectiveness up to 25.1 °C in the summer in the tropical island climate.

This suggests that the cooling effectiveness of the extensive green roof becomes more significant when the temperature is higher.