Heat Island Reduction LEED Credit
According to the EPA, U.S. cities are 5.6°C warmer than the surrounding area, this phenomenon is called urban heat island. To understand the heat island effect and its consequences, we wrote this blog post to help you build your future developments. To pursue a LEED Certification we will also give you solutions to earn points for one of the LEED credits.
Heat Island Effect:
Heat island effect is caused in urbanized areas, where vegetation is replaced by asphalt, concrete, and building roofs. These areas have a higher temperature due to the absorption of the heat for example, by the roof of a building. In fact, the roof being dark coloured and made with absorbing material, he cannot reflect the heat. For green building, it’s a priority because the less the house gains heat, the less it consumes energy to cool and the better it is for its carbon footprint.
Moreover, in addition to warming up a building it also increases the temperature of the urban area and has an impact on the microclimate. This is not only saving energy for your building but also reducing the heat gained by the local environment.
Therefore, LEED recommend for a total of 2 points to apply these solutions:
The most common method is to use vegetation to provide shading on the roof and reduce its direct contact with the sun. This vegetation can only be natural and then need to have a good irrigation system.
These roofs are called high-albedo roofs or white roofs due to their ability to reflect 65% of the sun’s heat. They are made from reflective material such as reflective paint and coating using a white or silver color with reflective pigments. Being the most common method, the cool roof is a cheap solution and easy to set up alone.
Not only being a method to reduce indoor heat gain in a building, this solution improves the roof durability by reducing the heat gained by the roof material and then their likely degradation.
To measure the roof albedo of a building, LEED asks for the SR (Solar Reflectance) average. This measure is the solar radiation that is reflected back and the emissivity of the surface. For LEED, this SR should be around 0.3.
Energy generation systems:
As a last solution for roofs, solar thermal collectors, photovoltaics, and wind turbines are useful to cover an area while producing energy for the building.
Non roof areas:
Pavements and gardens can be shaded by vegetation and covered with high albedo material.
Furthermore, in order to obtain this LEED credit, it is important to also cover car parks, which are important heat sources in a city. In fact, cars and asphalt present in these areas have a high absorbency.
Therefore, to cover parkings, stakeholders use vegetated and/or photovoltaic roofs as well as high albedo covering and material.