Have you ever wondered why it seems so much hotter in Boston, New York, or any big city? Wonder no more – the answer is the “urban heat island effect.”
The heat island affect can be found in areas that are dense with buildings and paved surfaces (roads and sidewalks) that absorb the sun’s heat. This causes the area to be several degrees warmer than surrounding areas.
Some factors that contribute to this are:
- Paved surfaces absorb solar radiation as heat.
- Dark surfaces such as dark colored roofs and blacktop absorb more heat
- Very little vegetation
- Waste heat being pumped out of buildings
- Changing climate
What Is the Solution?
Building owners and managers can take steps to offset the phenomenon.
- Building owners or managers can check with their local government to find out if there are any rebates for implementing some heat island mitigation technologies
- Make the rooftop green – literally. Adding vegetation to the roof is not just beautiful—the plants are useful in managing storm water, reducing the urban heat island effect, and providing more usable space for building tenants.
- When the building requires maintenance, more heat resistant materials, such as lighter colored roofs and permeable pavement, can be used.
- Coatings and retrofits are available that improve surface temperatures.
- Check with the Cool Roof Rating Council, which maintains a rigorous rating process that tests roofing products for solar reflectance (the solar radiation reflected away from the roof) and thermal emittance (how efficiently the roof sheds absorbed heat). Its Rated Products Directory lists around 3,000 roofing products, along with their solar reflectance and thermal emittance values and their Solar Reflectance Index score, a measure that combines the other two values into a 0-100 rating.
Such steps can deliver energy, air conditioning and financial savings to the building.