Toronto City Hall Green Roof
One common phenomenon we see in large cities is the Urban Heat Island (UHI) effect. Temperatures in urban areas are are significantly higher than in the surrounding rural areas. The temperature difference is larger at night, especially when winds in the area are weak. The biggest concern with UHIs is that they contribute to overall global warming.
The increase in heat retention and the inability to cool urban areas is partly due to the use of construction materials such as concrete and asphalt. We can counteract this by incorporating strategies that are proven to minimize the UHI effect into our urban design. Creating green roofs, increasing plantings of trees, smart landscaping designs that use natural ventilation and the use of other asphalt alternatives in outdoor spaces are all examples strategies to combat the UHI effect.
Asphalt Alternatives
Urban planners suggest the use reflective pavements as possible alternative materials to use in urban construction. But, certain studies (NAPA) show that reflective pavements are not nearly as effective as originally believed. While they do reflect heat back up from the ground, they do not return it to the atmosphere. The heat simply reflects onto nearby buildings and pedestrians.
Clearly, another answer must be found. Decomposed granite and other similar aggregates, combined with stabilizer solutions such as Organic-Lock offer a better outcome. They do not absorb heat to the same degree as concrete and asphalt and thus contribute less to the UHI effect. They can be used for pathways, various other open spaces and parking areas. Their ability to remain water-permeable means that they are especially effective when used for pathways in green roofs.
As urbanization continues to grow we need to respond to the problems it creates. When we use stabilizer solutions with pathway aggregates it can help balance the environment with urbanization and city infrastructure. With strategic approaches and materials, municipalities have new options for maintaining their landscape while reducing the heat island effect.