Green and Growing
The Atrium, courtyard and crossing areas of the Meeting House, completed in 2008, have a live roof system which integrates a layer of plants and soil. This is a carefully engineered and designed system with a number of benefits. The live roof areas of the building have a fairly standard vinyl roofing system, special containers filled with four inches of specially engineered soil, and a layer of plants selected for our environment.
The soil is primarily an inorganic aggregate, which is designed to last indefinitely. The plants are several of varieties of Sedum, a plant which is very hardy and disease resistant in our climate and requires minimal care. If the vinyl roof requires repair, the Live Roof system is easily moved and replaced.
Financial Benefits
Although the roof costs more up-front for the soil/plant system and the additional building structure, it is expected to be have positive financial benefits over its life.
- It increases the life of the vinyl membrane from 100 to 200% by shielding it from radiation, large temperature fluctuations, drying winds, and punctures.
- It saves energy by reducing the need for air conditioning. As plants move water from the soil to the air (the "evapotranspirative effect") they act as a natural cooling system in the same way sweating cools the human body. This typically has reduced air-conditioning costs 25 to 50 percent.
- Because of this cooling, we have been able to reduce the size of our cooling systems, lowering our capital costs and operating costs.
Environmental Benefits
Live roofs really shine in their environmental benefits. In addition to the energy savings:
- Reduce the Urban heat island. Heat islands form as vegetation is replaced by asphalt and concrete for roads, buildings, and other structures. These surfaces absorb - rather than reflect - the sun's heat, causing local temperatures to rise and even changing the local weather. Green roofs reverse this.
- Help to control storm water discharge. By soaking up large amounts of rainwater and then helping it evaporate or discharge slowly Live Roofs strongly mitigate the damage from storm events.This has been a major concern at the First Unitarian Society campus which has typically contributed to flooding in the buildings south of us and has only limited access to storm water control . They also help to filter and detoxify storm water by removing suspended solids and other pollutants.