Political Correctness and Marketing
With an emphasis on recycled components, energy conservation, sustainability and minimal environmental impact (via development), green roofs score points with city planners, the community and tenants. This is oftentimes rewarded with zoning that allows for more intensive development. Building with green roofs may also receive tax credits or municipal grants.
Corporations, institutions and municipalities use green roofs to demonstrate a commitment to sustainability which resonates with their customers, employees and residents.
Higher Occupancy and Rents
Green roofs are often used to improve the views of leased space, which may otherwise be difficult to rent when overlooking traditional roof membranes. Greener buildings have proven to lease faster and at higher rates than traditional buildings.
Conservation of Municipal Septic Systems
Sponging up excess rainwater means municipal septic systems do not have to be expanded as much. It also means reduced overflows as well as reduced pollution and associated costs.
Extension of Roof Life
Plants and soil act as a protective shield from the elements.
- No U.V. radiation/photo degradation of roofing components.
- Minimal thermal contraction and expansion (green roofs can reduce temperature fluctuations by as much as 90%). Studies show that on a sunny 95°F day, conventional rooftop surfaces can reach 175°F. Green roofs bring these temperatures in line with the ambient air temperature.
- Protection from drying winds.
- Protection from mechanical damage.
- Reduction or elimination of cracks and leaks.
- Potential 200% – 300% extension of membrane
The evapotranspirative effect of the plants and four inches of growing medium typically reduces indoor temperatures 6 to 8 degrees during warm/hot weather and can reduce air-conditioning costs 25 to 50 percent in single story buildings. This not only allows for ongoing cost savings but an initial reduction in the size of the required air conditioning equipment.
Minimal insulation (R-Value) exists during cool or winter weather. The pore space of the growing medium tends to be more water saturated at this time, and the plants won’t be as large and therefore will not trap as much air (essential to insulation value). But, in snowy winter locations, the vegetation helps to trap blowing snow which adds insulation value.