Wholly H2o - California's Integrated Water Reuse Management Center

A traditional impermeable roofing system does not capture, retain, or filter water at the source. Green roofs also improve air quality by collecting dust and pollutants. The air in urban environments like those in California is hot and dry; in this situation the limited number of trees cannot transmit enough water into the air to cool it. Green roofs can improve air quality when installed in this type of climate.

Drawbacks to green roofs include costs and architectural constraints. Contrary to common belief, flat roofs are not an ideal green roof setting since they require an extra layer to drain extra water away from the root zone. A roof with a slope between 5 degrees (1:12) and 20 degrees (4:12) is ideal because gravity will cause the water to drain naturally. Costs are another factor, they range from $15 to $20 per square foot, which includes everything from waterproofing to plant selection. But consider the reputation and expertise of the company providing the waterproofing for the green roof. A bad waterproofing installation can end in roof leakage, resulting in water damage and expensive repairs.

Additional Information on Living Green Roof Benefits

• Green Roof Benefits