Building Green Futures

Green Roof Applications

Roof deck: typically plywood for residential; concrete or steel for commercial
Waterproofing: membranes range from modified bitumen to rubber/plastic hybrids such a thermoplastic polyolefin (TPO); we typically use modified/reinforced polyvinyl chloride (FibertTite manufactured by Seaman Corporation)
Drainage and root barrier: drainage may be as simple as pea gravel; we prefer synthetic materials with built-in root barrier and landscape felt layers
Growth medium and plants: choice of plants emphasizes lateral rooting, light-weight, and low maintenance; growth medium provides nutrients and structural support
Fireproofing: a gypsum board is placed under the membrane if the deck is combustible (required for class A fire assembly with the FiberTite membrane); the growth medium and plants are also fireproof due to high percentage of inorganic material in medium and succulent plants
Flat vs. sloped roof: green roofs can be installed on relatively flat to steeply sloped roofs; most are from 2 - 25% or 0.25:12 - 3:12; flat roofs offer accessibility and ease of installation; sloped roofs have greater visibility, but may require additional measures to stabilize plants and growth medium

Intensive green roofs: > 6 inches of growth medium with saturated weights from 50 - 300 lbs/sq ft; many plant choices including small shrubs or trees; can include seating or walkways
Extensive green roofs: 2- 6 inches of growth medium with saturated weights of 10 - 35 lbs/sq ft; some limitations in plant diversity and accessibility but provide all the other benefits

Modular green roofs utilize pre-assembled units whereas loose-laid integrate separate layers and offer more versatility as well as lower cost

Green roofs can be included in plans for new construction or added to existing buildings
In the case of existing buildings; additional structural support may be required depending on depth of growth medium and planting

Beauty & aesthetics: provides all the amenities of ground-level gardens including re-connecting people to nature
Habitat restoration: replace building footprint; can use native plants and thus provide a haven for local birds and butterflies
Increase longevity of roofing assembly: reduce UV damage and diurnal T fluctuation; lower maintenance costs
Insulation & energy efficiency: lower heating and cooling bills
In densely populated regions, can alleviate urban heat island effect due to heat absorption from typical roof materials such as bitumen, and by evaporative cooling properties of plant material
Improved air quality: filters pollutants and carbon dioxide from the air and adds oxygen
Storm water run-off: green roofs reduce the rate and quantity of storm water run-off and may mitigate or even eliminate the water run-off pollution problems associated with excessive urban development
Food production: green roofs provide an opportunity for local food production
A green or ecoroof is self-sustaining and regenerative; once established it needs no fertilizer or pesticides, and minimal maintenance (once or twice per year)