Vegetative roof systems, sometimes referred to as "green roofs,"
are rapidly gaining popularity and acceptance in the U.S. For many,
the appeal of vegetative roof systems involves their aesthetics and
environmental attributes, including reduced storm water runoff,
air-quality improvement, mitigation of heat island effects and
noise reduction for building occupants.
However, vegetative roof systems' compliance with U.S. building
codes is questionable. Although vegetative roof systems'
waterproofing components can be tested and evaluated for code
compliance bythe same means used for conventional roof systems,
vegetative roof systems' growth media and plants largely have been
untested for the purposes of code compliance.
Because growth media and plants serve as the topmost surface of
most vegetative roof systems, these components are an important
consideration in determining vegetative roof systems' wind
For example, the 2006, 2009 and upcoming 2012 editions of the
International Building Code (IBC) restrict the use of aggregate
surfacing on roof systems based on maximum building height, basic
wind speed and exposure category for the building being evaluated.
This restriction is based on the concern that aggregate could scour
and become wind-borne debris during high-wind events. For
additional information regarding IBC's restrictions on the use of
rooftop aggregate, see "What will
happen to aggregate?" August...
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