We can all assume that thick intensive green (vegetated roofs) provide a measure of insulation - but what about thinner, extensive green roofs? Do extensive green roofs, say 2 to 4 inches thick provide insulation benefits?
Jincy, Ruairi and I have tracked the insulating factors of several extensive roofs, comprised of the MetroVerde mat roof system during the 2008 summer season.
What we found was very interesting.
Using a Extech Infrared IRC40 thermal imaging unit we measured the temperature of the roof decking undersides for roofs with (A) extensive 3" thick mat based vegetated roofs planted with allium and iceplant, and (B) asphalt shingle covered decking.
Not surprisingly, the underneath of the roof decking on asphalt shingle roofs averaged 125 - 130 degrees F during July, August and September 2008.
Temperatures of the undersides of the roof decking below asphalt shingles covered with the MetroVerde extensive mat systems averaged 84 - 86 degrees F at the same time of day.
Moreover, it is expected that the green roof mat system will protect the asphalt shingles from solar degradation.
So do extensive green roofs insulate a roof from solar gain? The answer is an undeniable Yes!