Washington roofing contractor Troy Wagner came to a gradual realization during 15 years of working on other peoples' roofs.
“When inspecting the roof system that should only last 20 years and finding those covered with moss lasted 40 to 50 years, and only were changed out because the home was being sold or an insurance company saw it, I scratched my head.
After seeing this a few times I started to believe that the moss was protecting the roof from the sun’s radiation. The sun’s radiation can cause a roofing system to loose the ability to expand and contract with the change in temperature causing it to crack, curl and become brittle.”
“Over 15 years I figure I have looked at 15,000 roofs, and occasionally I would come across a roof covered in moss. In the western side of the state of Washington we are blessed with 50 inches of rain a year, this means moss on all the roofs. Insurance companies require the roofs to be moss-free, believing it leads to leaks, so to find a roof covered completely with moss is rare.”
But during his professional life inspecting roofs, Troy observed that moss-covered roofs lasted much longer than ‘clean’ roofs — sometimes more than twice as long:
“Five years ago I ran into a house with a low pitch 3/12 that had wood shingles, no felt paper and on skip sheeting (1×4s with a 4” space) the roof was 75 years old, covered with grass that had grown in the moss. This caused a light bulb to go off in my head and I said ahhhh, then ran home and tore off my roof.”
Troy started investigating vegetative options and now he and his wife grow dinner on a roof that, if he is right, will last longer than the traditional roof - and certainly it will work harder for them, by helping them put food on the table.
He has no qualms about putting himself out of business. As he sees it, this is a greater good.
Growing your vegetables on your roof has another advantage, too. Garden pests like deer and squirrels can't get at them.
From Greenroofs Australia