Washington roofing contractor Troy Wagner came to a gradual realization over the course of 15 years of working on other peoples' roofs.

What he found was that roofs covered with moss lasted 40 or even 50 years -- far longer than a normal roof.  

"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," Troy says. He discovered that typically, moss-covered roofs were only replaced when a home was for sale or if an insurance company demanded it.

Troy said that his observations led him to believe that the moss was actually protecting the roofs from the sun’s radiation, which can cause a roofing system to lose the ability to expand and contract with the change in temperature causing it to crack, curl and become brittle.

Finally, after seeing a particularly long-lived moss-covered roof, he had an inspiration. “Five years ago I ran into a house with a low-pitch 3/12 that had wood shingles, no felt paper and skip sheeting. 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 roofing options, and now he and his wife grow dinner on a roof that -- if his theory is correct -- will last longer than the traditional roof.  In any event it certainly will work harder for them simply by helping them put food on the table in addition to doing its job as the roof over their heads.

Via Greenroofs Australia