Planning for Green Roof

I have been interested in green roofs ever since a USGBC conference in Denver featured them. Our house has a nice flat and almost flat roof on the south side. I had an engineer study the photos and evaluate the design and he concluded the existing roof could take the weight.

South facing roof with old asphalt roofing.
South facing roof with old asphalt roofing.

When Tesla installed the solar roof they quoted redoing the flat roof as well but it could not use the solar tiles as the slope was too low. I asked if they could install an EPDM roof and they said it’s not what they quote nor could they change so I didn’t have them redo the flat roof. Then I had a bit of trouble getting a roofer to commit to the job. I would even have taken a tpo roof. But no call backs.
During the solar home tour the first weekend in October I helped at a new build that had a beautiful EPDM roof deck. I asked the builder, who volunteered his time to the tour, to share the name of his roofer and he enthusiastically recommended someone. This nice man called me back right away, came out and took a look and scheduled the job for the next week. I was lucky because at that late time of year he was happy to do a few small jobs.
He thought the roof had two layers of asphalt but when he took off the first layer it was a tar and gravel roof. That was why the aging asphalt had not leaked into the house.

Tar and gravel to be scraped off
Tar and gravel to be scraped off

This substrate had to be scraped off and discarded which was extra work but the roofer declined to charge me more.
I asked him to remove the old disconnected chimney but when his roofer touched it he felt heat so was unsure it was abandoned. Turned out that heat was just from the sun that day so they had to go back and remove the chimney and patch it. No big deal with EPDM.

Finished section later removed non-functional chimney
Finished section later removed non-functional chimney

The roof is additionally insulated with 1.5 inches of polyiso that makes a better underlayment for EPDM. Polyiso was in short supply but this roofer has long standing relationships with his suppliers and he went to two different places to get enough for my small roof. Polyiso is rated at r7.5 for heat and a bit more for cooling. So that part of the finished roof is now over r60.

Polyiso roof underlayment
Polyiso roof underlayment

It is very exciting to have the whole house well roofed and the EPDM is warranted for 40 years. Other jobs are more pressing right now but eventually we can have a garden patio on the roof.

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