Helpful? 0

Green roofs: what's the verdict?

I'm intrigued by the idea but see several obvious problems: 1) leaks, 2) expense, 3) maintenance (weeding etc.), as well as a less tangible but possibly significant issue: 4) prospective home buyers viewing a green roof as a liability (we plan to be in the house for a long time, but plans can change.)

The project in question is about 350 sf. I suppose you could look at the small scope a couple of ways: it's small and therefore more doable, with less at risk; or, it's so small as to be hardly worth the bother. Mostly I'm drawn by the romance of it, inspired in part by childhood visits to Scandinavia. Plus, a green roof would look nicer from the second floor than would a conventional flat roof. The rational part of me says, Why ask for trouble?

What is your experience? How would you advise a client? What resources are available?

Thanks,
Ray
Portland, OR

Asked by Ray Sten
Posted Thu, 02/14/2013 - 14:42

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6 Answers

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1.
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what is the R value of dirt? I think there are other less problematic ways to get better R value in a roof.

A roof top garden would be a different idea all together and could be done in containers

Answered by Robert Hronek
Posted Thu, 02/14/2013 - 14:50

2.
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Ray,
A vegetative roof is probably the most expensive way ever invented to add R-value to a roof.

It's also a little nuts to put damp soil and vegetation on top of your house.

That said, if you have a lot of money in the bank and really want to do it, you can.

Here's the opinion of the inimitable Joe Lstiburek on the matter of vegetated roofs: Seeing Red Over Green Roofs.

Answered by Martin Holladay, GBA Advisor
Posted Thu, 02/14/2013 - 15:02

3.
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Thanks to you both, Martin and Robert -- I've snapped out of my reverie. I'm persuaded by Lstiburek that a reflective membrane is the way to go. Could you steer me to a primer on flat roof membranes, ideally one that includes information on the cost and prevalence of different options? Or perhaps the Energy Nerd would be willing to muse at column length?

Answered by Ray Sten
Posted Fri, 02/15/2013 - 16:36
Edited Fri, 02/15/2013 - 16:42.

4.
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Martin, thanks for re-posting that piece by Joe Lstiburek. Whatever misgiving I may have harboured about his approach have been washed away by that tide of good sense and sensibility.

Answered by Malcolm Taylor
Posted Fri, 02/15/2013 - 23:59

5.
Helpful? 0

Green roofs though looks great aren't easy to implement. Green roofs can provide benefits like increased roof insulation, protection of the roof, they also pose difficulties or inconveniences that should be carefully considered.

Answered by Jenny Belman
Posted Tue, 02/19/2013 - 09:54

6.
Helpful? 0

Jenny Belman: have you read the mr Lstiburek article linked by Martin ?

It seemed to me that mr Joe insisted that green roof had no real insulation value when i read it...nah?

Answered by Jin Kazama
Posted Tue, 02/19/2013 - 10:07

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