[Greenbuilding] epdm vs. tar g(r)een roof
John Straube
jfstraube at gmail.com
Mon Aug 29 15:13:38 CDT 2011
Whatever the motives of researchers almost all compare Green roofs to exposed membrane black roofs.
The reason the conventional roof is conventional is because it is cheap. Eg EPDM on polyiso for $2 per square foot installed! Hard to find green roofs under $20.
I like green roofs. I have one on my own apartment. But the studies do not justify the cost premium any more than they justify granite in the lobby: I personally paid the premium to have a good looking roof. I know cheaper and better ways to safe energy control stormwater protect the membrane etc etc. But I try to keep the science clear and I can't honestly explain green roofs on economical or technical grounds.
Sent wirelessly from my BlackBerry device on the Bell network.
-----Original Message-----
From: RT <Archilogic at yahoo.ca>
Sender: greenbuilding-bounces at lists.bioenergylists.org
Date: Mon, 29 Aug 2011 15:11:22
To: GBioEL<greenbuilding at lists.bioenergylists.org>
Reply-To: archilogic at chaffyahoo.ca,
Green Building <greenbuilding at lists.bioenergylists.org>
Subject: Re: [Greenbuilding] epdm vs. tar g(r)een roof
On Mon, 29 Aug 2011 11:31:37 -0400, John Straube <jfstraube at gmail.com>
wrote:
> Speaking of cooking the books, Dr Lui's report, like most you will find,
> over sell the performance benefits of green roofs. They do this by
> comparing an excellent green roof design with the dumbest low slope roof
> we know how to build (an exposed membrane black roof).
I don't know if this is a fair criticism.
The first study that Dr. Lui did used a conventional roof that was
available on the NRC campus, and she simply installed a rudimentary Green
Roof over one half of the roof and then monitored what the two did over
the course of a year or so.
I think that was a fair comparison that highlighted the benefits of a
Green Roof over a "conventional" one because the "conventional" is a
fairly common type throughout North America.
At the time, I suggested to Karen that to be fair, her next study might
involve an IRMA (for comparison of thermal benefits) or a PMR and she
agreed, while at the same time wincing and rubbing the fingers and thumb
of an up-turned hand together indicating that acquiring funding was the
biggest problem. I don't know if Karen ever got the funding to do further
studies.
A PMR would of course provide similar protection for the membrane and
perhaps a similar reduction in the cooling load (my guess is most likely
"less" due to minimal contribution via evaporative cooling) but then the
Green Roof goes further and provides additional benefits which in an urban
core setting, extend beyond financial.
Do Green Roofs make much sense in a climate like Canada's where greenery
is either dead or dormant for a third or a quarter of the year ? Nyeh.
--
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c at Y a h o o dot c a >
(manually winnow the chaff from my edress if you hit "reply")
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