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Re: GSBN:Data on Living Roofs



John an all,

Giving hard data on living roofs is very difficult because there are so many variables. Basically what a living roof will do is add mass ie cuase a phase shift. Which means they are the most effective in climates with big dinural temperature swings. Besides this the living mass roots etc add a bit extra insulation.

The type of roof I have recently made has very little mass only 40kg/m^2 thus the phase shift effect is marginal but again significant when compared too the rest of the roof membrane weight which is only 40kg everything else. The fact that the roof is covered with plant mass does improve the thermal performance somewhat because a bigger layer of stationary air is captured this gets better as the roof matures as more root and plant mass accumulates. In its mature state the roof I made more then 50% is pure plant mass. A downside to this effect though is that when you need this effect most ie blistery weather the green roofs thermal performance is at its worst. So besides the green roof you also need a lot of insulation. I use the same amount as I would use without a greenroof.

Due to the huge amount of variables I am not prepared to give any numbers the only indication I can give is that the added mass should give you a phase shift which should come up in a dynamic simulation.

The reasons I use a green roof:

It adds more green to heavely developed areas.
It buffers rainflow ie resulting in a lower runoff spike after rainfall therefore lessening pollution in surface water. Actually this is significant a high percentage of rain never leaves a green roof.
It gives a flat roof membrane a longer life
It improves the interior climate by adding mass to the roof.
Last but not least is simply looks better.


Rene
On Mar 17, 2006, at 22:17, André de Bouter wrote:

Michel Bergeron in Quebec also might be of help.
His 'pen pal'(Serious StrawBale) Paul Lacinski should be able to track him down.

bye,
Andr?

Selon Chris Stafford Stafford@...:

John,
I don't have your answer, but can give a couple of leads where you may
find out about the thermal qualities of green roofs.
Patrick Carey, pkc@...,  is leading green roof expert in Seattle
Chapter of NW EcoBuilding Guild. Another is a landscape contractor that
has been doing many commercial buildings in downtown Portland, Oregon.
I don't have their name but Carey will, if you can't find anything on
web.
Good luck,
Chris

Christopher Stafford Architects, Inc.
1044 Water Street, #326
Port Townsend, WA 98368
360.379.8541
www.building-green.net

On Mar 17, 2006, at 10:05 AM, John Swearingen wrote:

Hi,

Does anyone know of some hard data on the thermal qualities of living
roofs.
I've done some preliminary energy modeling, in Energy 10, and come out
with
very little difference.  I presume that's because the program can't
account
for the shading of plants, evaporative cooling effects of moist soil,
and
perhaps the ability of the earth to hold heat, then release it to the
night
sky.  Is there some real data on this?

John

John Swearingen
 SKILLFUL MEANS
design and construction
 HYPERLINK "<a  target="_blank" href="http://www.skillful-means.com/"www.skillful-means.com";>http://www.skillful-means.com/"www.skillful-means.com</a>



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GSBN is an invitation-only forum of key individuals and representatives of regional straw construction organizations. The costs of operating this list are underwritten by The Last Straw Journal in exchange for use of the GSBN as
an advisory board and technical editing arm.

For instructions on joining, leaving, or otherwise using the GSBN list, send
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GSBN is an invitation-only forum of key individuals and representatives of regional straw construction organizations. The costs of operating this list are underwritten by The Last Straw Journal in exchange for use of the GSBN as an advisory board and technical editing arm.

For instructions on joining, leaving, or otherwise using the GSBN list, send email to GSBN@...HELP in the SUBJECT line.
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GSBN is an invitation-only forum of key individuals and representatives of regional straw construction organizations. The costs of operating this list are underwritten by The Last Straw Journal in exchange for use of the GSBN as an advisory board and technical editing arm.

For instructions on joining, leaving, or otherwise using the GSBN list, send email to GSBN@...HELP in the SUBJECT line.
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