[Bldg-sim] Modeling a Green Roof
Jeremy Poling
jpoling at epsteinglobal.com
Fri Jun 25 07:04:51 PDT 2010
Penn State University (http://horticulture.psu.edu/cms/greenroofcenter/)
and Michigan State University (http://www.hrt.msu.edu/greenroof/) both
have significant research programs on green roofs. I would recommend
looking at the results of the Penn State study on energy transfer in
Green Roofs (
http://etda.libraries.psu.edu/theses/approved/WorldWideFiles/ETD-4616/Th
esis_Paulo_Tabares_revised.pdf). In general, green roofs handle energy
through the insulating effects of soil, the cooling effects of
evapotranspiration in the plants, and water flows within the green roof
assembly. This means that a calculated R-value will be different
depending on the amount of plant material participating in
evapotranspiration, the wetness of the soil, and whether the roof is
intensive or extensive. A straight R-value approach is very simplified
and should be used with the understanding that model results are much
less likely to be accurate. The Penn State study gives a review of
published literature showing extensive green roofs have R-values between
1.8 and 4.8 while intensive green roofs have R-values between 5 and 20.
In general, the average R-value of soil is 0.25 per inch, so for a 12"
soil depth the R-value of the soil would be R-3 excluding assumptions on
soil wetness and evapotranspiration. We typically go conservative and
just model the R-value of the additional soil since you would need a
TRNSYS or MatLab model to take into account the other energy benefits of
a green roof.
JEREMY R. POLING, PE, LEED AP
Associate Vice President,
Senior Sustainability Analyst
Strategic Services
Site Solutions | Operations | Sustainability
EPSTEIN
Epstein is a firm believer in sustainability. We ask that you please
consider the environment before printing this e-mail.
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Fareed Syed
Sent: Friday, June 25, 2010 8:05 AM
To: Jason Boehning; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Modeling a Green Roof
I heard from our director of sustainability to use R-5 for a typical
green roof. It was confirmed by few senior architects.
Thanks,
Fareed
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Jason
Boehning
Sent: Friday, June 25, 2010 8:46 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Modeling a Green Roof
Howdy!
Has anyone modeled a green roof? I have a standard roof with 12 inches
of soil and grass. I have been searching the web for thermal properties
such as U values, thermal absorptivity and so on. Are there any good
references to find these values or does anyone have tips to model a
green roof? I appreciate your help.
Jason Boehning, EIT
Mechanical Engineer
6161 Savoy, Suite 1212
Houston, Texas 77036
v. 713.482.2322
f. 713.482.2314
e. Jason.Boehning at ricegardner.com
<mailto:Jason.Boehning at ricegardner.com>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20100625/f052c59a/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/gif
Size: 3662 bytes
Desc: image001.gif
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20100625/f052c59a/attachment-0001.gif>
More information about the Bldg-sim
mailing list