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I am wondering how EnergyPlus handles the effect of saturated soil in
insulation value; especially in winter when the damp/wet soil would be
frozen. I am interested mostly in heating loads.<br><br>
<br>
At 07:26 PM 6/26/2010, Drury B Crawley wrote:<br>
<blockquote type=cite class=cite cite="">From the EnergyPlus Input-Output
Reference, the fields describing the green roof top layer include:<br>
<dl>
<dd>Height of Plants {m}<br>
<dd>Leaf Area Index {dimensionless}<br>
<dd>Leaf Reflectivity {dimensionless}<br>
<dd>Leaf Emissivity<br>
<dd>Minimum Stomatal Resistance (s/m)<br>
<dd> <br>
<dd>(this is on page 183 of the IORef PDF (page number 144):
<a href="http://apps1.eere.energy.gov/buildings/energyplus/pdfs/inputoutputreference.pdf">
http://apps1.eere.energy.gov/buildings/energyplus/pdfs/inputoutputreference.pdf</a>
)<br><br>
</dl> <br>
The Engineering Reference describes the equations beginning on page 114
of the PDF (page number 90): <br>
<a href="http://apps1.eere.energy.gov/buildings/energyplus/pdfs/engineeringreference.pdf">
http://apps1.eere.energy.gov/buildings/energyplus/pdfs/engineeringreference.pdf</a>
<br>
<br>
<br>
<br>
On Fri, Jun 25, 2010 at 10:41 AM, Nick Caton
<<a href="mailto:ncaton@smithboucher.com">ncaton@smithboucher.com</a>
> wrote: <br>
<br>
<dl><br>
<dd>Open question:<br><br>
<dd> <br><br>
<dd>I’ve ascribed to the “tack an R / thermal mass value onto a new
layer” approach in the past… but would appreciate a more nuanced approach
if it could be done quickly enough.<br><br>
<dd> <br><br>
<dd>I’m curious: Does EnergyPlus or any other option/model out
there account the variable shading effects of the foliage on the roof
construction, as a user might define it? I’ve speculated this
element could be handled relatively simply in eQuest using a
geometrically adjacent shading surface with an annual fractional
schedule, but eQuest (to my experience) doesn’t have a clean approach to
account for the varying thermal mass and insulative properties of soil
that varies in moisture over time…<br><br>
<dd> <br><br>
<dd>~Nick<br><br>
<dd> <br><br>
<dd> <br>
</b><br>
<dd>NICK CATON, E.I.T.<br>
</b><br>
<dd>PROJECT ENGINEER<br><br>
<dd>25501 west valley parkway<br><br>
<dd>olathe ks 66061<br><br>
<dd>direct 913 344.0036<br><br>
<dd>fax 913 345.0617<br><br>
<dd>Check out our new web-site @
</i><a href="http://www.smithboucher.com/">www.smithboucher.com</a> <br>
</u><br>
<dd> <br><br>
<dd>From:</b>
<a href="mailto:bldg-sim-bounces@lists.onebuilding.org">
bldg-sim-bounces@lists.onebuilding.org</a>
[<a href="mailto:bldg-sim-bounces@lists.onebuilding.org" eudora="autourl">
mailto:bldg-sim-bounces@lists.onebuilding.org</a>] On Behalf Of </b>Drury
B Crawley <br>
<dd>Sent:</b> Friday, June 25, 2010 9:25 AM <br>
<dd>To:</b>
<a href="mailto:bldg-sim@lists.onebuilding.org">
bldg-sim@lists.onebuilding.org</a><br>
<dd>Subject:</b> [Bldg-sim] Modeling a Green Roof<br><br>
<dd> <br><br>
<dd>EnergyPlus has a model for green roofs built in -- based on
experimental measurements and experience of researchers at Portland State
University, Prof David Sailor:
<a href="http://web.cecs.pdx.edu/~sailor/">
http://web.cecs.pdx.edu/~sailor/</a><br><br>
<dd> <br>
<dd> <br><br>
<dd>---------- Forwarded message ---------- <br>
<dd>From: Jeremy Poling</b>
<<a href="mailto:jpoling@epsteinglobal.com">
jpoling@epsteinglobal.com</a>><br>
<dd>Date: Fri, Jun 25, 2010 at 10:04 AM<br>
<dd>Subject: Re: [Bldg-sim] Modeling a Green Roof<br>
<dd>To:
<a href="mailto:Jason.Boehning@ricegardner.com">
Jason.Boehning@ricegardner.com</a>,
<a href="mailto:bldg-sim@lists.onebuilding.org">
bldg-sim@lists.onebuilding.org</a><br>
<dd> <br>
<dd> <br><br>
<dd>Penn State University
(<a href="http://horticulture.psu.edu/cms/greenroofcenter/">
http://horticulture.psu.edu/cms/greenroofcenter/</a>) and Michigan State
University
(<a href="http://www.hrt.msu.edu/greenroof/">
http://www.hrt.msu.edu/greenroof/</a>) 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
(<a href="http://etda.libraries.psu.edu/theses/approved/WorldWideFiles/ETD-4616/Thesis_Paulo_Tabares_revised.pdf">
http://etda.libraries.psu.edu/theses/approved/WorldWideFiles/ETD-4616/Thesis_Paulo_Tabares_revised.pdf</a>
). 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.<br><br>
<dd> <br><br>
<dd>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.<br><br>
<dd> <br><br>
<dd>JEREMY R. POLING, PE, LEED AP</b> <br>
<dd>Associate Vice President,<br><br>
<dd>Senior Sustainability Analyst <br>
<dd>Strategic Services<br>
<dd>Site Solutions | Operations | Sustainability<br>
</i>
<dd> <br>
<dd>EPSTEIN<br>
</b>
<dd> <br>
<dd>Epstein is a firm believer in sustainability. We ask that you please
consider the environment before printing this e-mail.<br>
</i></b><br>
<dd> <br><br>
<dd>From:</b>
<a href="mailto:bldg-sim-bounces@lists.onebuilding.org">
bldg-sim-bounces@lists.onebuilding.org</a>
[<a href="mailto:bldg-sim-bounces@lists.onebuilding.org" eudora="autourl">
mailto:bldg-sim-bounces@lists.onebuilding.org</a>] On Behalf Of
</b>Fareed Syed <br>
<dd>Sent:</b> Friday, June 25, 2010 8:05 AM<br>
<dd>To:</b> Jason Boehning;
<a href="mailto:bldg-sim@lists.onebuilding.org">
bldg-sim@lists.onebuilding.org</a><br>
<dd>Subject:</b> Re: [Bldg-sim] Modeling a Green Roof<br><br>
<dd> <br><br>
<dd>I heard from our director of sustainability to use R-5 for a typical
green roof. It was confirmed by few senior architects.<br><br>
<dd> <br><br>
<dd>Thanks,<br><br>
<dd> <br><br>
<dd>Fareed<br><br>
<dd> <br><br>
<dd>From:</b>
<a href="mailto:bldg-sim-bounces@lists.onebuilding.org">
bldg-sim-bounces@lists.onebuilding.org</a>
[<a href="mailto:bldg-sim-bounces@lists.onebuilding.org" eudora="autourl">
mailto:bldg-sim-bounces@lists.onebuilding.org</a>] On Behalf Of </b>Jason
Boehning <br>
<dd>Sent:</b> Friday, June 25, 2010 8:46 AM<br>
<dd>To:</b>
<a href="mailto:bldg-sim@lists.onebuilding.org">
bldg-sim@lists.onebuilding.org</a><br>
<dd>Subject:</b> [Bldg-sim] Modeling a Green Roof<br><br>
<dd> <br><br>
<dd>Howdy! <br><br>
<dd> <br><br>
<dd>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.<br><br>
<dd> <br><br>
<dd> <br><br>
<dd>Jason Boehning, EIT<br><br>
<dd>Mechanical Engineer<br><br>
</dl>Error! Filename not specified.<br>
</b><br>
6161 Savoy, Suite 1212<br><br>
Houston, Texas 77036<br><br>
<br><br>
v. 713.482.2322<br><br>
f. 713.482.2314<br><br>
e.
<a href="mailto:Jason.Boehning@ricegardner.com">
Jason.Boehning@ricegardner.com</a><br><br>
<br><br>
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