Green Roof

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Have any of you modeled a Green Roof?

If I put soil as my outermost layer, will eQuest think it is in earth


Kevin A. Felt

Kevin Felt's picture
Joined: 2011-09-30
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Equest will think of something as earth contact only if you have used
the underground keyword. Soil as outer layer should work - this is what
I usually do.

Any one has other parameters they consider (in eQuest).



Brahme, Rohini            UTRC's picture
Joined: 2011-09-30
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I am not an expert in eQuest modelling, but are getting into it recently.
As for Green Roofs, one must be able to consider various factors to
determine effectively the overall energy savings provided by it. The most
common way is assigning a R-Value.

Factors to consider:

1. Not all soils are the same. Depending on their composition (refer to
FLL standards), each soil will have a different R-Value per inch depth.
2. Soil depth.
3. Does the Green Roof system have an air/vapor layer within it?
4. Location of the Green Roof. Its not the same a Green Roof in Chicago
versus one in San Juan, Puerto Rico. Rainfall and ET rates affect the soils
moisture content, which in turn affect the R-Value. A wetter soil is much
"better" at reducing temperatures than a dry soil.
5. Does the green roof have an irrigation system?
6. Enough of the soil: now lets move on to the vegetation.
7. Must consider type of vegetation. It?s not the same to have an
extensive grass cover versus having an intensive shrubs/trees cover.

I believe there is model out there sponsored by the USGBC specifically for
Green Roofs, but I cannot confirm that right now. Will try to find more
info on that.


Ing. Francisco Rodriguez-Ema, PE, MSCE

Francisco Rodriguez-Ema's picture
Joined: 2011-09-30
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I'm new to this and I went through the Tutorial but I may have missed
How do you add more than one piece of equipment, several fans, for

Karen Palmieri's picture
Joined: 2011-09-30
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Hi Karen:

You can only add multiple pieces of equipment in the Detailed Edit mode.
So be sure you don't need to go back to the Wizard, or you will lose
your changes.

In the Detailed Edit mode, be in the Component Tree tab (at the page
bottom), point the Cursor at the Project component, and right click on
the Project Component. Depending on whether you are in the Building
Shell, Internal loads, Water-Side HVAC, etc, a different set of "create
xxx" appears.

Hope this pictures help.

John R. Aulbach, PE, CEM

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Joined: 2011-09-30
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I have run a Base Case and a Parametric run for a Central Plant serving an office complex. Everything in both runs is the same, EXCEPT that the Base run has a 10?F differential temperature and the Parametric run has a 15?F differential temperature. The CHW pump is variable speed.

As expected, electric energy is saved (about 40,000 kWh/year for a 600 ton plant). However, about 15,000 kWh is saved at the Chilled Water pump, and 22,000 kWh is saved at the chiller.

I changed the Loop Design DT to 15?F and the CHW Coil Design Delta T to 15?F.

Why is my chiller energy reducing?


John R. Aulbach, PE, CEM

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Joined: 2011-09-30
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Probably because the chiller's EIR is reduced due to a more favorable
inlet temperature. Have a look at your chiller performance curves in the

*Xavier Garc?a Casals*

=?ISO-8859-1?Q?Xavier_Garc=EDa_Casals?='s picture
Joined: 2011-09-30
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