[Equest-users] Adjacent Shells

[Bishop, Bill]

Jeremy,

Well, every one of those extraneous exterior walls (and roofs) is going to be simulated as envelope loads on those spaces. The model doesn't know that they aren't actually exposed to the outdoors. I would certainly delete them for any model, calibrated or otherwise, if it were me. You could determine the impact, relatively quickly, by modifying the U-factor of your wall construction based on the ratio of modeled exterior wall area to actual exterior wall area. Get your modeled wall area from the last page of the LV-D report, and divide by the actual wall area of the existing building. Divide the wall construction U-factor by the modeled-to-actual wall ratio, and modify the wall construction accordingly. Simulate and see how much the energy is reduced. Okay, never mind that sounds like too much work. Just delete the walls.

If you're in that much of a hurry, don't replace the exterior walls with interior walls. Just delete the exterior surfaces and be done with it. I usually add the interior walls, especially if the adjacent spaces have different thermostat setpoints or different internal loads. These edits can be pretty quick when you modify the 3-D view to more easily see where the extra surfaces are:

[cid:image002.jpg at 01CDF97A.3E198A80]

Regards,
Bill

[Senior Energy Engineer 28Jun2012]<mailto:wbishop at pathfinder-ea.com>

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Jeremy Poling
Sent: Wednesday, January 23, 2013 2:33 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Adjacent Shells

Two questions in the same day...I may have more still :)

Has anyone taken the time (maybe Nick?) to determine if there is a major impact due to leaving walls of adjoining shells as exterior instead of changing them to interior, air-walls, or deleting them?  I only ask because I have a 4M+ SF building that is requiring 20+ shells stacked and adjacent and I'm looking for every time saver I can find.  I simplified the shells as much as possible, but due to geometry this is the smallest number I can squeak by with from an orientation/geometry/overlap.

I should note, this is an existing building and the model is being more or less calibrated, so just having a rough idea of the impact of this nuance will allow me to decide to take the time or to chalk it up in my model error.

Thanks much!
Jeremy R. Poling, PE, LEED AP+BDC


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