[Equest-users] Indirectly conditioned space

David Eldridge DEldridge at grummanbutkus.com
Mon Aug 11 10:10:53 PDT 2014

Your space A may be considered unconditioned or semi-heated depending on the capacity that results from the heat exchanger. Assuming you are using ASHRAE 90.1 you might review the definitions for spaces. Space A may not technically be "indirectly conditioned" although depending on the goal of your study this may be not matter either way.

Anyway, about your model - it depends if you are making the model for energy calculations, or for IEQ evaluation.

The OA-from keyword should give you supply air from Space B's air system, but it won't be pulling air directly from Space B. Therefore the OA supplied to Space A won't be the exhaust air temperature of Space B that you are looking for, although it may be much closer than the outside air conditions. This might be close enough for your purposes as long as pressure drop and fan energy are accounted for appropriately, which it sounds like you can do with the unit ventilator.

Whether this approximation would be important depends on the rest of your goals for your study, how large Spaces A and B are compared to the rest of your building, etc. Also if this is a LEED project then you need to follow LEED's rules which may require some explanation of your approach.

1.       Model as you proposed, or if Space A is a minor part of a much larger facility, you might just combine A & B in order to simplify.

2.       If the scope of your study is these two particular rooms, and what temperature and humidity conditions result in Space A, then you might need to consider this in more detail or use a different simulation program.


David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Buddi Heendeniya
Sent: Monday, August 11, 2014 6:00 AM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] Indirectly conditioned space

Dear forum users,

I have a space that is indirectly conditioned (say Space A) from an adjacent space (say Space B) through a heat transfer box that transfers heat from Space A's OA supply to the exhaust air from Space B.

In the proposed case I plan to model this by using a unit ventilator to Space A with "Outside Air From System = Space B". Does anyone see a problem with this approach?

Thank you very much,
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