ASHRAE 90.1-2007 Table G3.1 Design Model

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We have a project that we are pursuing LEED certification on and have a question on how it should be modeled.  The project is a heated and ventilated aircraft hangar with an adjoining conditioned office building and it was modeled as such.

When the energy model and supporting LEED documentation were provided to the Client for preliminary review, we received the comment that the hangar should be modeled as though it was heated and cooled.  They cited Table G3.1 1.b, which states:

All conditioned spaces in the proposed design

shall be simulated as being both heated and cooled even if no heating or cooling system is to be installed, and temperature and humidity control setpoints and schedules shall be the same for proposed and baseline building designs.

Is it the intent of the performance rating method to model a fictitious system as being part of the proposed design in this case?  If so, this artificial energy use will have a negative impact on proposed energy savings.

Thanks.

BCPratt's picture
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That is their intent.

As you ascertained, the effect will be negative. I think their point is that a heated only system (if modeled as such in the proposed and baseline) would easily yield more points than a heated and cooled system - for which LEED is intended for.

In any case, they never specified the temperature at which you need to condition the hangar. You will still have the added fan energy for cooling, but at a 90 degree setpoint, you will not get much cooling energy.

Bob F's picture
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Thanks, that is the tack I will take.  As you suggest, I will drive the model to minimize energy used to cool the hangar.  By definition, a "conditioned" space uses > 5 Btuh/sqft to provide the cooling effect and so that will be my target in order to minimize cooling energy.  Thanks again for the feedback.

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