Daylighting and heating penalty

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I have noticed that on a couple of my eQUEST models, when daylighting is used, that turning the daylighting controls on creates a small reduction in heating energy. Intuition (and a number other modeling projects) suggests that the opposite should occur; when daylighting is implemented the decrease in lighting energy should create an increase in heating energy. In my model this occurs largely in the winter months, so it is not likely to be due to reheat effects. And the load component reports do not reveal this increase, so I don't know what part of the load is changing.

In one example, I'm doing a small daylighting study on a typical office unit in Wisconsin...I've attached the .inp and .pd2 files for your review. I have turned daylighting on in parametric run #7, if you'd like to compare that with the baseline. If anyone sees a quirk in my model setup, or feels there's some good reason that eQUEST would give this result, I'd be happy to hear your thoughts. Thanks for your time -

Scott Hackel

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Scott:

Just a quick shot. You may decreasing lighting (and thus not getting the
heating energy provided by that light), but you are certainly adding a
bunch more in solar gain. Being originally from Chicago, I remember
sitting in my parent's car in the dead of winter, but wanting to take my
coat off with the full winter sun shining into the car windows.

I will see about looking at your model later.

John R. Aulbach, PE, CEM

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That would be my guess too.

Carol Gardner

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Thanks for the reply John. But, I haven't changed anything about the glazing between the two runs - solar gain through the windows should be unchanged. All I did change was the controls on the lights.

If you do have a chance to look at my model I'd be happy to hear any additional thoughts. Thanks again -

Scott

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Date: Mon, 1 Dec 2008 11:56:49 -0800

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