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Building Cooling Peak load on Oct

asked 2016-03-04 11:07:39 -0600

Yupeng gravatar image

updated 2016-03-04 12:05:12 -0600

This is an eQuest model for a office building in Texas, zone pattern is Perimeter/Core. Most of the space cooling peak loads are in the summer time, June July August. But my building peak load is on October with 90 F outside air temperature. Also, for the zones facing south, the peak load is during winter time. Is anyone know the reason? How to adjust the model?

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answered 2016-03-04 13:03:13 -0600

You may need to add more information about your building to get a good answer to this question. At what time of day is the building peak in October? What directions do the various walls face? What is the window to wall ratio on each face of the building? What is the form of the building? Are there a lot of core zones which would be internal load dominated for cooling (wide floor plate) or are there more perimeter zones (narrow floor plate)?

When you say that the building peak load is in October, where are you getting this information from? Is it from the LS-C report? Does the building peak cooling load include outdoor air or is it for the envelope only? The LS-C report does not typically include the load for cooling ventilation air, which may be affecting the timing of the building peak.

As for your south facing zones, they will get more low angle sunlight in the winter than in the summer, and this is likely responsible for the higher cooling load in winter.

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answered 2016-03-07 15:16:21 -0600

nigusse gravatar image

It is possible the zone cooling load to peak in October. If you window is on south facing facade, the incident angle of the beam solar radiation can be close to normal (almost zero incident angle around solar noon) depending on your location, which implies high solar heat gain and hence higher cooling load due to solar. And if the other components of cooling load (internal heat gains contributions to cooling load) are smaller than solar, then in mild climate zones there is a good chance for your zone cooling load to peak in October or November. If you want to play with your model, reduce the window wall fraction of your south facing zone, and see how your zone peak cooling load and peak month changes.

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answered 2016-03-17 20:16:53 -0600

Nick Caton gravatar image

The answer to all your queries in part lies with interaction between solar loads the envelope/glazing systems for the building.

Northern-hemisphere buildings with particularly decent envelope/roof insulation levels should observe their peak cooling days shift away from the hottest ambient days of the year (with the sun arcing overhead) towards a time of the year when more Southerly sun angles penetrate more often & more directly onto the building glazing.

Window shading/overhangs, fenestration properties (i.e. SHGC) play a role in this interaction as well, of course.

Ultimately I don't think any of these trends are particularly "right" or "wrong," but are symptoms of a building where solar loads are the dominant component for determining peak cooling loads (as opposed to envelope conduction or internal gains leading the charge).

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Asked: 2016-03-04 11:07:39 -0600

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Last updated: Mar 17 '16