Exhaust Fan for Humidity Control

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Hi All:
Is there anyway to model an exhaust fan that only runs when the humidity in a crawl space is above a certain setpoint?
Thank you,?Paul Diglio
87 Fairmont Avenue
New Haven, CT 06513

Paul Diglio's picture
Joined: 2011-09-30
Reputation: 400

Hi Paul,

To my knowledge, there?s no explicit option in equest for tying a fan/process energy to an interior/exterior humidity state. Some pre-processing/work outside your model would be necessary.

You could do an analysis separately in excel (ideally informed with field measurements of an existing/built situation) with intent to ultimately estimate fan runtime, and then ?spoon feed? the outcome of your efforts into an eQuest model in the form of a fan schedule and some power inputs at the meter. The likes of EMIT can make the transition from spreadsheet efforts easier.

I might however first want to take a step back and draw caution towards understanding more of the context behind this measure? I?m reminded that Mr. Lstiburek?s articles in the ASHRAE journals and beyond (hosted here: https://buildingscience.com/document-search <-- you can filter results by ticking the box for ?Crawlspaces?) repeatedly warn against passively/actively ventilating building crawlspaces to/from the exterior. It?s my general sense that active ventilation with exterior conditions can generally cause more problems than it solves with regard to humidity/moisture issues. If however we?re talking about circulation of conditioned (interior) air and treating the crawlspace like a conditioned/sealed basement, that?s approaching an ?ideal? state WRT moisture control.

I hope this is a little helpful!


[cid:image001.png at 01D44C19.6DAEC290]
Nick Caton, P.E., BEMP
Senior Energy Engineer
Regional Energy Engineering Manager
Energy and Sustainability Services
Schneider Electric

D 913.564.6361
M 785.410.3317
F 913.564.6380
E nicholas.caton at schneider-electric.com

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

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Nicholas.Caton at schneider-electric.com's picture
Joined: 2016-02-26
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Hi Nick:
Thanks for the idea.? I can calculate in Excel and tweak a fan schedule in eQuest to match the energy consumption of the fan.

This crawlspace is 20' from the ocean and the designer assumes there will be excessive humidity buildup.

Regards,?Paul Diglio
87 Fairmont Avenue
New Haven, CT 06513

Paul Diglio's picture
Joined: 2011-09-30
Reputation: 400