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wallacemann
Starting Member

USA
2 Posts

Posted - 08/28/2017 :  6:29:44 PM  Show Profile  Reply with Quote
I'm new to smart homes, and after some bit of research have failed to find a clear solution to the following problem: I'd like to use outside air to cool a room, but only when the outside air is cooler than the room temperature.

I live in an area of California where summer days are quite hot but evening air is quite cool. My current manual solution works fine, but I want to automate it. During the day the room gradually heats up. Toward evening, when the outside temperature drops, I open a window and turn the exhaust fan on and, voila, cool room. In the morning I shut the window and keep the fan off, and the room stays reasonably cool for the day (on all but the hottest days).

A single thermometer on the exhaust fan doesn't work because sometimes it turns on when the ambient temperature is still really hot and it just draws in even hotter air.

It seems like this must be a simple, solved problem. I imagine a passive backdraft damper allowing the fan to draw in ambient air, with the fan controlled by two thermometers (outdoor and indoor) that turns on whenever outdoor is cooler than indoor, and indoor is hotter than some threshold.

Suggestions?

Thanks,
Wallace

Wallace Mann

stusviews
Moderator

USA
15603 Posts

Posted - 08/28/2017 :  7:21:18 PM  Show Profile  Visit stusviews's Homepage  Reply with Quote
What kind of exhaust fan, window, whole house, something else?

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wallacemann
Starting Member

USA
2 Posts

Posted - 08/28/2017 :  8:23:01 PM  Show Profile  Reply with Quote
I was trying to simplify the problem description ... perhaps I overdid it. I have several variations in mind.

(a) Garage: single 1.5 car garage that is open through to a peaked, insulated roof with a partial attic-y space, existing 14" gable attic fan and one window. I imagined an additional backdraft vent to the outdoors. This is the simplest, single room scenario.

(b) Attic: approximately 20 x 20 foot x 5 foot tall "finished" and insulated attic space above single story home, existing 14" gable attic fan and no windows. I imagined a backdraft vent to the living space. Currently what I do is turn the attic fan on and crack open the attic stairs and ground floor windows ... it cools the attic nicely and contributes to air pull into the ground floor.

(c) Whole house: Two story home with first floor half buried into a hill and second story open architecture up to a peaked, insulated, no-attic roof. No existing fans. Half buried first floor is always cool when second story is hot. Imagined an exhaust fan at the peak, backdraft vent into the cool, buried first floor, and active/passive vent/fan moving air from first floor to second. What I do now is put a monster floor fan at the base of the stairs and blow air upwards ... works like A/C.

Wallace Mann
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