# Whole house ventilation



## Stuart Pidassle (10 mo ago)

Thanks for letting me join. I would like some feedback on a project to implement some ventilation to reduce the use of room air conditioners. I hope this is not a repeat question, I used the forum search to help me get my ideas in order.

The background is that we have a small house (1600sf) that does not have central AC in a location where the temperature drops significantly in the evening. I am trying to figure out a low cost, simple why to create the effect of a whole house fan without getting into the complication of a full system. The house is a Cape Cod set up with very limited attic space. The attic is basically a crawl space gable vents on each end. There is an entrance to the crawl space located at the top of the stairs to the second floor in the perfect spot to pull air from the first floor. 

I am thinking that adding an attic fan to the gable vent and opening the crawl space entrance to allow passive air circulation from the main house to the attic would make a big difference. The idea is that we would just open the windows and turn on the fan to cool the house down before turning on the bedroom ac units at night. Would doing this help cool the whole house or just the attic? Any other suggestions or thoughts?


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## Chris616 (Dec 31, 2019)

The fan might be redundant. On nights when the air temperature drops we often just open the attic hatch and open windows and the hot air in the house rushes into the attic and out the attic vents to be replaced by cool outdoor air from the windows. In your case, adding a fan to the gable vent might not increase the airflow from the house, since some of the extra air might come into the attic from other attic vents. 

The “passive whole house ventilation” failed for us in last June’s heatwave because the overnight temperature stayed high. Tomorrow a mini-split is being installed so that we have cooling. This was bound to happen as a result.


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## 3onthetree (Dec 7, 2018)

By "crawlspace" you mean the attic above the ceiling to the peak of the roof (a crawlspace is at grade). The access panel to the attic has to remain, and I don't imagine you want to lift and move that over every night (or your wife or kids when you are not home). You can install a ceiling whole house fan next to the access panel, it can only move the amount of cfm that can be pushed through the gable vents (and how much it pulls through the windows that are open and other leakage), but that would be enough no matter the exact cfm to feel a difference in any room a window is open. So they are not perfectly designed systems cfm-in/cfm-out but don't need to be for effectiveness. There are also smaller ducted whole house fans where the fan unit is at the gable vent and just a grille in the ceiling. That I would only use if you have available gable venting beyond what you need for passive venting, because with a cape and hot upstairs I imagine your passive venting is inadequate.


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## SW Dweller (Jan 6, 2021)

Whole House Ventilators are a great way to cool your home. I grew up with a 30" fan and 1/2 horse motor in the second floor hall window. It literately helped you up the stairs. Noisy yes.
We opened windows down stairs and in the bedrooms and let it roar. By morning the house was close to outside temp. Takes a long time and huge volume of air to cool down a structure.
Dad got up at O'dark thirty and turned off the fan and closed most of the windows. Then the slow temp rise in the house happened until sun went down and we started it over again. 

Ideally the windows would open and close automatically with the fans operation. 
I have used a 6000 cfm swamp cooler with no water. Usually could get within 4-6 degrees of the morning cool temp by morning. As the morning temps rose it did less and less until it was about 10 degrees above the outside temp. Then I turned on the ac. 

You can practice with some floor fans that move over 5000 cfm. I have put two in my patio door, outside, left the door open as wide as the fans. Then used a carpet drying fan to make the 90degree turn down the hall. Opened a bedroom window and instant cooling as long as the morning temps are below 65F.


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## Old Thomas (Nov 28, 2019)

If you put in a whole house fan of some type, you should interconnect it with a nearby smoke detector to shut down the fan, especially if you are planning to run the fan while you sleep. A whole house fan can pull a fire through a house faster than s—t goes through a goose.


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## SeniorSitizen (Sep 10, 2012)

You may soon tire of opening / closing windows . Been there done that .


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## Bud9051 (Nov 11, 2015)

My go to solution has been this:








Lasko 16 in. Window Fan with EZ-Dial Ventilation W16900 - The Home Depot


Lasko's 16



www.homedepot.com




Closest I could find. But I live in a cape in Maine so lots of cool evenings. In fact I have to be careful and shut that fan off before I go to sleep. Burrr.

Bud


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## Stuart Pidassle (10 mo ago)

Thanks all for the replies. Bud's summary is in line with my situation. One bit of context is that we currently employ a process of shutting down the windows/doors on the front of the house during the heat of the day and opening things up in the evening with window ventilation fans used as needed. Would simply adding a louvered vent that can be manually opened and closed to the crawlspace door make enough of a difference to notice? Open it in the summer to keep things cool, shut in the winter to prevent losing heat. This would avoid all of the complications and potential downsides of a powered solution.


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## snic (Sep 16, 2018)

If your attic has vents to the outside, then the attic fan will pull air not just through the house, but through those vents. So that will reduce the airflow through the house. I know this from experience - a house I owned had a huge attic fan, and I had the same idea as you: let's open the door to the attic and pretend it's a whole-house fan. But the attic was well ventilated and very little air actually flowed from the house up into the attic. Also, keep in mind that commercial whole-house fans are very powerful (look at their cfm ratings), probably more powerful than standard attic fans. I've been in houses in California with whole-house fans, and you can really feel the breeze when they're turned on full blast. That certainly wasn't the case with my make-pretend whole house fan.

I suggest figuring out a way to properly install a whole-house fan in your attic. In your climate it really makes a difference.


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