fanpower needed to cool house overnight

[Lacustral]

Do you know how many CFM your box fan is?

Thanks Laura

[jah213]

No, I don't know, sorry. It's a 20-inch fan, the cheapo kind that goes on sale at the hardware store for $12.97. Plastic housing, plastic blades. Nothing very special about it, but it works just great for exhausting the hot air and pulling in the cool air.

Jo Ann

Lacustral wrote:

[StLouisMike]

Like some of the other comments regarding exchanging air not affecting the overall temperature of the house, I would also add that a simple fresh air exchanger won't do the trick either. We have a very good system tied into our regular household ductwork (a $2,000 RUUD system not to control air temp as much as humidity and getting fresh air into our 'super tight' panelhome). Running the furnace fan 100% and the fresh air exchanger on high over night with the outside temp in the low

60's doesn't bring the air temp in the home down a degree. The heat build up in the structure itself does not dissipate easily.

Mike

[Lacustral]

I know leaving my windows open cools my house down much more than if the windows are left closed, so bringing in outside air helps. I wonder if you have a heat exchanger.

Laura

[Phil Scott]

[Joshua Putnam]

Just double-checking, do you have a very small home? 4800 cubic feet would be a 600 square foot house with 8-foot ceilings. A 240 cfm fan

*would* be enough to create a breeze you could feel in that small a space.

[jah213]

I don't know how many cubic feet I have, but my house is about 1600 sq. ft. and I have 10-foot ceilings downstairs, 8 feet upstairs. When I put my box fan in an upstairs window and open windows downstairs, I can literally feel the breeze coming up the stairs. The method that works best for me is to open windows at night and put the box fan in the window blowing out, which exhausts the hot, stale air in the house and brings in the cool night air. During the day, I keep the windows closed and curtains pulled where the sun is coming in. I don't open up again until it cools off in the evening. My house is well insulated and has good windows but, at 100+ years old, is far from airtight. This method works really well except during periods of hot, humid weather when it stays hot at night. At that point I resort to a couple small (5K) air conditioners and put my box fan on the floor to circulate air. It's not high tech, but it works great.

Jo Ann

Joshua Putnam wrote:

[Lacustral]

Yes. The upper story, the one that gets hot, is 600 sq feet.

Laura

[Lacustral]

Actually it's 640 sq feet (just measured it). x 8 feet high, = 5120 cubic feet.

Laura

[BobK207]

Stick a 3 speed 20" box fan in one of the upper room windows.......blowing outward. Place a carboard shield on the sides as needed to create a reasonable seal.

Open windows in the rooms you want to cool (open more windowns or open them further in the "most impotant" rooms to cool)

The rooms with the open windows will cool FIRST & the room with the fan will cool LAST.

Experiment with fan speed & window opening, adjust window openings & fan placement to get the desired result.

fwiw I have a 2300 sq ft home in OC SoCal. It's a 1.5 story design built in 1930 We typically get good nightime cooling (into the low

70's or less with low humidity) we can get temps in the mid / high 90's & even low 100's.

I used to have a Nat Gas AC unit but it bit the dust & I haven't replaced it.

A single 20" box fan funning on high speed will cool the house to outside temp by morning & will provide a comfortable (& adjustable) breeze in the bedrooms.

cheers Bob

[nospamtodd]

Some other things to consider:

1. The cooler it is outside, the farther the temp will drop overnight. Even if it doesn't drop much, at least you get fresh air in. In the fall, I was able to pull in warmer air during the day and raise the temp in the house by a few degrees.

1. Since you have to leave windows and doors open, consider the security issue.

2. You'll be pulling in dust from outside.

[Una]

A key point that seems to need underlining here is that there are two elements. The air exhaust (via fan), and air *intake*. You can put in a humongous monster of a fan but if you don't open enough windows and interior doors throughout the house, the fan cannot get enough house air to exchange hence cannot cool the house. This is especially true in a newer, "buttoned up" heating/AC efficient house.

Also, a good reason to install a whole house fan in an attic gable end (if you have one) is so that you have the choice of running the fan to cool just the attic (indirectly cooling the house, but with less perceptible noise and no draft), or to cool the whole house directly, by opening the attic door, selected windows, and interior doors (especially the bedroom doors).

Catalogs (and websites) that specialize in farming equipment usually include a huge selection of ventilation fans.

Una

[Clark W. Griswold, Jr.]

And in this situation, you run the risk of back venting furnaces, water heaters and any other vented devices in the house, which is a very bad thing.