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Old 11-07-13, 09:54 AM   #1
BobD
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Default Insulating a whole house fan louvered vent

I have a whole house attic fan in the upstairs hallway that has a louvered opening into the living area. Especially during the summer season, Since the fan is not often used during the hottest part of the year when the A/C is on, I can feel the heat blasting down thru this louvered opening. Has anyone constructed an insulated cover that can be easily opened to allow occasional operation of the fan? I have been considering just building a 2" thick foam wall around the fan with a 3/4" thick polystyrene foam lid. The lid would be cut into four sections and each hinged (with tape) so that they woud be blown into an open position when the fan was turned on and would fall back closed when the fan was off. Has anyone else had this situation and how did you solve it?

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Old 11-07-13, 11:02 AM   #2
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Welcome to the site BobD!

I moved your thread out on its own so it get a bit more attention.

Your solution sounds pretty good. I would just make sure that it seals up very well. You don't air infiltration through it.
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Old 11-08-13, 07:15 AM   #3
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I'm not an HVAC expert but it sounds like there is a different issue. If air is pushing out from the attic it means the attic pressure is higher than the pressure in the house. Air should be entering the vent from the house not coming out of it from the attic.

What kind of system do you have venting the attic to the outside?
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Old 11-08-13, 10:43 AM   #4
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My attic has the normal vents in the eaves and at the roof peak, so when the whole house attic fan is running with windows or doors open, the air is drawn in the house and is pulled up thru the fan louvers to the fan and then up thru the attic where it is forced out thru the vents. This effectively removes the hot attic air and cools the attic and house. However, when the air conditioner is running and attic fan is not on, the heat in the attic migrates down thru the fan opening, much more so than thru the rest of the attic area which is well insulated to reduce this heat migration. My request was for ideas to provide some insulation to the fan opening that would still allow the fan to be turned without having to manually remove the insulation covering the opening. The attic fan opening has automatic-opening aluminum louvers on the ceiling side which prevents much of the heat from coming down from the attic into the living area, but I can still feel the large temperature difference below the opening. And conversely, during the winter, a huge heat loss from the interior of the house occurs up thru this area. Appreciate your comments.
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Old 11-08-13, 06:40 PM   #5
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Hot air usually moves to where cold air is. It's the dynamic of pressure which causes convection. Stack effect creates pressure but it doesn't always mean that the air will move up. The cooler air moves in through soffit vents, then gets heated by the roof and pressure drives it both into the house and out the ridge(or turtle/etc vent).

Since you seem to want the use of the attic fan with periods between that time to not have the airflow, my suggestion would be to buy some thick plastic and either use a reusable double sided tape or glue a magnet to the perimeter of the plastic and put it in place when not in use and remove it prior to turning on the fan. Just be sure that when you are not in the whole house fan season that you cover the entire unit with an insulated box that is sealed with a gasket so it isn't an energy sieve.

The easiest solution though to making sure you are always sealed and insulated when the fan is off is to have one of these instead. Indoor air quality, whole house fans, exhaust and ventilatio

In my house, I ended up buying 4 box fans and I stack two on top of eachother in my slider windows. Two as an intake for two different windows downstairs with the rest of the window open and it really moves a pile of air. Saved a ton of money over the whole house fan and takes two minutes to open windows and place the fans in and power them up and as soon as I'm done the house is as sealed as it always is.
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Old 11-08-13, 09:29 PM   #6
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Ok, so what you want here is one of two things:

1- Coffin: Larger version of an ice chest. Cap the opening with a coffin made of 2" extruded polystyrene board. Rig a stick or rope to open from below with ease. Cost: under $50



2- Cork: Build up a cone around the fan opening that is airtight from below. Shave a section of xps board to fill the opening. If you're sly, this one might work by gravity alone. If not, rig as above example. Cost: under $50.

Both of these designs can be sealed magnetically or with fur. I prefer shaggy felt.

Or, you can go buy a self-sealing, microprocessor controlled, automated, high r-value whole house fan blower for thousands of dollars.

Last edited by jeff5may; 11-09-13 at 09:44 AM..
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Old 02-10-14, 03:51 PM   #7
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We use whole house fan, no A/C

Run fan all night.
Run fan in morning till inside temp equals outside temp.
Shut off fan, close doors and all curtains in house.

In late afternoon when inside temp equals outside temp.
Open all doors and windows.
Two bedrooms, living room and kitchen have six foot sliding doors. Rest of rooms all have a crank out from the bottom window.

Turn on house fan. Fan is sized for house twice as big.
All curtains blow straight in.

Fresh air is exchanged in less than 1 min through whole house.
Inside temp drops even with out side temp till morning.

Sample
7:00 o’clock in morning 60 F inside and out.
2:00 in afternoon outside temp 90 inside 70.
5:00 in afternoon outside 85 inside 80 to 85.
Most of the time, at this time, 5 degrees is no longer an issue, so we opt for the fresh, fast moving air, even though it is still hotter outside and turn on the fan.
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Old 02-10-14, 08:19 PM   #8
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Quote:
Originally Posted by MN Renovator View Post
\

In my house, I ended up buying 4 box fans and I stack two on top of eachother in my slider windows. Two as an intake for two different windows downstairs with the rest of the window open and it really moves a pile of air. Saved a ton of money over the whole house fan and takes two minutes to open windows and place the fans in and power them up and as soon as I'm done the house is as sealed as it always is.
I'd like to read about and see your setup.
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Old 02-10-14, 09:54 PM   #9
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Quote:
Originally Posted by iamgeo View Post
I'd like to read about and see your setup.
When we get to the comfy spring temperature, I'll take a picture and start a thread. Remind me if I forgot. 4 box fans moves a huge amount of air. Also consumes 100 watts for each fan, I think a mini-split would use less. I'm considering just cardboarding the top half and just running two. The reason why I went with 4 is because that two stacked on top of eachother fits in the window.
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Old 03-18-14, 11:06 AM   #10
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Hey Bob, did you ever end up doing anything with insulating your whole house fan vent?

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