Whole House Fan Installation

We’re thinking about installing a whole house fan. Anyone ever done it? We know nothing about electricity, so we’ll probably have to hire someone unless it’s a plug ‘n’ play situation. What would the cost for said installation be? The unit is about a deuce.

I’ve never heard of such a thing. Can you link to a photo?

ChefGuy: Whole House Fan (how it works)

It’s a big, powerful fan that goes in the ceiling of your main hallway and sucks air from inside the house - and thus through open windows - into the attic, which then vents to the outside.

I can’t give the OP any instructions on installing one (mine was here when I got here) but I can give my experience having one. My opinion is that it’s better than nothing. Since it’s not de-humidifying like an air conditioner, my house is still humid as hell. And it’s not very useful until the air outside is fairly cool. Right now it’s about 90+ degrees here and I have my whole house fan off because it would just suck in all that hot air. However, I used it last night starting around 6 PM and it was lovely and cool in here. By midnight it was downright chilly.

The biggest thing about the fan installation is making sure you have the proper ventilation out of your attic. Most things I’ve read suggest a louvered opening in one of your eaves. The louveres would be shut when the fan is not on and open when it’s running. I think the pressure of the air from the fan controls the louvers - like it controls the louvers underneath the fan, in the hallway. My fan vents into a large hole in the garage ceiling, meaning I have to keep my garage’s back door open when the fan is on. Otherwise I just blow hot air into the garage and it builds up in there and doesn’t go anywhere, and the fan isn’t able to suck more air in from outside. This was demonstrated last night when I accidentally had the back door closed and when my friend opened it, the house got about 10 degrees cooler. That being said…my house is a POS with very poor construction and this sort of venting is NOT the way to go.

Anyway, the fan installation itself looks like a breeze (!) but the venting is something you need to research when installing. If you don’t think you can vent it properly yourself, it means more $$ to have it installed. If installation starts looking like $2000-3000 for you…go for air conditioning. Otherwise, whole-house fans are, like I said, better than nothing.

But it wouldn’t suck in hot air unless your windows were open, would it?

We had a whole-house fan in another house. We didn’t run it very often though. The house was shaded by trees on all sides, and I’d pull the shades and run the dehumidifier and a floor fan. It’d stay pretty comfortable until the temps got to the high 90’s.

I wonder if an attic fan would do just as well, or almost as well. Ours turns on whenever the attic temp reaches 80, and the second story stays cool without running the A/C.

As described, a whole house fan is mounted in a central location on the ceiling, and pulls air in through windows and doors, discharging into the attic. Several problems exist for the DIY installation:

[ul]If the fan width exceeds attic floor joist span (typically 16"), one member will need to be cut and headered to the adjoining joists. Not so big a deal if the members are solid sawn, but if they’re part of a lightweight wood truss (increasingly common in residential construction), cutting the bottom chord of a truss reduces it’s design load capacity (it’s in tension).[/ul]

[ul]Depending on the motor size, it may or not be wise to place it on a dedicated circuit. Fans can be made to operate with timers, thermostats, and humidistats, or a combination of these devices. Electricity doesn’t forgive a slow learning curve.[/ul]

[ul]Attic discharge area is critical for proper performance. Gable end vents typically provide insufficient area for discharge when a whole house fan is employed. Maximum perfomance starts with determining the fan CFM at full speed. Then determine the CFM that will move through the gable vents based on their area @ close to 0 w.c. Unless they’re huge, you’ll quickly reduce the fan’s effectiveness. If you have a ridge vent, that’s another story, and you’re in luck. Although they seem to be small, ridge vents are great, either alone or in conjunction with gable vents.[/ul]

Thanks all, for your responses. We plan to use it in conjunction with our central air, the idea being that the air wouldn’t have to work as hard, and at times we wouldn’t have to run the air at all. This really sounds like a job for Someone Who Knows What He’s Doing ™. I can see we won’t even begin to tackle it ourselves.

Sounds like something that would compromise your heating/cooling efficiency to me, i.e., a giant hole in your ceiling, unless there are closeable louvers.

I grew up in house in suburban Philly that had a whole house fan. It was at least 30" in diameter and didn’t turn that fast. Nonetheless, it cooled the whole house quite well, but only after the temperature fell in the evening. It was located at the top of the staircase to the third floor, maybe 20’ down a corridor to a window that was closed in the winter. It had glass louvers to keep out rain. I would love to install one in my house now, but no one around here seems to know anything about them. It is easy to buy the fan; several companies sell them, but you need local installation and that is what I have been unable to locate. Our house is a pretty conventional two storey house with a peaked roof and an attic with insulation that you can access from a closet. What I woul like is a hole cut near the top of the stairs into the attic with the fan in it, covered by louvers that can be sealed in the winter and controlled by a thermostat, although that is not important.

I can’t even find a decent window fan. Some forty years ago, I bought one at JC Penney, and I still use it, but I am very afraid that one day it will die and it seems irreplaceable. It certainly helps cool the house, but is not in the same class. It would do better if I dared put it on high speed, but I am trying to nurse it.

The purpose of the fan is to quickly exhaust the air in the house, and replace it with the outside air. Close the windows and the fan will be rendered useless.

If you have cool nights, it should work like a charm, rather than trying to cool your house down via AC, you let the cool outdoor air do the work. It will get the place comfortable much faster than just opening windows, because it quickly exchanges the air, and gets rid of the hottest air first.

The models I looked at had provisions for closing/insulating the ceiling hole when the fan is not in use.

I suppose it could be a DIY project, but you really do need to know what you’re doing.

In the two houses that I’ve lived in that had them, the louvers opened by the suction created by the fan above them. I assume that they all work in a similar way.

Whole-house fans usually have automatic louvers. There are also insulated caps that can be slipped over the louvers for added insulation in the winter.

I installed one of these fans in a house near Chicago, and frankly, the overall insulation of the house was poor enough that there would be no point to insulate just one 2x2 foot bit of the ceiling.

I’m about to put one into my house near San Francisco, where it doesn’t get cold enough (Mid-30’s is rare, actual freezing is unheard of) to be concerned about a 2x2 foot section of un-insulated ceiling.

These are not the same as attic fans - attic fans exist soley to ventilate the attic and do nothing for the living space. The benefit to attic fans is that they’ll remove a big static lump of heat from over the living space.

Whole-house fan installation is pretty basic carpentry. The one I did in Chicago involved no cutting of ceiling joists - the fan sits on top of the existing framing, and the only modiffication needed was to put in some blocking to “box off” the joists so the fan wouldn’t be pulling air (and loose insulation) from the joist space.

Electrical needs are pretty simple - IIRC, about two or three amps worth, and in my case, it was easy to tag into an existing junction box that the attic lightbulb was mounted to.

If you’re comfortable with being able to find electricity in the attic, or run a new circuit, and know which end of a hammer to hold, these fans are pretty easy to install. The bugaboo might be the outflow venttilation from the attic through gable or roof vents. Your fan will say how many square feet of ventilation it needs, and yoou may be better off calling a roofer to climb up there and add more.

I think Home Cheapot will install them for you, but it’ll probably cost you an arm and a leg.

Mr. K just bought an industrial strength pivoting floor fan for his garage. He has a window shaker in there, but wants the circulation of a jet engine. He’s all about the fans. I hate ‘em. The sound drives me freekin’ nuts.