# Whole house fans **URL:** \ **Category:** Factual Questions\ **Created:** [July 18, 2018, 10:42pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171 "2018-07-18T22:42:35Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [July 20, 2018, 3:32pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/21 "2018-07-20T15:32:12Z")
I’m a fan of a whole house. I once spent a winter campout in a leanto. Never again. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [July 20, 2018, 5:57pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/22 "2018-07-20T17:57:10Z")
Vast piles of misinformation here… If anything, modern codes call for MORE attic and roof venting, specifically to cut down on mold/mildew growth in the attic. If the attic is already properly vented, a whole-house fan will not increase the humidity in the attic simply by pushing ambient air through the space. What will increase humidity up there is improper venting of bathroom fans or clothes dryers into the attic. You really do want the whole-house fan to blow “through” the attic. In the summer, it gets to 130 or more in my attic. A whole-house fan blows this hot air out, reducing the load on the air conditioner, especially if the air handler and ducts are in the attic. Many years ago, I installed an “old style” helicopter fan in my mother’s house. Big 36" blade, so there was framing to be cut and headed off, making for a fairly serious project. Last month, I installed a Quiet Cool QC3100 in my current house. Worlds easier with no framing to cut into - the louvers fit between normal 16" spaced joists and the fan itself hangs in mid-air on a steel strap that’s screwed to whatever roof framing is convenient - in my case, it hangs from the collar ties. The typical way to install these things is with a timer switch and speed switch. When I want to run my fan, I just press a time button on the timer and set the speed to low or high. (the timer buttons are something like 5,15,30 minutes and 1,2,4 hours) If you run the fan without enough windows open, you can backdraft a fireplace, pulling soot and crap into the house, which is just messy, or worse, blow out gas pilot lights. At a quick look, the OP has about four square feet of vent, so more than enough for the QC2250. ---
**Author:** ![spifflog](https://avatars.discourse-cdn.com/v4/letter/s/c5a1d2/32.png) [@spifflog](https://boards.straightdope.com/u/spifflog)\ **Post date:** [July 20, 2018, 6:42pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/23 "2018-07-20T18:42:29Z")
I don’t have any scientific data, only practical experience and info. We live in Washington DC. We purchased a different home about two years ago. It had a non-working attic fan and a barely working whole house fan. The home inspector told us to replace the attic fan and use it, and to remove the whole house fan and seal up the hole. We called an older company to come out and do the work. (I’d normally do it myself, but I just started a new job and didn’t have the bandwidth.) The owner of the company came out to estimate the work and he told my wife - remove the attic fan and seal up that hole, and replace the whole house fan and use that! His argument on the attic fan was that most homes have inadequate attic ventilation which I agree with. One should either have two large gable vents, or a combination of a roof vent and a soffit vent, but not both, as the air flow between the two tend to be counter productive. Either way, without the ventilation required, the attic fan will draw the cool air from the inside of the house, into the attic. He said the whole house fan would be great. We went with his advice. My wife (because I’m at work) usually runs the whole house fan in the morning for 15-20 minutes. That sucker is like a jet engine and within that time, we have really cooled of the house when it’s cool in the morning. We are sold on the whole house fan. The attic fan I had replaced anyway, but I don’t use it (the breaker is off) so I really don’t know if that would be an asset or not. My $0.02. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [July 20, 2018, 8:28pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/24 "2018-07-20T20:28:51Z")
> [@Folacin](#): > > I need to get our fan replaced. We use it spring and fall when the humidity is lower. It no longer self-starts - if you turn it on, you get an electric motor hum. But if I open the louvers and give it even a light spin, it starts right up. If I spin it the wrong way, it will run backwards (and keep the louvers closed tight), which is what makes me think the one FoieGras is familar was wired wrong. Save yourself the installation hassle and don’t replace the whole fan just because the motor failed. You’ve got one of two scenarios - either the motor’s start winding burned out or the starter capacitor failed. Either will be an easier fix than changing the entire fan. ---
**Author:** ![The\_Man\_In\_Black](https://avatars.discourse-cdn.com/v4/letter/t/bcef8e/32.png) [@The\_Man\_In\_Black](https://boards.straightdope.com/u/The_Man_In_Black)\ **Post date:** [July 24, 2018, 12:27am UTC](https://boards.straightdope.com/t/whole-house-fans/818171/25 "2018-07-24T00:27:53Z")
> [@watchwolf49](#): > > This still defeats the purpose of the attic venting … if it’s 25º outside, then we want it 25º in the attic … if we want it 25º in our house, just lower the upper sash the same amount we raise our lower sash … that’s the whole point of double hung windows … If you lower the upper sash the same amount you raise the lower sash what do you about the bug screen. If you open the bottom and top of one window, the screen is only on the bottom. If you open the top of one window and raise the screen to the top, it won’t seal, even if you flip the screen upside down (I tried). ---
**Author:** ![The\_Man\_In\_Black](https://avatars.discourse-cdn.com/v4/letter/t/bcef8e/32.png) [@The\_Man\_In\_Black](https://boards.straightdope.com/u/The_Man_In_Black)\ **Post date:** [July 24, 2018, 12:40am UTC](https://boards.straightdope.com/t/whole-house-fans/818171/26 "2018-07-24T00:40:16Z")
To answer some questions, I live in Northeast Pennsylvania. I want the whole-house fan for warm weather use when it is hotter inside the house than it is outside. At the moment it is 72 outside and 80 inside, with all windows and doors open and two of these [https://www.amazon.com/Holmes-Dual-Blade-Window-White/dp/B00008XET9/ref=sr\_1\_1\_sspa?ie=UTF8&qid=1532392604&sr=8-1-spons&keywords=holmes+fan&psc=1](https://www.amazon.com/Holmes-Dual-Blade-Window-White/dp/B00008XET9/ref=sr_1_1_sspa?ie=UTF8&qid=1532392604&sr=8-1-spons&keywords=holmes+fan&psc=1) fans in second store windows blowing out. ---
**Author:** ![california\_jobcase](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@california\_jobcase](https://boards.straightdope.com/u/california_jobcase)\ **Post date:** [July 24, 2018, 3:15am UTC](https://boards.straightdope.com/t/whole-house-fans/818171/27 "2018-07-24T03:15:34Z")
You don’t have to have a fan mounted in the attic to exhaust the living space. One good high-velocity fan mounted in a window will do the job just fine. ---
**Author:** ![Tastes\_of\_Chocolate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tastes_of_chocolate/32/3232_2.png) [@Tastes\_of\_Chocolate](https://boards.straightdope.com/u/Tastes_of_Chocolate)\ **Post date:** [July 24, 2018, 3:16am UTC](https://boards.straightdope.com/t/whole-house-fans/818171/28 "2018-07-24T03:16:55Z")
> [@The\_Man\_In\_Black](#): > > If you lower the upper sash the same amount you raise the lower sash what do you about the bug screen. If you open the bottom and top of one window, the screen is only on the bottom. If you open the top of one window and raise the screen to the top, it won’t seal, even if you flip the screen upside down (I tried). You order your double hung windows with full size screens. I replaced all my windows a few years ago, and for the couple of double hungs I have, I requested screens that cover the whole window. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [July 24, 2018, 3:28am UTC](https://boards.straightdope.com/t/whole-house-fans/818171/29 "2018-07-24T03:28:47Z")
> [@gotpasswords](#): > > Vast piles of misinformation here… > > If anything, modern codes call for MORE attic and roof venting, specifically to cut down on mold/mildew growth in the attic. Not, however, if you use spray foam. Those are unvented assemblies. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [July 24, 2018, 3:47am UTC](https://boards.straightdope.com/t/whole-house-fans/818171/30 "2018-07-24T03:47:53Z")
> [@The\_Man\_In\_Black](#): > > If you lower the upper sash the same amount you raise the lower sash what do you about the bug screen. If you open the bottom and top of one window, the screen is only on the bottom. If you open the top of one window and raise the screen to the top, it won’t seal, even if you flip the screen upside down (I tried). Triple track storm windows make it hard too because the screen isn’t usually full height either. Full size screens may not be practical on older windows that need storms in the winter. That requires replacing the screen panel with a storm panel twice a year. It takes a decent amount of storage space and time on a ladder too. I don’t think most people have the patience for that anymore. I’ve found that the “just open some windows” or “just use a good box fan” arguments don’t fly in a lot of places. Michigan? Sure. Vermont? Ok. But much of the country not near bodies of water doesn’t get cool enough at night for double hung windows to induce their own draft (that requires a decent temperature differential) and wind tends to totally die down overnight. It takes a strong fan and a lot of air changes to cool a house when it’s only dropping into the mid or upper 60s (and then not until after sunrise) and you may still have hear radiating through brick walls along with internal heat sources like TVs, computers, humans, lights, and appliances. Also, don’t underestimate the value of flushing the hot air out of the attic. In all but the best insulated homes that heat up there is forcing its way down to the living space. The whole house fan does the job of both an attic fan and window fans, and it does it better than both of them. ---
**Author:** ![The\_Man\_In\_Black](https://avatars.discourse-cdn.com/v4/letter/t/bcef8e/32.png) [@The\_Man\_In\_Black](https://boards.straightdope.com/u/The_Man_In_Black)\ **Post date:** [July 24, 2018, 4:27pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/31 "2018-07-24T16:27:13Z")
> [@california\_jobcase](#): > > You don’t have to have a fan mounted in the attic to exhaust the living space. One good high-velocity fan mounted in a window will do the job just fine. I was looking into that, but my windows are only 24.75" wide and 17.5" tall. All the large window fans I have seen require a larger window. ---
**Author:** ![The\_Man\_In\_Black](https://avatars.discourse-cdn.com/v4/letter/t/bcef8e/32.png) [@The\_Man\_In\_Black](https://boards.straightdope.com/u/The_Man_In_Black)\ **Post date:** [July 24, 2018, 4:37pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/32 "2018-07-24T16:37:23Z")
> [@Tastes\_of\_Chocolate](#): > > You order your double hung windows with full size screens. I replaced all my windows a few years ago, and for the couple of double hungs I have, I requested screens that cover the whole window. I didn’t know that was an option. I installed new windows throughout the house a few years ago, so I just E mailed the manufacturer to see if full screens can be made for the existing windows. ---
**Author:** ![Khendrask](https://avatars.discourse-cdn.com/v4/letter/k/3e96dc/32.png) [@Khendrask](https://boards.straightdope.com/u/Khendrask)\ **Post date:** [July 25, 2018, 2:42pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/33 "2018-07-25T14:42:13Z")
> [@CookingWithGas](#): > > I would think it would be the opposite. The more windows that are open, the less force the fan has to exert to pull the air in. Extend this to an extreme: Suppose you have only one window open a tiny crack. The fan has to try to suck a large volume of air through that tiny crack, creating a negative pressure in the house, and a big load on the fan. Now go to the other extreme: you have no walls. There is no pressure differential inside vs. outside and the only significant load on the fan is from pushing the air into the attic. That is backwards. A normal fan, or centrifugal pump only draws current as it is moving the working fluid. Block off the intake, and the motor current will drop as no work is being done. The most common example of this is a shop vac. Block the inlet hose, the motor speeds up, as it isn’t delivering torque to moving any air. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [July 25, 2018, 2:57pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/34 "2018-07-25T14:57:39Z")
> [@Khendrask](#): > > That is backwards. A normal fan, or centrifugal pump only draws current as it is moving the working fluid. Block off the intake, and the motor current will drop as no work is being done. The most common example of this is a shop vac. Block the inlet hose, the motor speeds up, as it isn’t delivering torque to moving any air. Supposing this is correct then I don’t understand the advice I was responding to, which is not to have many windows open to reduce the load on the fan. It seems that the whole point is to move air. The fan was designed to do the work, so you don’t need to protect the fan by lowering the load. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [July 25, 2018, 4:59pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/35 "2018-07-25T16:59:23Z")
> [@CookingWithGas](#): > > Supposing this is correct then I don’t understand the advice I was responding to, which is not to have many windows open to reduce the load on the fan. It seems that the whole point is to move air. The fan was designed to do the work, so you don’t need to protect the fan by lowering the load. As I said, you misread me. I said: “DON’T run it WITHOUT a lot of windows open.” IOW, have an ample number of windows open to avoid straining the motor. We’re saying the same thing. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [July 25, 2018, 5:00pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/36 "2018-07-25T17:00:37Z")
> [@Khendrask](#): > > That is backwards. A normal fan, or centrifugal pump only draws current as it is moving the working fluid. Block off the intake, and the motor current will drop as no work is being done. The most common example of this is a shop vac. Block the inlet hose, the motor speeds up, as it isn’t delivering torque to moving any air. That is true only if NO air is coming in, and the fan is working on a vacuum. It’s doubtful that an attic fan can create much of a vacuum in an ordinary house, even with most windows closed. I say if your intention is to ventilate one room, open only the window(s) in that room. If you want to ventilate more rooms, open more windows. You can have volume or speed, as you wish. ---
**Author:** ![elfkin477](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@elfkin477](https://boards.straightdope.com/u/elfkin477)\ **Post date:** [July 25, 2018, 11:39pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/37 "2018-07-25T23:39:25Z")
> [@Tastes\_of\_Chocolate](#): > > Why would you vent a whole house fan into an attic, and not directly outside? It’s basically a large bathroom fan. I wouldn’t vent my bathroom fan or my drier into the attic, so why would I vent a whole house fan into the attic? If you put a hole in the roof, what would happen if you got a big snowstorm, or a couple of moderate ones one after another? It’s not terribly uncommon here to get two or three feet of heavy wet snow in less than a week (this year we got nearly 4’ of snow in 4 days and had to pay to have the roof cleared), and I can easily imagine the weight of that much snow caving in at the point of where the fan is. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [July 26, 2018, 12:34pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/38 "2018-07-26T12:34:18Z")
> [@elfkin477](#): > > If you put a hole in the roof, what would happen if you got a big snowstorm, or a couple of moderate ones one after another? It’s not terribly uncommon here to get two or three feet of heavy wet snow in less than a week (this year we got nearly 4’ of snow in 4 days and had to pay to have the roof cleared), and I can easily imagine the weight of that much snow caving in at the point of where the fan is. ??? If you have a bunch of snow _inside_ your attic on top of your whole house fan you have a completely different and very serious issue. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [July 26, 2018, 1:01pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/39 "2018-07-26T13:01:08Z")
I’m not sure what **elfkin477’s** point is … but there is some “robbing Paul to pay Peter” here … Yes, in the summer things get uncomfortable … and knocking a hole in your ceiling will cool things down inside … but if it’s that much hotter inside than outside, maybe just go outside … if you have kids then it’s tons of fun sleeping on the porch … However, in winter you’ll be running your heater and things will stay warm inside … the hole in your ceiling will just cause your heater to run more … whatever baffles this unit has is no match for 14" of fiberglass insulation, so this is going to be a major heat leak in winter as well … you’ll still be comfortable, until the heating bill comes … As a final test, call your nearest building code enforcement agency, see if this is even legal where you live … ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [July 26, 2018, 7:53pm UTC](https://boards.straightdope.com/t/whole-house-fans/818171/40 "2018-07-26T19:53:22Z")
I’m fixin’ a hole where the … heat gets … out. We have a whole house fan. The previous owner rigged up a thing with a piece of plywood and a chunk of foam rubber (:eek:) to fit into the framing between the fan and the louvers. In the fall you take out a couple screws, lift up the fan, hook on some wire hanging down, put in the plywood then the foam rubber. Drop the fan back down. I pull the knob on the fan switch to keep anyone from accidentally starting it. In the spring reverse the process. I replaced the foam rubber with thick fiberglass insulation, added some weather stripping and “handles”, etc. But since it’s so humid here and just opening the windows at night during the small periods in the spring and fall when the outside air is cool/dry enough works just as well I long gave up taking it out. I’m not worried about thermal losses from the fan opening. It’s pretty well sealed and insulated. [Previous page](https://boards.straightdope.com/t/whole-house-fans/818171.md?page=1)