Whole House Fans - Love 'Em or Not?

I just searched this forum for "Whole House Fan", but I didn't find much about them (except this and this).

I'm curious to hear what experiences you all may have with these simple and relatively inexpensive devices out in the real world.

Here are some pictures and a basic definition of the type of fans I'm talking about:

4.7.12 Alternative Systems - Ventilation Cooling (2013 CA Energy Efficiency Standards)

The CEC also maintains a list of models approved for sale in California. Does this list adequately represent the state of the art?

Or are there other emerging whole-house ventilation technologies that home professionals ought to know about?

For this discussion, let's try to not confuse an old school "Attic Fan" (which isn't designed to ventilate a conditioned space) with a "Whole House Fan" (which is).

Don't hold back!

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  • A whole house fan is usually installed on the attic floor near the center of your house. In the late evening or early in the morning this fan is turned on to exhaust hot or humid air from the house. Cooler outdoor air enters through open windows to lower the indoor temperature. Whole house cooling using a whole house fan can substitute for an air conditioner most of the year in most climates. Whole house fans combined with ceiling fans and other circulating fans provide acceptable summer comfort for many families, even in hot weather. In addition to whole house fans, the ducts of your central heating and cooling system can be modified to provide whole house cooling. For more information on whole house fans, you could consult the leader in residential HVAC services experts at White Mechanical, Inc.

  • Great read...!

    Thanks for sharing...

    But I am still confused about which one to choose. I recently purchased a condo pre construction condos in Markham. I'll be moving into the condo this year itself. The construction is going smooth and on time. So, I was thinking of air conditioners. But sort of in a confusion after hearing about the whole house fans from one of my friends. So I started searching for the same online, that's when I bumped into this thread. 

    So, just wanted to make sure if this will be good for condos too? Please help!

    Your Condos has access to a full range of market warranty options, helping you to find your dream condominium in Markham, all while protecting your i…
  • I am not in favor of this whole house fan. Maybe they are more cheaper than air conditioners but It is not really works for everyone. I highly recommend mini split systems.

  • I am thinking of buying a Central Heat Pump. The climate here is very cold, especially in winter.

    I have a very old central system that brings me many costs. I was thinking about something like that.


    I should always ask a professional about central air conditioner sizes and which will fit my home the best. But I need an idea of what these systems do.

    3 Ton 16 SEER Heat Pump and Air Conditioning System DSZC16/AVPTC
    Hover over any item with a red dotted underline Important information and tips! for more information! This system is a Central Heat Pump with Air Con…
  • Roderick,

    Sorry - no photos. But it was similar to many other projects easily found. I used multiple, overlapping layers of 2" polyisocyanurate (2 on the sides, 3 on the top) glued together with urethane construction adhesive (I also used duct tape to hold the panels together so the adhesive could set up properly). Side panels were foamed/caulked/sealed to the existing ceiling joist areas around the fan base; top panel was partially inset into the side panels (the first 2 polyiso layers) and also had door weatherstrip at the joint of the uppermost polyiso layer and the side walls (just in case someone in the future wanted to re-use the fan). The box structure was large enough to contain the entire fan/motor/belt drive assembly.

    • Thanks  

      • Roderick, I see that comments here have waned since the 6th.There are a lot of comments before that. 

        I want to respond to your comments about Airscape. Neil, the founder, went to a great deal of time trouble and , likely, expense to create the world's first 7 speed whole house fans that can be remotely controlled by smart phones from anywhere in the world. Then, apparently because customers were turning the systems on while away with windows closed, he announced a new vacuum sensor to inhibit his systems when windows are closed. 

        His systems ARE good but the cost per CFM is a bit high, much like Tamarack. Invisco now has the latest in efficiency, a totally automatic speed control that can be remotely controlled or not, and when turned on starts the fan up at high speed for maximum cooling at temps over 85F, then the speed reduces (and power) linearly from 85 to 70F when the fan is off. There is a manual option as well for winter air changes. 

        Invisco also offers thermally broken dual dampers for cold climates where IECC2012 specs are needed. 

        I would be interested in your thoughts on this new product line. 

  • Stop Squeezing it, There's NO JUICE IN THAT ORANGE!

    Funny tweet from Summer Camp:  "A system is fundamentally better if it's more Simple, Repeatable, Reliable, and Lasting" - J. Wells

    • Simple?  (teach psychrometrics, CO safety, open and close windows, deal with noise, dust, condensation and safety issues)
    • Repeatable?  (see simple..)
    • Reliable? (As reliable as the weather man)
    • Lasting?  (everything about this approach assumes we should make the outdoors in.  It is the opposite of what Building Science is all about, which is creating comfortable, healthy, durable shelters from the outdoors).  

    “The great enemy of truth is very often not the lie--deliberate, contrived and dishonest--but the myth--persistent, persuasive and unrealistic. Too often we hold fast to the cliches of our forebears. We subject all facts to a prefabricated set of interpretations. We enjoy the comfort of opinion without the discomfort of thought."


    Yet the unmeasured "savings" wives tale persists.  Dogmatic belief being tightly held on to.  Not a single case study to prove cost/benefit.

    #bscamp hashtag on Twitter
    See Tweets about #bscamp on Twitter. See what people are saying and join the conversation.
    • @ Tedd - Respectfully, sir, I see no indication here that anyone is intending to "lie" or perpetuate myths. Instead, I see colleagues from different parts of the country sharing their informed and HONEST opinions. Frankly, that's all I had hoped for.

      Clearly Whole House Fans are not for everyone / everywhere. But as I, and others here have indicated, in some hot dry climates (especially the marine-influenced zones where most people in California live), the temperature can really cool off at night. For >25 years our family's been using a WH fan to take active advantage of this natural ventilation resource that's available to us.

      Still, this exchange has given me plenty to think about beyond my own limited anecdotal experience with WH Fan technology.

      We have no A/C, but in the summer friends often remark how cool our house feels, because we have a decent envelope, control our solar gains with triple-wall cellular shades, and charge our mass overnight by opening some strategic windows (thanks, stack effect). If the forecast high is going to be over 90F, we just run the WHF for ~20 minutes in the morning (to super-charge the floors and pre-chill the attic) and for ~30 minutes at night (maybe as much as two hours when we know it's going to be over 100F for >3 days). During heat waves, we've learned to pay closer attention to our timing, open the closet doors, and other tricks to ensure the mass is fully charged.

      My wife is the self-appointed fan-master. She watches the weather report, the pollen count, and the indoor/outdoor thermometer, and runs her own proprietary algorithm accordingly. It might sound a little over-deliberate, but for us it's become as easy and routine as brushing our teeth. It also makes us feel more in touch with the seasons (which may sound strange coming from a Californian, but hey, it's all we've got).

      We've never missed not having an A/C (not since we replaced 64sf of west-facing glass upstairs), except for maybe a few evening hours during the hottest week or two of the year. But for us, that's just a good reason to go out for a walk or drink a glass of wine on the deck until the fan can catch up.

      And at ~$45/month peak electric (PG&E Tier 1 ~$0.147/kWh) if somebody forgets to close a window and we overheat, we can still afford to just take the whole family out to dinner!

      Meanwhile, our neighbors live in a flop plan of ours (1986, 2-story, 2200sf), and sadly their A/C seems to run day & night, all summer long. For us, the noise of their A/C is probably a bigger "comfort" complaint than any we've ever have with our own indoor temperature or IAQ. (Funny what starts to matter as we age.)

      I suspect that our adaptation to our mass radiant conditions (vs. air temperature) and our anticipation of the temperature swing are both key to our perceived high comfort with this admittedly low-tech cooling system. To this point, I recall Danny Parker remarking that his SF Bay Area friends operate their home similarly, which, when visiting from Florida, he finds uncomfortably TOO COLD for summer evenings. To each his/her/zir own.

      I realize our climate and our behavior are atypical (everyone's is), but I'm curious where the cross-over point for this technology really belongs (particularly now that sealed, insulated, variable-speed, and sensor-controlled models are coming onto the market). The few formal technical assessments of these devices that I've seen to date strike me as a good start, but inadequate, and I suspect probably too conservative to estimate their true potential when installed and used properly. I'm encouraged that some others in other climate zones are curious about this too.

      If anything, this discussion proves that we still have a long way to go before "home energy pros" are in consensus about what measures to recommend to a public even less informed than we are.

      Thanks everybody for another spirited discussion!

  • My parents built a split-level house in the '60s that had a large, belt-driven whole house fan with louvers in the ceiling of the 2nd floor. It was right beside the pull-down attic stairs. In the '80s they had AC installed (in the attic) and one of the returns was in the same hallway ceiling as the stairs/WHF. They rarely used the WHF as there are few nights here that are cool enough (and dry enough) where the fan improved comfort. Their second floor was extremely uncomfortable in Winter (Mid-Atlantic state). A couple years ago my father and I removed the stairs (created an insulated/gasketed hatch panel) and created a R-36 foam box to cover the entire WHF. That and adding additional attic insulation, sealing some gross leaks and some duct sealing made the upstairs much more comfortable.

    The take away for me is that WHFs are mainly dependent on climate (my brother/sister-in-law have one in the Bay area (no AC) and it works real well for them), proper attic ventilation to match the fan flow, and - a topic that has not been voiced here - neighborhood security. If you live in a home where the open windows are available to home invaders (and this is becoming a very likely scenario in all places, not just urban) then the reduction in cost of operation vs AC is much less valued than the security of using AC. If you are using a WHF to only cool off the upper-floor(s) at night (again, maybe for security reasons), then you probably need a much smaller fan capacity (to match the input area) vs the "whole house"; maybe a window fan exhausting air while opposite-room windows admit outside air will work just as well and be far less costly, invasive, and impacting to your pressure/thermal shell. It all depends...

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