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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Whole house fan basically serves the purpose of exhaust fans. They are more cheaper than air conditioners ad they can lower the temperature of your house more rapidly. They are best for roof ventilation also.

In Connecticut’s climate, I am not in favor of them .

Either they are the big old style that move 3-5000 cfm and are not easily insulatable, or they are newer ones that seal  and are somewhat insulated, but move a lot less air.

I just finished ripping one out and re insulating/ patching the ceiling this morning.  Matching a textured sand ceiling is no fun.

If I was  in a predominantly low humidity area where the winters were mild, I might think differently.



That makes sense. This is one of those technologies that helps remind us that climate drives everything. (No one ever doubted this before old Willis Carrier started "treating air".)

Even so, I'm hopeful that the addition of proper air sealing, insulation, and controls might make them a cost-effective option to consider, even in some hot/cold/humid areas.

You must have at least some hours of the year when it's more pleasant outside than in, no?

I was aware of but unfamiliar with them until moving to Southern California in 2012. Now, after having seen several dozen of them, I can get behind their theory of operation, although I don't like the trade off of a compromised thermal boundary. From the first link in your post, it appears that models with insulated dampers on the exhaust side are available, but I've never seen a well-insulated whole-house fan period, let alone one of those.

If I were doing an insulation retrofit on an attic that had one, I might try something like this

I'm also concerned about the installation quality I see on some of them. Below is a recent picture of a ducted fan where the duct had almost completely separated (this was completely ignored by the HVAC contractor who had just installed a new furnace a few feet away). Makes me wonder what the homeowner thought when they turned the fan on but their house didn't cool off.

Another project had four 1500 CFM fans installed in a 900 sq ft attic with just a handful of eave vents. Eleven more vents had to be added to bring it up to the manufacturer's minimum recommended total ventilation area.

Bottom line, I think that for climates like California, they're a great concept for that needs some perfecting. (I've been known to set up my blower door on summer nights where the mercury's higher than I like -- works just fine on my 600 aq ft apartment!)

Excellent snapshot, Griffin. You didn't happen to notice the fan manufacturer's name on this one, did you?

I am more familiar with the traditional louvered units that install in the ceiling plane, but I have been interested in these newer remote-mount (ducted) models, primarily because they promise so much less noise pollution. However, your picture is worth a thousand words because it clearly demonstrates a design flaw that needs to be addressed.

Your comment about inadequate exhaust vent area is apt too. That's why California now requires verification by a HERS rater (new construction).

Looks like an Airscape - basically improperly installed - probably after any HERS or building dept oversight was gone - not that people might notice a duct that is missing a key component but that will fall apart after a few weeks. The HVAC man probably did not notice it or use deductive reasoning as he may not have really focussed on what it was - seemingly not part ofhis task.

Thanks for the plug on my video, Griff! I liked the Dubstep one, though... It's still not a perfect solution, but better than nothing. 

Nate, no kidding, I didn't realize till just now that was your video! (I guess I should pay closer attention to my sources.) It's orders of magnitude better than 99.9% of what I see out here, and I've shared it recently in our community to inspire similar solutions. Small world!


Tom, great new post! Thank you for the focus.

As you know, the term "whole house fan" is a unique "long tail keyword" that describes a very specialized ventilation system. 

For the record, the CEC IS just about the most comprehensive list of fans you can find. The primary reason is that the CA Dept of Energy requires ALL whole house fan suppliers who want to sell their systems in CA to be listed on their list. 

Getting listed is not simple. CA refers to HVI916 and requires that all fans submitted for listing be tested and certified to the detailed air flow measurement method specified by HVI. The average price for the test if done by a third party such as a lab in Texas is about $1,500 per model. 

The list contains every whole house fan supplier in the U.S. as far as my research shows. So it does represent the present state of the art. 

Another resource is http://www.WholeHouseFanGuy.com

About emerging technologies, there are some that are not on that list. Most notable are the NightBreeze and SmartVent systems that are now part of the State of CA Title 24 that was just updated and released July 1 2014. Those systems integrate into HVAC systems to provide fresh cool evening air for circulation through the HVAC ducts when the temperature outside is cooler than inside. Another system nearly identical to the SmartVent is FAMCO's IAQ (indoor air quality) system.


Is this really the link you offered?


About compromising the thermal boundary, there are two sources for very effective R rated ceiling interfaces - one offers a clamshell motorized damper they claim is R50 and the other has a thermally broken dual damper. Both are designed to meet the new 2012IECC recommendations for attic insulation in new homes.


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