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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IS THE JUICE WORTH THE SQUEEZE?  What are we saving?  Show me the numbers!  

Buying something you want then placing the label "energy saving" on it without proof is harmful to the energy efficiency industry.  Suggesting "might save something" improvements is a low rigor low integrity product selling approach rather than solution approach.  It is exactly why the public thinks EE and Home Performance are promises without substance.  Currently they are correct.  

If people make cost benefit decisions based upon the claim "saves something", is that good for them or our industry?  I think we should do everything in our power to avoid attaching our names to such recommendations so we can move from selling snake oil and false promises to becoming a profession with integrity. 

Charlie, you are a person I know to have high integrity.  I hope you do not fall into this trap.  There is no scientific method here.  You don't see Mike MacFarland making false promises.  He GUARANTEES energy use of his retrofit projects. 

If you can't be accurate about "savings"  don't claim it saves. If you failed first grade math, don't talk about the savings "you saw."  If you saw savings, provide the case study and show what rigor was applied.  Nobody expects MIT phd level statistics, but a sense of due diligence efforts will allow us to determine confidence level. 

I see a lot of backward looking justifications.  People NEVER want to admit they've done something "stupid."  But let's face it, we all make stupid decisions all the time.  That's human.  

I get people buy toys, then attempt to justify their high cost with "it's saving me enough to retire on" fallacies. I say buy your toys and don't worry about justifying them.  If you must justify them, do the math with more rigor than a first grader and stop saying things like "I believe I'm saving."

William Ramsey:  I think a lot of your conditions start to exclude you AND the majority of people as candidates for these fans.  Be very careful of people talking about potentially esoteric unquantified benefits then claim/imply there are also measurable savings that amount to something meaningful.  Just because they bought into the ponzi scheme doesn't mean you should come in behind them.

Got a crappy house?  FIX THE HOUSE!

Got crappy AC?  FIX THE AC!

WHF are best for people too cheap to fix things.  People looking for shortcuts.  Go ahead if you don't have AC and don't have combustion appliances.  (Beware: If you are in moist climates, having cool surfaces may be adding more cost than you think.)  


It would be best if you offered valuable comments on this forum like others do. 


While I agree with fix the house anywhere in the country before adding measures. AC is not installed in many homes here in Southern California which includes mine and Kurt Shafers area. Moisture is normally not a problem we are a warm dry climate very different than wherever in New York you are. I think on is not being lazy by investigating the benefits of a system to reduce heat load in a home.

Looking at  weather Data for Temecula Valley there is a historical more than 30 degree swing each day from hottest to coldest in the month of August.I think one would be foolish not to consider it as an option.

As far as complication of design and installation it is far less complicated than a central air unit. 

The energy to operate watts are far less as well.

Before you label horse and buggy and claim there is no juice to squeeze you should look at it regionally rather than from the perspective of your own climate.

While I am not in love with these units as I have mentioned in my blog for the reasons I put forward that does not mean that they can not work. I think a properly designed unit operated correctly can be a huge benefit in our area.Using the prevailing climate to provide comfort.

I have instead of using a whole house fan employed other methods to avoid AC installation. A shade tree on my west face which took some years to work but with a little water the acorn is a tree. A trellis on my south side to provide beauty with climbing vines and shade. Air sealing to disconnect my attic from my conditioned space. More attic insulation to reduce thermal transfer.

Wall insulation which did not exist in the home before I blew it in. Dual glazed windows with low e to reduce solar gain. The windows were also a ascetic upgrade as my wife wanted new windows regardless of energy. A solar power gable fan to exhaust air from the attic when the sun is shining. Ceiling fans for comfort when in the room. When the temperature reached the mid 90's last week my home never went above 78 degrees. I open the windows at night and flush the home with cool night breezes and close during the day to keep my cool thermal mass. 

During the dog days of Santa Ana when night temperatures remain high I suffer a bit and complain. But with a modern state of the art AC costing in the 10k range installed before I turn the power on it and a cost in tier 4 cost of almost 30 cents a KwH and one cannot run AC without getting into Tier 4, I choose to suffer a couple of weeks out of the year and enjoy the extra cash on other things I deem more important



You have done a lot to improve your home. You might be intrigued by the upgrade I am planning for my 2 story here. I have applied for and received permission from my HOA to install a ridge vent. This will be one of the first in Temecula and the first on my block. 

I am installing Atticfoil.com radiant barrier to all roof rafters with a gap at the bottom and at the top of each rafter channel. Last I will drill more soffit vents - at least one or two per rafter channel. 

I have been monitoring my ceiling each day and it is getting into the 80s and even low 90s by the end of the day. I have plenty of insulation but the heat goes right through. 

The radiant barrier is dramatic. The day I put in 1/4 of the attic (about 500 SF) the roof was 102 F underside and dropped to 85F on the bottom side of the foil. 

I am sure that this will dramatically reduce my home's hot surfaces - mainly the ceiling. 

My walls contribute very little and I have dual panes and window shades. 

I will be posting updates on wholehousefanguy.com and invisco.com


Radiant barrier certainly works well when installed as you are doing. you should meter attic temperature before and after for a delta. Make sure the outside temperature is also included.  Kudos to your association for allowing you to perform the ridge vents.

My projects were not done all at once. Well before I got started in this business I was worried about comfort.The tree was planted about 15 years ago. At that same time I did the trellis project and installed a gable fan. This was electric and kicked on when the attic was 110 degrees. I noticed an immediate difference in the home as I performed this in Summer. The windows were not done all at once. My single glazed aluminum windows were not only ugly but were extremely leaky. When the wind blew in the winter I could hear the operable slider shake and feel the wind gust in. I did not need training in building science to conclude the window needed replacement. The rest followed with other projects. My method was like eating an elephant. One piece at a time as we had the cash to perform the tasks

The insulation and air sealing was performed after my training. Also I switched to the solar gable at this time. Not only did I reduce watts used but reduced the cfm as well. No risk based on the fan size and my openings of depressurizing the attic. The higher AC fan certainly moved more air but the solar fan is more than adequate and my attic stays cool. My gables have a north south facing and the unit is on my south side. With the west to east prevailing breezes I pull air from the north cool side and out the south. Nature helps with the wind.

Good luck with your project. Post your blog here on HEP with pictures of course.

Cool! Radiant foil in a retrofit.

Sounds like a quick/cheap DIY job - Just be careful and don't fall through!

"William Ramsey:  I think a lot of your conditions start to exclude you AND the majority of people as candidates for these fans.  Be very careful of people talking about potentially esoteric unquantified benefits then claim/imply there are also measurable savings that amount to something meaningful.  Just because they bought into the ponzi scheme doesn't mean you should come in behind them."

Ted, could you please rephrase your comment.  I have no idea what you're talking about.  What's the point?


Where are you? I am in Temecula. Hot days, cool nights. 

You are right on with ducted machines and multiple speeds. I am guessing you have QC based on your watts. 

Have you seen the SmartSpeed automatic speed control and infinite speed motors?

I have been in the building business since 1972 installing whole house fans since 1999 and training in all sorts of energy efficiency and greenbuilding since 2001.

I would say; and do, that the two examples ( this and this) are irrelevant as the situations were for various reasons extraordinary for any appliance of that type.

I do not do any fresh installs of the old style whole house fans.

Only if I have to replace an old style whole house fan I will use the Triangle fans http://trianglefans.com/whole-house-fans/ but have to get higher quality louvers than come with the fan.

They also work fine in a leaky house with people who are fine at 80 degrees - never using A/C is not losing money over it. if they are in a climate suitable for whole house fans.

The Triangles' 2' x 2', 30" x 30", or 3'x3' hole in the ceiling which has no R-value and leaks in winter and summer.

I put in Airscapes 98% of the time - they are strong, built with parts that are reliable and very; very: quiet. They have strong motors on the doors and seal adequately enough for the penetration to not make for significant cooling loss in the summer or heat in the winter. http://www.airscapefans.com/products/Shop/Natural-Cooling/Whole-Hou... 

(Kohilos do not have electrically operated doors)

Air volume replaced is 1,700 cfm - 4,400cubic ft per minute (the 1,000 cfm is only for places that can't take ANYTHING else).

The super high cfm (cubic feet per minute) old style fans don't cool any faster unless you have a huge house and often roof venting is inadequate for them so there are health risks to impropr installation apart from blowback of heat from the attic into the house.

Their cfm statements were tested by outside labs and are therefore more accurate than most others - I think they still do it that way (check details on all fans you look at and find out if they have independent testing)

They ship direct so the fans cannot be marked up by middle men - they are not cheap but are easier to install than the old type. If you have been willing to buy a new car to get to work and back a few hundred dollars does not compare to the thousands that drop of your car value the first hour of use and the comfort of a home you've been living in for years is more important looking back than a car you got rid of a few years ago.

I'm in the Sacramento valley with its mild climate and often evenings in the 70s and a delta breeze from the sea these are ideal. Further south - if it's 95 at night they are useless.

We have cool mornings most of the time so bringing in the morning air will cool the sun warming the attic till 9-10 am sometimes lengthening the heat penetration time - cutting off A/C time. In the winter, if it's colder in than out , you can bring in the warm air.

In the areas that are right for whole house fans:

It is important to have (after a short blast of high speed venting to empty attic air)

Then have a continual flow of cooler air to carry away the heat generated during the day in the house and especially the attic (hereabouts 150-160 degrees often - attics are a perfect solar radiators in the summer when you don't need it) all the trusses insulation and joists have to cool down over time. Like 4-8 hours.

This is why quietness and low power consumption are important.

If you are in an area where whole house fans will save you money and energy - check the wattages of all the models especially on the lower speeds - some are 25-50 watts per hour. When contemplating solar panels the extra cost of ultra  low wattage whole house fans will become more and more important - especially with the increasing price drop per watt and especially when solar is cheaper than coal and China has scaled up their production again a few times. I also have a strong feeling that USB 4.0 will be a big game changer - producing low volt - low watt appliances and energy independent houses and offices

There are gadgets that can help make life easier that can be added on - remotes etc. 

There are also extensive installation instructions. 

Attic Fans: Expelling air from the attic during the day with attic fans can often help things out although most experts will disagree with me. I was able to test and get results in a few places I installed attic fans - anything that increases the time it takes for heat to penetrate the insulation in the attic helps comfort and A/C bills. 

For properly built actual super insulated houses I would not recommend a whole house fan they adjust environmental temperature with so little energy cost and should vent passively. 

I don't know for sure but people with allergies may not be able to use them even with the pollen filters. 

As far as priorities: 

Sealed HVAC duct systems (tests available)

A well sealed attic (and rest of envelope)

Properly installed insulation (rare in existing houses and many new ones also)

Correctly sized air conditioners (many are oversized)

Well designed duct and HVAC system (difficult to find a skilled designer - checker)

Then a whole house fan where it is a good climate proposition (unless you are an 80-90 degree person like me in which case it can be #1 priority)

(All appliances and lights are presumed up to date on efficiency as the effort to change this factor is so small)

Great information, thank you!

ABOUT ATTIC FANS - Special Cases

In some houses attics gradually get hot during the day especially with the right configuration of trees and sun. Then the attic heat starts penetrating the house before sundown and the house continues staying hot until 11-12 at night when the hot air finally vents passively from the attic (passive venting is not reliable or that effective in many cases - spinners look interesting but often do not function to any great effect).

A WHF will take care of this.

However an attic fan with a thermostat will cost much less, be easier to install and do what is necessary using around 200 watts per hour (only during the time the fan is turned on by the thermostat).  

It will cool the attic and therefore the house without any windows open and independent of the t (in this case the temperature difference between the outside of the house and the inside living areas) it's only actual 'concern' will be the temperature of the attic based on the thermostat setting.


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