Whole House Fans

[Garet Jax]

Hello all,

I am looking to put in a whole house fan. Our basement is sub level and is always cool compared to the rest of the house. I want to try and draw that cool air up and think the whole house fan is the best way to do so.

I am reading competing things online and want to get the story from someone who has installed one or knows them through their profession. Things like:

Where to buy?
How to size?

Thanks a lot in advance.

 

[BoomerD]

I've never seen a whole house fan used this way. Usually, they're designed to draw in cool outside air then vent it up through the attic to get rid of the hot air in the attic.

 

[Scouzer]

I've never seen a whole house fan used this way. Usually, they're designed to draw in cool outside air then vent it up through the attic to get rid of the hot air in the attic.

I've never seen one the way you're describing. The ones in the OP are the only ones I'm familiar with.

 

[BoomerD]

I've never seen one the way you're describing. The ones in the OP are the only ones I'm familiar with.

http://www.wholehousefan.com/HOW-IT-WORKS/Ceiling-Mounted.html

http://en.wikipedia.org/wiki/Whole-house_fan

 

[Garet Jax]

I've never seen a whole house fan used this way. Usually, they're designed to draw in cool outside air then vent it up through the attic to get rid of the hot air in the attic.

Boomer,

What you say is true, but if I open the windows in the basement (there is an egress and two small above grade windows) closing all other windows in the house, then the air from the basement will more or less be forced up through the house since the replacement air is coming in through the windows in the basement.

 

[vi edit]

They don't work that way. You'd have to open windows in the basement to create the proper air flow and then all you are doing is bring in warmer air into the basement to negate the benefit.

They are made to do as Boomer said - to bring in cool air from outside (like at night) to rapidly cool down your home.

I had one in my last house and rarely used it. You had to prop open doors or it would suck them shut and negate the air flow benefits. It had such a strong draw that it would actually pull the stank smelling air from the kitchen sink drain (connected to a septic tank) up and make the house smell horrible. It also did nothing for the humidity in the summer which is about 70% of the overall discomfort.

 

[BoomerD]

Boomer,

What you say is true, but if I open the windows in the basement (there is an egress and two small above grade windows) closing all other windows in the house, then the air from the basement will more or less be forced up through the house since the replacement air is coming in through the windows in the basement.

As long as you have good airflow from the basement to the rest of the house, you might realize SOME benefit from this, but I think it'd be marginal at best.

Keep in mind, whole house fans are designed to move a LOT of air. If your basement windows aren't big enough, they won't allow enough air to feed the fan, reducing its efficiency.

Depending on the humidity where you live, you might also get dryer air into the basement spaces...which is always a good thing for basements.

There used to be "ducted fans" that would draw air from one area and push it to another. Not sure if they're still around or not. I don't think they were terribly efficient either.

 

[Garet Jax]

They don't work that way. You'd have to open windows in the basement to create the proper air flow and then all you are doing is bring in warmer air into the basement to negate the benefit.

They are made to do as Boomer said - to bring in cool air from outside (like at night) to rapidly cool down your home.

I had one in my last house and rarely used it. You had to prop open doors or it would suck them shut and negate the air flow benefits. It had such a strong draw that it would actually pull the stank smelling air from the kitchen sink drain (connected to a septic tank) up and make the house smell horrible. It also did nothing for the humidity in the summer which is about 70% of the overall discomfort.

I have heard and read similar stories and it seems to me that the fan may have been too strong for the house or not enough windows were opened when you were running it.

I agree the humidity is the killer, but the humidity is only a factor for 30%-40%
of the summer. The rest of the time, I believe the whole house fan might have some benefit if run at night or early in the morning.

 

[Azraele]

The house I'm in has a whole house fan. It's noisy, but it's also a great way to quickly ventilate the house. Anyone know how much current these monsters draw? It's an old house, so I'm assuming the fan's not very energy efficient. It has enough suction to open and close doors.

 

[vi edit]

The house I'm in has a whole house fan. It's noisy, but it's also a great way to quickly ventilate the house. Anyone know how much current these monsters draw? It's an old house, so I'm assuming the fan's not very energy efficient. It has enough suction to open and close doors.

Can't tell you exactly...but it's a fraction of what a compressor costs to run on an AC unit. Plus it's probably cheaper to run that single beastly fan than a number of smaller box fans in the windows.

 

[DayLaPaul]

I'm also interested in this subject. I've thought about installing a whole house fan in my house.

I've got a one story that is pretty well insulated. On a hot day, it takes several hours after it's already cooled down outside for my house to catch up.

I would really like to be able to open some windows/door, flip a switch and immediately exhaust all that hot air.

 

[GuitarDaddy]

24" to 36" seems to be the normal size range

What size you get needs to be determined by where you are going to place it and the spacing between joists in your ceiling, They are normally placed in a hallway centrally located in the house. If you need a larger one or your joists are on 16" centers you may have to cut out a joist and build a support box for it.

http://www.google.com/products?hl=en&safe=off&rlz=1T4SUNA_enUS266US269&q=attic%20fans%20whole%20house%20fans&um=1&ie=UTF-8&sa=N&tab=wf


I have a 36" 2 speed unit in my 3600sqft 2 story on high it will completely clear the air in the house in about 3 minutes

 

[rockyct]

I've never seen a whole house fan used this way. Usually, they're designed to draw in cool outside air then vent it up through the attic to get rid of the hot air in the attic.

My parents have a setup like you describe. They seem to really like it. It's a nice way to cool down the house if it's cooler outside than inside.

 

[Garet Jax]

24" to 36" seems to be the normal size range

What size you get needs to be determined by where you are going to place it and the spacing between joists in your ceiling, They are normally placed in a hallway centrally located in the house. If you need a larger one or your joists are on 16" centers you may have to cut out a joist and build a support box for it.

http://www.google.com/products?hl=en&safe=off&rlz=1T4SUNA_enUS266US269&q=attic%20fans%20whole%20house%20fans&um=1&ie=UTF-8&sa=N&tab=wf


I have a 36" 2 speed unit in my 3600sqft 2 story on high it will completely clear the air in the house in about 3 minutes

Well this is one of the confusing parts. There seem to be products available that fit between a standard 16" on center joist and therefore do not require cuts to be made.

 

[Rubycon]

Well this is one of the confusing parts. There seem to be products available that fit between a standard 16" on center joist and therefore do not require cuts to be made.

That is too small for a conventional fan. 24" would be the minimum for a "whole house" fan and can be mounted between rafters as they fly 24" apart IIRC. Larger fans can be fitted by cutting and reframing with cripple cross members. 36" is a decent sized fan and can be run at slower speeds (quieter) yet still move a decent amount of air.

Typically what happens is the attic is pressurized and the hot air is relieved through the gable louvers or ridge vents.

Cooler outside air of the evening time is drawn in through open windows. Even when it's cooler outside and there is no breeze you can experience higher comfort without running expensive a/c compressors.

Basements may be cooler but this source of coolth is hardly infinite. Once the warm air of the mid day is drawn in to the basement it will quickly warm up to surrounding temperature.

 

[dabuddha]

My attic gets really hot (no fans installed by the cheap ass previous owners) and I have two gables (one on each end). I was thinking I could install two gable fans (one sucking air into the attic and the other one blowing the air out of the attic) Is this overkill/dumb and if so, would a single gable fan blowing air out be sufficient? My upstair bedrooms get very hot even with the AC on. The other thing I plan on doing this summer is installing ceiling fans in all of the bedrooms.

 

[db]

The ceiling joist spacing does not matter since the fan does NOT fit "between" the joists, but rather sits on top of them.

But there is a problem with whole-house fans in general: the air being blown out of the attic's eve vents gets sucked right back through the windows below them. That means that all of that decades-old dust, spider webs, dead insects, etc, along with insulation in your attic, is being blown from your attic and sucked into your living space through your open windows, and continuously re-cycled.

(The above applies to a typical home which has both eve vents and roof vents).

 

[db]

dabuddha, the outside wind direction can change and your fan/s might be fighting the wind direction, ie trying to blow out when the wind is trying to blow in.
You can install more vents or replace existing vents with larger vents.

As for ceiling fans, they are well worth it.

 

[Rubycon]

LOL what kind of fan can blow so hard that dust from the attic would come out of the vents and get pulled in through the windows? Usually people have screens on their windows too.

The fan I remember was definitely framed in and large (four feet?). To feel a breeze only half the windows could be opened and that about half way. But it definitely worked to cool down the bedrooms at night.