Fire and ceiling-to-attic fans

[Stephen Tashiro]

I've seen a few houses that have "attic fans" in the sense of fans in the ceiling of the room that blow air into the attic. Such a fan creates gap in the fire barrier that a ceiling makes between a room and the attic. Is there a way to frame for such a fan that reduces the fire hazard? - or are such fans just a bad idea?

[Dan Hintz]

Maybe I'm not understanding you, but why would anyone blow conditioned air into an unconditioned space?

[George Bokros]

These fans are used to pull cool night air in through the windows and exhaust the heat into the attic. You would not use this and A/C simultaneously. This is an old method of cooling the house.

[Brian Elfert]

You still see older houses with these in Minnesota although most have A/C now for the 50 or 60 days a year you might need it. Newer fans like these have good shutters so heat doesn't escape in the winter. The shutters would keep fire out too if the shutters are flame resistant.

Is fire in the attic really that big a deal? Fire usually spreads upwards so other rooms shouldn't get involved through the attic. If there was an issue with these I think fire marshals would have had them outlawed long ago.

[Jason Roehl]

They're somewhat common around here in houses build in the '50s and '60s without central A/C, known as "whole house fans". The idea was that you would run them at night or early morning when it was cooler to draw lots of cool air into the house (they're quite large and somewhat noisy--fans are typically about 3' diameter and move some serious air), then the house would be shut during the heat of the day. They're most effective when coupled with houses that have the wide overhangs with windows tucked up under them to not allow much sun into the house when it's high during the summer.

The downside is that your window screens had better be good, or your house will be full of bugs.

[Jim Matthews]

I investigated this as a supplement to passive cooling strategies.

The consensus here (at 41 degrees North, Atlantic coast) was that
it would be more efficient to put a radiant barrier in the attic.

The theory is that it reduces the amount of heat radiated by the structure
into the conditioned space below, through the night.

Between that, reflective film on the South facing windows and closing windows
in the house on really hot days, it's been effective.
(And purely passive - no electric motors.)

As mentioned above, there's no pathway between the spaces and no
perforation for fire to breach the ceiling.


*****

As has been pointed out by some active Firefighters on this site,
it's largely a foregone conclusion if you can't put out small fires
with a household extinguisher - modern materials burn quickly.

[Mike Henderson]

I added a "whole house fan" to my house. It's really not "whole house" because the CFM of the fan is too low.

Around here, the temperature drops quickly once the sun goes down so my idea was to pull in cool air before we went to bed and maybe to let it run all night with the windows cracked. My wife, however, objects to the noise at night so I only use it before bed. It works okay - not great. You need a minimum of 10 degrees F between the outside temp and the inside temp for it to do any good, and a greater difference is better. I close off the rest of the house and just use it to vent the bedroom.

It has shutters that close when the fan is off. The shutters are thick insulation so the heat doesn't come down when you're not using it and I expect they are fire resistant.

I grew up with whole house fans in the south and that's why I added one to my present house. But I don't know if I would recommend them. It would depend on your environment and temperatures.

Mike

[John Lohmann]

When I was a kid in GA, 1965 or so everyone had a big fan in the attic, crack the windows & you got poor mans AC. We had it in GA & at my grannies in NC. If you didn't you just sweated a lot at night

[Brian W Smith]

We love ours......30 y.o. and counting.I thinks there's an assumption here that attics are not living spaces?Ours is arguably the nicest rm in our 1810 Federal,2 story(attic is a complete 3rd fl).The "whole house" part of the system applies to us because it's part of a larger HVAC planning.We simply cover it with foiled HVAC blanket in the Winter......and make sure to pull the controls,so it can't be turned on.

[Brian Elfert]

We love ours......30 y.o. and counting.I thinks there's an assumption here that attics are not living spaces?Ours is arguably the nicest rm in our 1810 Federal,2 story(attic is a complete 3rd fl).The "whole house" part of the system applies to us because it's part of a larger HVAC planning.We simply cover it with foiled HVAC blanket in the Winter......and make sure to pull the controls,so it can't be turned on.

How does a whole house fan help if the attic is living space? Does it exhaust outside instead of into the attic? I've personally never seen a whole house fan except in a house where the attic is not living space.

[Bill Huber]

I love attic fans, the house I am in now is the first house that I have owned that didn't have one, I bought my first house in 1969.

The one thing you need to make sure of is that you have enough vent area for the fan to exhust out of the attic.

When I moved to Texas in 1986 and bought my house it didn't have one and most of the houses here don't. The first thing I did was to install one, it is so nice in the spring and fall to open the house and get a nice breeze blowing though.

All my fans had good shutters on them and I also had covers that I put on in the winter and summer. I also had a timer on them so I could turn them on when I went to bed and they would turn off after a few hours so you didn't wake up getting cold.

[John Huds0n]

Here in S Cal, "whole house" fans works great!

The idea is to create a draft to cool you off once the outside temps go down. Open a window so that the cooler incoming air flows across you and towards the fan.

This is what the newer style looks like (what we have) versus the older centrally located type. You have a grate in the ceiling followed by about 6' of flexible ducting and then the fan assembly - which hangs from the attic joists and greatly reduces the noise and vibrations
fan.jpg

http://www.wholehousefan.com/product...FUKCMgodlA8AFA

[Art Mann]

My current house has such a fan. I sealed it over just a couple of years ago. We used to turn the A/C off in the evenings and run the fan the whole night. It was a cost effective way to keep cool at night and during mild days in the spring and fall. The problem with it is that the air isn't filtered (except for the window screens) and it pulls in all sorts of dust and pollen. Also, no matter how good the louver is, the 3 foot square hole in the ceiling is only covered by thin aluminum and I think we were losing a lot of heat that way in the winter. I am glad I sealed it over though I do occasionally miss the switch operated strong breeze it created.

[Mike Henderson]

Here in S Cal, "whole house" fans works great!

The idea is to create a draft to cool you off once the outside temps go down. Open a window so that the cooler incoming air flows across you and towards the fan.

This is what the newer style looks like (what we have) versus the older centrally located type. You have a grate in the ceiling followed by about 6' of flexible ducting and then the fan assembly - which hangs from the attic joists and greatly reduces the noise and vibrations
fan.jpg

http://www.wholehousefan.com/product...FUKCMgodlA8AFA

That's essentially the one I have - made by Quietcool. Two problems: It's not quiet and it doesn't draw enough air to cool more than a room or two. The main source of the noise is the air noise coming through the grate in the ceiling. I called Quietcool before I bought the fan and they assured me it was so quiet that I could install it in the bedroom and it would create no more noise than an air conditioner. I installed it in the hallway outside our bedroom and it makes enough noise that my wife refuses to sleep (or try to sleep) with it running.

The second issue is that it just doesn't move enough air. Even if you had a 10 degree difference between the inside and outside, it would never cool the whole house down. I block off the hallway so that it only pulls air through the bedroom and bath and that works okay.

Don't buy one of these thinking it will work like the large (say 36") whole house fans that you may have known in your youth.

Mike

[Ole Anderson]

I have a "whole house fan" I installed at least 35 years ago. Works well here in SO Michigan, gets used maybe 10 days a year, about the same as our A/C. Usually run it for an hour or two in the evening on days not quite hot enough to run the air. Noisy but it pulls massive amounts of air.