Whole House Fans

Steve_Slota

I am seriously considering installing a Whole House Fan. I have a friend that had one in the gable of his ranch. When he turned it on, louvers in his hallway ceiling opened up (via the suction of the fan) and cooled both the living area and attic. Everything that I have been reading and researching, suggests that I put the whole house fan itself in the ceiling of my hallway. I also have a ranch. I'd prefer a belt driven fan in the gable, especially for the noise.

I am trying to kill two birds with one stone here. My attic is poorly ventilated and very hot. I would like to be able to cool everything down (house and attic) or, put a cover over the louver in the hallway so that I can cool just the attic in the summer without sucking out the air conditioning from the living area.

If I were to put the fan in the gable, do I put it on the opposite side of the house as the hallway louver? Do I need to add more venting in the attic?

I welcome any input. Have a great day!

ethicalpaul

You'll need enough venting in the attic to expel the air.

A home inspector friend of mine said they were not good, but that was in Michigan where the concern was sucking in a bunch of humid outside air throughout the house and into the attic. I imagine they are better in hot dry climates.

The houses I have had that had them had nice louvers in the ceiling (of a hallway) and they did a decent job of preventing unwanted leaking. The AC doesn't want to rise to go up there.

Since you would need the attic venting anyway, maybe just try improving that situation first and see how much better things get.

STEVEusaPA

junk...
Properly insulate and vent the attic. All you'll do is pull in outdoor pollutants, making your house dirty and dusty.

But the serious consideration is putting your house in a negative draft situation, which will affect/downdraft other appliances and fireplaces, which is bad and dangerous.
I had a call from a person with a whole house fan, and an oil fired boiler with domestic coil.
Their boiler was having nuisance lockouts and there was soot around the boiler in the basement, and the other companies couldn't figure it out/fix it.
Before I even went into the basement I saw the louvers in the ceiling. The basement door swung into the basement, and with the fan running would pull itself shut at 3".
Cleaned the boiler, disconnected the fan, never a problem again.
If that was gas or a gas water heater, they could've been killed by CO

The big problem is in the shoulder seasons, you can get cool enough to run heat, but early morning sun beating on the roof triggers the attic fan, so both run. And a domestic call can happen at any outdoor temperature.

EBEBRATT-Ed

I would insulate the attic floor well. Install a gable end fan of the correct size to vent the attic. Add venting on the far end gable. This will cool the attic and keep the house below cooler.

If you put a "whole house fan" in you can cool the house somewhat but you have to be consious of it's pitfalls as @STEVEusaPA pointed out.

Leon82

My parents have the 36" fan in the gable and louvers in the hallway. It is quiet that way but if you don't have enough windows open it will have the problems mentioned.

I did mine in the hall but built a 16" tall box and insulated it so it want right on top of the louvers to keep the sound down

HVACNUT

How about a simple attic fan? Installed near the roof peak on the back side and just low enough so it cant be seen from the road if that's a concern. Working off its thermostat it'll pull air through the soffits and vents and suck it out through the fan.
Leave the living space out of the equation.

KC_Jones

Airscape, Invisco, and Tamarack

I love whole house fans, would never own a house without one. If you are an AC fanboy like many, you don't want one.

Intplm.

What @HVACNUT and @KC_Jones say above ^^^^ is exactly what my parents had and what I had as a kid growing up. Worked wonders when in use. The fan was controlled by a simple light switch and was only one speed. They just turned it on when they needed it.
Now a days you can get more fancy with auto on and off and have different speeds. Having a whole house fan is definitely worth the investment.

HVACNUT

> @Intplm. said:
> What @HVACNUT and @KC_Jones say above ^^^^ is exactly what my parents had and what I had as a kid growing up. Worked wonders when in use. The fan was controlled by a simple light switch and was only one speed. They just turned it on when they needed it.
> Now a days you can get more fancy with auto on and off and have different speeds. Having a whole house fan is definitely worth the investment.

Dont lump me in there. I'm totally against whole house fans if there are any fuel burning appliances in the building. A whole house fan and an attic fan are two different animals.

Leonard

I think a fan is a low electricity consumption solution only good for mildly hot days. Not days that are very hot and humid, for that you need A/C to be comfortable , in my opinion, but I'm older.

Here in NH we always had a 20k BTU window A/C in the house, used standing fan to circulate air between rooms. My cousin bragged about how good a ceiling whole house fan was, then had one installed. We went over her house one miserably hot HUMID August day, it was too humid and hot. We were glad to get back to my house that had A/C and pretty dry air

Other issue is with whole house fan have to seal it pretty well in winter. Both from air drafts and conducted thermal losses.

When running the fan need to open enough windows so don't have reduce air pressure inside building, it can suck air down your chimney. Especially a problem if exhaust doesn't have a fan ( gas water heaters). This happens frequent in restaurants from cooking exhaust fans, felt a hurricane coming down a chimney once.

Sam81

I personally have tamarack HV1600 with speed control and timer, love that so much it’s definitely worth a dollar

SlamDunk

Had it in a house I rented once. Loved it!

Leonard

Guess my point is in general it's nice, but it has limits,,,,,,, it can't make a real HUMID hot day feel good.

Brewbeer

Yeah, a whole house fan is good at night when it's not too humid, they work well in central and norther new england, but I wouldn't want to rely on one if I lived in the mid atlantic.

Leonard

My cousin here in NH and old friend in CT had them, nice ...... but still sweated on hot HUMID days.

We have tons of trees shading the house. Before we had A/C we used to open windows all night to cool house then in AM when sun got hot we'ld close up the house tight to keep cool air in .

SlamDunk

Im in NC. Crack a few windows open and its wonderful during nights in the sixties, low seventies. But youre right. Hot humids nights render it useless.

RonnieJ

We had an Airspace unit on our home until we foamed in the attic. I loved it. Pros - if you burned something on the stove, you could air out the house in minutes ;-) We would open windows in each room just an inch or so - this would create airflow everywhere.
The bomb-bay style, self-closing, insulated doors solved any air exchange issues between the house and attic when not in use. Low voltage activated - just close contacts - easy to place on a timer. Efficient fans used little energy. Cons - as mentioned by others, it would draw in pollen in spring, and cause downdraft in the fireplace if you don't have a good seal on the damper. Our boiler has a fresh air intake - so not an issue there - but definitely something to be aware of.

mikeg2015

They works OK on old homes with TONS of windows and a lot of mass and deep roof soffits for good shading.

They worked better when electricity was cheap and air conditioning systems were expensive. Homes before 1940 have >30% window area. I think mine approach 40%. Even high end luxury homes rarely exceed 25% now.

The don’t work well in term of economy on newer low mass construction.

clammy

I m not the biggest fan of them ,when not in use they lower your humidity in the winter and migrate heat to your attic and in the summer when your ac is running they do the opposite . The biggest issue that I have is the possibility of pull a back draft on your chimney while on and while your hot water heater or boiler is running a no no .i have seen it people do not have enough common sense to open there windows just can’t put 1+1 together .been there seen it done w it when I get service calls related to co alarms and whole house ventilators I do that smart thing I take the belt off cut it and un wire the motor done .if some re hooks it there on the hook not me Peace and good luck clammy

Paul Pollets

Exchanging the air in a home is required in the state of Washington. Air must be moved(exchanged) .35x per hour and there are 3 ways to do it, per code...furnaces with a fan timer and dedicated fresh air duct on a damper; HRV's or Whole House fans. If WHF are used, doors must be undercut and fresh air must be provided by make up air in all habitable rooms. It's an inexpensive method but has it's aesthetic disadvantages and noise factor. It never works well or substitutes for air conditioning.

Steve_Slota

Thank you everyone for your input! I live in North Jersey, and want the fan to serve (2) purposes; the first and most important one is to relieve the heat trapped in the attic. This heat tends to seep into the house starting in the late afternoon/early evening. The house is well insulated. It's a prefab ranch that was built with 2x6 walls and 2x10 floors/ceilings. So the insulation in the walls and ceiling is thick. I have a direct vent propane furnace in the basement. No chimney. The 2nd purpose would be to cool the house down quickly when its super hot inside (from the heat of sun all day) when it drops into the 50s and 60s outside at night. My wife and I prefer fresh air over AC whenever possible. We're lucky to not be affected by allergies.

It can be 95F outside, as long as I keep the windows closed, and blinds shut, it stays 68F-72F inside all day. It's not till the evening that the house starts to heat up.

Paul Pollets

An attic fan can be installed with a thermostat attached to vent only the attic once it reaches a certain temp...typically 85-110 degrees. It will remove heat from the attic without having to be connected to the living space below. You'll need 250-500cfm depending upon attic volume.

Dollr

Don't know if this is of any use to you. I installed this fan in a small storage room upstairs that has a double hung window. We love it. It was a simple solution. You can leave it in the window and open and close it as needed (fan off of course). I just open a few windows around the house and it's cool in a few minutes. Doesn't help with your attic heat though. We take it out in the winter but you don't have to. "Air King 9166F 20" Whole House Window Fan"

Leon82

In my own home I installed the fan Lowe's sells. It has a belt drive and came with the louver. It's not crazy loud. But it's not quiet either.

Based on your posts, it seems like you will be happier with the gable unit which requires an additional shutter for the outside and additional labor.

Dave Yates (GrandPAH)

I have seen, first hand, far too many danger issues where whole house fans have been in use. The negative air pressure and energy leaking from home-to-attic can be an issue. New home, panicked call from homeowner stating we almost burned down their home certainly got my attention. The water heater's gas valve and plastic shroud looked like a Salvador Dali painting. Black streaking covered the tank's jacket leading to charred floor joist above. I replaced the gas valve and relit the pilot. Worked without any issues, which had me wondering what had gone wrong. They had added a whole house fan and I asked them to turn it on. The burner was ON due to the cold tank of water. Within seconds, the flame reversed itself and was drawn out of the combustion chamber to the exterior. Next we closed the basement door and repeated the experiment. Same result. Then we opened windows on the upper floor of the rancher with basement door closed - same result. Finally, with upper floor windows open, basement door closed, and basement windows and a sliding glass door open - same results. I have seen the exact same issues in other homes with chimney-vented equipment. The louvers leak energy in winter.

ChrisJ

I need to ask something because it's something that's baffled me for a while.

I often see claims that a cooler attic means a cooler house.

My attic isn't vented, never has been and it has some insulation all of which is in the attic floor. But many areas are 100% bare.

My attic gets upwards of 130F in the summer and yet the ceilings in the house don't get hot. Not even warm to be honest. When I go in the attic all of the heat is radiating off of the underside of the roof and the attic floor is warm, but you can tell it's not even close to what the upper layers of the space are.

To me, it seems like the hot attic has little effect on my conditioned space and I would think if I actually had a respectable amount of insulation it would have even less.

The A\C equipment I installed up there is a whole other story, that is effected and I know it is.

Are the claims of attic temperature effecting the space below it in the summer bologna?

Leon82

I have been told it helps the shingles last longer. Not sure if true

ChrisJ

Leon82 said:

I have been told it helps the shingles last longer. Not sure if true

Yeah,
Yet the companies that offer to spray foam between the rafters claim it doesn't matter.

Leonard

I think hot attic won't heat house much over 1/2 a day because of insulation, but seems likley to make house ceiling hotter over several days or week of hot weather, if no A/C. Insulation only slows the heat transfer rate, thermal mass of sheetrock ceiling keeps house cool in the short term

We have lot of trees so our attic is only ~ 112 degs in hot weather. I once gave some thought to putting an old split AC condenser radiator/fan in attic and run water thru it to warm small 10 ft pool. But was concerned it might cool attic too well and run out of heat. Plus electrical/water safety issues.

-------------------------------------
Of course people selling foam between roof deck rafters say it doesn't reduce shingle life, you wouldn't buy it if they didn't. The foam will slow heat loss from roof into house, so roof will run bit hotter

Shingles use a tar like substance to bind hold them together and keep them water proof. So anything that makes them run hotter should increase outgassing of lighter weight molecules in tar and result in drying out /cooking of the tar that binds the shingles together sooner (shorter life). Thats why they sell silver coatings for flat roofs to reflect sunlight and, make roof cooller and last longer .

STEVEusaPA

My fear of foam on the underside of the deck is when the shingles allow a leak, and the plywood gets damaged, I wonder what kind of mess you're into replacing plywood on the rafters.

ChrisJ

STEVEusaPA said:

My fear of foam on the underside of the deck is when the shingles allow a leak, and the plywood gets damaged, I wonder what kind of mess you're into replacing plywood on the rafters.

Use wax paper between the foam and plywood before spray foaming?

Leonard

Problem is you run into the same problem when they put sheet of plastic over the roof rafters for a vapor barrier. NEED the vapor barrier or house humidity condensation in winter can rot the roof deck too.

ChrisJ

Leonard said:

Problem is you run into the same problem when they put sheet of plastic over the roof rafters for a vapor barrier. NEED the vapor barrier or house humidity condensation in winter can rot the roof deck too.

The sheet of plastic doesn't glue it self to the rafters and sheathing.

I think @STEVEusaPA has a good point. However his point applies to every use of spray foam. The stuff is an absolute disaster if any repairs or changes ever need to be done.

ScottSecor

@ChrisJ I did an experiment at my house years ago with regard to attic temperatures with and without an attic fan.
Typical mid-summer heat here in NJ and my twenty year old gable mounted attic fan fails. I let it go for a few weeks and did not notice a significant difference in temperatures on our second floor while the air conditioning was running almost non-stop. However, what I did notice was when we went away for the weekend and came home Sunday night (the a/c was off all weekend) my bedroom (second floor) was significantly warmer that normal.

With the attic fan operational, my bedroom thermostat would typically read about 77-80 degrees when we got home on Sunday evening on a day that hovered around 90 degrees. After the attic fan failed, my bedroom would read about 87-90 degrees under the same conditions.

My point is that in my relatively well built and well insulated home the gable mounted attic fan (with fully vented soffits), the second floor of the house is significantly cooler than it would be without the fan.

With regard to "whole house" attic fans, I am not a fan (pun intended). While it can cool the home in certain conditions, why would I want pollen and whatever else is floating around coming into my living space while stirring up dust that is was hiding somewhere?