I'm thinking of putting 1 or 2 whole house fans in the ceiling of my 20 x 50 RV garage to get rid of some of the summer heat. Would it be better to put one near each end or a single larger capacity fan at the center? The single fan will cost less but I'm wondering if I'll get better air exchange with 2 fans. The total cfm will be about the same either way.
Whole house fans
- Thread starter Al G
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Walkers
Well-known member
Due to the nature of radiant heat transfer those fans are not quite as effective as you might believe. Your money is probably better spent on insulation.
Shiftless
Well-known member
I have a single 24 inch whole house fan roughly in the center of our 2000 square foot house. It’s powered by a 1/3 HP Dayton motor and I’ll tell you that it pulls plenty of air from the windows I open on the cool side of the house. It blows into the attic and then out through eave and gable vents.
If you don’t have insulation, I would install that first, just like Walkers said. In your case, I bet one fan would be just fine as long as you provide vents down low to admit outside cooler air.
If you don’t have insulation, I would install that first, just like Walkers said. In your case, I bet one fan would be just fine as long as you provide vents down low to admit outside cooler air.
It's already fully insulated.
Shiftless
Well-known member
Insulation in place... great!
Just put in big vents that you can open or close to admit cooler outside air from the cooler side of the garage depending on the time of day..
Just put in big vents that you can open or close to admit cooler outside air from the cooler side of the garage depending on the time of day..
like2wheel
Well-known member
Im sure one is fine, the circulation will be more about where you let the air in from & it's easier to get complete air changes the farther the window is away from the fan.
Be aware that the shutters don't seal very well at all if you ever need to retain heat.
For my house, I hinged the shutters, & the fan, and made a plug with door seals around the perimeter for the heating season. It doubles as attic access for me.
Maybe not an issue in your climate, but thought I'd mention it in case.
Be aware that the shutters don't seal very well at all if you ever need to retain heat.
For my house, I hinged the shutters, & the fan, and made a plug with door seals around the perimeter for the heating season. It doubles as attic access for me.
Maybe not an issue in your climate, but thought I'd mention it in case.
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jack stand
Well-known member
Are you insulated under the roof deck or on top of a ceiling?
Is the building surrounded by concrete or asphalt?
Ventilation in an attic can be very helpful, but drawing in hot outside air off of the blazing hot heat reservoir into your workspace...
You may be ahead (if you have a ceiling- attic condition) to ventilate the attic and keep the insulated interior closed and run some ceiling fans.
Is the building surrounded by concrete or asphalt?
Ventilation in an attic can be very helpful, but drawing in hot outside air off of the blazing hot heat reservoir into your workspace...
You may be ahead (if you have a ceiling- attic condition) to ventilate the attic and keep the insulated interior closed and run some ceiling fans.
cvairwerks
Well-known member
If you are doing this to exchange air, just remember that your area for incoming air has to be larger than the exhaust area, or you will get lots of induced noise....
Walkers
Well-known member
Then where is the heat coming from?
My question was simply which option would provide better air exchange - 1 or 2 fans. Since there has been a lot of speculation and assumptions I'll provide a few more details.
The garage walls and ceiling are fully insulated. The attic is vented sufficiently to allow a fan capacity of about 5000 cfm. I live near Phoenix so the garage gets hot (low 90s) when the afternoon temperatures can be over 110. Even then the mornings can be in the 70s or low 80s. Opening the overhead door and the 2 man doors at the other end can drop the temperature 5 degrees if there is a little breeze. I want the fan(s) to bring in more outside air to drop the inside temperature closer to the outside temperature if I'm going to be working in there for a while.
So I'm back to my question of whether I'll get better exchange with a fan at each end or a single fan in the middle, assuming the total cfm is approximately the same in both cases. Thanks for the responses that did offered an opinion on that.
The garage walls and ceiling are fully insulated. The attic is vented sufficiently to allow a fan capacity of about 5000 cfm. I live near Phoenix so the garage gets hot (low 90s) when the afternoon temperatures can be over 110. Even then the mornings can be in the 70s or low 80s. Opening the overhead door and the 2 man doors at the other end can drop the temperature 5 degrees if there is a little breeze. I want the fan(s) to bring in more outside air to drop the inside temperature closer to the outside temperature if I'm going to be working in there for a while.
So I'm back to my question of whether I'll get better exchange with a fan at each end or a single fan in the middle, assuming the total cfm is approximately the same in both cases. Thanks for the responses that did offered an opinion on that.
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In Ohio we get all kinds of weather and we do both with insulation and Heat/cool.
Air movement is very important along with controlling humidity up or down.
I my Garage I have a Wall exhaust/Fume Fan I installed 40+ yrs. ago that I use all the time.
Remember air in as well as Air out no matter what the Temperature.
Good Luck.
LtF
Air movement is very important along with controlling humidity up or down.
I my Garage I have a Wall exhaust/Fume Fan I installed 40+ yrs. ago that I use all the time.
Remember air in as well as Air out no matter what the Temperature.
Good Luck.
LtF
danski0224
Well-known member
I'd put the fan the furthest away from your anticipated relief air opening location. That way, outside air should be pulled through the whole space.
I guess if you put 2 fans like your suggesting you're still moving air! In my situation and as others were saying some of us bring in fresh air to replace the existing air. In the heat as your describing maybe that's not your best option. If you choose not to cool your air and you want to just circulate the existing air, I don't see anything wrong with placing 2 fans like your thinking.
Good Luck,
LtF
Good Luck,
LtF
I had a WHF in our MA home at the head of the stairs. It was summer operation only and in the fall I had a @“ Ridgid foam insulation box I’d drop over it. Once the sun was low I’d turn it on for cooling overnight. Essentially we used it to cool the mass of the house with the cooler night time temps. Once I installed the mini-splits we rarely used it.
brandonsmash
Well-known member
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- Sep 8, 2016
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Do any of y'all with whole house fans find that you have increased issues with allergies or dust?
racecougar
Well-known member
OP, IMO, you'll be completely happy with one central fan. I utilize a 30" unit mounted in the center of my 30x60 for the same purpose as you describe. You can see the shutters in the ceiling here:
cherokee
Well-known member
I can't tell you about the fan in the shop but I can tell you in the house. I have the same sized house as @Shiftless, open a few windows and it will really get the air moving. It does make a HUGE difference. I don't need to run the AC as soon.
In the shop where I am building a loft, I can see it being on a short list. The loft is 8' above the ground, and just up there nailing you can tell the difference in temp, this time of year it will be cool down on the ground, 8' up, getting hot, take off sweat shirt. This summer it is going to be real stuffy up there even with the AC in the shop running. I can see I will need vent work, get that hot air out of there.
In the shop where I am building a loft, I can see it being on a short list. The loft is 8' above the ground, and just up there nailing you can tell the difference in temp, this time of year it will be cool down on the ground, 8' up, getting hot, take off sweat shirt. This summer it is going to be real stuffy up there even with the AC in the shop running. I can see I will need vent work, get that hot air out of there.
rkevins
Well-known member
with the CFM's the same or close the only difference would be with 2 if 1 should fail you would still have some airflow, otherwise ether would have the same effect, if you use air intakes other than having the door open, having them on the afternoon shaded side will also help some.