get the heat out

[BFHgarage]

Here in Illinois, this summer has been much warmer than last summer and the garage isn't as pleasant to work as it was last year. I have an access door to the attic space above the garage, so I was thinking about making a new "summer" door for it with a fan to pull the hot air up and out of the garage. I'd open the window to provide a source of fresh air.

the access door can be seen in the ceiling here:

My main concern is that the attic area above the garage is seperated from the attic above the second story by a vertical wall for the second floor bathroom that is located above the back wall of the garage. The two attic areas are connected together with rafter baffles.

example of the rafter baffle I'm talking about:

I am guessing that the rafter baffle channels are going to limit my flow out of the garage attic to the second story attic and it's ridge vent. I don't want to unintentionally create a new problem by trying to blow too much air through the attic. Would 1 or 2 80 cfm bathroom style vent fans move enough air to help cool things down or should I go to a small gable fan type fan?

Also, since it is a temporary seasonal thing and there isn't a constant power supply up there, I was thinking about using a extension cord that I would run along the ceiling to a wall plug. Is that too ghetto to be safe/wise?

 

[pseudorealityx]

Air from the outside will be hotter than the air inside the garage. Air movement will help keep you feeling cooler. Air exhausting to the attic and made up for by pure outside air will only make it hotter.

 

[mayday0017]

Insulate the garage door and put that fan in front of the door that goes inside, mooch a little HVAC, 20 min of HVAC and a fan can cool a garage down to something much easier to put up with.

 

[Falcon67]

Well - here's my 1/50 of a dollar. I put in a 1600 CFM fan centrally located in the large section of the shop. I put in a pair of vent covers to seal it off when not in use.

To date, it has
- demonstrated that screwing OSB to joists leaves 100,000 air gaps and I need to caulk every joint in the entire ceiling
- that it doesn't really move much air, or pull in enough to make any kind of difference. It does help pull exhaust fumes into the attic from a car

Now in the fall, it might work better. I have 5 large 10" roof vents and 10 eve vents so it is moving air out. Just not really at any kind of rate you could tell. It's more like a bath vent fan in a big bathroom. YMMV.

PS - mine is on an extension cord for now. It's too dang hot to get up there and try wiring anything permanent.

 

[BFHgarage]

Good points. Not sure how the wife will react to the AC theft from the house, but that is an idea. It still cools off decently outside once the sun dips down, so I'm not sure pulling air from the window in the evening/night would be a total waste.

Falcon : you can't really tell that it is doing anything? That looks like pretty much what I was thinking about doing.

 

[Falcon67]

I think right now that the ceiling is too leaky to really tell much. That is in spite of the attic being full of R13 batt insulation. If I open one 2x3 window, I can tell it's pulling in air. Open 3 of them and you really can't tell. Now the caveat is that it runs high 80s in the shop sealed up all day and at night it's still in the 90s outside, so without a candle it's hard to tell any air is moving.

 

[Gary S]

If your garage is well insulated, it doesn't take much Air conditioning to make a huge difference.
So, insulate well first.
Put in a small window air conditioner second.
Enjoy yourself from there.

 

[pop pop]

1st add a window fan. If that doesn't meet your expectations,
2nd add a window AC and insulate.

 

[pseudorealityx]

Good points. Not sure how the wife will react to the AC theft from the house, but that is an idea. It still cools off decently outside once the sun dips down, so I'm not sure pulling air from the window in the evening/night would be a total waste.

If it cooling off in the evenings, can't you just open the garage door?

 

[BFHgarage]

The garage walls and ceiling were insulated when the house was built 1.5 years ago. Unfortunately, the window isn't big enough for a window unit and I'm not sure I want to hack a hole in the wall to permanently mount one.

If the garage doors didn't face the street, I'd just leave the door open... While we are in a safe area, there are still houses being built in the neighborhood and I don't want to tempt someone by allowing them to browse my collection as they are passing by.

I might just go buy a $15 box fan and throw it up there just for the heck of it. I thought my concept was sound, glad I posted it here before spending $100 on a gable fan.

 

[Falcon67]

Sounds like a plan. I had to use my floor fan to vent some fumes out of the shop last night. Opened the big door, turned on the fan and it went from 89F in there to 95F. And this was at 8PM. I had good luck in the spring with a box fan in the back window pulling in cool air, back when we had cool air and way before I put in the ceiling vent fan. I suspect part of my problem may be that 10 3x10 eve vents and 5 10" holes in the roof are really not enough to let out 1600 CFM. That created back pressure and the fan loses efficiency quickly. I'd go back and use a continuous ridge vent, but I don't think that would provide enough exhaust area either.

 

[JimVonBaden]

When my garage was a one car attached to my house I always used the house HVAC with a fan in the doorway to cool off the garage. It works surprisingly well, especially if your garage is insulated.

Now I have a detached two-car with no insulation, and no attic venting, and the place is a sauna in temps over 80°. I really need to work on that!

Jim

 

[mayday0017]

+1 if it's really hot and I need to get some work done I close the garage door and stick my old HVAC blower inside the house door and **** out some of that wonderful HVAC. If I am going to be working on a car I just pulled in I park out in the driveway for 10 min first with the hood popped and the HVAC blower facing into the radiator area and let it cool down. Amazing how much use I get out of my old blower....

 

[kbs2244]

Before you get too carried away just open to access door.
The natural convection out the ridge vents may very well be enough to vent the garage.
You will be sucking the air out of the garage instead of through your soffit vents.

 

[BFHgarage]

I went out tonight and pushed up the access door, we'll see what it does over the next couple days.

Being out there with the lights on and the garage door open reminded me of the other reason why I'd like to get this sorted out: Bugs!