Roof vent or fan for hot shop?

[Jason White]

My new "shop" is a 2-car detached, uninsulated garage in sunny Los Angeles with no shade trees overhead. Insulation and AC are not a practical option because it's a rental house and I don't want to spend that kind of money on a house I don't own.

Except for the main garage door, there are no windows or other smaller entry doors and no roof vents, so temperatures in there can reach well over 100 degrees and it's obviously worse with the door closed. I can barely stand to be in there right now, even with the big door open and a pedestal fan running full blast.

I'm thinking about adding a couple of roof vents or maybe some type of electric fan in the roof to suck the heat up and out of the building. If I go the electric fan route, I imagine it'll help get some of the sawdust in the air out of there, too.

It's a hip roof, so gable end vents are not an option (there are no gable ends). I'll have to cut into the roof, which my landlord has no problem with, but I'm wondering what kind of roof vents or fans you guys like best.

Thanks for any suggestions!

- Jason

[Jim Andrew]

They used to sell a thermostatically controlled roof vent fan at lumberyards. It installed like a roof vent, of course it had to be connected to power. I have installed the turbin style roof vents that use the wind to pull air from the attic, they work pretty well if the wind is blowing. As close as houses are together in LA, I would guess the wind probably wouldn't hit your roof much.

[Larry Frank]

I have a solar powered vent on my house which seems to work really well. It is better than a plain vent and you do not have to run any wiring.

[Charles Lent]

I would go with a turbine type roof vent, the spinning ball shaped vents that you frequently see on commercial buildings. The hot air rising through it will make it spin or any breeze from any direction will also make it spin, so you will have ventilation without paying high dollars for solar powered or utility powered electric fans. Don't forget that you need a place for cooler air to enter just below the bottom edge of the roof. As the roof heats it up it will draw air in to rise along the underside of the roof and exit through the turbine ventilator. Without a way for the cooler air to enter the building, your ventilator, no matter which kind you buy, will not be able to remove much hot air. You can mount these vents near the roof peak, but on the back side of the roof so that it can't be seen from the front of the building if it's appearance is objectionable to your better half. To me, anything that works well and doesn't add to my electric bill is beautiful.

Charley

[Jason White]

I think I definitely want to go with an electric fan; something powerful enough that will suck most of the hot air up and out of the garage in just a few minutes so I can get to work in there relatively quickly. I remember seeing whole-house fans in older homes that worked like this. A multiple speed unit would be ideal, if something like that exists. That way it can be running on low (off of a thermostat) when I'm not in there and then I can crank it full blast when I'm getting ready to make some sawdust.

The solar fan units that I've seen tend to be kinda weak and operate more like vents than actual fans. They're also intended for enclosed attics or crawlspaces. In my garage, there is no attic. It's just a giant box with exposed studs, ceiling joists, and rafters. I have no problem hard wiring it for a thermostat or switch. I'll probably cut in some vents down near the floor instead of the roof so that it's sucking all of the hot air out of the building from the bottom up and not just the heat up near the roof.

I would go with a turbine type roof vent, the spinning ball shaped vents that you frequently see on commercial buildings. The hot air rising through it will make it spin or any breeze from any direction will also make it spin, so you will have ventilation without paying high dollars for solar powered or utility powered electric fans. Don't forget that you need a place for cooler air to enter just below the bottom edge of the roof. As the roof heats it up it will draw air in to rise along the underside of the roof and exit through the turbine ventilator. Without a way for the cooler air to enter the building, your ventilator, no matter which kind you buy, will not be able to remove much hot air. You can mount these vents near the roof peak, but on the back side of the roof so that it can't be seen from the front of the building if it's appearance is objectionable to your better half. To me, anything that works well and doesn't add to my electric bill is beautiful.

Charley

[Chris Padilla]

I think without some way to keep the heat out (i.e. insulation), you aren't going to accomplish much with venting. Moving air in general might be the way but if it is hot outside, you're just moving in hot air albeit perhaps less hot air.

[Ruperto Mendiones]

A commercial kitchen exhaust fan that will do > 1000 cfm should give you ~ 5 min to change the entire volume of your garage [assuming 25'x25'x8'] Check this out: http://www.fantech.net/5BDU18_enus-49805.aspx. Overkill perhaps but it would give you a powered roof vent that is shielded from rain [if it ever happens in LA ]

posted by a fellow Angelino.

[glenn bradley]

I have a gable fan at about 1600CFM to empty the hot air captured in the rafters. That and a couple of these do the trick for all but the hottest weather. I put them shooting down opposite walls in opposite directions to sort of whirlpool the air. It cools things down without blowing things around. I'm inland about 70 miles and so our hot is a bit more aggressive than downtown.

[Jason White]

I'm in the valley, not downtown. It's regularly 10-20 degrees hotter here.

I have a gable fan at about 1600CFM to empty the hot air captured in the rafters. That and a couple of these do the trick for all but the hottest weather. I put them shooting down opposite walls in opposite directions to sort of whirlpool the air. It cools things down without blowing things around. I'm inland about 70 miles and so our hot is a bit more aggressive than downtown.

[glenn bradley]

I'm in the valley, not downtown. It's regularly 10-20 degrees hotter here.

Ah, then you know of what I speak ;-) If your area over the rafters is open, the gable fan will really push out that hot air mass. I have been running the current one for about a decade without issue. You can feel the temperature shift when the thermal switch kicks it on. Its still hot but, very workable with the other fans keeping things circulating.

[Jason White]

No gable in which to install a fan; it's a hip roof. Otherwise, a gable fan would be a no-brainer!

Ah, then you know of what I speak ;-) If your area over the rafters is open, the gable fan will really push out that hot air mass. I have been running the current one for about a decade without issue. You can feel the temperature shift when the thermal switch kicks it on. Its still hot but, very workable with the other fans keeping things circulating.

[John Lifer]

if it was me, I would put in least $ as you are renting. Put in a couple of non powered, or if you can get deal on powered roof vents, do those. I would then buy an industrial 36"-42" floor fan. Move some air around. you can take it with you.

[Myk Rian]

I have 3 roof vents in the garage, with a Tornado equipment fan in the center one. A bulb type thermometer up there shows a temp drop of 10° when I turn it on.

[Bill Huber]

Does it have a ceiling in it?
My shop is a 12x16 Tuff Shed with a low slope and I could not stand to be in it when it was over 90 degrees and that is from May until October here in Taxas.
I bought some of that 3/4" foam that has aluminum on one side and just white on the other. I installed it as my ceiling, with the aluminum side up and the difference was unreal.
I do have a ridge vent but that did not help much but the foam made all the difference in the world.

[Kevin McCluney]

I have a similar "problem" - detached garage, unfinished interior, hip roof, and hot (Houston, TX). It came with a turbine at the apex of the roof. I've since installed soffit vents (hard to believe it didn't have those to begin with). I also bought an exhaust fan designed to be used as a gable fan and mounted it under the turbine. I know convection is drawing a lot of the hot air out the turbine, but I've found the fan helps things along. Coupled with some floor fans I stay reasonably comfortable. I'll also open the large garage door occasionally, once the sunlight isn't streaming in (east-facing).