Power Gable Venting in the shop

[Dave Gaul]

First, I'll describe my shop... ~ 8' X 20' barn style shed. Concrete slab. Standard 2x4 construction, osb sheathing, vinyl siding, shingle roof etc... inside of the roof is insulated with Radiant Guard radiant barrier, walls are ~ 1/2 way insulated with fiberglass batts (still working on getting that all finished)...

No that summer is here and temps are high, getting quite warm in the shop! Not willing to put an AC in there yet, so this past weekend I installed on of those 500cfm "duct booster" fans to exhaust throught the gable vent at one end.. thinking that heat rises and is basically trapped by the radiant barrier, so the gable fan should pull some heat out...seems to help some.

My question is, if I install another fan in the gable vent at the other end, would it be better to set up as another exhaust or make it an intake to get some cross-flow through the upper areas?

[David G Baker]

Dave
I had gable fans in a house I owned in California. The house ran East and West. The most heat would show up at around 5:00 PM on the West end of the house while the East end was in the shade. I mounted the fans so that the air draw was from the East and exhausted on the West end. The set up cut my attic temp by at least 15 degrees or more. The fans were temperature controlled and would start when the attic temperature reached 90 degrees. Not sure if 500cfm is enough to do a great job but it is better than nothing and with the size of your shop it may be enough. Drawing air from the cooler side of the building helps too,

[Dave Gaul]

Dave
I had gable fans in a house I owned in California. The house ran East and West. The most heat would show up at around 5:00 PM on the West end of the house while the East end was in the shade. I mounted the fans so that the air draw was from the East and exhausted on the West end. The set up cut my attic temp by at least 15 degrees or more. The fans were temperature controlled and would start when the attic temperature reached 90 degrees. Not sure if 500cfm is enough to do a great job but it is better than nothing and with the size of your shop it may be enough. Drawing air from the cooler side of the building helps too,

This is kinda what I was thinking... the side I'm exhausting out of now gets all the direct sunlight, the other end is all shade, so I was leaning towards pulling from the other end rather than have two exhausts...

[Alan Lightstone]

I accomplished the same thing with multiple solar fans, in different parts of the roof. Only works during daylight hours, but has made about a 15-20 degree difference in the attic temperature.

[Dave Wagner]

In my attic gable end window/vent, I put a box fan in the end window Pulling in outside air and forcing the hot air up and out the roof turbines and ridge vents. It works good and keep the upstairs of the house much cooler.

I have 2 gable vents in the garage, I don;t have a ceiling or all the insulation in yet, so it ventilates pretty good, but might put a solar vent fan once I get it closed up.

[glenn bradley]

If you have a common wind direction (I do, the wrong way), draw and exhaust along with it. If no wind, draw from your shade and exhaust to your sun. I can only have one fan in this shop and it faces into the wind; bummer but still helps immensely.

[Josh Bowman]

First, do you have passive eve and ridge vents? If so I would think exhausting would be the right thing and let the soffits vents draw in cooler air.
Second, I have some imperial data.....for what it's worth. From another thread I'm trying to kill some bugs in some cherry wood I got, so I stored it in my passively vented shop attic. Curious about the temperatures, I put in a remote reading thermometer and here's what I have learned: On a 90+ degree F day in SE Tennessee, the attic will get to 125+ degree's on the wood pile (about 2 feet from attic floor level). Here's what you want to hear. If I run my "whole house" attic fan (sucks from shop/open windows through the fan into the attic and out the ridge vent). The attic temperature drops quickly to about 85 degrees as compared to the shop at 82 degrees.
That's got to help things, and the shingles have to do better with the lower temps. The bottom line is the more air flow you can get into the attic the better. So IF you have vented soffits and enough of them, then sucking out the attic with 2 fans is nearly twice the air flow.

[Dave Gaul]

First, do you have passive eve and ridge vents? If so I would think exhausting would be the right thing and let the soffits vents draw in cooler air.
Second, I have some imperial data.....for what it's worth. From another thread I'm trying to kill some bugs in some cherry wood I got, so I stored it in my passively vented shop attic. Curious about the temperatures, I put in a remote reading thermometer and here's what I have learned: On a 90+ degree F day in SE Tennessee, the attic will get to 125+ degree's on the wood pile (about 2 feet from attic floor level). Here's what you want to hear. If I run my "whole house" attic fan (sucks from shop/open windows through the fan into the attic and out the ridge vent). The attic temperature drops quickly to about 85 degrees as compared to the shop at 82 degrees.
That's got to help things, and the shingles have to do better with the lower temps. The bottom line is the more air flow you can get into the attic the better. So IF you have vented soffits and enough of them, then sucking out the attic with 2 fans is nearly twice the air flow.

Wow that is pretty hot! My 'attic' space in my shop is composed of 3 lumber lofts.. any time I get up there the sweat come pretty quickly! There are no other vents besides the gables... Gonna try pulling in from the other end, it was still in the mid to high 80's in the shop this weekend with 90+ temps outside...