New shop build vent question?

[miscjames]

I am in the process of ordering my shop 28x40 and i am torn between getting 12”x12” frame out put in for fans. The intent of the fans is to pull the heat (and fumes) out of the shop during summer. However i do intend to heat the shop during winter. So then i would have to deal with the holes. I am in the Knoxville TN area. So looking for advice put them in or no? Pro/cons?

Fans: Amazon.com

Shop image:

 

[EddieWalker]

I've seen this done in homes and consider it a feel good way to spend money that doesn't accomplish anything, but does create a few problems.

First goal of any roof is to be able to allow air to enter at the eaves and exit at the peak. A ridge vent works best for this, it allows the most air flow under the entire surface of the roof. With metal roofs, this is especially important to dry off the dew that forms under the metal roof in the morning.

Ridge vents don't really add anything to what is happening naturally in a properly vented roof. They allow air to exit the side of the building, at the gable, instead of the peak. This changes the natural air flow from eave to peak.

Odds are that you will never notice the difference by installing them, but it will be something else to fix and replace when they go bad. If you have a good, open, ridge vent, then the air will flow naturally when the fans break down.

 

[ericm979]

If you're going to heat the shop you should get it insulated. And not with the bubble wrap. How you do the insulation will determine if and how to vent the roof. With insulation directly on the underside of the roof (i.e. spray foam) you don't vent. With a ceiling with insulation on it, the attic above gets vented. Passive vents should work for that.

If you heat the shop with a mini split you can also cool it with the mini split.

 

[Runner]

I assume the vent you are talking about is not for an attic space, and that this would be in the wall below that attic area, i.e., you basically have a vaulted ceiling in your shop. That being said, I have a vaulted shop ceiling and would LOVE to have a fan in the wall above my overhead door to vent the space when welding or plasma cutting. I'm pretty sure you can get such fans with louvers, similar to those found on attic fans. Now is the time to do it, or at least have it framed-in and run the wiring to it (if you're going to finish the walls).

I'm no engineer, but I don't think a 12 x 12 is big enough. I would want something more along the size of an attic fan. Also need a relief opening or door on the other end of the building for it to work best.

 

[FPGT72]

I am in the process of ordering my shop 28x40 and i am torn between getting 12”x12” frame out put in for fans. The intent of the fans is to pull the heat (and fumes) out of the shop during summer. However i do intend to heat the shop during winter. So then i would have to deal with the holes. I am in the Knoxville TN area. So looking for advice put them in or no? Pro/cons?

Fans: Amazon.com

Shop image:
View attachment 873408

My shop is roughly your size. My question would be first how tall are the side walls. Mine is 24', so quite tall. In the summer up there it is VERY hot, like to change out lights or something, you are dripping in short order.

Now I have built a loft, both to store and work up there. Now you can't be up there in the summer, well over 100F. I am planning on two of those fans for mine to vent out that heat. I figure I can rig up something to cover them with in the winter. I am in MO.

I do not heat mine unless I am out there, and that heat will raise very quickly. It can be sweatshirt and jacket down stairs and Tshirt up stairs in the winter with the heat running. The fan is really helpful in moving that warm air down. In the summer that fan just brings the warm air down. I need to get that heat out of the building as it is not livable up there. I am not so sure on the short life of the fans, that is not exactly new technology.

I think your solution will be a good one.

 

[miscjames]

Thank you all! Does anyone else want to chip in?

 

[KennyG]

Roof and soffit vents work pretty well. Looks like you are planning a free span metal building so a ceiling may not work, but a ceiling with vented attic is ideal for both summer and winter. I did have an open ceiling building once and I installed unpowered turbine roof vents. In the winter, I blocked the opening in the roof with a foam panel and it worked pretty well.

 

[sandman2234]

I got ahold of some 48" fans that were removed from a Bellsouth building when they changed over to A/C. I installed two of them next to each other in a slab of wood the size of the garage door opening but only as tall as the fans. When it got hot, we moved the fans into the doorway, and closed the garage door down to the top of the slab of wood, then plugged them in. The amount of air those fans moved was incredible! We only had doors on each end, so the air was drawn across the entire floor of the building. Made it nice. Later, I removed two windows on one end and put a fan in each one, and that "seemed" to help even more because it was pulling air from a higher level which pulled the hotter air from higher up.
I had sheet metal covers made for these two fans after they were installled in the window openings, so that prying eyes wouldn't see what was in the shop, and also to allow better heating in the winter. They were made with lips that slipped over the top, and a pair of screws held the bottom down. Louvers can be installed that would make that easier, but I traded some work with a sheet metal shop to get the covers made. If it had been an issue, I could have had the sheet metal covers insulated similar to the way they internally insulate metal A/C duct. I was afraid it would make it too heavy for a single person to hang the covers when it started to get cold. (not that it really gets cold in Florida, lol)
David from jax

 

[ericm979]

The standard in code for passive vent area is 1/300th of the building sq ft, on the intake and the exhaust. Or 1/150 in some cases (this is from memory so it may be wrong, look it up if you want it correct). You need a low intake and a higher exhaust so the hot air will rise out the upper exhaust vents and cooler air will be drawn in through the lower vents. Screened vents don't flow as much as the same size non screened vents, but the vent manufacturers usually publish the equivalent open area for calculating vent area.