AC for shop/shed

[EddieWalker]

My garage has a metal roof without a ceiling or any type of insulation. My Mom's house has R13 fiberglass insulation in the walls and 2 feet of blown in insulation in her attic.

In Summer, it's hard to just breath in my garage, the heat is so oppressive. You are better off standing outside in the sun then you are inside my garage. I would guess it's ten degrees hotter inside my garage compared to the outside temperature.

My Mom's garage is pleasant. No AC, or anything to keep it cool, just the insulation. I've never checked the temperature in there, but I would guess it's at least 10 degrees cooler inside her garage then outside, and I wouldn't be surprised if it was even cooler.

My long term goal is to insulate my garage by putting metal R panels on the ceiling. My trusses are every 4 feet, so metal roofing will be perfect. Then blow in 2 feet of insulation.

 

[ruffdog]

Being that the main issue is "tons of dust/dirt/dog hair", maybe a large volume fan to move air THROUGH the building?

Sidewall Propeller Exhaust Fan, Product # SBE-2L30-7X-QD-DR3, 7992-10921 CFM | Greenheck

 

[bigtiller]

If you can get the ceiling insulated to some where close to an R50, it will probably cool it enough that you won't need anything else.

My sheds ceiling and walls are well insulated and I have an undersized de-humidifier running. I go in there to get cooled off before I go in the house for supper.

I go to the shed about 3pm every day of the year to check the temp and empty the de-humidifier in the warm months. At that time, it has never been above 81° or below 33°

 

[paulsharvey]

If you can get the ceiling insulated to some where close to an R50, it will probably cool it enough that you won't need anything else.

My sheds ceiling and walls are well insulated and I have an undersized de-humidifier running. I go in there to get cooled off before I go in the house for supper.

I go to the shed about 3pm every day of the year to check the temp and empty the de-humidifier in the warm months. At that time, it has never been above 81° or below 33°

Yeah, R-50 is never gonna happen; if I could get it a consistent R-5, with no air leaks, that would be awesome. It's frankly harder to retro fit a pole barn into conditioned space than it is to build it with that intent from the ground up.

 

[paulsharvey]

Even when I worked on PEMB (red iron buildings; pre-engineeered metal buildings), with the roll insulation between the frame and skin; we would chase light holes in corners, and dang birds getting in, forever. I dont think we ever did one conditioned without a drop cieling...

 

[paulsharvey]

I just went ahead and picked up the cheapest window unit ac in stock; a 5000 btu Toshiba, and some additional 3/4" foil and Styrofoam board; as well as ordering a 2 can pack, gun, and cleaner of Kraken spray foam. It wasn't cheap, and 2 cans is going to do only like 40 sq ft; but I couldn't make my self just make the leap to order a 6 or 12 can kit. Gonna do some of the odd shaped areas of the cieling with that; where I have nothing to attach foam board too.

That foam; I see it widely used in E. Europe on videos; but only a handful of videos in US of people using it; with mixed reviews.

Hindsight being maybe not 20/20; but closer; I really wish I would have started from the ground up with an intent to insulate this structure. But when it was first built; it was just a place to keep the rain off a mower.

 

[MossRoad]

Could you use thinner lumber and make a lattice frame in the high areas to attach the foam board to instead of using expensive spray foam?

 

[KennyG]

Since you are concerned with humidity, I would focus on air intrusion first - sealing doors and windows, vapor barrier, etc. You don't want to oversize the A/C unit. I had a house with an oversized central air unit. It only had to run about 20 or 30% of the time to keep the temperature down so it wouldn't control the humidity. Kept the house cool and clammy.

 

[paulsharvey]

Since you are concerned with humidity, I would focus on air intrusion first - sealing doors and windows, vapor barrier, etc. You don't want to oversize the A/C unit. I had a house with an oversized central air unit. It only had to run about 20 or 30% of the time to keep the temperature down so it wouldn't control the humidity. Kept the house cool and clammy.

No worries about oversized unit

Sealing air intrusions is a never ending battle in a pole structure, and that's part of what I'm working on.