Trying to cool metal shop building

westbrooklawn · Jun 28, 2010

I have a 28 x 36 metal building with two 10x7 insulated garage doors and one walk in door. The inside is open to the peak of the roof which is about 16 high. The building is insulated with a thin foil/bubble wrap which is white on the inside and foil against the siding/roofing. I heat it with a 45k Modine heater which does fine with outside temps in the high teens.

I recently installed a 24k btu window air conditioning unit to try to cool the building... it blows a tremendous amount of cold air, but won't keep up with the task of cooling the building. With outside temps of 92, it would only get the inside down to around 85.

I am thinking about trying to get a self contained ouside ac unit, and running just a supply duct and return duct through the wall. The inside of the shop is wide open, so my thought is that just dumping the cool air into the shop would work. My questions are 1. will this work, and 2. if so, what size unit do I need (summer temps here are in the low to high 90's).

magicheater · Jun 28, 2010

Just plain not enough insulation.

dstig1 · Jun 28, 2010

Ditto. You are asking the wrong question. The correct question is how much insulation do I need? The bubble wrap is all but zero insulation value. A couple inches of foam around the inside (sprayed or sheets attached to the walls and sealed) will go a long way towards allowing you to heat and cool it without needing a ton of energy. It's only going to get more expensive you know...

You are looking at R13-15 for walls and 30-38 for ceilings, to hit what would be required for a residence. 2" of foam on the walls and 4" on the ceiling would be killer. But frankly anything would be an improvement here.

So you may spend a couple grand on insulation. How much are you going to spend on a new AC unit? Then how much to run it? If you are asking this question at all, I have to assume you are using the building a lot, in which case the insulation makes a lot of sense. Much harder to justify if it is rarely used.

My $0.02

-Dave

carpenter383 · Jun 28, 2010

If there is any way you can put an insulated ceiling in there it would be a major help.
Walls too, you need a heat barrier before you can efficiently maintain a warm or cool shop.
If insulation isn't an option there is a product that sprays a fine mist of water (can't remember the name) the water mist is directed toward you to help keep you cool.
Might not be a good idea if mold is a concern though.

Alan L. · Jun 28, 2010

Yep, the problem is insulation.

Ozarks Moon Shiner · Jun 29, 2010

+1

I been tryin to tell some fellow farmers around here that they really need to finish insulating their homes roof. It will help with the heat up there but nope they just don't get it.

Gary Fowler · Jun 29, 2010

Insulation is the key, I have a slightly smaller shop 30 x 30 with 16 foot wide and 10 foot wide insulated garage door and I can cool it to about 80F with a 14000 BTU window unit. It is a wood frame building with 6" thick fiberglass bat insulation in walls and ceiling. Mine has a 10 foot ceiling in it so it isnt open to the roof like your. But if you expect to cool your shop without spending a small fortune on energy costs, then invest in R 15 walls and R19 minimum insulation on ceiling. Newest energy guides spec R21 walls and R 38 ceiling for residences in the Arkansas area. I just finished insulating my new residence and had them put R 50 in the ceiling.

Eagleview · Jun 29, 2010

westbrooklawn said:
(summer temps here are in the low to high 90's).

The most important thing is the outside reflectance of the building . A coat of White paint makes a heck of a difference . A vented ridge cap also helps a lot as the hot air rises it can escape , as it is doing this , as a side product , fresh air is drawn in the doors and windows which creates a breeze .

The workshop I built was like this and was cool in summer . My neighbour put up a Mission Brown shed and I told him he would cook . He said I was wrong , the first summer , all his work benches and lathes were moved to the center away from the walls so they could work .

jayste · Jun 29, 2010

Iron Horse said:
The most important thing is the outside reflectance of the building . A coat of White paint makes a heck of a difference . A vented ridge cap also helps a lot as the hot air rises it can escape , as it is doing this , as a side product , fresh air is drawn in the doors and windows which creates a breeze .

The workshop I built was like this and was cool in summer . My neighbour put up a Mission Brown shed and I told him he would cook . He said I was wrong , the first summer , all his work benches and lathes were moved to the center away from the walls so they could work .

Iron Horse, you took the words right from my "keys"!

A reflective roof would help as well right along with ventilation and some fans to move that rising heated air. Not saying insulation isn't important. I think all these would have to help. Thankfully, mine is positioned to where the breeze (if any) will run right through the middle of it. Of course, here in Oklahoma, where the wind comes sweeping down the plains, that's not always good!:laughing: