Insulation help

[goldenboy9r]

I live in Houston and would like to install a mini split system A/C in the garage so I can work on my motorcycle in August and not die of heat stroke. Just had the contractors install a new breaker box in the house so they could run a 220V line to garage for the A/C. It is a 20X22, 2 car garage with no insulation and no ceiling installed. Just bare. I have no soffits and no ridge vent. I would like to leave the rafters open for storage space (no ceiling).

I have searched this forum for a solution to insulate it with no luck. At first it seemed like spray foam would be the way to go but the cheapest bid I got was 1600 but most were around 2 grand and I cannot afford that.

I do not want to compromise on the ceiling. I like the openness feel of the exposed rafters and storage.

What can I do that will look nice, work, and not cost me thousands of dollars?

 

[joe6749]

Can you cut 2"foam between the rafters and seal with cans of spray foam?

Sent from my SCH-I535 using Tapatalk

 

[Tim The Tool Man]

The cheapest method I can recommend is for the ceiling, styrofoam baffles against the roof sheathing and then faced fiberglass insulation between the rafters. Then in the walls (I'm assuming they are finished) blown in cellulose insulation.

 

[Fueler]

Got to ask. If you can work on a motorcycle what stops you from doing this yourself rather than paying someone? Not all that tuff once you have a plan. For the moment I don't think much of the spray foam for your app.

Any plans to work in the winter and need heat?

 

[goldenboy9r]

Walls are not finished.
Yes, i will be working in it during the winter. The 2 weeks of winter that we do have...

Thats my problem, i need a plan.

 

[8man]

I built a lot of homes in Houston with R-13 Owens Pink "faced" batts in the walls. Go to Home Depot, check the price and coverage and see how much you need to do the walls. This is about all we need down here for the heat and cold.

The ceiling is a little trickier. I recommend R-30 blown with vents in the soffit and ridge or roof vents. This is the least expensive way to do it and it gives good results. If you do it this way you have to cover the exposed ceiling joists which will block your view. The foam for the ceiling would help seal this and you wouldn't need the vents in this area, and the cost may not be much different for just foaming the rafters than doing the more conventional blown fiberglass after you cover the ceiling joists with sheetrock, plywood or whatever so the insulations will have a place to sit.

If you need to discuss this more, I'm at [email protected]

Good luck.

 

[Fueler]

I wonder if a radiant barrier followed with bat insulation would do the trick for the roof. Reasonable price and a DIY project.
I'm using some radiant barrier in my shop and home attic projects.
Start here for an idea. http://www.atticfoil.com/applications-and-uses-2/cathedral-ceilings.html

I have become a Roxul insulation fan but for that roof line stapled up batts might make more sense.

 

[goldenboy9r]

Thanks.
I'd rather not cover the ceiling joists though...

 

[zurud]

If you want the joists and rafters expose, good luck in the summer in Houston.

 

[Libertyflyer]

Just had the contractors install a new breaker box in the house so they could run a 220V line to garage for the A/C. It is a 20X22, 2 car garage with no insulation and no ceiling installed. Just bare. I have no soffits and no ridge vent. I would like to leave the rafters open for storage space (no ceiling).

I do not want to compromise on the ceiling. I like the openness feel of the exposed rafters and storage.

I have a very similar situation. 20x20' detached garage , open from floor to peak. Just ordered Foam it Green spray foam. 800sqft, $1127 delivered.

Plan to do it next weekend. I'll let you know how it goes.

 

[J Persons]

I wonder if a radiant barrier followed with bat insulation would do the trick for the roof. Reasonable price and a DIY project.
I'm using some radiant barrier in my shop and home attic projects.
Start here for an idea. http://www.atticfoil.com/applications-and-uses-2/cathedral-ceilings.html

I just received my order of radiant foil barrier from atticfoil.com to cover the rafters in my 32X48 shop, I bought a 2000' roll for $250 plus shipping. From what I've read here at GJ, this is exactly what I need. The foil has 0 insulating value, but it stops radiant heat. This is exactly what I need, something to stop the heat from transferring down. Heat loss is not a problem as it hardly ever gets below 50º in the daytime, even in the dead of winter.

For the foil to be effective at reflecting the heat, the roof needs some type of soffit vent and a way for the heated air to escape at the ridge. I'm using two powered gable vents, and later on I may install a couple of roof turbine vents.

According to an insulation contractor that I talked to, do not install insulation batts directly under the roof deck between the rafters. This will concentrate heat on the shingles and shorten their life, you need an air gap between the insulation and the roof deck.

 

[8man]

In H-town our biggest problem is the sun heating the top of the building. The radiant barrier is a big help up against the decking, in fact we use the CDX with the radiant barrier glued onto the back side. To leave the rafters "exposed" as much as possible, you could put the radiant foil on first and then use whatever thickness batts as will fit "inside" the rafters. I will say this will help, but won't be as good as the other way. However, if you are just trying to get the garage down from 100 to 80 is will work, but make sure the AC guy knows what the envelope will be when planning the AC. Oh, DO NOT oversize the AC as it needs to run long enough to pull enough moisture out of the air for you to feel comfortable. Big mistake is oversizing because the unit doesn't run long enough to remove the humidity and even though the temp is 72 it'll feel 80 and cost more in electricity. Start up is the big energy expense. so the fewer times it starts up the better. IMO!

 

[goldenboy9r]

I have a very similar situation. 20x20' detached garage , open from floor to peak. Just ordered Foam it Green spray foam. 800sqft, $1127 delivered.

Plan to do it next weekend. I'll let you know how it goes.

yes, please let me know how it goes

 

[goldenboy9r]

Ok, foam is scheduled to go in Monday. Lets see what happens!