New 2 Car Garage Project - Starting with Insulation

[Woodward_Dreams]

Hello all,
I purchased the house I'm in about 4 years ago and I am finally getting around to doing what I really want to do, the garage.

Aside from putting in better lighting, it is just getting started.

The main reason I am posting is to ask for advice on insulation. I live in Michigan and will eventually heat the garage with a natural gas powered furnace. What is the preferred kind of insulation for this kind of space? The studs are 14 1/2 inches apart and I plan on either drywalling it or using OSB.

Here are a few photos, please excuse the mess as I am doing some spring cleaning.

 

[dfiler2]

I would use mineral wool on the walls then cover with 6 mill poly, then use 6 inch kraft faced fiberglass in the ceiling then blow in on top of that after the ceiling covering is on.

 

[billconner]

Depending on the locality, you may have to meet energy codes. We do in NYS and just 4" batts in wall would not be acceptable for a heated accessory structure. You need to know that first. (I'd sheath inside with 2 "XPS and then blow in cellulose and finally seal joints with foam in a can to get required R and a vapor barrier.

The ceiling is easy, just put in ceiling - metal liner panel seems popular and easy - with poly behind and blow cellulose (my choice) or fibreglass on top to depth that will provide the code required R value.

Spray foam entirely is another option, leaving "cathedral ceiling" but usually more expensive.

 

[dfiler2]

Wow, glad I don't live there.

Just doing a little research shows blow in cellulose at 3.5 per inch and foam board of 4.2 per inch. That would give you a total best case of 20.25 and the mineral wool shows an r-23.

 

[billconner]

Wow, glad I don't live there.

Just doing a little research shows blow in cellulose at 3.5 per inch and foam board of 4.2 per inch. That would give you a total best case of 20.25 and the mineral wool shows an r-23.

Are you sure mineral wool is R23 in a 2x4 wall?

Also, like fibreglass between studs, the effective R value will be less. The continuous insulation, like XPS over the studs, is much more effective. And is R4.7. IRC says R25 walls but allows 2x4 with 4" fibreglass and 2" XPS recognizing the value of the continuous insulation.

I like cellulose (dense packed) because it fills irregular spaces so much better than batts. Scandanavuan research has shown the gaps of as little as 1/8" allow thermo siphoning within walls and significantly lowers the insulating performance. And dense packed cellulose has an R value of 3.8 to 4, better than fibreglass and I think better than mineral wool, and has been proven to perform better in a fire.

 

[Cairo94507]

All of the above are good solutions. Before you add insulation, think about electrical needs and add outlets where you might need them. Also, if you might ever own an electric car, think about a 220 outlet. Run all of your lighting runs first.

 

[CraigStu]

All of the above are good solutions. Before you add insulation, think about electrical needs and add outlets where you might need them. Also, if you might ever own an electric car, think about a 220 outlet. Run all of your lighting runs first.

Great point. I like a 120v outlet every 4 feet and about 4ft off the floor. That way they are above most work benches and tool boxes but below most shelves or cabinets.

 

[Woodward_Dreams]

All of the above are good solutions. Before you add insulation, think about electrical needs and add outlets where you might need them. Also, if you might ever own an electric car, think about a 220 outlet. Run all of your lighting runs first.

I appreciate the insight. Last year I had the panel updated in the garage with two separate circuits for 110 outlets (7 total, since my air compressor is on its own 110 circuit). The lighting is completed (I always consider adding more) since there are 8 T5HO bulbs.

I probably should run electrical for a furnace, but that will not be installed for at least another year.

 

[Firebrick43]

Are you sure mineral wool is R23 in a 2x4 wall?

Also, like fibreglass between studs, the effective R value will be less. The continuous insulation, like XPS over the studs, is much more effective. And is R4.7. IRC says R25 walls but allows 2x4 with 4" fibreglass and 2" XPS recognizing the value of the continuous insulation.

I like cellulose (dense packed) because it fills irregular spaces so much better than batts. Scandanavuan research has shown the gaps of as little as 1/8" allow thermo siphoning within walls and significantly lowers the insulating performance. And dense packed cellulose has an R value of 3.8 to 4, better than fibreglass and I think better than mineral wool, and has been proven to perform better in a fire.

+1

And if you put 2x2 horizontal over the vertical studs, with dense pack cellulose you eliminate much of the thermal bridgeing and get another 6 ish added to the r value. Google "mooney wall" . It works very well and very energy efficient. Fiberglass is terrible for convection currents as the temp diff is high. Rock wool is much better but as bill says, gaps(impossible to eliminate with batts) still allows for some convection to happen.

 

[billconner]

That would work ok. 5" dense pack would be close to a R18 or 19. If instead of strapping and netting you used 2" of XPS, more like R22. But both provide the benefit of continuous insulation. The foam version would cost more.

Code wise, in Michigan, you could be zone 5 or 6. With 2x4 walls, high performance fiber glass, mineral wool, or densed pack cellulose - at least R13 nominally - with 1" foam in zone 5 or 2" in zone 6 works. R49 in ceiling: 14" - after settling - of cellulose or equal in fibreglass.

 

[K'ledgeBldr]

Hello all,
I purchased the house I'm in about 4 years ago and I am finally getting around to doing what I really want to do, the garage.

Aside from putting in better lighting, it is just getting started.

The main reason I am posting is to ask for advice on insulation. I live in Michigan and will eventually heat the garage with a natural gas powered furnace. What is the preferred kind of insulation for this kind of space? The studs are 14 1/2 inches apart and I plan on either drywalling it or using OSB.

First and foremost, it's a garage! I would caution the amount of budget toward insulating. Even though you said you're going to add heat- I would assume that it's just for when you're in there- not continuously during the cold seasons(?). If that is in fact the case, I probably wouldn't even bother insulating the walls, they appear to already have an insulating/vapor barrier material installed. Drywalling, or some other form of paneling the interior will create a bit of a dead-air cavity between the studs. Since most heat loss is through the ceiling, i would definitely insulate that- I don't think you need to go to R-30+, but at least R-19 (which also help deter heat gain during the summer).

If you don't already have an insulated overhead door, I would certainly consider it, along with good vinyl weatherstripping and bottom seal.

 

[billconner]

Which is why I said find out if he will have to meet code. If it's not enforced or you want to ignore the law, don't insulate.

 

[dfiler2]

"Are you sure mineral wool is R23 in a 2x4 wall?

You are right, the insulation I looked at was 5.25 for a 2x6 wall.

 

[rayra]

I appreciate the insight. Last year I had the panel updated in the garage with two separate circuits for 110 outlets (7 total, since my air compressor is on its own 110 circuit). The lighting is completed (I always consider adding more) since there are 8 T5HO bulbs.

I probably should run electrical for a furnace, but that will not be installed for at least another year.

Run the wire now, before you fill and cover the walls and ceiling. Or at least an empty conduit and junction boxes with a pull string installed.

 

[Woodward_Dreams]

Overdue update:

I ended up keeping it simple and installing fiberglass R-13 and used a vapor barrier.

A good friend of mine helped with hanging the drywall. It is still a work in progress but I am really happy with it now.

I also had an insulated garage door installed about a month ago. It was definitely an investment, but worth it.

 

[Woodward_Dreams]

Drywall progress and insulated garage door

 

[Woodward_Dreams]

And a new Optispark for the Camaro