Insulating garage

[Wooden nickel]

I know this topic makes people come out of the woodwork.
If anyone could provide solid info that has been proven and not what the pros usually say.
Building science sites and questions to local roofers/ foam sprayers all yield the same responses.
Now to the info:
My shop (garage) is a typical 1 ½ detatched garage without soffits or ridge vent or gable vent.
I sheathed and insulated the walls.
The ceiling area I left open for astetics.
I added an 18000 btu a/c wall unit.
This is sized to the sq ft - although a little larger than needed- the open roof fills that space needed.
Very important is that I live in Houston.
Yes, very humid.
Now for the question.
With no ventilation and trying to make an air conditioned space like in some home attics now.
Would sealing, and adding rigid foam with a sealing around the rigid with spray foam produce enough of a closed environment?
Before anybody suggests adding a ceiling and insulation on top of that... I would rather keep the open area all the way to the roof.
I can add pics if needed.
I have not fully finished to see how the a/c works only because I have to insulate the garage door and replace the entrance door which is a disaster of an install and will need to be replaced.
FYI - the a/c at this time works well enough in 80 degree weather to make it comfortable but in 90 degree and high humid days it struggled naturally because of the door gap and hot pocket at the roof.
Thanks for any help or known proven techniques given.
Especially someone from Houston would know my pain.

 

[tjbnwi]

If you can, add a ceiling fan.

2" XPS foam will yield you an R-10 value. Cut it to fit the bay spaces the best you can with your track saw, slightly snug is good. Get a foam gun, seal the edges and butt joints.

If this was a residence you would have to cover it with a fire barrier, check with your AHJ to see if you need to cover it in a shop.

Only empirical evidence I have is how well it worked in our home. Our issue was cold weather not hot weather.

Tom

 

[antss]

I'm in ATL, very similar to Houston conditions.

We re-did our garage two years ago to add some space, windows and a door.  Had the whole thing foamed like a cooler. 3 1/2 - 5". It stays very comfortable in the spring, fall, winter.  In the summer it will climb to around 80 btw 1-6pm because it gets full sun from around 9am til 6.  No a/c. Wish I had even though it's just for parking cars and toys. If I had ac I have no doubt I could keep it 65 deg. with little trouble and expense.  I still may add a split , but have to decide btw that or an elect. car charger.

I can tell you all the attics never get above 78 deg. And we have a dark roof. The only empirical numbers I can give you are that our elec. and gas bill went up about $50 and we added another HVAC system, 1600sq.ft and on demand water heaters. The foam is the difference.  It's clearly better , but more expensive.  The other kicker is , you've gotta have the xtra money today to buy into the savings tomorrow.

The conundrum is that it's difficult to give hard numbers for future actual savings and benefits. Even with computer modeling , it's still a bit of a crap shoot.  I believe there is still a component of art and voodoo mixed in with the science when it comes to spray foam.  Like I said, it's better. Assigning a value to how much better is a lot trickier.

 

[Cheese]

I converted an attic into a loft master bedroom. With 5" deep bay spaces, I spaced the Foamular insulation (think Pink Panther) 1" from the roof to act as a chute for the ridge vent. Then I cut 2 each 2" layers of foam for each bay space with the track saw, making sure it was a snug fit. For the last 2" layer, I sealed the edges, as Tom suggested, with a foam gun. I then added poly as a vapor barrier and drywall.

The upstairs with windows on 3 sides and a 4' skylight, tracks within 3º of the downstairs area.

 

[tjbnwi]

I converted an attic into a loft master bedroom. With 5" deep bay spaces, I spaced the Foamular insulation (think Pink Panther) 1" from the roof to act as a chute for the ridge vent. Then I cut 2 each 2" layers of foam for each bay space with the track saw, making sure it was a snug fit. For the last 2" layer, I sealed the edges, as Tom suggested, with a foam gun. I then added poly as a vapor barrier and drywall.

The upstairs with windows on 3 sides and a 4' skylight, tracks within 3º of the downstairs area.

You don't need the poly with XPS.

Tom

 

[Cheese]

You don't need the poly with XPS.

Ya I know Tom,  [embarassed]  but at the time I was taking the belt & suspenders approach.  [tongue]

 

[Sparktrician]

I'd suggest looking vary carefully at using Roxul batts and/or blankets.  The increased fire resistance is a big thing for me in workshops and garages. 

 

[Wooden nickel]

I'm in ATL, very similar to Houston conditions.

We re-did our garage two years ago to add some space, windows and a door.  Had the whole thing foamed like a cooler. 3 1/2 - 5". It stays very comfortable in the spring, fall, winter.  In the summer it will climb to around 80 btw 1-6pm because it gets full sun from around 9am til 6.  No a/c. Wish I had even though it's just for parking cars and toys. If I had ac I have no doubt I could keep it 65 deg. with little trouble and expense.  I still may add a split , but have to decide btw that or an elect. car charger.

I can tell you all the attics never get above 78 deg. And we have a dark roof. The only empirical numbers I can give you are that our elec. and gas bill went up about $50 and we added another HVAC system, 1600sq.ft and on demand water heaters. The foam is the difference.  It's clearly better , but more expensive.  The other kicker is , you've gotta have the xtra money today to buy into the savings tomorrow.

The conundrum is that it's difficult to give hard numbers for future actual savings and benefits. Even with computer modeling , it's still a bit of a crap shoot.  I believe there is still a component of art and voodoo mixed in with the science when it comes to spray foam.  Like I said, it's better. Assigning a value to how much better is a lot trickier.

I agree antss.
I checked the spray foam closed cell but It is pricey and I know the roof will have to be changed so I opted for the rigid and spray foam from a can for now.
I just wanted to verify if it is possible to fully close and seal a garage as a conditioned space. I know it won't be the same as a home. But tolerable in the sense that my sweat won't drop on top of my work pieces.

 

[tjbnwi]

I'd suggest looking vary carefully at using Roxul batts and/or blankets.  The increased fire resistance is a big thing for me in workshops and garages.

Roxul is a very nice product.

Tom

 

[Wooden nickel]

I'd suggest looking vary carefully at using Roxul batts and/or blankets.  The increased fire resistance is a big thing for me in workshops and garages.

I don't think it's possible because of not having vents at all.
Yes, I could install them but why? If I am going to condition the space.
Add the humidity and I then have real problems.
Foam is the only solution i understand in a climate like Houston.
On another note i am going to put my dust collection for the stationary tools outside.
This maybe a plus. Because I thought that I could create a manual vent that when I just enter the garage, turn on the DC for a minute or two and suck all the hot air out. close the vent back to the tools connection and Then start the A/C?

 

[antss]

If you have bad roof decking, you shouldn't do anything until it's replaced.
That's a messy , invasive job. 

If you're just talking a re-shingle - foaming the roof isn't going to hamper that.

 

[tjbnwi]

Another option---move? [big grin]

Tom

 

[Wooden nickel]

Another option---move? [big grin]

Tom

Tom!! No more moving. I moved 3 times in the last 10 years.
I am planting my bum right here
Unless I hit the lottery.
Then I'll just buy 3 sets of Festool tools and make my garage
The way I want it.
There will be frost on the windows by the time I am done with it

 

[antss]

"On another note i am going to put my dust collection for the stationary tools outside."

No, no, no, no , not if you're going to foam that garage now or in the future.
Where is your make-up air going to come from ? And how are you going to get it in there? 10-12" pipe in the side of the garage ?

It's gonna come from outside, that same hot humid Houston air you're trying to get rid of inside your garage.

Seems to me you're overthinking this trying to re invent the wheel and or pick and choose aspects of different systems.

Best approach is to keep the inside air a comfortable temp and humidity all day , year round.  More energy is used in wild temp swings than maintaining a constant temp with superior insulation and air sealing.

 

[Wooden nickel]

Antss
This may need it's own topic but  i have the micron filter and was going to plum that back inside the garage.
That would be my makeup air.
So when the DC is on it will take air from the tools, dump chips outside, air continues back into garage and gets filtered from micron.
I am still working on the design but it makes sense to me?
I will definitely look into simplifying this but one thing is that  I do have the time and enjoy the challenge.

 

[antss]

That would certainly reduce the amount of hot humid air coming back in while the collector was running.

Makes the design a lot more complex and you'd prob. Want to increase the cfm your setup will pull after calculating your tool's needs. 

That is for another thread, and could go on for a while.

 

[tjbnwi]

Antss
This may need it's own topic but  i have the micron filter and was going to plum that back inside the garage.
That would be my makeup air.
So when the DC is on it will take air from the tools, dump chips outside, air continues back into garage and gets filtered from micron.
I am still working on the design but it makes sense to me?
I will definitely look into simplifying this but one thing is that  I do have the time and enjoy the challenge.

Rotary air lock...

Tom

 

[Steven Owen]

Cellulose is still the cheapest if you don’t need to space above for storage.  I’m in Canada.  You pretty much can’t do anything under R-20 or you’ll hate yourself in the winter.  R-40 is the standard up here.

Foam sheets should work for Texas.  I doubt you’ll ever need anything aboive R-10 if you’re not planning to install air conditioning in your garage.