Closed cell spray foam - 1.25 inch vs 2 inch

[goldenfri]

I am looking at insulating my 30x40 stand alone garage shop with closed cell spray foam.

The best quote I got was:

1.25" walls and 2" ceiling at around $6500
2" walls and 3" ceiling at around $8000

Right now I am leaning towards just going with the 1.25/2 because it isn't a living space and that will be a big improvement over the zero insulation I have now, but for those that have done it, will I regret not adding the extra insulation now?

Thanks in advance for the advice!

 

[jack stand]

There's a lot of "wall science" these days with the walls getting so tight (a good thing). I believe that it's advised to have the dew point of your wall insulation to be IN the foam. Living space or not your apparently going to heat the space so this dew point (condensation) is something to deal with just as you would for a house.
Run this concern by your insulation guy after your own investigation/education of this issue. I understand that 2" of iso foam does the trick in much of the country.
Years ago they used to spray an inch or so (very hard to spray less) just to absolutely air seal the wall, then fill the rest with regular fiberglass batts. They called it "flash&batt" and it caused (condensation) water problems.
I'm no expert so an evening in the web will be beneficial for your building and purchasing.
Have you considered a better option than normal FG but not the premium spray foam? Some type of mineral wool or one of the other very dense batt types? Like you said "it's not living space"

 

[PCustoms]

1.25"?

How is the installer getting that level of control?

Not enough foam IMHO. Go 2" minimum. It's not additional labor and shouldn't be much more in material, $1500 seems reasonable

 

[75gmck25]

I am in Northern VA and had my attic insulated with foam, and they used 8.5" of Agribalance open cell foam on the roofline and 3" on the newly framed walls and gable ends. However, there are many places where it goes to at least 10" on the roofline. I can't imagine keeping it to 1.5" unless the crew is really good, and the gun has a more granular way to control it.

As a guide they used paper strips with inch markings, stapled to the rafters sticking down, since in most cases the foam is deeper than the wood used for the rafters. It appears to be really effective, since the attic temp is now within a couple degrees of the house temp, regardless of whether we are our running A/C or heat.

We used the Agribalance open cell foam (Southwest Insulators from Manassas, VA) because its R value was 4.45 per inch, which is higher than most other open cell foam products.

 

[goldenfri]

Thanks for the advice everyone, there seems to be so much conflicting information from different installers and information I can find online etc.

For those with spray foam in a shop do you still use some kind of attic gable fan to get fumes/smells out? I've been told I no longer need the fan with foam, but with cars/welding etc there are a lot of fumes I don't really want sticking around. I guess the alternative is just stick a big box fan in front of the garage door.

 

[75gmck25]

One additional item to ask your installer about is whether the foam in an occupied area has to be sprayed with fire retardant. When they foamed our attic they said that it could not be used as living space or storage unless they treated the foam with fire retardant. I don't recall it to be real expensive, but we were already spending quite a bit on the foam itself.

 

[goldenfri]

Good call... the thing that started this whole journey was my Gable/attic fan catching fire and almost burning the whole place down.

 

[TheEquineFencer]

FYI

Barn Siding Looks Distorted After Spray Foam

I just had my 42x63 Pole Barn spray foamed with 3" of closed cell on the walls and 8" of open cell on the metal ceiling. After the job was done the foam seemed to push off itself and distort the metal siding. You can really see it along the horizontal 2x4's where the siding screws too. Seems...

www.garagejournal.com

 

[allinon72]

2" is the standard, which in practice is usually more like 2.5 or 3" if your installer is any good. Do it right the first time and be done with it.

 

[karoc]

1.25"?

How is the installer getting that level of control?

Not enough foam IMHO. Go 2" minimum. It's not additional labor and shouldn't be much more in material, $1500 seems reasonable

Exactly, there’s no way he can maintain that kind of control. Had my roof done in living space and shop, depth is all over place. Depending where he was standing and his reach

 

[86turbodsl]

My advice, after having done this a few times, put your ceiling in, spray down onto the ceiling and hit the walls. Then you can put in batts or cellulose and you've got that infiltration and moisture barrier so your insulation performs better and you save a ton. cellulose is cheap.

 

[dcg9381]

Right now I am leaning towards just going with the 1.25/2 because it isn't a living space and that will be a big improvement over the zero insulation I have now, but for those that have done it, will I regret not adding the extra insulation now?

To me it comes down to how much you have to heat/cool the structure. As you're not using this 24/7, you can go for less than regional recommended R values.

Are you going to frame this out? If so, you can supplement the walls with traditional insulation at a much lower cost. It's the roof that's kinda a beeotch.

And open cell in terms of dollar per R value is usually "cheaper". Closed cell is fine, but I'd probably only choose it in areas where available insulation space is at a premium.

 

[Kapn]

Where in Maryland are you? Is the project done? Any updates?

 

[meathooker]

Exactly, there’s no way he can maintain that kind of control. Had my roof done in living space and shop, depth is all over place. Depending where he was standing and his reach

Depends on the sprayer. I used to own a spray foam company with a buddy and he could EASILY hold 1/4” variance but I be seen him hold 1/8”. It’s impressive.
to the OP 2” is the minimum. It’s vapor impermeable at 2”. The cost is super reasonable for the extra R value.