Spray Foam-Closed Cell

[JeffK]

Hi All
Unfinished Basement:
I have 180 sq feet of rim joist to spray at 1" to 1 1/2" . There is already 1/2" to 1" of closed cell on the rim joist area now.
This is in the Chicago area.
Perma Seal's price is $2300 for 2".

1. What is the difference between a 2 canister system and a 1 canister system.

2. What is the optimal
temperature to apply.

3. There was R13 unfaced insulation covering the spray foam. I removed it because of the condensation between the spray foam an R13 when outside temps were in the high teens to high 20's.
The condensation ended after removal.
By the way the basement humidity was 35-45 percent.

4. I want to hang drywall once the rim joist are insulated.
With 2 inches of spray foam, I'm thinking that R13 insulation won't be necessary. I really don't trust batt insulation in the rim joist.

Thank You!!

 

[bud16415]

If you already have the good air seal of the inch or so and wanted to do it DIY, I would think about maybe using sheet foam cut to fit tight over what you have and then use canned spray foam to fill the gaps.



I don’t have the information on the 1-2 part and temps. Others should be along with more info.

 

[Steve123]

1. What is the difference between a 2 canister system and a 1 canister system.

Two component does a chemical reaction when mixed. I think one component also does a chemical reaction, but uses moisture in the air as the second component (Great Stuff is like that, anyways). (A moisture cure polyurethane, rather like Gorilla Glue or PL Premium). Just make sure it is closed cell, and purchase by R value per inch. One component could be safer for a rookie, because you can't screw up the mixing ratios.

2. What is the optimal temperature to apply.

Follow manufacturer's directions.

3. There was R13 unfaced insulation covering the spray foam. I removed it because of the condensation between the spray foam an R13 when outside temps were in the high teens to high 20's.
The condensation ended after removal.
By the way the basement humidity was 35-45 percent.
4. I want to hang drywall once the rim joist are insulated.
With 2 inches of spray foam, I'm thinking that R13 insulation won't be necessary. I really don't trust batt insulation in the rim joist.

Sprayfoam gives off toxic fumes when burning, so code required a XX minute fire barrier over it. Insulation over the sprayfoam (often rockwool) is commonly used for this purpose.
Half inch to one inch is not thick enough in Chicago to avoid the inside surface of the sprayfoam to get cold enough for condensation to form on the inside surface of the sprayfoam. So a plastic vapor barrier over the batt insulation would have been necessary, which is difficult to get airtight in a joist bay anyways. Thicker sprayfoam is a better solution. Drywall is a good fire barrier, but I can't interpret for you if a ceiling sheet of drywall is close enough to the foam to be accepted as the fire barrier.

Consider also using 2" XPS sheet cut to fit the joist bay, and cheap acrylic caulk on the perimeter to seal. Might be hard to do if the sprayfoam was not neatly applied. But every time I used Great Stuff, half of it ends up on the wall and the floor. And really difficult to clean up.

 

[JeffK]

Thank you. I'm trying to reason this out. I've reached out to the local inspector, construction manager and our housing track contractor and get mixed theories.

In the association Facebook group, I've asked if anyone has had this problem and get no response. There are many units going up and I can see the consistent manner that the rim joists are sprayed and batted (R13/R15). The housing track started 4 years ago.

My basement is unfinished.
All basements, whether they are unfinished, ceiling only or completely finished, the perimeter of the rim joist is sprayed with about 1" and the field is about 1/2", with the unfaced batt layed against the spray foam.

Last winter when the temp got down to 20, I just happened to stick my hand behind the batt insulation and felt the condensation. After removing a section of batt, the condensation dried up in 4-6 hours. The basement temp was 65 and humidity around 45, which I don't think are extreme specs.

Since the foam, as you pointed is inconsistent and not a flat surface, there would be air gaps that I'm thinking would encourage condensation, if dense poly board were applied. Am I wrong on that thinking?

If 2" of additional foam is applied, giving a 2 1/2" to 3" thickness, roughly a R15+ value and no condensation, I would be thrilled with that. I do plan on finishing the basement. The sheet rock will lessen the warmer basement air from contacting the rim joist.

Anyway, sorry about this novel but it's really got me paralyzed and hesitant to proceed.

Thanks for listening.

 

[Steve123]

d up in 4-6 hours. The basement temp was 65 and humidity around 45, which I don't think are extreme specs.

Since the foam, as you pointed is inconsistent and not a flat surface, there would be air gaps that I'm thinking would encourage condensation, if dense poly board were applied. Am I wrong on that thinking?

If 2" of additional foam is applied, giving a 2 1/2" to 3" thickness, roughly a R15+ value and no condensation,

It's not so much the air gaps --- half inch simply is not thick enough for Chicago weather. One inch (R7) would probably be about minimum required thickness to avoid condensation
If its 20F outside, the inside surface of that half inch of sprayfoam might be at 40F (just a WAG to make a point). Cold enough to form condensation. Since the batt insulation overtop was unfaced, it would possibly dry towards the inside after it warms up, but still not a great situation. (I am neglecting the insulation contribution of the rim joist)

You should be fine at R15+. The inside face of the sprayfoam wouldn't be getting cold enough to allow condensation to form.

 

[JeffK]

It's not so much the air gaps --- half inch simply is not thick enough for Chicago weather. One inch (R7) would probably be about minimum required thickness to avoid condensation
If its 20F outside, the inside surface of that half inch of sprayfoam might be at 40F (just a WAG to make a point). Cold enough to form condensation. Since the batt insulation overtop was unfaced, it would possibly dry towards the inside after it warms up, but still not a great situation. (I am neglecting the insulation contribution of the rim joist)

You should be fine at R15+. The inside face of the sprayfoam wouldn't be getting cold enough to allow condensation to form.

It's not so much the air gaps --- half inch simply is not thick enough for Chicago weather. One inch (R7) would probably be about minimum required thickness to avoid condensation
If its 20F outside, the inside surface of that half inch of sprayfoam might be at 40F (just a WAG to make a point). Cold enough to form condensation. Since the batt insulation overtop was unfaced, it would possibly dry towards the inside after it warms up, but still not a great situation. (I am neglecting the insulation contribution of the rim joist)

You should be fine at R15+. The inside face of the sprayfoam wouldn't be getting cold enough to allow condensation to form.

So, you think that 2 inches of spray foam without fiber batting will stop the condensation? That is if the basement humidity is below say 45 and temp around 72.

I believe if the ceiling has DW, fiber batting isn't necessary because DW is a fire retardant.
Once again, I'm not confident in fiber batting in the rim joist.

I appreciate you thoughts.