Insulation Question

[Dropsix]

Good day!

I have an approx 30 x 30 attached garage here in Ontario which I started insulating and drywalling last week. We did the ceiling first and used rockwool batts, vapor barrier and then 5/8 firecode drywall. No issues there.

The issue came with the walls. The south side facing wall in particular. I have 2x6 studs so I got Roxul R22 2x6 (16" spacing) and crammed all of that in, then vapor barrier and then was ready for drywall. Last night, I noticed a bunch of condensation all along the south facing wall where the sun was pounding on it all day. The temp inside the garage was cooler and so condensation accumulated between the rockwool batts and the vapor barrier.

From the outside of the garage, it goes vinyl siding, house wrap, sheathing (OSB plywood) and then studs (and insulation inside the studs then vapor barrier of course).

I am wondering how I could remedy this issue?? Thanks in advance!!

 

[Dropsix]

Only going to bump this once, I apologize, just want to see if I can get any suggestions before I move on to other options.

 

[Hallucar]

For what it's worth, I had a small patch of condensation forming between the insulation and vapour barrier that I noticed just before drywalling this past summer. It was only a very small patch and it was located near an electrical box. I know this doesn't answer your issue, but just mentioning that perhaps it's something that happens on occasion just based on random events (moisture content in lumber, outside temperature fluctuations, etc).

 

[K'ledgeBldr]

"...all along the wall"

Along the wall at the sheathing and plate could be air leak, under plate is an air leak, moisture was in the the insulation, moisture in the framing before you "sealed it".

Yeah, there's several possibilities and no one place to point because it could be a combination of several possibilities.

 

[yeldogt]

Is this a new garage and green wood?

If you are using plastic --- That's your problem. Plastic is a barrier - total. It stops drying -- it's not like foam in the middle.

plastic can cause big problems .... that's why VB membranes are used

 

[Dropsix]

For what it's worth, I had a small patch of condensation forming between the insulation and vapour barrier that I noticed just before drywalling this past summer. It was only a very small patch and it was located near an electrical box. I know this doesn't answer your issue, but just mentioning that perhaps it's something that happens on occasion just based on random events (moisture content in lumber, outside temperature fluctuations, etc).

Hmm ya, I was hoping it would have been a fluke but I just got home and the whole wall has condensation on the inside of the vapor barrier. The inside of the garage stays very cool during the day (from cool night time temps) and it’s been fairly warm and sunny during the afternoons.

Not quite sure... thanks for answering. I was hopeful until I got home, haha.

 

[rlitman]

...Plastic is a barrier - total. It stops drying...

Polyethylene sheeting is a semi-permeable membrane, with it's permeability inversely proportional to its thickness. That's why thin zip-loc bags aren't good in the freezer.

 

[Dropsix]

"...all along the wall"

Along the wall at the sheathing and plate could be air leak, under plate is an air leak, moisture was in the the insulation, moisture in the framing before you "sealed it".

Yeah, there's several possibilities and no one place to point because it could be a combination of several possibilities.

Maybe I’ll take a photo and try to add more detail.

Is this a new garage and green wood?

If you are using plastic --- That's your problem. Plastic is a barrier - total. It stops drying -- it's not like foam in the middle.

plastic can cause big problems .... that's why VB membranes are used

Not a new garage, it is 10 years old.

I used 6mm poly vapor barrier

 

[paredown]

These are my go-to guys when I have questions like this.

Take a look at the wall assembly examples and see if you can do something different?

https://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers

 

[Dropsix]

image upload

 

[speed bump]

Your temperature drive today was from outside (hotter) to inside (cooler). Condensation happens on cold side which is why in most climates that switch back and forth between hot and cold you should to be very selective with the use of an impermeable barrier. Typical rules of thumbs are: Almost all heating climates impermeable barrier on the inside, primarily cooling climate vapor barrier on the outside. Switching back and forth, probably best to have a lot of solid insulation on the outside so that the dew point isn't in the middle of your rock wool.

 

[yeldogt]

Polyethylene sheeting is a semi-permeable membrane, with it's permeability inversely proportional to its thickness. That's why thin zip-loc bags aren't good in the freezer.

For a wall it does not breath ,,, not good to use ,,,, caused huge problems in the 70's when it was first widely used. bad things linger.

like vented attic's and crawl

caulking everything

 

[yeldogt]

Your temperature drive today was from outside (hotter) to inside (cooler). Condensation happens on cold side which is why in most climates that switch back and forth between hot and cold you should to be very selective with the use of an impermeable barrier. Typical rules of thumbs are: Almost all heating climates impermeable barrier on the inside, primarily cooling climate vapor barrier on the outside. Switching back and forth, probably best to have a lot of solid insulation on the outside so that the dew point isn't in the middle of your rock wool.

Ideally -- you want to be able to have things dry from both sides. Nothing should be impermeable.

closed cell foam works because it's in the middle and inert ...

when you put poly against drywall -- you can get condensation on either side .. and it does not dry easily to the outside

 

[Dropsix]

alright, I'll try a couple different things I suppose and report back in case anyone has the same issue.

 

[zak77]

Was the condensation on the interior of the garage or on the insulation side of the poly? Was the temp difference all that great? The way you did everything is the standard in building, at least in the Northeast, so either it was extenuating circumstances that caused this or it's a major issue. Makes you wonder if you might be better off taking the poly down, putting up drywall and using a good primer and 2 topcoats of latex to act as the "vapor" barrier.

 

[Dropsix]

Was the condensation on the interior of the garage or on the insulation side of the poly? Was the temp difference all that great? The way you did everything is the standard in building, at least in the Northeast, so either it was extenuating circumstances that caused this or it's a major issue. Makes you wonder if you might be better off taking the poly down, putting up drywall and using a good primer and 2 topcoats of latex to act as the "vapor" barrier.

Condensation is on the inside of the poly, sandwiched between it and the insulation.

I think honestly it's just that it's fall so overnight the temps drop very low and due to it being insulated it keeps all the cold in the garage all day. The back of my house is beaten on by sun all day long (beautiful and nearly 20 degrees celsius) and being home all day today I was able to keep an eye on it. I'd say around 3pm is when the condensation started happening again. It seems to mostly go away overnight. If I remove the vapor barrier, the R22 rockwool is definitely warm to the touch. I can see how this is an extreme and likely wouldn't be an issue in winter at all, just summer probably. Garage will be heated in colder weather.

I am debating these "smart" vapor barriers. I think they might be a solution. I'm actually thinking that drywall on top of the vapor barrier MIGHT be enough to take the edge off that cold hitting the plastic, however, I don't really want to chance that and it won't help me sleep at night! Not to mention I live in Canada, hot summers cold winters, there is plenty of room for insane weather and I want to make sure all bases are covered.