Gambrel wall insulation

[dziskovs]

Trying to work out the best method for insulating this sloped wall assembly in 2nd floor master bathroom remodel of my gambrel roof house. Note the backside of this wall is a steep pitched asphalt shingled roof.

There are obvious signs of moisture in the walls now, so I will be removing the vapor barrier and insulation and replacing. It is 2x4 construction with unfaced batts today. There is not a knee wall.

Debating between flash and batt, full closed cell foam, or just mineral wool batts. I will be demoing the soffited ceiling area to raise the height in that area, so I will have access the the full height of the exterior wall all the way across this room.

The roofing and siding company cut soffit vents at soffit between 1st floor and 2nd floor sloped roof assembly, which I think was a mistake as it promoted air flow through the wall assembly with no way to pass it to the attic. I do not know if the moisture was present before they cut the soffit vents or not.

 

[billconner]

What I can see of the existing vapor barrier, it's poorly done. A well done vapor barrier certainly would have lessened the moisture issue, most certainly interior moisture condensing on exterior sheathing.

I think your flash and batt approach is probably your safest approach but I might consider a near perfect vapor barrier with rock wool or fiberglass or - my preferred - dense packed cellulose. And a vapor barrier like StegoHome 15 mil very carefully installed and sealed.

To improve insulation, you might consider an interior layer of rigid foam with seams taped or sealed with spray foam so it's also the vapor barrier.

I'd come up with an interior wiring system, like a tall vertical baseboard, to avoid sealing around receptacles and outlets.

 

[PCustoms]

I see signs of air infiltration, but not much moisture. Looks like maybe a leak around the window?

 

[dziskovs]

What I can see of the existing vapor barrier, it's poorly done. A well done vapor barrier certainly would have lessened the moisture issue, most certainly interior moisture condensing on exterior sheathing.

I think your flash and batt approach is probably your safest approach but I might consider a near perfect vapor barrier with rock wool or fiberglass or - my preferred - dense packed cellulose. And a vapor barrier like StegoHome 15 mil very carefully installed and sealed.

To improve insulation, you might consider an interior layer of rigid foam with seams taped or sealed with spray foam so it's also the vapor barrier.

I'd come up with an interior wiring system, like a tall vertical baseboard, to avoid sealing around receptacles and outlets.

Thanks for the suggestions. The only electrical on the exterior wall is the junction box for the exterior flood lights that you can see near the closest window, so it should be relatively easy to seal around it.

In regards to the flash and batt, I've used the diy froth pack 200 kits on rim joists in the past. Would that be an acceptable method, or am I better off paying a professional? The shingle nails would need to be fully encapsulated to my understanding.

 

[dziskovs]

I see signs of air infiltration, but not much moisture. Looks like maybe a leak around the window?

Certainly there is air leaking around and through windows, and wall insulation has visible mold from moisture. This house had a leaky roof, termites and carpenter ants which are all mitigated now, and this is the last room we are renovating in our two year process. The windows are also being replaced.

 

[Kaizen]

on my 2x4 exterior walls i add some 2x strips to get to enough depth for 2x6 rockwool batts. If not that and you have the money do all spray foam.

 

[billconner]

Thanks for the suggestions. The only electrical on the exterior wall is the junction box for the exterior flood lights that you can see near the closest window, so it should be relatively easy to seal around it.

In regards to the flash and batt, I've used the diy froth pack 200 kits on rim joists in the past. Would that be an acceptable method, or am I better off paying a professional? The shingle nails would need to be fully encapsulated to my understanding.

I have not and would not personally attempt diy spray foam for an entire roof. I believe someone posted on GJ they did but most say don't diy a spray foam roof.

Interior moisture and the pressure of a tall stack of warm air in cold weather is the key. 2" of spray closed cell foam should keep the interior condensing surface - the foam - above the dew point and prevent condensation. A near perfect vapor barrier can also keep warm moist interior air out of wall/roof cavity.

Filling the cavity with closed cell is probably best, safest, and most expensive. I couldn't afford that, and could afford loosing 1 1/2", I'd probably strap across the rafters/studs - Mooney wall - and dense pack cellulose with very good vapor barrier. Easy diy, low cost materials, pretty tolerant design.

 

[dziskovs]

Wanted to close out this thread. I ended up using my closed cell spray foam guy that I have used in the past, and he knocked it out between rough in and drywall and fit me in last minute for ~$500 all in. We used a menards mineral wool product for interior wall sound proofing.

Thanks for the advice along the way. Now its on to remembering how to lay tile and have it look good!