# insulating walls next to garage attic



## lonesomefugitiv (Oct 15, 2016)

I live in NJ and had an energy audit done last year but I found that two of my rooms still remained cold.

These are two bedrooms where half of the rooms are above a garage. The exterior walls of these two rooms have part of the walls with no sheathing (see photo one). This area is cold because the garage roof has soffit and ridge vents so there is cold air in the winter. dense pack cellulose was blown into the garage ceiling joists below these two rooms, but it is still cold near these exterior walls.

The house is a 1960 split level that has a finished attic on the third floor and as part of the energy audit they put 2 inch polyiso rigid foam board over the existing insulation for the knee wall area in the attic along with blowing in dense pack cellulose in the floor joists (covered with plywood in the photo)

I was hoping that if I replaced the old fiberglass and then covered it with the 2 inch polyiso board and used spray foam to seal the gaps (similar to what they did in my attic knee wall in photo 3) that it would help make those rooms warmer, but I wasn't sure if it would cause potential moisture issues. Is this OK or is there another better solution?

I have attached three photos:


1. shows the area of the wall in question when looking through the garage ceiling
2. shows the outside of the house for the area in question
3. shows attic knee wall area insulated with Dow Super Tuff-R 2 inch polyiso rigid foam board from the energy audit


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## lenaitch (Feb 10, 2014)

I think sealed rigid foam board as suggested would work, but other, smarter people might have other thoughts. There is a lot of staining on the fiberglas that looks like evidence of air infiltration indicating that you may lack a vapour barrier. Rigid board should help that. It could also be mould but it looks more like dirt left behind as air moves through the insulation.

You could go 4" but others might say that the additional R isn't worth it.

There appears to be evidence of moisture on the roof rafters. You mention that the space is vented - is it adequate?

You should also do something with that vent. If it is a warm supply, it really needs to be insulated (which will complicate your rigid board solution). If it is a cold return, perhaps not so critical but an HVAC contributor might differ.


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## joecaption (Nov 30, 2011)

Not there to see it in person but from those pictures something looks really wrong or I'm missing something.
Why is that gable end even insulated? Is there a room on the back side?
Why is there not R50 insulation in that attic in that crawl space?
Is there a ridge vent on the roof?
Did they allow an air space to allow for venting from the crawl space to the peak of the roof?
Did they add blocking to prevent air flow from between the floor joist to under the floor?


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## lonesomefugitiv (Oct 15, 2016)

Regarding the garage roof:

Previously the roof was not vented. I had the house resided and re-roofed. I had them install a ridge vent and open up the soffit vent on the front of the house. The rear of the house does not have an overhang for soffit vents. It seems adequate to me. 

Regarding knee wall area in finished attic:

Yes there is a finished room on the other side of the foam board wall

Soffits are vented and there are two box vents towards top of knee wall ceiling 

Not sure where r50 insulation should be? In the floor where they blew in dense pack cellulose. There was floor subfloor planks there since the area was used for storage. In the remaining attic on the right of the house they blew in 10" of cellulose rated at R48

The attic area has kneewall on one side and dormer on rear of house so no ridge vent. There is a small gable vent on exterior wall and then the other side is connected to the rest of the attic

No they blocked off the roof rafters from the kneewall area to roof. I asked them the same question. There was fiberglass insulation along that area previously and roof rafters are only 2x6"

Yes they added blocking between floor joist under the floor

It is a traditional split, but attic is finished on one side, so you have four levels:
basement , 
family room on slab, 
Kitchen and living room
3 bedrooms
4th bedroom in attic with rear dormer

Attached photo shows the layout of house. Knee wall area is on the left above bay window.


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## Bud9051 (Nov 11, 2015)

I'll let others handle this, but wanted to comment that the discoloration on those rafters and the insulation says you have a significant moisture issue. Your energy audit should have commented and made recommendations.

Bud


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## lonesomefugitiv (Oct 15, 2016)

The view of that garage roof was not accessible at the time of the energy audit. There was drywall ceiling in the garage. I had new garage doors installed afterwards and the electrician had to cut an opening in the ceiling for electrical and so I stuck my phone up there to get a picture

Here is a crude drawing of kneewall area for attic


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