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Insulation and vapor barrier

I have a problem that I need some help with deciding what to do. I live in a 2 story townhouse + walkout basement. The 2nd story back bedrooms overhang my rear deck by about 2-3ft. I've always noticed that the rear bedrooms are much colder then the rest of the house (with the exception of the basement) and the floor near the back wall is colder then the rest of the floor. I finally got around to prying back the in floor vent of my son's room slightly and shined a flash light down in there. No suprise, no insulation in the 2x12 cavity. Since the rest of the floor seems equally as cold in both bedrooms I suspect there may not be insulation in ANY of the cavities of the overhang.

I was originally planning on pulling down the panels of the overhang and putting up some 1" foam board insulation, putting the panels back up and calling it a day. However, with no insulation I am thinking of adding batt insulation as well.

My problem is that there is exterior vapor barrier, but it doesn't appear there is any interior vapor barrier (at least not in that one cavity). I live in Maryland and with the cold weather the vapor barrier should be on the inside of the cavity. What are my options with this?

Would faced insulation help much on reducing vapor transfer?

Would using the foam board with vapor tape on it sealing everything up well be enough to prevent condensation in the cavities?

Would the two in combination be enough if one isn't?

Also since I don't know that there is any vapor/thermal break between this overhanging and the ceiling of my living room. Would filling the overhang cavities be enough, our should I put some king of additional vapor/thermal break between the living room ceiling and the overhang? My thoughts were an additional cut to size piece of the faced insulation with the face towards the interior of the house (at a 90 degree angle to the rest of the insulation).

Lastly, if these are 2x12, what R value batt insulation will fill the cavity properly? R-38 or R-30 fiberglass?


I look forward to much better comfort and heating bills.

Re: Insulation and vapor barrier

I forgot to add, here is a diagram of the structure. The red part is where the empty void(s) is/are located.


Re: Insulation and vapor barrier

Well I ended up tearing down the panels. Turns out it was insulated, just very poorly. There was anything from a 2inch up to a 10 inch gap in insulation in each void. The vent areas was the worse with that 10 inch gap with no insulation further along then the edge of the vent.

I added R30 to fully fill the voids, then R3.3 1/2 foam board with radiative barrier facing in to the house (though not reall any air gap in any of the voids for the radiative barrier to work with) and then reinstalled the panels. Just need some primer and paint on the panels and it looks as good as new. I used a little spray foam on a few of the 'holes' up in there as well such as where electrical wiring is run for a just because.

The floor is noticably warmer now. Still a little cool, but that is mostly from the walls/window there. Also it appears that the portion of the wall that sticks out beyond the two neighboring townhouses has no insulation beyond about 1 1/2 inches of foam board on it (which is probably why it is so much colder).

*sigh*, probably a project for a future home owner.

Sunny H
Re: Insulation and vapor barrier

Well done!

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