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Old 01-02-2010, 11:17 PM   #1
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Insulate/air seal shared walls in townhome?

I want to thank you up front to dedicating your time to reading my post. Yes it is long, but I havenít been able to find much information on the subject. Maybe I havenít looked hard enough? I wanted to get this out there sooner rather than later so I can make the decision for my problem.

I have attached a crude drawing (thanks MSPaint) of a top view layout of my 2nd floor.

I've been concerned with my shared walls of my townhome not being insulated for quite some time. It never really was a problem until after I had a baby. I started spending more time in the room and noticed that the shared wall was much colder to the touch than the exterior wall.

For starters, I added insulation in my attic, going from R-19 to R-38, I also used some canned spray foam to seal some air gaps from within the attic. More specifically, the ceiling joist in the room that was closest to the cinderblock walls in the attic had a gap between it and the block. I sealed that gap with foam to prevent cold air from the attic to fall down into the wall and to prevent heat to escape.

We also replaced our 20 +/- year old heat pump with a newer, more efficient and effective unit.

These steps reduced our electric bills significantly, but, the room remains cold.

As I researched and learned more about insulation, air flow, and home construction in general, I came to realize that part of the issue is that my townhome extends 2 feet further than my adjoining neighborís house. There's only brick fascia, cinder block, a 1" air gap, and drywall separating this room from the elements for about 2' of the wall.

I spoke to a few contractors and economically it was suggested that I just raise the temperature slightly as that cost vs. the cost of insulating the wall in any fashion would be cheaper.

I could've lived with this, but new discoveries were made. Over the past year or so, in the room next door to this bedroom (bedroom 1), I have noticed a crack forming in the exterior corner of the wall. This house has had some severe "settling" so I chalked it up to that. All 4 corners of the house on both floors show signs of the walls shifting causing the tape or whatever was placed there to join the drywall to crack or warp. I didn't think anything of it until tonight.

In my childs bedroom (bedroom 2), the exterior wall is outlined with 1" shoe molding on the ceiling and walls. Seeing the other problems with the corners led me to believe it was installed to hide the cracks. And it may have been, but the shoe molding and drywall have slightly separated and now there is a draft coming through on both sides of the room. And there is a draft coming through the crack in the room next door (1) as well.

It doesnít seem too bad in the summer, but it is bad in the winter. There have been a lot of strong winds this winter and I think thatís what made me notice it this year.

What can be done? Iíve thought about:

-Tearing the walls in the bedrooms down and framing it out properly with 2x4ís, insulating, and calling it a day.

-Looking into the pour foam product by Icynene, but I donít know if the 1Ē gap between the blocks and drywall is enough to make the investment worth while.

-Tearing the walls out, installing 2Ē rigid foam board along the wall and using a can of spray foam to seal where necessary, adding on some furring strips then covering it with drywall.

-Another less practical/effective solution I read about would be to drill into the cinder blocks from within the attic and pour in foam insulation. The only problem is that the foam would likely fall to the basement through all the holes in the blocks and Iíd never know if the room even got insulated.

Since there is a draft, obviously thereís some holes/cracks/openings outside underneath the siding thatís allowing the air to come in. Iíve considered removing the siding from the back of my house and checking out the wood covering my walls and sealing from the outside.

Iím at a loss here. Raising the temperature spending a few extra bucks a month to combat an obvious problem seems ludicrous to me and goes against my better judgement. Before I made any decisions I was hoping to get some feedback to what solution makes the most sense.

Thank you for your time!
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Old 01-03-2010, 02:12 AM   #2
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It seems to me that there is a bad design issue here. In many instances, townhomes are required to have an increased fire rating in the shared wall. The design of your building is almost like two completely separate houses built next to each other with a cinder block wall in between. Usually the only thing that connects the two buildings is the roof sheathing and the siding, and sometimes a shared basement wall. The design may have not left enough room for insulation, or the contractor failed to take into account that these are in fact exterior walls that need insulation. I believe that the cracks in the drywall are a separate issue. There are new products being introduced all the time, but my gut feeling is to go with the tried and true fiberglass batt insulation. This may involve your suggestion of tearing walls down and re-framing, but in the end, you will know that it has been done right. Some of the details are a little unclear to me regarding your air infiltration, so just be sure that you do some research about using a vapor barrier in your circumstance.
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Old 01-03-2010, 06:00 AM   #3
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Even 1" of Icynene might make a noticeable difference, as much or more as a result of an improved air barrier as from its insulating properties.

However reading you account, my first question is: has the cause of the "settling" been identified and corrected?
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Old 01-07-2010, 05:39 AM   #4
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has the cause of the "settling" been identified and corrected?
According to the experts in my area (contractors), the settling isn't true settling. The wood beams used to support the house actually fluctuate so much with the temperature change/humidity change, that it actually causes door frames to change, walls to crack, and everything to look "off" in the center of the house. All of the corners of my house, except for the one in "Bedroom 1" (per the graphic) had identifiable damage since I've been here (about 6 years). All of my neighbors have the same issues with the house fluctuation, I'm guessing it's all due to whatever wood they used for the support beams.

After we replaced our heating system, I disconnected the existing humidifier. The installer said that I don't really need it, but if I wanted it, I could probably replace it with a newer/smaller unit. I don't really know what caused the crack in Bedroom 1, but I wonder if it's due to the lack of humidity in my home. Maybe over time, the stress caused by the decreased size of the beams made that seam crack? Not too sure.

I think the easiest solution (besides moving) would be to contact the Icynene installers and see what it would take to pour some of that into these walls. The air barrier is probably the biggest bonus, and I shouldn't have to rip anything out as long as it can be poured through the gap in the attic.

I can't wait until we can find a house that has a solid foundation/structure, that's near gutted, where we can really do what we'd want to do on the inside, without having to tear everything out to do it up.

Thanks for the replies guys!!
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Old 01-07-2010, 09:50 AM   #5
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You could remove the drywall in the corner, put up 1" of rigid foam, and put a new piece of drywall in. Fast and cheap, and adding R-7 to what you have will make a big difference.

You'll probably find though, that the block 4' in is just about as cold as the block in the corner, so you might want to do the whole room. But then you'll start thininkg about doing the whole house, and all of a sudden you have a huge project. Tug on a loose thread and you know what happens.
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