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Home Repair Remodeling

How Best Insulate Old Walls

5 years ago

Hi,

I've got a house built around 1950 in SE Michigan. The outer walls are like this:

2x4 studs 16" apart

pine 1x6s spaced roughly 1/4" apart

tar paper

cement shingles

Aluminum siding added long after construction

on the inner side:

drywall with 1/2" holes randomly knocked in it making DIY plasterboard

rough & finish plaster about 3/8" thick

No insulation, just air between inner & outer. Seems to keep out the cold well, but anything leaning against the wall will cause mildew to form. The plaster has come loose in many places, there's no fixing it. I would like to rip out the existing drywall & plaster and add insulation & new drywall. I would like suggestions how to insulate. I originally planned to just staple in batt w/vapor barrier, but after some investigation I'm not sure if it wouldn't be better to use some kind of spacing to create an air gap between the insulation and the outer wall. But with only 4" studs that wouldn't leave much room for the insulation. I'm really not sure at all what to do.

I'm not a builder, Just a DIYer, I would appreciate any and all suggestions! Thanks!

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Comments (3)

emho23
5 years ago
I recently spun myself in circles and delayed our renovation a bit over a similar topic (how to insulate a 1914 stucco house with a slightly leaky tile roof). I can tell you that we put most of our energy into the roofline (baffles and closed cell foam) and secondarily to the walls and gable ends we had open for the reno (furring strips, rock wool, certainteed membrain smart vapor barrier). Your situation is different, but I think you are right to think about this carefully.

1. Is your roof/attic insulated? If not, do that first, much more bang for your buck

2. I agree with putting an air gap between the outer wall and the insulation, to the extent that cement shingles are permeable (are they?). We used furring strips for that.

3. People seem to like rock wool batts.

I would recommend posting your question at greenbuildingadvisor.com. Someone here gave me that pointer, and GBA gave me some great advice.
yewmonger
Original Author
5 years ago
Thanks! After more googling, I think I will use rock wool, with plastic sheeting for the vapor barrier on the inner side. I don't believe the siding is permeable and basically the 1x6s look like new. Upgrading the attic insulation and ventilation will be the next project. I will check out that web site. Thank you!
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GreenDesigns
5 years ago
last modified: 5 years ago
Your walls aren’t deep enough to be able to use high the R insulation needed to move the dewpoint. You need to open them up to fur them out and add foam insulation. That accomplished vapor sealing and insulation both. Read BuildingScience.com
yewmonger thanked GreenDesigns

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