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bpatton 03-26-18 01:08 PM

Insulating old house walls
Okay, so this is a long post but I'm looking for some advice in a project I have coming up in the near future. I have an old farmhouse built in the early 1940s that I'm slowly bringing back to life. Its a weekend type house that gets visited about once a month year round. The house currently has NO insulation anywhere. Its like a clean slate! :) The attic is completely void of insulation as are the walls and the floor (its pier and beam with a vented crawl space). The siding is horizontal lap siding but covered with an "Insulshake" paper asphalt siding that is probably 60 years old. The Insulshake is falling off in large chunks because the asphalt is giving it up finally. Also the building has wood windows that are rotten. So my thoughts are removing and replacing the windows and horizontal siding and replacing all to stabilize the house and bring up the efficiency. This is a budget conscious project but the replacement windows will definitely be double plane Low E. Now, my original idea was to remove the Insulshake and the horizontal lap siding and install fiberglass batts in the walls then install sheathing, board insulation, and a new siding.
The thought did come to mind that instead of removing the horizontal lap siding (because its in good condition) to remove the Insulshake and replace with 2.5in of XPS foam then sizing on top of that. That might cut out quite a bit of time because time is always limited with these projects.
Now this house is in a very dry climate so I'm not too worried about the lack of vapour barrier internally.
Any thoughts? I may be totally wrong here but I thought I would give it a shot.
Thanks for reading!

JRMichler 09-29-18 07:17 PM

Foam on the outside is an excellent idea in an older house. A friend once put new siding on an older house. He took the advice of his neighbors who told him that foam was not necessary if he was careful installing tar paper. He was quite upset when the finished job leaked almost as bad as the original house.

I once added foam to the outside of an old house that was sheathed with some sort of fuzz board. The house was much more comfortable afterward, especially in the summer.

Foam on the outside becomes your vapor barrier. If you make it thick enough, the inside surface of the foam cannot condense, even if you fill the stud cavities with insulation.

A deluxe job would be 3" or 3.5" of foam, with 1/2" thick plywood/OSB on the outside for nailing the siding.

oil pan 4 10-02-18 09:55 PM

What I did was hole saw a 4.5 inch hole near the header and hand fill the insulation. I hole sawed the dry wall so the hole I cut couldn't fall down into the wall. Then I filled the void and used 1 sheet rock screw to hold the circle I previously cut and mudded it back into place.
Do the first ones inside a closet so if it looks funky no one will notice.
I used cellulose based insulation.
Then up top I added a layer or r13 fiber glass then went back over it with r19 fiber glass.

bpatton 10-08-18 08:24 AM

Thanks for the replies! I still haven't begun working on this project yet, school has had me behind for this last year or so. Once I finish my central air/heat install out there the windows and siding will be next on the list.

bpatton 10-08-18 08:30 AM

"I once added foam to the outside of an old house that was sheathed with some sort of fuzz board. The house was much more comfortable afterward, especially in the summer."

How did you do deal with the trimming around the windows and doors? That is where I'm stuck at right now. Planning on using Tyvek as an air barrier and taping all of the seams and flashing everything heavily then putting 2in poly-iso over the top of that, siding on top of that with furring strips. I was planning on the windows being installed in the plane with the existing wall sheathing instead of jacking them out to the (new) siding. But that leaves me trimming out the areas around the windows (on the outside) to try to cover up the foam.

JRMichler 11-07-18 06:36 PM


Originally Posted by bpatton (Post 59889)
How did you do deal with the trimming around the windows and doors? That is where I'm stuck at right now.

On that job, I used 1" foam. The windows had been installed such that I could just butt the foam up to them.

If I was doing a similar job today, I would use 3" to 4" of foam. I would remove the siding and windows, then install the new foam over a whole wall. Two layers of foam, tape all joints of each layer. Then 1/2" of OSB on top. Then I would go inside, cut out a window opening, then put in a casing out to the OSB. Install the rain screen (Tyvek or whatever), then install the window. Repeat until the entire wall is done, then install the siding. The windows would be flush with the outside.

That's similar to my present house, which was built with 3.5" stud walls and 4" of foam on the outside.

n7mog 11-30-19 10:30 PM

I know this is a year later than the last post. I completed a project of adding 4" XPS to the outside of our manufactured home this year. It was built in 1988 with no wrapping at all and typical vertical 4x8 pressed siding. All "trailer house" double hung windows were replaced with Pella casement style windows in sizes smaller than originals. I followed the R.E.M.O.T.E. wall system out of Alaska for construction. After replacing windows, I house wrapped with a Lowe's product with very low moisture permeability over the existing siding, considering it as a layer of sheathing instead. I boxed all the openings outward to slightly exceed the expected thickness of the foam, furring and new siding. After painting, the end result was a quieter structure. Now with cold weather upon us, we have already enjoyed a warmer, non air leaking home. Our propane usage is down from past history. Since I did this myself, I saved the labor costs, although it increased the time of construction. This is a cost effective upgrade for us, and I do suggest a study of this method for a positive solution for an energy improving retrofit.

crad1970 06-18-20 07:45 PM

If you find some insulation, cut out a 12- to 16-inch horizontal band of drywall or plaster midway up the wall. Then just pull out the old insulation. If you choose loose fill or expanding foam, it can go in through the same holeĀ—though you'll need to make more holes along the top of the wall to complete the job."

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