A project I would never go again, but (rigid foam insulation on concrete basement walls)

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ctviggen

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I've been insulating the concrete walls of my basement with Dow Thermax rigid (sheet) insulation. It's the only stuff I found that does not have to be covered in the basement or attic, up to 4 inches thick.

On the "top" surface (near rim joist) of the concrete wall, I added 1 inch of Dow Thermax (can't add 2 inches, as there's only about 1.5 inches there). On the side walls, I've been adding two inches. In the attachments, I show a small, but difficult part of the basement:

20210130_115713.jpg

I put glue on the "inside" of the sheet, then put the sheet against the concrete, then drill through the sheet and concrete and install a plastic "anchor". The bumps on the picture are the tops of the anchors, covered with tape. I tape all seams and penetrations. I spray foam (with fire-retardant foam) all seams and any penetrations.

The wooden structure (to the left of the ladder) is a temporary structure to support electrical for our solar installation. This is what it looks like after I glued and screwed on some plywood and attached the electrical to the plywood:

20210131_152033.jpg

That little section of the basement took 7+ weekends, due to the number of wires, electrical that had to be moved, pipe, etc. The whole process has been so time-consuming, it's literally almost divorce-causing.

Here's part I did around an oil tank and on a half wall:

20200906_125043.jpg

Same thing after taping:

20200907_081527.jpg

Behind the tank:

20200907_081542.jpg

Another several weekends for that.

On the other hand, on a quite cold day here in New England, here's the temperature of the cement:

20210131_152538.jpg

Here's the temperature of the insulation, just to the right of this location:

20210131_152550.jpg

While this is by far the most time consuming house project I've done, it actually will have a benefit. I just have to slog through the other 30 feet of walls.
 

oldognewtrick

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On any project I do, I try and start with the hardest area first.

Looks good, I believe you'll enjoy the temp difference once it's all done.
 

ctviggen

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Normally, that's not a bad idea. In this instance, it might not be a great idea. The only way I was confident enough to tackle that part of the basement was because of all the work I did before then.

I guess those pictures don't really show the scale of the project. Here are the first two walls I did:

20210201_131737.jpg

I learned from this that even if you have 2 inches between the pipe and the rigid insulation, that does not mean you can tilt the insulation behind the pipe. Thus, that cut that goes across the middle of the insulation: I couldn't get the insulation under the pipe, and had to cut the insulation -- while the glue was on it.

And then near the water system (soft water, iron, well), I did my first attachment of plywood to the insulation:

20210201_131744.jpg

I removed the electrical, temporarily supported it, put up the insulation, taped. Then I used some pieces of plywood I had, drilled pilot holes bigger than the holes for the 3/16 inch concrete drill bit, put glue on the plywood, held up while drilling through the insulation and into the concrete. I put 4 inch, 3/16 inch concrete screws through the plywood and the foam and into the insulation. So, the plywood is both glued to the Thermax and screwed into the concrete.

I made up this process, based in part on a Dow Thermax paper that said you could glue drywall to the insulation. I've never seen anyone do this (attach plywood to rigid foam insulation for electrical), so I made up the process myself. (Ideally, I'd put up a wall and hide all the insulation...but that's a whole level of time and money that I don't have now.)

Here's another shot, where the original picture I had of the breaker boxes/solar power boxes is behind the black fridge.

20210201_131752.jpg

This shows part of the "bump out", where I learned to do both inside and outside corners:

20210201_131819.jpg

I had to put 2 inches of foam on the bottom, one inch behind the pipe, then another 1 inch over the first one inch and between the 2 inch and the piper and over the 1 inch and between the pipe hangers.

To do this, I learned I couldn't put 2 inches on the bottom, then get the one inch past there, under the pipe, and up. Instead, I had to cut the one inch to the correct height, put it behind the pipe, put the 2 inch on the bottom (both 4x8 sheets are on their sides), cut the other 1 inch to fit around the pipe and between the pipe hangers. In other words, everything had to be dry fit.

Then, I had to take all that down, put glue on the 1 inch that goes on behind the pipe, put glue on the 2 inch on for the bottom, put the 1 inch behind the pipe, put the 2 inch on the bottom, tighten everything. Then drill a few anchors through the 2 inch to hold it. Put glue on on the 1 inch parts that need to go up, put them up, and drill anchors through the two 1 inch parts to anchor them together to create the 2 inches thickness I wanted. And drill more anchors through the 2 inch. And do all that within about 20 minutes, which is the time they give you for the glue.

Another picture of the pipe and hangers and the insulation that had to be cut around the pipe and hangers (and also the blocks of insulation in the rim joists -- another thing that's way hard to do):

20210201_131806.jpg

Between each hanger and pipe, there's a separate piece of 1 inch insulation I hand cut.

It's all the learning I did from this, which is what allowed me to attempt that corner.
 

soparklion11

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Wow. I bet that heavy bag took a few shots during the project... I need one of them ;)
 

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