Insulating old house 2×4 walls
Old 2×4 Wall Insulation Plan
- In the cavity I plan on adding 3/4″ x 3/4″ blocking on each side to create a drainage (or drying?) plane between the siding and the to be installed rigid insulation
- On top of that blocking I plan to cut and install used 1″ polyiso rigid foam paper backed. (cut and cobble)
- Is the paper backing going to be a problem?
- Do I need to foam all the edges or can I get away with construction adhesive (assuming that it does not attack the foam) acting as a gasket preventing moisture from getting further into the wall?
- Given the shallow cavity to start and the even more shallow cavity after installing the rigid foam I was looking at methods to increase the depth while avoiding at all costs using any 2×2 from any lumber yard. Came across an article in FHB from April/May 2015 illustrating a technique used by builder Stephen Bonfiglioli (LINK). 1″ rigid foam strips nailed to 1×3 furring strips then nailed to the framing. His method seems interesting as it would both build out the depth of the wall (right to where I would need it for R13 fiberglass batt) but it would also seem to help minimize/eliminate the thermal bridging of the framing.
- With the rigid foam nailed to the furring strips and the final assembly nailed to the existing framing with a framing gun I am assuming that the finished assembly will act and be as strong as a standard framed wall (drywall hanging, picture hanging, etc.). Has anyone worked with this assembly before and/or have any opinion on it?
- Once assembled I could then lay in my R13 batt and hang the drywall.
- The 1″ paper faced polyiso is available locally used (CL) for about $6 less than new plus it will be repurposed. I still need to go and check the condition and confirm (through this Q&A if the paper backing will be a problem.
- The R13 fiberglass batt is something I have a lot of on hand due to insulating the rafters during the winter to keep the pipes from freezing.
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