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BasementsRenovatingBuilding a Home
kellisean

spray foam quote too $$$ use XP’s or eps?

Kelli
5 years ago
Insulating the interior of the walkout basement walls. Finishing the basement and want to insulate and air seal the walls. We used 2” XP’s in the rim joists should we use the same treatment in the stud cavities since spray foam is too expensive? I’m in climate zone 4
Thank you
Featured Answer
  • worthy
    5 years ago
    last modified: 5 years ago

    If the exterior is already finished, use rigid foam on the interior face of the foundation walls, followed by fg or Roxul.

    If the stud walls are already in place, consider removing them so you can get a tight fit for the foam boards. Use tongue and groove, if available. Be sure to use horizontal glue lines, even if you're attaching the boards with concrete fasteners; this stops convection loops between the foam boards and the foundation.


    Comments (7)

    • PRO
      GN Builders L.L.C
      5 years ago

      You can do the same or use insulation rated for basement use since you already have insulation which will not be in the direct contact with a masonry foundation.

    • seabornman
      5 years ago

      Are studs already in place? Best route is to apply XPS to the wall then build stud wall. If you don't need stud wall in some areas because you won't need to run electrical or similar, there are ways to install drywall without studs (built-in furring, tap-cons, etc.). I have tap-conned osb over foam in a basement utility room. Great for hanging tools, conduit, pipes.

    • Kelli
      Original Author
      5 years ago
      The area in question is an exterior wall that is sheathing and vinyl on the outside on the walkout side. It has fiberglass insulation and we want to seal and insulate it better before the drywall’s come.
    • PRO
      PPF.
      5 years ago

      Your best option is rigid foam on the exterior under the vinyl.

      See this recent thread for some info.

      https://www.gardenweb.com/discussions/5640711/insulation-options#n=20

    • PRO
      Dishington Construction - Jensen Hus
      5 years ago
      buy once, cry once. spend the $$$ on the closed cell spray foam. superior in all ways, especially air sealing which is critical.
    • seabornman
      5 years ago

      Now that I understand the issue, you could add depth to your studs with ripped 2xs or I've seen people use foam strips to bump out wall depth so you can fit thicker batts in. The foam would give you a thermal break. There's a thread on greenbuildingadvisor.com for this. You do end up doing some blocking for electrical boxes and perimeter conditions.

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