I have a wooden screened-in porch on a cabin that I am remodeling, with approximately 30 inches from the ground to the bottom of the porch tongue-and-groove boards. I am considering insulating the porch, with the eventual goal of being able to place polycarbonate panels over the screen in the cold months to help with heat loss.

Before I replace the floor, I would like to add insulation board between the floor joists and staple wire mesh underneath to keep any critters from chewing up the exposed insulation board.

The caveat: this is near a river, and on rare occasion it does flood. I'm worried that placing the foam board would trap a large amount of moisture after a flood between it and the joists / tongue and groove that would keep it from drying out relatively quickly and therefor rot / mold.

Are there ways to mitigate this? Raising the structure isn't an option, but I'm unsure how/if it's possible to vent the individual compartments created by the insulation board / floor joists.

  • you probably don't lose all that much heat though the floor anyway, compared to single-pane plastic windows, so a thick rug might be the better/simpler option.
    – dandavis
    Jun 15, 2020 at 4:24
  • how common are floods that reach the joists but don't go over the floor?
    – Jasen
    Jun 15, 2020 at 12:32

1 Answer 1


Indoor / outdoor carpet?

Maybe you can insulate by carpeting on top of the floor you have. There are lots of options. This will leave air movement under the porch as it is which I think is smart given flood risk. The indoor / outdoor carpet can be hung up to dry if the river floods, and replaced if it wears out or tastes change.

Anticritter mesh is a good idea, though.

  • I've been tossing around ideas.. I wonder if I could drill ventilation holes through the blocking, lightly slant the foam board during installation with small weep holes, and drill closable exterior vents in the outer rim to ventilate each cavity individually...
    – Ramrod
    Jun 15, 2020 at 0:17
  • Pretty involved for a glorified porch. It must get cold where you are. Saskatchewan?
    – Willk
    Jun 16, 2020 at 22:11

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