How to insulate a drafty floor over a basement or porch
Cold air often leaks in where the foundation connects to a porch or through completely uninsulated spaces between a porch ceiling and the bedroom floor above it. People end up just laying down towels to block the air because they do not know what materials to use or whether they must pull up the entire subfloor to install proper insulation.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1laying down towels
- 2filling gaps with wood glue and sawdust
- 3installing insulation under the floors
- 4using oakum hemp cord between boards
- 5Pulling down the unconditioned space's ceiling instead of removing the subfloor above.
- 6Using closed-cell spray foam to achieve air sealing and insulation in a single step.
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Hanging a ceiling fan on the screen porch I noticed there is zero insulation between the ceiling of the screen porch and the floor of the bedroom above it.”source ↗
“My questions is do we pull up the subfloor to install this insulation and when we do...what needs to be used?”source ↗
Where this came up
People with this problem also raised
- 3How to stop cold drafts coming through a sliding glass door
- 6Do I need a moisture barrier under basement LVP flooring?
- 2How to cover ugly hardwood floors cheaply
- 4Can you put new flooring over old pine boards without a subfloor?
- 5Can you put heated floors under luxury vinyl tile?
- 4How to stop heat loss through an attic hatch or open carport