Glossary · Insulation & windows
Knee wall
Also called: knee walls · attic knee wall
A short wall, often in a 1½-story house, that separates a finished upstairs room from the unheated attic space behind it.
What it means
Knee walls are often poorly insulated, and the floor joists beneath them are often open to the attic, letting outside air flow under the room above. The usual fix is to seal that opening flush with the back of the knee wall finish, then insulate and air seal the wall itself.
Why it matters in an audit
Rooms with knee walls are often hard to keep comfortable, so audits check them closely in older 1½-story homes.