How can I install insulation in my downstairs, built with cinder blocks.


How can I install insulation in my downstairs, built with cinder blocks.

Asked by Carlos

There is no insulation and its cold.

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Harold Remlinger, AIA, LEED AP, NCARB's picture


If you intend to insulate your basement you must then also consider installing a finish surface to conceal the insulation per the International Building Code.

There are two ways to insulate your basement, which both will incorporate the installation of studs or hat channels and either drywall of panelling along the perimeter of the basement.

  • The first way is by installing conventional blanket or foam board insulation min. R-10 (varify with your local State energy code). On the warm side of the studs or hat channel install a vapor barrier prior to the installation of the finish surface.
  • The second method would be to install 1.5" of closed cell spray foam between the studs or hat channels and directly to the face of the block walls. The closed cell foam acts as an air barrier and there is no need to install a vapor barrier on the studs or hat channels prior to the installation of the finish wall board.

Either method you should also consider insulating the bond beam and sill plate above the block wall. This is the location where most of the air infiltration occurs.

Now I must mention that there is another method. Closed cell foam can be installed directly to the block wall minus studs and a finish wall board.

  • However to meet the current fire and smoke spread codes the insulation must be covered with a fire rated paint.
  • Now this is not the most visually pleasing method and it also makes it hard to keep clean from dust since the surface is irregular.
  • I would suggest discussing this with your local building official prior to proceeding with this method since they will have the ultimate say and may not be aware of this approach.

For more information:

Read "Do you recommend blue 2" + 1" Dow foam board between studs for a cinder block basement wall?" a Q&A answered by Anthony Addesso.