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Earth is one of the best insulating materials for a home.
On those upper floors, wood stud walls enclose soft fiberglass insulation batts.
The batts are faced with paper.
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The edges of the paper are stapled to the studs.
This system does not work for basement walls.
Fiberglass insulation facing foundation walls readily absorbs moisture if it is exposed to humidity or if it becomes wet.
After being water-logged, fiberglass loses some of its R-value.
Worse, the highly porous material becomes a breeding ground for mold and other allergens.
Rigid foaminsulation is the material of choice for insulating against foundation walls in basements.
You have two options withrigid foam: rigid foam only or rigid foam with a stud wall system.
The screws are driven through one-by-three wood furring strips.
Later, drywall is installed on the furring strips.
This method is straightforward and less expensive than the stud system method.
Being thinner, the wall conserves room.
But it has about half of the insulating value of the stud system method.
Plus, driving multiple screws into concrete can be taxing.
This method works well forbasementsthat need minimalinsulationand where space is at a premium.
A stud wall system, similar to those on upper levels, is built using wood or metal studs.
The wall system touches the rigid foam but is held in place at the top and bottom.
Finally, drywall is added.
This method gives the basement more insulating value, by allowing you to add fiberglass in watertight wall cavities.
The wall system is structurally independent of the foundation wall.
But this method requires more building materials, making it more expensive and overall more difficult to construct.
The full stud system is best for larger basements that need maximum insulating value.
With fiberglass insulation, full PPE is required, including a NIOSH-approved dust respirator (N95 or greater).
It cannot be left uncovered.
Tightly cover all four sides.
If condensation does not collect between the plastic and the wall, the wall is dry enough for insulation.
If necessary, apply basement waterproofing sealer to the wall.
The wall must be clean.
Kill and encapsulate mold and mildew.
Each section between floor joists needs to be insulated.
Cut small sections of rigid foam to fit in these areas.
Adhere the foam to the band joist with foam adhesive.
Fill the gaps with low-expansion spray foam adhesive.
When the rigid foam needs to be cut lengthwise, first look for the pre-cut scores on the board.
If not, score the board lengthwise with the utility knife down to the depth of the blade.
The blade does not need to fully penetrate the board.
Then snap the board on the score line.
Start in a corner.
Apply a continuous ribbon of foam adhesive to the back of the board.
Press the board into place.
Lean a section of scrap two-by-four against the board.
Cut the boards on the electric miter saw or with a hand saw.
load the Furring Strips
Fit the foam boards side-to-side.
Butt the edges against each other.
plant the furring strips horizontally on the face of the insulation.
Use the drill and concrete screws to attach the furring strips.
The screws must penetrate the concrete by 1-inch.
The boards fit into the depressions, flush with the face of the rigid foam.
If your boards have this, drop in the furring strips vertically in these side laps.
Install and Finish the Drywall
load the drywall to the furring strips with drywall screws.
Tape, mud, and sand the drywall.
Prime and Paint the Drywall
Apply drywall primer to the finished drywall.
Paint with interior acrylic-latex paint.
Frame the Wall
Frame out the wall with studs.
The back of the framing can touch the front of the foam insulation.
Use apowder actuated nail gunto nail the bottom plate to the concrete floor.
As this tool uses live charges, observe all safety precautions.
Add Fiberglass Insulation
Fiberglass insulation can be used in the framing.
While this step is optional, it will double the R-value of the basement insulation.
Staple the paper edges of the insulation against the studs.
Install and Finish Drywall
Attach the drywall to the stud framing.
Finish the drywall by taping, mudding, and sanding it.
Finish by priming the drywall with drywall primer, then painting the wall with acrylic-latex interior house paint.
Amold remediationcompany can help kill and encapsulate the mold.
Armstrong, M. Ruest, K. Swinton, M.C.
Assessing the Impact of Cold Climate on Basement Temperatures.
Canada National Research Council, 2011. doi:10.4224/20373827
Section 2603 Foam Plastic Insulation.2018 International Building Code (IBC)
