Basement wall thermal insulation cost & R

Measure the wall run and height, drop in your $/ft² and the R of your rigid and batt layers: you get the job total with a contingency and the assembly R-value — thermal work only.

Planning estimate: this is a planning estimate from the numbers you enter — not a bid or a contract. Insulation pricing depends on material, R-value, access, prep, air-sealing, removal and local labor. Get itemized written quotes from licensed, insured insulation contractors before you commit.

Calculator

ft
Total run of basement wall you are insulating (add the runs).
ft
Floor to top of wall — often 8 ft; insulate the full height.
$/ft²
From your quote — rigid + framed batt runs higher than an attic.
(0.10 = 10%)
Buffer for furring, fasteners and access. 10% is a sane default.
R
e.g. 2" XPS ≈ R-10 against the wall. 0 if you skip it.
R
Batt in a furred/stud wall in front, e.g. R-13. 0 if none.
Result
Estimated total$2,323.20
Wall area (120 ft × 8 ft)960 ft²
Assembly R (rigid + cavity)R-23
Contingency10% ($211.20)

A 960 ft² basement wall at $2.20/ft² is about $2,323.20; rigid + cavity gives about R-23. THERMAL insulation of the basement wall only — waterproofing, drainage and radon are out of scope (basementcalcs / a pro); confirm the moisture/vapor detailing on the data sheet and local code.

Formula

wall_area = wall_length_ft × height_ft

total = wall_area × your_$/ft² × (1 + contingency%)

assembly_R = rigid_R + cavity_R

The $/ft² is your quoted price — a basement wall is usually rigid foam against the concrete plus a furred or stud wall with batts, which is why it runs higher than blowing an attic. The R line just adds the two layers so you can see the assembly total.

Worked example

A 120 ft run of 8 ft basement wall at $2.20/ft² installed with 10% contingency, 2" XPS (R-10) plus an R-13 batt:

Area: 120 × 8 = 960 ft². Total: 960 × $2.20 = $2,112, then × 1.10 = $2,323.20. Assembly R: 10 + 13 = R-23.

So about $2,323 for the wall and R-23 for the assembly. If you go rigid-only (skip the batt), set cavity R to 0; if you dense-pack a stud wall with no foam, set rigid R to 0 — but continuous foam against the concrete is what keeps the wall warm and dry.

Foam first, water separate

Rigid foam goes against the concrete, for a reason. A layer of rigid or spray foam in continuous contact with the wall keeps the concrete above the dew point so warm indoor air never hits a cold surface and condenses. A stud wall with batts alone against bare concrete is the classic mistake — it grows mold behind the drywall. This tool lets you set both layers so the R line reflects a foam-first assembly.

THERMAL only — fix water first. Insulation does not fix a wet basement. Waterproofing, exterior drainage, the sump and radon are separate work, set by code and often a different trade (see basementcalcs / a pro). If the wall leaks or the space is damp, solve that before you cover it, or you will trap moisture. This calculator sizes the thermal spend and R, nothing about water.

Insulate the full height, and mind the code. Insulate from the sill plate down — the top of a basement wall (the above-grade part) loses the most heat. Foam in a basement almost always needs a code-required ignition/thermal barrier (often 1/2" drywall) over it; confirm the barrier, the vapor detailing and any fireblocking with your local code.

What this is not. It is a planning estimate and an R tally, not a bid or a moisture design. Enter your own price; get itemized written quotes from licensed, insured contractors, and a pro for the water and code details.

Reference table

Labeled R/inch of common wall-side foams and the R of a 2" layer against the concrete — add your cavity batt on top.

Foam against the wallR per inchR at 2"
Rigid EPSR3.6–R4.2/inR-7.8
Rigid XPSR4.5–R5.0/inR-9.5
Rigid polyisoR5.6–R6.5/inR-12.1
Closed-cell spray foamR6.0–R7.0/inR-13

Labeled planning typicals — polyiso drops in cold temps; confirm the rated R on the board.

Frequently asked questions

How much does it cost to insulate a basement wall?
At a typical installed $2.20/ft² with 10% contingency, a 120 ft × 8 ft wall (960 ft²) runs about $2,323. A basement wall is rigid foam plus a framed batt wall, so it costs more per ft² than an attic. Enter your own quote price — this is a planning estimate, not a bid.
What R-value do I get from rigid foam plus a batt?
The tool adds the layers: 2 inches of XPS (~R-10) against the wall plus an R-13 batt in the framing in front gives R-23. Set either layer to 0 to model a foam-only or batt-only assembly.
Can I just put fiberglass batts against the concrete?
No — that is the classic basement mistake. Batts alone let warm air reach the cold concrete and condense, growing mold behind the drywall. Put continuous rigid or spray foam against the wall first, then frame and batt if you want more R.
Does this cover waterproofing or a wet basement?
No. This is THERMAL insulation cost and R only. Waterproofing, drainage, the sump and radon are separate work set by code — solve any water problem first (see basementcalcs or a pro), then insulate, or you will trap moisture.
Do I need a fire barrier over basement foam?
Almost always. Foam plastic in a basement typically needs a code-required ignition/thermal barrier over it — commonly 1/2-inch drywall. Confirm the barrier, vapor detailing and fireblocking with your local building code before you finish the wall.

Related calculators

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