What is the average cost to insulate an 11 foot by 18 foot room

Insulating an 11-by-18-foot room with standard eight-foot ceilings costs between $600 and $2,400 across the United States and Canada, averaging $1,200 to $1,800 depending on the insulation type, R-value, and framing requirements.

An 11x18-foot floor plan yields 58 linear feet of perimeter and approximately 464 square feet of gross wall area, or 662 square feet when including the ceiling. Builders and remodelers upgrading existing spaces face stricter thermal envelope standards under current energy conservation codes, where uninsulated masonry or standard stud cavities create thermal bridging and moisture accumulation.

If you only do one thing: Calculate the total net square footage of the 464-square-foot wall perimeter and choose continuous insulation with integrated stud channels to eliminate thermal bridging without building separate wood stud framing.

• Fiberglass Batts ($0.60–$1.40/sq ft): Total material costs range from $280 to $650 for wall cavities, requiring existing wood framing at 16-inch on-center spacing and a separate vapor barrier.
• Continuous Foam Panels ($2.50–$4.50/sq ft): Interlocking expanded polystyrene (EPS) panels cost between $1,150 and $2,100 for walls, delivering continuous R-8.5 to R-15 performance, built-in attachment studs, and integrated electrical raceways.
• Closed-Cell Spray Foam ($2.50–$4.50/sq ft): Professional application of two-inch closed-cell foam costs $1,200 to $2,100 for 464 square feet, yielding R-13 to R-14 with complete air sealing and vapor retardation.
• Bracket and Hybrid Systems ($0.63–$0.89/sq ft bracket base): Installing continuous framing brackets like Batt-Brackets or X-Brackets adds $50 to $80 in bracket hardware across 464 square feet, allowing friction-fit batts or blown insulation over masonry.
• Rim Joist Air Sealing ($150–$300): Sealing the 58 linear feet of rim joists and sill plate perimeter with expanding foam prevents draft infiltration that accounts for up to 30% of room heat loss.

• Watch out for: Hidden framing costs, which add $400 to $900 in lumber and fasteners for traditional stud walls if using conventional batt insulation against bare concrete.
• Watch out for: Interior space loss, as standard stud walls consume four inches along the perimeter and reduce usable floor area in an 11x18 room by roughly 18 square feet.
• Watch out for: Trapped moisture behind vapor barriers on basement foundation walls, which can lead to mold formation inside stud cavities.

Measure ceiling height and subtract door or window openings to determine net square footage, then request a project quote based on your climate zone's target R-value.

General information only, not an exact quote.