Garage Insulation Calculator

Understanding Garage Insulation

Proper garage insulation is crucial for energy efficiency, comfort, and climate control. Understanding insulation types and installation methods ensures optimal performance.

  • R-Value Requirements Walls: R-13 to R-21 (climate zones) Ceiling: R-30 to R-49 (under living space) Door: R-8 to R-18 (insulated steel) Slab edge: R-10 (frost protection) Windows: R-2.5 to R-5 (double/triple pane)
  • Material Properties Fiberglass batts: R-3.1-3.4 per inch Mineral wool: R-3.0-3.3 per inch Spray foam: R-6.0-7.0 per inch (closed cell) Rigid foam: R-4.0-6.5 per inch Cellulose: R-3.2-3.8 per inch
  • Air Sealing Impact Infiltration reduction: 30-50% Energy savings: 15-30% typical Moisture control: 40-60% RH target Sound transmission: 5-10 STC improvement Comfort improvement: 5-10°F differential
  • Installation Factors Coverage factor: 1.10-1.15 waste Compression loss: 20% R-value typical Thermal bridging: 15-20% performance loss Vapor barrier: Required zones 4+ Air barrier: Continuous system required

Installation Methods

Wall Systems

Cavity fill: 2×4=R-13, 2×6=R-19. Double layer: Add R-5 rigid. Vapor barrier: 6 mil poly zones 4+. Air gap: 1" behind rigid foam.

Ceiling Systems

Depth required: 10-16". Ventilation: 1:150 ratio. Baffles: Required at eaves. Cross ventilation: Required. Vapor barrier: Facing down.

Door Treatment

Weather stripping: Compression type. Bottom seal: U-shaped vinyl. Edge seals: Magnetic preferred. Perimeter gap: 1/8" maximum.

Foundation Details

Slab edge: 24" vertical/horizontal. Frost protection: Required below grade. Termite barrier: Required. Drainage plane: 1/4":12" slope.

Performance Standards

  • Energy Code Requirements Zone 1-2: R-13 walls, R-30 ceiling Zone 3-4: R-13+5 walls, R-38 ceiling Zone 5-6: R-19+5 walls, R-49 ceiling Zone 7-8: R-21+5 walls, R-49 ceiling Air changes: 3 ACH50 maximum
  • Moisture Management Vapor retarder class: - Class I: 0.1 perm or less - Class II: 0.1-1.0 perm - Class III: 1.0-10 perm Placement: Warm side of assembly Exception: Hot-humid climates
  • Fire Safety Thermal barrier: 15-minute rating Ignition barrier: Required Flame spread: Class A/B required Smoke development: <450 rating Fire blocking: Required at plates
  • Sound Control STC rating: 45-55 target Impact noise: IIC 50+ preferred Mass law: 6 dB per doubling Resilient channels: 24" O.C. Absorption: 0.7-0.9 NRC target

Material Selection

  • Fiberglass Batts Density: 0.5-1.0 pcf Width: 15"/23" standard Length: 93" typical Facing: Kraft/unfaced options Cost: $0.64-0.85/sq.ft
  • Spray Foam Density: 1.75-2.0 pcf closed cell Yield: 4,000-5,000 bd.ft/set Cure time: 24 hours full cure Temperature: 40-100°F application Cost: $1.00-1.50/sq.ft/inch
  • Rigid Foam Types: XPS, EPS, Polyiso Sizes: 4'×8' standard Thickness: 1/2"-4" common Edge treatment: T&G available Cost: $0.75-1.25/sq.ft/inch
  • Mineral Wool Density: 4.0-4.5 pcf Fire rating: 4 hours at 2" Water resistance: Hydrophobic Sound absorption: NRC 0.95-1.05 Cost: $0.95-1.20/sq.ft

Installation Quality

  • Inspection Points Grade I installation: - No gaps/voids - Full depth achieved - Proper compression - Continuous barriers - Complete coverage
  • Common Defects Compression: >20% loss Gaps/voids: >2% area Missing insulation Improper vapor retarder Thermal bridging paths
  • Quality Assurance Visual inspection Infrared scanning Blower door testing Moisture meter readings Documentation photos
  • Performance Verification R-value verification Air barrier continuity Vapor retarder integrity Thermal imaging results Final documentation