Insulation Calculator

R-value requirements vary by climate zone and location: Attic/Ceiling: R-38 to R-60 (most critical), Southern climates R-38, Northern climates R-49 to R-60. Walls: R-13 to R-21, 2x4 walls R-13 to R-15, 2x6 walls R-19 to R-21. Floors over unconditioned space: R-25 to R-30. Basement walls: R-10 to R-15. Check local building codes - requirements updated regularly. Higher R-values save more energy but cost more upfront. ROI typically best in attics, then walls, then floors.

Calculate attic insulation in steps: 1) Measure attic floor area (Length × Width), subtract any unusable space. 2) Check existing insulation depth and type - may only need topping off. 3) Determine target R-value for your climate zone. 4) Calculate material needed based on insulation type coverage rates. Example: 1,000 sq ft attic, want R-38 fiberglass batts (R-3.2 per inch needs 12 inches), bags cover 40-60 sq ft at R-38, need 17-25 bags. Add 10% waste for irregular spaces and compression.

Common insulation types and R-values per inch: Fiberglass batts: R-2.9 to R-3.8 per inch, cheapest, DIY-friendly, good for standard stud spacing. Blown-in fiberglass: R-2.2 to R-2.7, fills irregular spaces, requires blower. Cellulose: R-3.2 to R-3.8, eco-friendly (recycled paper), settles over time. Spray foam closed-cell: R-6 to R-7, best R-value, air/moisture barrier, most expensive, professional install. Spray foam open-cell: R-3.5 to R-4, allows moisture passage, cheaper than closed-cell. Mineral wool: R-3.0 to R-3.3, fire-resistant, soundproofing. Choose based on: Budget, DIY ability, space constraints, moisture concerns.

Yes, adding insulation over existing is common and effective: Check existing first: If wet, moldy, or damaged - remove and replace. If compressed or settled - may need removal. If dry and intact - can add on top. Best practices: Remove any vapor barriers on new insulation (only one barrier needed). Use unfaced batts or blown-in for adding layers. Maintain attic ventilation - insulation should not block soffit vents. Seal air leaks first before adding insulation (around pipes, wires, chimneys). Cross-layer perpendicular to existing for better coverage. New R-value adds to existing: R-19 + R-19 = R-38 total.

Insulation costs vary widely by type and installation: Fiberglass batts DIY: $0.50-$1.50/sq ft (R-13 to R-30), professional install adds $0.50-$1.00/sq ft. Blown-in cellulose/fiberglass: $1.00-$2.50/sq ft installed (includes equipment rental). Spray foam open-cell: $1.50-$3.00/sq ft installed. Spray foam closed-cell: $3.00-$7.00/sq ft installed. Rigid foam boards: $1.50-$3.50/sq ft. Factors affecting cost: R-value needed (higher = thicker = more expensive), accessibility (attic easier than walls), labor rates by region, project size (bulk discounts). Average home re-insulation: $1,500-$5,000.

Faced vs unfaced insulation serves different purposes: Faced insulation: Has vapor barrier (kraft paper or foil) on one side. Use for: First insulation layer in walls/attics, enclosing conditioned spaces, preventing moisture from entering insulation. Install vapor barrier toward heated side (inside in cold climates). Unfaced insulation: No vapor barrier. Use for: Adding to existing insulation, soundproofing interior walls, locations already having vapor barrier. Benefits: More flexibility, no double vapor barrier issues. Rule: Only one vapor barrier per cavity - multiple barriers trap moisture causing mold and rot. Some codes prohibit faced insulation in certain applications.

Vapor barrier requirements depend on climate and location: Cold climates: Vapor barrier on warm (interior) side prevents warm moist air from condensing in cold insulation. Use faced insulation or poly sheeting. Hot humid climates: May need vapor barrier on exterior side, or none at all - check local codes. Mixed climates: Often skip vapor barriers, use "smart" vapor retarders that adjust permeability. Exceptions: Spray foam acts as own vapor barrier, basement walls need exterior waterproofing not interior vapor barriers. Modern building science: Air sealing more important than vapor barriers - air carries 50x more moisture than diffusion. Consult local building codes and climate zone requirements.

Insulation lifespan varies by type: Fiberglass batts: 80-100 years if kept dry and undisturbed. Cellulose: 20-30 years (settles over time, may need topping off). Spray foam: 80+ years, most durable option. Mineral wool: 50-100 years. Replace insulation if: Wet or water-damaged (loses R-value, promotes mold), compressed or settled significantly, contaminated by pests or mold, outdated and far below current R-value standards. Signs needing replacement: High energy bills, uneven temperatures, ice dams, drafts. Often more cost-effective to add layers than completely replace. Inspect attic insulation every 10-15 years for settling or damage.