Question 1

How much does it cost to insulate a house?

Accepted Answer

Insulation costs vary by type, area, and installation method. Per square foot installed: Fiberglass batt insulation costs $0.65-$2 per sq ft (R-13 to R-38), most economical DIY option. Blown-in fiberglass costs $1-$2.50 per sq ft (R-30 to R-60), good for attics. Blown-in cellulose costs $1.20-$2.80 per sq ft (R-30 to R-60), eco-friendly option. Spray foam insulation costs $1.50-$4.50 per sq ft for open-cell (R-3.6 per inch), $3-$7 per sq ft for closed-cell (R-6.5 per inch), best air sealing and insulation. For whole-house insulation: 1,500 sq ft attic insulation costs $1,500-$4,500 depending on R-value and method. Wall insulation (if accessible) for 2,000 sq ft costs $3,000-$10,000. Crawlspace insulation (1,000 sq ft) costs $1,000-$4,000. Basement walls (1,000 sq ft) cost $1,500-$7,000 depending on method. These prices include materials, labor, and basic air sealing. Additional costs: Vapor barriers ($0.50-$1 per sq ft), removing old insulation ($1-$2 per sq ft), air sealing services ($350-$1,500), and energy audit ($200-$500, often rebated by utilities).

Question 2

What R-value insulation do I need?

Accepted Answer

R-value measures insulation's resistance to heat flow - higher numbers mean better insulation. Required R-values vary by climate zone and location in home. ATTICS: Climate Zone 1-2 (Florida, South Texas, Hawaii) needs R-30 to R-49. Zone 3 (Southern states) needs R-30 to R-60. Zone 4 (Mid-Atlantic, Pacific Northwest) needs R-38 to R-60. Zones 5-8 (Northern states, Mountain states) need R-49 to R-60. Most energy experts recommend R-49 minimum, R-60 optimal for significant energy savings. WALLS: New construction targets R-13 to R-21 depending on wall thickness and climate. Existing homes typically have R-11 to R-15. Adding insulation to existing walls achieves R-13 to R-23. Southern zones need minimum R-13, northern zones benefit from R-19 to R-23. FLOORS (over unconditioned space): Zones 1-3 need R-13, Zones 4-5 need R-25, Zones 6-8 need R-30. BASEMENTS: Interior wall insulation should achieve R-10 to R-15 in all zones. Exterior insulation works better (R-10 to R-20) but costs more. CRAWL SPACES: Unvented crawl spaces need R-10 to R-15 on walls. Vented crawl spaces need R-25 to R-30 under floor. MORE R-VALUE PAYS OFF: Upgrading from R-30 to R-49 in attic costs extra $400-$1,000 but saves $100-$300 annually on heating/cooling, paying back in 3-5 years then providing ongoing savings for life of home.

Question 3

How much can insulation save on energy bills?

Accepted Answer

Proper insulation saves 15-50% on heating and cooling costs depending on current insulation levels and climate. TYPICAL SAVINGS BY PROJECT: Adding attic insulation from R-11 to R-49 saves $200-$600 annually in cold climates, $150-$350 in hot climates, $100-$200 in moderate climates. Insulating uninsulated basement walls saves $150-$400 annually. Adding wall insulation to uninsulated walls saves $300-$800 annually. Insulating floors over crawl spaces or garages saves $100-$300 annually. Combined whole-house insulation upgrade saves $400-$1,500 annually depending on home size (2,000-3,000 sq ft), current condition, and climate. PAYBACK PERIODS: Attic insulation (DIY): 2-4 years. Attic insulation (professional): 3-7 years. Wall insulation (retrofit): 5-10 years. Basement insulation: 7-12 years. Spray foam (premium): 8-15 years. FACTORS AFFECTING SAVINGS: Climate - greater temperature extremes yield higher savings. Current insulation - going from R-0 to R-30 saves dramatically more than R-30 to R-50. Air sealing - poorly sealed homes waste energy regardless of insulation (seal first, then insulate). HVAC efficiency - newer efficient systems reduce absolute savings but improve percentage. Energy costs - higher electricity/gas rates increase dollar savings ($0.15/kWh vs $0.08/kWh doubles savings). LIFETIME VALUE: Insulation lasts 50-100 years. $3,000 attic insulation saving $300/year returns $15,000 over 50 years. Combined with comfort improvements (fewer drafts, more even temperatures), insulation is one of best home improvement investments available.

Question 4

Is spray foam insulation worth the cost?

Accepted Answer

Spray foam costs 2-4x more than fiberglass but offers superior performance in specific applications. SPRAY FOAM ADVANTAGES: Creates air barrier plus insulation (two benefits in one), highest R-value per inch (R-6.5 closed-cell vs R-3.5 fiberglass), prevents air infiltration (responsible for 30-40% of energy loss), stops moisture penetration (closed-cell), strengthens structure (closed-cell adds racking strength), never settles or compresses (fiberglass loses 2-15% R-value over time), lasts lifetime of home, and reduces sound transmission. COSTS: Open-cell spray foam costs $1.50-$4.50 per sq ft (R-3.6 per inch), good for interior walls and tight spaces. Closed-cell spray foam costs $3-$7 per sq ft (R-6.5 per inch), ideal for exterior walls, roofs, and moisture-prone areas. Fiberglass batts cost $0.65-$2 per sq ft (R-3.2 per inch) for comparison. BEST APPLICATIONS: Rim joists in basements ($800-$1,500 for typical home) - huge air leakage area, spray foam seals perfectly. Crawl space walls ($2,000-$4,000) - moisture barrier plus insulation. Exterior walls in new construction ($5,000-$12,000) - maximum efficiency and air sealing. Cathedral/vaulted ceilings ($3,000-$8,000) - only practical way to insulate thin spaces properly. NOT WORTH THE COST: Standard attics ($4,000-$8,000 for spray foam vs $1,500-$3,000 for blown-in achieving same R-value). Interior partition walls (fiberglass batts adequate for sound control at 1/3 cost). Well-ventilated areas where air sealing less critical. VERDICT: Worth premium for problem areas needing air sealing plus insulation, new construction exterior walls, and moisture-prone spaces. Overkill for attics and interior uses where blown-in or batts perform adequately at much lower cost.

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How much does it cost to insulate a house?

What R-value insulation do I need?

How much can insulation save on energy bills?

Is spray foam insulation worth the cost?