Weatherization

Homeowner Summary

Weatherization is the process of sealing and insulating your home to reduce air leaks and heat loss, making it more comfortable and less expensive to heat and cool. It is consistently the highest-ROI energy improvement you can make, typically costing $2,000 to $6,000 for a full-home treatment and paying for itself in 2 to 4 years through lower energy bills.

The biggest energy waste in most homes is not from old windows or an inefficient furnace — it is from invisible air leaks. Gaps around plumbing pipes, electrical wires, recessed lights, and the tops of interior walls allow conditioned air to escape into attics, crawlspaces, and wall cavities. A typical older home leaks enough air to equal leaving a window open year-round.

Weatherization projects range from simple DIY tasks (caulking, weatherstripping, door sweeps) that cost under $100 to professional air sealing and insulation projects. Many utility companies and state programs offer substantial rebates or free weatherization services, especially for income-qualified homeowners.

How It Works

Weatherization targets the building envelope — the boundary between conditioned (heated/cooled) indoor space and unconditioned outdoor or buffer spaces. The goal is to minimize uncontrolled air movement while maintaining proper ventilation.

Air sealing stops air leaks at specific points. Common materials include:

• Caulk: Fills gaps up to 1/4 inch around window and door frames, trim, and where different building materials meet. Silicone lasts 20+ years; acrylic latex lasts 5-10 years.
• Weatherstripping: Seals the moving parts of doors and windows. Types include V-strip (bronze or vinyl), foam tape, felt, and door sweeps. Replaced every 3-8 years depending on material and wear.
• Expanding foam: Fills gaps from 1/4 inch to 3 inches around pipes, wires, and larger penetrations. Low-expansion foam for windows and doors; high-expansion for larger cavities.
• Rigid foam board: Covers large openings like attic hatches, whole-house fan covers, and dropped soffits.

Attic bypass sealing is the single most impactful weatherization task. The attic floor is riddled with holes where wires, pipes, ducts, chimneys, and interior walls penetrate the ceiling plane. Sealing these from above (in the attic) with caulk, foam, and sheet metal dramatically reduces heat loss.

Rim joist insulation addresses the perimeter of the floor framing where it sits on the foundation wall. This area is typically uninsulated in older homes and is a major source of cold drafts. Cut-and-cobble rigid foam sealed with spray foam is the standard approach.

Storm windows add an insulating air layer over existing single-pane windows for a fraction of the cost of replacement windows. Modern low-e storm windows can improve window performance by 30-50% at $100-$200 per window vs $600-$1,200 for replacements.

Door sweeps seal the gap under exterior doors. A 1/8-inch gap under a 36-inch door equals a 4.5 square inch hole in your building envelope.

Maintenance Guide

DIY (Homeowner)

• Inspect caulking around all windows and doors annually; re-caulk any cracked or peeling areas
• Check weatherstripping on all exterior doors; replace if compressed, torn, or missing
• Verify door sweeps make contact with the threshold; adjust or replace if light is visible
• Check attic hatch or pull-down stairs for air leaks; add weatherstripping and insulation
• Seal any new penetrations from renovations (cable, plumbing, electrical)
• Inspect storm windows for broken glass, failed latches, or missing weep holes
• Feel for drafts around outlets and switch plates on exterior walls; install foam gaskets

Professional

• Every 3-5 years: Inspect attic air sealing for settling, displacement, or new penetrations from electrical or plumbing work. Reapply foam or caulk as needed.
• After renovations: Re-test with blower door to verify that construction work did not create new air leakage pathways.
• Every 5-10 years: Reassess insulation levels against current code recommendations. Insulation settles over time and may need topping off.

Warning Signs

• Drafts felt near windows, doors, electrical outlets, or recessed lights
• Ice dams forming on the roof edge in winter (warm attic air melting snow)
• Uneven temperatures between rooms or floors
• High energy bills relative to similar homes in your area
• Frost or condensation on interior window surfaces
• Dust streaks on carpet near baseboards or around outlets (indicating air movement)
• Attic insulation that is dark or dirty near penetrations (sign of air flowing through it)
• Pipes freezing in exterior walls or above uninsulated crawlspaces
• Pests entering through unsealed gaps (mice can fit through a 1/4-inch opening)

When to Replace vs Repair

Repair (re-seal) when:

• Caulk has cracked or separated but the substrate is intact
• Weatherstripping is compressed or torn on one or two doors
• A single door sweep is worn
• Foam insulation around a few penetrations has shrunk or fallen out
• Storm window hardware needs adjustment

Full weatherization project when:

• Energy audit shows ACH50 above 10 (or above 7 in cold climates)
• Multiple air sealing deficiencies identified throughout the home
• Attic has never been professionally air-sealed
• Rim joists are uninsulated
• Home predates 1980 and has not been weatherized

Cost rule of thumb: DIY air sealing materials for a whole home typically cost $200-$500. Professional air sealing runs $1,000-$3,000. Full weatherization including insulation upgrades: $2,000-$6,000.

Pro Detail

Specifications & Sizing

| Component | Specification | Notes | |-----------|--------------|-------| | Caulk (windows/doors) | Silicone or polyurethane, rated for exterior use | 20-50 year lifespan for silicone | | Weatherstripping (doors) | Compression type; kerf-in or surface-applied | Bronze V-strip is most durable | | Expanding foam | Low-expansion for windows; fire-rated around penetrations | Must be covered (UV degrades exposed foam) | | Rigid foam (attic bypasses) | 1-2 inch XPS or polyiso, sealed edges with foam | Fire barrier required if left exposed | | Rim joist insulation | R-10 to R-15 rigid foam, sealed perimeter with spray foam | Vapor barrier face toward interior in cold climates | | Attic hatch | R-30 minimum; weatherstripped perimeter | Consider pre-made insulated hatches | | Door sweep | Aluminum with vinyl or silicone seal | Auto-retract type for uneven thresholds |

Air sealing priorities (by typical impact):

1. Attic bypasses (plumbing, wiring, top plates, recessed lights) — 30-40% of leakage
2. Rim joists and foundation/sill — 15-20% of leakage
3. Duct boots and returns in unconditioned space — 10-15%
4. Windows and doors — 10-15%
5. Electrical outlets and switches — 2-5%
6. Recessed lights — 5-10% (especially older non-IC models)

Common Failure Modes

• Caulk failure: Acrylic latex caulk cracks in 5-10 years from UV and thermal cycling. Silicone resists this but does not accept paint. Polyurethane offers the best adhesion but is harder to apply.
• Weatherstripping compression set: Foam weatherstripping permanently compresses within 2-4 years. Vinyl or rubber lasts longer. Bronze is the most durable (30+ years) but is more expensive to install.
• Foam off-gassing and shrinkage: Some spray foams shrink slightly over time, opening gaps. Low-quality foams may off-gas volatile compounds. Use name-brand, low-VOC products.
• Moisture trapping: Improper air sealing can trap moisture in wall cavities, leading to mold or rot. The key rule: the air barrier and vapor barrier must be on the correct side (warm side in heating climates, cool side in cooling climates, or use vapor-permeable barriers).
• Incomplete attic sealing: Sealing some bypasses but missing major ones (open soffits, balloon-framed walls, chimney chases) achieves little. Air sealing is only effective when comprehensive.
• Ventilation compromise: Over-tightening a home without adding mechanical ventilation can cause indoor air quality problems, moisture issues, and combustion appliance backdrafting. BPI guidelines recommend mechanical ventilation for homes below 5 ACH50.

Diagnostic Procedures

1. Blower door baseline: Measure ACH50 before any work to establish the starting point and identify worst leakage areas.
2. Attic walk-through: With the blower door running (depressurizing the house), inspect the attic floor for air movement using a smoke pencil or thermal camera. Mark all penetrations for sealing.
3. Crawlspace/basement inspection: Check rim joists for air leaks and missing insulation. Inspect foundation walls for cracks. Test for moisture with a pin moisture meter.
4. Window and door assessment: Check operation, weatherstripping condition, glazing integrity, and frame-to-wall air sealing.
5. Duct inspection: Visually inspect accessible ductwork for disconnections, gaps at boots, and missing insulation. Duct blaster test if warranted.
6. Combustion safety test: Before and after air sealing, test all combustion appliances for backdrafting and CO production. Critical safety check that must not be skipped.
7. Blower door retest: After sealing work, retest to quantify improvement. Target at least 15-25% reduction in ACH50 from a comprehensive air sealing project.

Code & Compliance

• IECC: Current energy code specifies maximum air leakage rates for new construction (3-5 ACH50 depending on climate zone). Weatherization of existing homes is not required to meet new code, but should target these levels where safe.
• BPI standards: BPI-2400 (Standard Practice for Standardized Qualification of Whole-House Energy Savings Estimates). BPI auditors must follow combustion safety protocols.
• Fire stopping: Fire-rated sealant required around penetrations through fire-rated assemblies (party walls, floor/ceiling assemblies between living space and garage). Foam alone is not a fire stop.
• Asbestos consideration: Homes built before 1980 may contain asbestos in insulation, duct tape, or pipe wrap. Testing required before disturbing suspect materials.
• Lead paint: Homes built before 1978 may contain lead paint. RRP (Renovation, Repair, and Painting) rule requires EPA-certified contractors when disturbing lead paint during weatherization.
• Vermiculite insulation: Attics with loose vermiculite (often Zonolite brand) may contain asbestos. Do not disturb without professional testing and, if positive, abatement.

Cost Guide

| Service | Typical Cost | Notes | |---------|-------------|-------| | DIY caulking and weatherstripping | $50-$200 | Materials for whole-home door/window sealing | | Professional air sealing (attic) | $1,000-$2,500 | Attic bypass sealing is highest priority | | Rim joist insulation | $500-$1,500 | Cut-and-cobble rigid foam or spray foam | | Full weatherization package | $2,000-$6,000 | Air sealing + insulation improvements | | Storm windows (per window) | $100-$200 | Interior or exterior low-e storm windows | | Attic insulation (blow-in) | $1,500-$3,000 | Bringing attic to R-49 to R-60 | | Door sweep (per door) | $15-$50 | DIY installation | | Foam gaskets for outlets | $0.50-$1 each | DIY, buy in bulk | | Whole-house fan insulated cover | $50-$200 | Rigid foam or insulated box |

Rebate programs: The Inflation Reduction Act provides up to $1,600 in rebates for air sealing and insulation through the HOMES program. Many utilities offer additional rebates of $200-$1,000 for weatherization work completed through approved contractors. Income-qualified homeowners may be eligible for free full-home weatherization through the DOE Weatherization Assistance Program (WAP).

Energy Impact

Weatherization consistently delivers the highest return on investment of any home energy improvement. Typical results:

• Air sealing alone: 5-15% reduction in heating and cooling costs. Payback in 1-3 years.
• Air sealing + insulation: 15-25% reduction. Payback in 2-4 years.
• Full weatherization (sealing + insulation + duct sealing): 20-30% reduction. Payback in 3-5 years.

Dollar savings: For a home spending $2,400/year on heating and cooling, a 20% reduction saves $480 annually. A $3,000 weatherization investment pays back in roughly 6 years, then saves money every year for the remaining life of the home.

Comfort impact: Beyond energy savings, weatherization dramatically improves comfort by eliminating drafts, reducing temperature stratification between floors, and maintaining more consistent room-to-room temperatures. This comfort benefit is often valued by homeowners more than the energy savings.

Moisture management: Proper air sealing reduces the amount of warm, humid indoor air reaching cold surfaces in walls and attics, preventing condensation, mold, and wood rot. This protects the home's structural integrity.

Shipshape Integration

Energy monitoring: Shipshape tracks heating and cooling energy consumption over time. After weatherization work, SAM compares energy use to the pre-improvement baseline (weather-normalized) and reports actual savings vs projected savings.

Draft and comfort alerts: When integrated with smart thermostats and room-level temperature sensors, SAM can detect rooms with unusual temperature differentials that suggest air leakage or insulation gaps. These findings trigger weatherization recommendations.

Efficiency scoring: The Home Health Score includes envelope performance based on available data: age of home, known insulation levels, audit results, and energy consumption patterns. Completing weatherization work improves the Energy subscore.

Seasonal reminders: SAM sends weatherization maintenance reminders before heating and cooling seasons — check weatherstripping, inspect caulking, verify door sweeps, and test storm window operation.

Cost tracking: Weatherization project costs, utility rebates received, and ongoing energy savings are tracked on the home dashboard. Homeowners see cumulative ROI and can compare their home's performance to similar homes in the region.

Dealer actions: Service providers receive weatherization work orders prioritized by impact, including pre-populated scope of work based on audit findings or SAM's efficiency analysis. Post-completion verification testing results are logged automatically.