Insulation & Energy
Air Sealing / Weatherstripping Calculator
Estimates annual energy savings from air sealing based on ACH reduction
Updated May 13, 2026 · Live
What this tool does
Estimates the annual energy-cost saving from reducing air infiltration (ACH) in a room, based on room volume, existing vs target air changes per hour, indoor-outdoor temperature difference, and heating hours per year.
For a {length_ft} x {width_ft} ft room at {height_ft} ft high, reducing air leakage from {ach_existing} to {ach_target} ACH at a {delta_t_c}°C average indoor-outdoor difference gives an estimated annual saving of {result}.
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Formula Used
How the air sealing / weatherstripping calculator works
Estimates weatherstripping and caulk needed for air sealing. The calculator takes your dimensions and supplier rates, applies a standard US construction formula, and returns a quantity with an indicative cost. Every figure is an estimate — site conditions always move the final number.
Typical US insulation and energy wastage
Rigid foam wastes 5–10% depending on stud spacing. Batt insulation (R-13, R-19, R-30) wastes less when sized correctly to 16" or 24" o.c. cavities. Our defaults reflect common US trade allowances, and can be adjusted upwards for non-standard geometry or downwards where experience supports a lower figure.
What this tool does not do
It does not replace a professional quote, factor regional pricing, assess structural adequacy, or confirm building code compliance. Those remain the responsibility of a suitably qualified designer, engineer, or your local building official.
On-site considerations for air sealing / weatherstripping
Vapor retarders must be continuous and sealed at every penetration. In cold climates (CZ 5+), the warm-side vapor retarder is mandatory; in mixed climates, follow IRC Table N1102.4.1.1.
Codes and compliance
New and renovated building envelopes must meet IECC R-value targets by climate zone. Many states adopt IECC with amendments — check Energy Star and your local energy code. When in doubt, file a pre-application question with your local building department — early clarity is cheaper than a corrective inspection.
Before you order
Mineral-wool and fiberglass batts stored outdoors lose performance to moisture. Bring rolls and bundles inside the dry-in envelope before installation. Cross-checking the calculator’s output against a supplier quote helps catch differences in pricing assumptions — ask for exact product specifications (grade, finish, batch number) and confirm delivery timescales against your programme.
Adjusting the defaults
Every input in this calculator is editable. Enter your own dimensions, supplier prices, and wastage allowance — the output recalculates instantly. If the defaults feel off for your region or project type, your own numbers always override them.
Using this air sealing / weatherstripping calculator alongside other BuildMetricLab tools
This calculator works best as part of a planning workflow. Pair the quantity with our project contingency, labor-hours, and material-cost calculators to build a complete estimate before you pick up the phone to a supplier. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the math.
Sources & methodology
This tool estimates the reduction in sensible heat loss from air sealing using Q = ACH_diff × Volume × ΔT × 0.33 (W per m³·h·K), where room volume is derived from the entered length, width, and height, and ACH_diff is the difference between the existing and target air changes per hour (at 50 Pa blower-door test conditions). The resulting watt reduction is multiplied by annual heating hours and the entered energy price to estimate annual dollar savings. This estimates energy savings only; it does not calculate weatherstripping length or caulk quantity, which depend on door/window/penetration perimeters not captured by this tool.
Frequently asked questions
Are air sealing / weatherstripping calculator results accurate enough to order materials?
Use them as a starting estimate only. Verifying the final quantity with your supplier or contractor before ordering is good practice — site conditions, wastage and cut-offs all affect the true figure.
What wastage percentage should I use?
This calculator does not use a wastage allowance. It estimates annual energy-cost savings from reducing air changes per hour (ACH), based on the room volume, existing and target ACH, average indoor-outdoor temperature difference, heating hours per year, and your energy price. Adjust the ACH values to reflect a blower-door test or a conservative estimate if one is not available.
Does this replace professional advice?
No. This tool is a planning estimator. For work that affects structure, building code compliance, gas, electrical, plumbing, or drainage to a public sewer, consult a licensed contractor or design professional.
Can I change the unit prices?
Yes — every price field is editable. Plug in your supplier's quote to get a total that matches your project.
Spotted something off?
Calculations or display — let us know.
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