Overhead Door Infiltration Loss Calculator - Local CFM Rows, Fuel Math & Review Warnings
Calculate BTU loss from air leakage around closed doors and cold air dumped during door openings
Free overhead door infiltration calculator for shops, garages, fire stations, and loading docks. The app separates closed-door perimeter leakage from open-door airflow exposure using local CFM/ft seal rows and local wind FPM rows, then converts the sensible heat prompt into annual fuel-cost arithmetic. Those rows are planning prompts only: they are not ASHRAE-certified table values, measured blower-door or anemometer data, Manual J/S sizing, product selection, or a payback guarantee. Use the output to organize door dimensions, seal condition, schedule, weather exposure, fuel assumptions, quotes, and source gaps before measured leakage, current fuel bills, manufacturer data, and qualified HVAC/building-envelope review.
Check shop-heater load assumptions after resolving measured door leakage and other envelope gaps
Shop Heater BTU Sizing Calculator →Check slab heat loss at your door threshold where cold air meets exposed concrete edge
Concrete Slab Heat Loss Calculator →Compare source-screen prompts against actual heating bills before energy or payback decisions
Heat Load from Bills →Check insulation thickness assumptions for walls and ceilings before envelope review
Mechanical Insulation Thickness Calculator →How It Works
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Enter Door Dimensions
Input door width and height so the calculator can compute perimeter length for the closed-door row and open area for the open-door row.
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Choose a Local Seal Row
Select good, average, or poor/no seals as a planning preset. The CFM/ft row must be replaced by measured leakage, source-backed product data, or qualified review for decision-grade work.
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Set Open and Closed Hours
Enter daily open hours, heated closed hours, and operating days. Door cycles, partial openings, traffic, and controls still need separate site review.
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Enter Temperature and Wind Rows
Input indoor/outdoor temperatures and choose a local wind row. Actual wind direction, stack effect, pressure balance, and exhaust/makeup air can change airflow materially.
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Review Costs and Source Gaps
Use annual cost and seal-upgrade prompts as screening arithmetic only, then verify fuel bills, quotes, product data, rebates, and qualified HVAC/building-envelope review.
Built For
- Shop owners organizing door-leakage questions before an envelope or HVAC review
- Fire departments screening apparatus bay door assumptions before measured testing
- Warehouse managers comparing air curtain or strip curtain source gaps before quotes
- HVAC contractors documenting why door data is needed before heater sizing
- Building owners comparing local seal, wind, schedule, and fuel assumptions
Assumptions
- Door seal condition is represented by local CFM/ft rows rather than measured leakage rates.
- Open-door airflow is represented by local wind FPM rows rather than measured doorway velocity.
- Wind, pressure balance, stack effect, and exhaust or makeup air are not modeled.
- Indoor air temperature is assumed uniform with no stratification, latent load, or recovery cycling.
Limitations
- Does not model the effect of building pressurization from HVAC systems on infiltration direction.
- Cannot account for partial door openings or doors held open at varying heights.
- Does not calculate latent heat loss from moisture differences between indoor and outdoor air.
- Strip curtain, air curtain, and high-speed door effectiveness values must come from product data and site review.
References
- ASHRAE Handbook - Fundamentals source pointer for HVAC load-calculation context
- ACCA Manual J and Manual S source pointers for residential load and equipment-selection boundaries
- EIA energy-unit source pointer for fuel heat-content context
- NIST SP 811 Appendix B.8 source pointer for unit conversion and rounding context
Frequently Asked Questions
Learn More
Why Your Shop Is Always Cold
Review common shop heat-loss paths - doors, slabs, insulation, and air leakage - with source warnings before using the math for heater sizing or payback decisions.
Overhead Door Heat-Loss Source Checklist
Use overhead-door heat-loss math as a source checklist. Local seal, wind, fuel, product, and payback assumptions need measured leakage, quotes, and qualified review.
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