How is door infiltration load calculated?

Warm air enters and cold air leaves through an open doorway because the two air columns have different densities. The calculator converts that buoyancy-driven exchange into an air mass flow per doorway, multiplies it by the enthalpy difference between ambient and room air, scales it by the door protection's effectiveness and averages the result over the day with the duty cycle.

Why is the average load lower than the open-door load?

The open-door figure is the instantaneous peak — what the room gains while a door stands open. The daily average spreads that peak over running hours using the duty cycle: 30 minutes of open door per hour is very different from 5. Size plant margins on the peak, and budget energy on the average.

How effective are strip curtains, air curtains and high-speed doors?

Strip curtains typically cut exchange by roughly 50–70% when well fitted; air curtains 30–50% depending on design, wind and traffic; high-speed doors up to 90% when disciplined use is enforced. Actual values depend on wind exposure, traffic frequency and installation quality — treat the model's factors as planning values.

What does the estimate not include?

Wind pressure on exposed doors, pressure imbalance from evaporator fans, gaps at dock levellers, and forklift traffic patterns that hold doors open longer than the duty cycle assumes. Validate with measured room data where the doors dominate the load, and feed the average added kW into the refrigeration load calculator so the plant is sized on the full picture.

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Insulated industrial cold room with refrigeration units

For commercial and industrial refrigeration projects (cold rooms, cold stores, process cooling) — not household fridges, home freezers or appliance repair. Results are planning estimates, not engineering design or safety advice; a qualified refrigeration engineer must confirm sizing before purchase.

Free engineering calculator

AI-generated · ColdMatch Group

Cold Room Door Infiltration Load Calculator

Estimate how door size, opening frequency, warm outside air and humidity add to refrigeration duty and moisture load. Use the result to scope door protection, capacity and a supplier brief.

Input units

1. Door width (m)2. Door height (m)3. Room temperature (°C)4. Outside temperature (°C)5. Outside relative humidity (%)6. Door openings per day7. Seconds open per opening8. Door protection

Added average duty

10.6 kW

3.02 TR · 36,224 BTU/h

Peak while door is open

254.8 kW

Check recovery and evaporator response

Daily heat gain

254.8 kWh/day

60 open minutes/day

Moisture entering

164.9 kg/day

Potential frost and defrost load

Door area: 7.20 m² · selected protection reduction: 35%. The average duty is the door-load contribution to add to the complete heat-load calculation.

Send this measured door-use scenario to the ColdMatch project team for review and inclusion in a supplier-ready brief.

Add result to quote request Calculate the full heat load

Indicative planning estimate, not an engineering design. Final capacity requires measured traffic, local design weather, pressure balance and confirmation by a qualified refrigeration engineer.

Calculation method

Door area = width × height
Air exchange = 0.22 × door area × √(g × door height × relative density difference)
Peak load = moist-air mass flow × indoor/outdoor enthalpy difference × (1 − protection effectiveness)
Average load = peak load × total daily open seconds ÷ 86,400

Metric and imperial entries are converted to SI before the same psychrometric and buoyancy-flow calculation is applied.

Worked example

Illustrative frozen-store doorway during a warm, humid operating day.

Inputs

• 2.4 m × 3.0 m door
• −20 °C room; 30 °C and 65% RH outside
• 40 openings × 90 seconds
• PVC strip curtain

Calculation

• Open time = 60 min/day
• Peak open-door load = 254.8 kW
• Average load = 254.8 × 0.0417

10.6 kW average added duty, 254.8 kWh/day and 164.9 kg/day of moisture.

Limitations

• Wind, pressure imbalance, forklift traffic and adjacent dock conditions can materially change airflow.
• Protection effectiveness is an indicative planning allowance, not a guaranteed product performance figure.
• Moisture may appear as frost, condensate or defrost load depending on coil and room conditions.
• Add this result to transmission, product, people, lighting, fan and defrost loads; do not treat it as total plant duty.

Illustrative planning result only. Confirm the final design, duty, equipment selection and performance with a qualified refrigeration engineer and supplier quotation.

How the door infiltration calculation works

How is door infiltration load calculated?: Warm air enters and cold air leaves through an open doorway because the two air columns have different densities. The calculator converts that buoyancy-driven exchange into an air mass flow per doorway, multiplies it by the enthalpy difference between ambient and room air, scales it by the door protection's effectiveness and averages the result over the day with the duty cycle.
Why is the average load lower than the open-door load?: The open-door figure is the instantaneous peak — what the room gains while a door stands open. The daily average spreads that peak over running hours using the duty cycle: 30 minutes of open door per hour is very different from 5. Size plant margins on the peak, and budget energy on the average.
How effective are strip curtains, air curtains and high-speed doors?: Strip curtains typically cut exchange by roughly 50–70% when well fitted; air curtains 30–50% depending on design, wind and traffic; high-speed doors up to 90% when disciplined use is enforced. Actual values depend on wind exposure, traffic frequency and installation quality — treat the model's factors as planning values.
What does the estimate not include?: Wind pressure on exposed doors, pressure imbalance from evaporator fans, gaps at dock levellers, and forklift traffic patterns that hold doors open longer than the duty cycle assumes. Validate with measured room data where the doors dominate the load, and feed the average added kW into the refrigeration load calculator so the plant is sized on the full picture.

Indicative planning figures only — final sizing belongs to the supplier's detailed design. Request comparable supplier quotes · all cold chain tools · common cold chain questions

Direct answer

Door infiltration adds both sensible heat and latent moisture load. The estimate combines door area, buoyancy-driven air exchange from the indoor/outdoor temperature difference, moist-air enthalpy, total open time and the effectiveness of strips, air curtains, high-speed doors or vestibules. The result is an average kW load for plant sizing plus the much higher instantaneous load while the door is open.

Frequently asked questions

How do door openings increase cold-room refrigeration load?

Warm outside air replaces dense cold air through the doorway. The refrigeration system must remove both the air's sensible heat and the latent heat from its moisture, which can also freeze on evaporator coils.

Should I size refrigeration for the peak or average door load?

Use the average door load as one part of the 24-hour heat-load calculation, but check the peak open-door load when reviewing temperature recovery, evaporator capacity and operating controls.

How much do strip curtains or high-speed doors reduce infiltration?

This planning model applies indicative effectiveness values of 35% for PVC strips, 50% for an air curtain, 65% for a high-speed door and 80% for a vestibule. Actual performance depends on installation, wind, traffic and maintenance.

Is the result enough to select refrigeration equipment?

No. It is an indicative planning estimate. Final selection needs a verified heat-load calculation using measured traffic, local weather design conditions, pressure balance and the actual door system.

Next steps for your project

Submit your project for expert review

Send your requirements. A ColdMatch specialist reviews every request, prepares a brief and introduces qualified suppliers — free for qualified buyers.

Not sure which tool fits? Open smart search — every question mapped to the right calculator

Free engineering calculator

AI-generated · ColdMatch Group

Cold Room Door Infiltration Load Calculator

Estimate how door size, opening frequency, warm outside air and humidity add to refrigeration duty and moisture load. Use the result to scope door protection, capacity and a supplier brief.

Input units

1. Door width (m)2. Door height (m)3. Room temperature (°C)4. Outside temperature (°C)5. Outside relative humidity (%)6. Door openings per day7. Seconds open per opening8. Door protection

Added average duty

10.6 kW

3.02 TR · 36,224 BTU/h

Peak while door is open

254.8 kW

Check recovery and evaporator response

Daily heat gain

254.8 kWh/day

60 open minutes/day

Moisture entering

164.9 kg/day

Potential frost and defrost load

Door area: 7.20 m² · selected protection reduction: 35%. The average duty is the door-load contribution to add to the complete heat-load calculation.

Send this measured door-use scenario to the ColdMatch project team for review and inclusion in a supplier-ready brief.

Add result to quote request Calculate the full heat load

Indicative planning estimate, not an engineering design. Final capacity requires measured traffic, local design weather, pressure balance and confirmation by a qualified refrigeration engineer.

Calculation method

Door area = width × height
Air exchange = 0.22 × door area × √(g × door height × relative density difference)
Peak load = moist-air mass flow × indoor/outdoor enthalpy difference × (1 − protection effectiveness)
Average load = peak load × total daily open seconds ÷ 86,400

Metric and imperial entries are converted to SI before the same psychrometric and buoyancy-flow calculation is applied.

Worked example

Illustrative frozen-store doorway during a warm, humid operating day.

Inputs

• 2.4 m × 3.0 m door
• −20 °C room; 30 °C and 65% RH outside
• 40 openings × 90 seconds
• PVC strip curtain

Calculation

• Open time = 60 min/day
• Peak open-door load = 254.8 kW
• Average load = 254.8 × 0.0417

10.6 kW average added duty, 254.8 kWh/day and 164.9 kg/day of moisture.

Limitations

• Wind, pressure imbalance, forklift traffic and adjacent dock conditions can materially change airflow.
• Protection effectiveness is an indicative planning allowance, not a guaranteed product performance figure.
• Moisture may appear as frost, condensate or defrost load depending on coil and room conditions.
• Add this result to transmission, product, people, lighting, fan and defrost loads; do not treat it as total plant duty.

Illustrative planning result only. Confirm the final design, duty, equipment selection and performance with a qualified refrigeration engineer and supplier quotation.

How the door infiltration calculation works

How is door infiltration load calculated?: Warm air enters and cold air leaves through an open doorway because the two air columns have different densities. The calculator converts that buoyancy-driven exchange into an air mass flow per doorway, multiplies it by the enthalpy difference between ambient and room air, scales it by the door protection's effectiveness and averages the result over the day with the duty cycle.
Why is the average load lower than the open-door load?: The open-door figure is the instantaneous peak — what the room gains while a door stands open. The daily average spreads that peak over running hours using the duty cycle: 30 minutes of open door per hour is very different from 5. Size plant margins on the peak, and budget energy on the average.
How effective are strip curtains, air curtains and high-speed doors?: Strip curtains typically cut exchange by roughly 50–70% when well fitted; air curtains 30–50% depending on design, wind and traffic; high-speed doors up to 90% when disciplined use is enforced. Actual values depend on wind exposure, traffic frequency and installation quality — treat the model's factors as planning values.
What does the estimate not include?: Wind pressure on exposed doors, pressure imbalance from evaporator fans, gaps at dock levellers, and forklift traffic patterns that hold doors open longer than the duty cycle assumes. Validate with measured room data where the doors dominate the load, and feed the average added kW into the refrigeration load calculator so the plant is sized on the full picture.

Indicative planning figures only — final sizing belongs to the supplier's detailed design. Request comparable supplier quotes · all cold chain tools · common cold chain questions

Direct answer

Frequently asked questions

How do door openings increase cold-room refrigeration load?

Should I size refrigeration for the peak or average door load?

Use the average door load as one part of the 24-hour heat-load calculation, but check the peak open-door load when reviewing temperature recovery, evaporator capacity and operating controls.

How much do strip curtains or high-speed doors reduce infiltration?

Is the result enough to select refrigeration equipment?

No. It is an indicative planning estimate. Final selection needs a verified heat-load calculation using measured traffic, local weather design conditions, pressure balance and the actual door system.

Next steps for your project

Send these inputs to an RFQ

Your size, cost and load inputs are copied into the quote form, so you don't type them twice. Nothing is sent until you review and submit.

Buyer guide · planning estimate

Why door traffic matters in your refrigeration brief

This calculator estimates the warm-air load entering through door openings. In busy distribution cold stores this can be a large share of the total load, so door type, protection and traffic should be specified rather than left to the supplier.

How to read your result

Compare scenarios: fewer openings, faster doors or strip curtains
Carry the result into the total cooling load
A high infiltration share suggests reviewing dock design and air locks

Put these in your RFQ

Door sizes and openings per hour at peak
Door type and any air curtain or vestibule
Dock seals and loading pattern
Room and adjacent space temperatures

Commercial projects from USD 250,000: ColdMatch reviews your brief and introduces suitable independent suppliers. Results here are planning estimates, not quotations.

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Common questions

Is this result a supplier quotation?

No. It is a planning estimate from your own inputs and the published method on this page. Supplier prices depend on site survey, specification, freight, duties and local installation, so use the result to set scope and budget expectations, then compare reviewed supplier proposals.

Do fast doors always pay back?

Not always. The value depends on traffic, temperature difference and energy price. Use your own figures in this tool and ask suppliers to justify door choices against them.

Does infiltration affect frost and defrost?

Yes. Warm moist air adds frost to evaporators, increasing defrost frequency. Mention humidity at the door in your brief.

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Project request

Submit your project for expert review

Send your requirements. A ColdMatch specialist reviews every request, prepares a brief and introduces qualified suppliers — free for qualified buyers.