Makeup Air Heating Load Calculator
Heating capacity needed to temper makeup air.
Enter your values
Enter the makeup air cfm in CFM.
Enter the indoor design temp in °F.
Enter the outdoor design temp in °F.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Heating capacity required
- 162,000 BTU/hr
- In tons of heating equivalent
- 13.5 tons
- Temperature rise
- 60 °F
- Gas furnace input (80% AFUE)
- 202,500 BTU/hr input
Quick answer
Tempering makeup air uses about 1.08 BTU/hr per CFM per degree F of temperature rise, which quickly adds up to a large heating load for kitchen-size airflows.
BTU/hr = 1.08 x CFM x (indoor temp - outdoor design temp)
At a glance
| What it does | Heating capacity needed to temper makeup air. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Makeup air CFM, Indoor design temp, Outdoor design temp |
| Main output | Heating capacity required |
| Formula | BTU/hr = 1.08 x CFM x (indoor temp - outdoor design temp) |
| Cost | Free — no sign-up, no download |
How to use the Makeup Air Heating Load Calculator
- 1Enter the makeup air CFM that must be tempered.
- 2Enter your indoor design temperature and winter outdoor design temperature.
- 3Read off the required heating capacity, converting to furnace input if needed.
Inputs explained
- Makeup air CFM(CFM)
- Enter the makeup air cfm in CFM.
- Indoor design temp(°F)
- Enter the indoor design temp in °F.
- Outdoor design temp(°F)
- Enter the outdoor design temp in °F.
Worked example
Using the values the calculator loads with:
Inputs
- Makeup air CFM2500 CFM
- Indoor design temp70 °F
- Outdoor design temp10 °F
Results
- Heating capacity required162,000 BTU/hr
- In tons of heating equivalent13.5 tons
- Temperature rise60 °F
- Gas furnace input (80% AFUE)202,500 BTU/hr input
Frequently asked questions
Why is makeup air heating so large?
Every CFM of cold outside air needs continuous heating whenever the exhaust runs, and kitchen exhaust systems often move thousands of CFM.
Can heat recovery help?
Yes — an energy recovery ventilator or heat wheel can recover 50-80% of this load from the exhaust air stream.
What do I need to enter into the Makeup Air Heating Load Calculator?
Just 3 values: makeup air cfm, indoor design temp, outdoor design temp. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Makeup Air Heating Load Calculator work out the answer?
Tempering makeup air uses about 1.08 BTU/hr per CFM per degree F of temperature rise, which quickly adds up to a large heating load for kitchen-size airflows. It applies the formula BTU/hr = 1.08 x CFM x (indoor temp - outdoor design temp) and shows the working so you can check each step by hand.
Is the Makeup Air Heating Load Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.