Attic Temperature Reduction Calculator
Cooling effect of attic ventilation.
Enter your values
Enter the outdoor temperature in °F.
Enter the current attic temperature in °F.
Enter the attic area in sq ft.
Enter the ventilation airflow in CFM.
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.
- Air changes per hour
- 12
- Estimated attic temperature
- 106 °F
- Reduction
- 39 °F
- Attic volume
- 4,500 cu ft
- Cooling load saved (rough)
- 1,748 BTU/h
Quick answer
Adequate attic ventilation typically drops peak attic temperature 20-40°F closer to outdoor air.
ΔT falls as air changes rise toward 10+ ACH
At a glance
| What it does | Cooling effect of attic ventilation. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Outdoor temperature, Current attic temperature, Attic area, Ventilation airflow |
| Main output | Air changes per hour |
| Formula | ΔT falls as air changes rise toward 10+ ACH |
| Cost | Free — no sign-up, no download |
How to use the Attic Temperature Reduction Calculator
- 1Record the attic temperature on a hot afternoon with a probe thermometer.
- 2Enter the ventilation airflow you have or plan to add.
- 3Combine ventilation with a radiant barrier and deep insulation for the biggest effect.
Inputs explained
- Outdoor temperature(°F)
- Enter the outdoor temperature in °F.
- Current attic temperature(°F)
- Enter the current attic temperature in °F.
- Attic area(sq ft)
- Enter the attic area in sq ft.
- Ventilation airflow(CFM)
- Enter the ventilation airflow in CFM.
Worked example
Using the values the calculator loads with:
Inputs
- Outdoor temperature95 °F
- Current attic temperature145 °F
- Attic area1500 sq ft
- Ventilation airflow900 CFM
Results
- Air changes per hour12
- Estimated attic temperature106 °F
- Reduction39 °F
- Attic volume4,500 cu ft
- Cooling load saved (rough)1,748 BTU/h
Frequently asked questions
Does venting beat insulation?
No — insulation and air sealing at the ceiling plane matter more, but ventilation protects shingles and prevents moisture.
Powered attic fans?
They can depressurise the house and pull conditioned air up; passive ridge and soffit venting is usually safer.
What do I need to enter into the Attic Temperature Reduction Calculator?
Just 4 values: outdoor temperature, current attic temperature, attic area, ventilation airflow. 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 Attic Temperature Reduction Calculator work out the answer?
Adequate attic ventilation typically drops peak attic temperature 20-40°F closer to outdoor air. It applies the formula ΔT falls as air changes rise toward 10+ ACH and shows the working so you can check each step by hand.
Is the Attic Temperature Reduction 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.