Attic Temperature Calculator - Calculator Academy

Enter the outside temperature and the solar gain factor into the calculator to estimate the attic temperature. The solar gain factor is a dimensionless ratio (often 0–1) representing what fraction of an assumed “maximum” solar-driven attic temperature rise above outside occurs (this calculator assumes a maximum rise of 60°F ≈ 33.3°C).

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Attic Temperature Formula

The following rule-of-thumb formula is used to estimate the attic temperature:

AT = OT + SG \times \Delta T_{max}

Variables:

AT is the attic temperature (°F or °C)
OT is the outside temperature (°F or °C)
SG is the solar gain factor (dimensionless; often 0–1 in this model, with >1 indicating a rise larger than the assumed ΔT_max)
ΔT_max is the assumed maximum attic temperature rise above outside due to sun (calculator uses 60°F of rise ≈ 33.3°C of rise)

To estimate the attic temperature, add the outside temperature to the solar gain factor multiplied by the assumed maximum solar-driven temperature rise.

What is Attic Temperature?

Attic temperature is the temperature within the attic space of a building. It is influenced by the outside temperature and the amount of solar radiation the attic receives, which can significantly increase the temperature inside the attic. Understanding attic temperature is important for proper insulation and ventilation to prevent heat-related issues and improve energy efficiency.

How to Calculate Attic Temperature?

The following steps outline how to estimate the Attic Temperature.

First, determine the outside temperature (OT) in degrees Fahrenheit or Celsius.
Next, determine the solar gain factor (SG), which is a dimensionless value (often between 0 and 1) representing the fraction of an assumed maximum solar-driven temperature rise.
Use the formula from above: AT = OT + SG × ΔT_max (the calculator uses ΔT_max = 60°F of rise ≈ 33.3°C of rise).
Finally, calculate the Attic Temperature (AT). If you are calculating manually, keep OT and ΔT_max in consistent units (°F with 60°F of rise, or °C with 33.3°C of rise).
After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Outside temperature (OT) = 85°F

Solar gain factor (SG) = 0.7

Using ΔT_max = 60°F of rise: AT = 85 + (0.7 × 60) = 85 + 42 = 127°F