Heat Loss/Gain Calculator

Detailed envelope heat transfer calculation by component.

Calculation Mode

Indoor Temp (°F)

Outdoor Design Temp (°F) Heating: 99% winter design. Cooling: 1% summer design.

Wall Area (sq ft)

Wall R-Value

Window Area (sq ft)

Window Type

Ceiling Area (sq ft)

Ceiling R-Value

Floor Area (sq ft)

Floor Type

Building Volume (cu ft)

Air Changes/Hour (ACH)

Q = U × A × ΔT

Where: Q = heat flow (BTU/hr), U = 1/R (BTU/hr·ft²·°F), A = area (ft²), ΔT = temperature difference (°F)

Heat Transfer Results