What Is the Heat Loss Transmission & U-Value Calculator?
Transmission heat loss is the conduction of thermal energy from warm indoor spaces to the cold outdoor atmosphere through solid building materials.
R-value measures thermal resistance, while U-factor measures thermal transmittance.
How Does the Heat Loss Transmission & U-Value Calculator Work?
The calculator converts R-value to U-value via U = 1 ÷ R.
It determines temperature gradient ΔT = T_inside - T_outside.
Total heat transfer is computed as Q = U × Area × ΔT.
Heat Loss Transmission & U-Value Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Thermal transmittance U-value is the mathematical inverse of R-value. Multiplying by surface area and temperature difference gives conduction heat loss.
How to Use the Heat Loss Transmission & U-Value Calculator
- Enter the surface area of the building section.
- Enter the R-value of the building envelope.
- Enter indoor and outdoor design temperatures.
Step-by-Step Example Calculation
500 sq ft R-13 Wall with 60°F Temperature Differential
Input Values:
Understanding Your Result
Reports continuous heat loss rate in both imperial BTU/hr and metric Watts.
Factors That Affect the Result
- Thermal bridging across wooden or steel structural framing studs.
- Air infiltration and draft leakage.
When Should You Use This Calculator?
- Sizing hydronic radiators, planning attic insulation upgrades, and calculating annual heating fuel demand.
Assumptions & Limitations
- Models steady-state thermal conduction; ignores solar radiation gains and transient thermal mass storage.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Fundamental Fourier law of 1D thermal conduction.