Thermal Conductivity & Heat Flux Calculator (Fourier's Law)
Calculate steady-state conductive heat transfer (BTU/hr and Watts), heat flux, thermal resistance R-value, and U-factor using Fourier's Law of thermal conduction.
Calculated Results
Frequently Asked Questions
What is Fourier's Law of Thermal Conduction?
Fourier's law states that the rate of heat transfer through a material is proportional to the negative gradient in temperature and the area: q = (k × A × ΔT) / L, where k is thermal conductivity, A is surface area, ΔT is temperature differential, and L is thickness.
What is the mathematical relationship between thermal conductivity (k) and R-value?
Imperial R-value equals thickness divided by thermal conductivity: R = L / k (in imperial units). Materials with low thermal conductivity (like polyurethane foam k=0.026) produce the highest R-value per inch of thickness.
What is the difference between R-value and U-factor?
R-value measures resistance to heat flow (higher is better). U-factor measures thermal transmittance, or how easily heat flows through a building assembly (U = 1 / R-value; lower is better, standard for window ratings).
Why does copper conduct heat nearly 10,000 times faster than fiberglass?
Metals like copper (k = 385 W/m·K) possess abundant free valence electrons that rapidly transfer thermal vibrational kinetic energy throughout the metallic lattice, whereas fiberglass traps stagnant air pockets.