These thermal engineering calculators cover steady-state heat transfer for building and HVAC applications. Thermal transmittance U [W/(m²·K)] measures heat flow per unit area and temperature difference through an opaque element (wall, floor, roof): the key parameter for building energy certification and code compliance. Thermal resistance R = 1/U = sum of layer resistances + surface resistances. Sensible thermal power covers air handling unit sizing.
U = 1 / R_total [W/(m²·K)]. Inverse of total thermal resistance. Lower U means better insulation. Typical values: uninsulated masonry wall ≈ 1–2 W/(m²K); code-compliant insulated wall ≈ 0.15–0.3 W/(m²K).
Thermal resistance
R = d / λ [m²K/W], where d is layer thickness [m] and λ is thermal conductivity [W/(m·K)]. For layers in series: R_total = R_si + Σ(dᵢ/λᵢ) + R_se. Surface resistances per ISO 6946: R_si = 0.13, R_se = 0.04 m²K/W for vertical walls.
Sensible thermal power
Q = ṁ × c_p × ΔT [W]. ṁ is mass flow rate [kg/s], c_p is specific heat capacity [J/(kg·K)] (air ≈ 1006 J/(kg·K)), ΔT is temperature difference [K]. Used for sizing heating/cooling coils in AHUs.
Temperature conversions
T[K] = T[°C] + 273.15; T[°F] = T[°C]×9/5 + 32; T[°R] = T[°F] + 459.67. The kelvin is the SI unit of thermodynamic temperature: absolute zero is 0 K = −273.15 °C.