Varmetapskoeffisienten

Varmetapskoeffisienten, or heat loss coefficient, is a parameter used in building physics to quantify how quickly heat is lost from an enclosed space to the surrounding environment. It represents the rate of heat transfer per unit temperature difference between indoor and outdoor conditions. The quantity is typically denoted by H and has units of watts per kelvin (W/K).

It can be calculated as the sum over all envelope elements of their heat transfer performance, H = Σ U_i A_i, where U_i is the thermal transmittance (U-value) of surface i and A_i its area. For a complete building, H is the total heat loss coefficient; the corresponding per-area value is the U-value.

Usage: The heat loss coefficient is used in energy balance calculations to estimate heating demand, to size heating and ventilation systems, and to evaluate energy performance or labeling of buildings.

Measurement and estimation: H can be determined from construction specifications by summing U_i A_i, or estimated from building energy simulations. In-situ methods may infer H from measured heat flux and indoor-outdoor temperature differences, but such measurements are sensitive to occupancy, ventilation, and weather.

See also: U-value, R-value, heat transfer coefficient, energy efficiency.