Building Physics Basics: U-Value, Heating Load & Thermal Protection

Every calculator on this platform is based on published engineering standards. This page explains the physics behind the tools — what the quantities mean and which standards govern the formulas.

U-value (thermal transmittance)

The U-value describes the heat flow through one square metre of a component at a temperature difference of one kelvin (W/(m²·K)) — the lower, the better. It is computed from the thermal resistances of all layers (DIN EN ISO 6946); windows follow DIN EN ISO 10077 with glazing, frame and spacer contributions. Moisture safety of assemblies is assessed with the Glaser method (DIN 4108-3). → U-Value Calculator, Window U-Value

Heating load

The standard heating load (DIN EN 12831) is the power a heating system must deliver on the coldest design day: transmission losses through the envelope plus ventilation losses plus reheating capacity. It is the basis for boiler and heat pump sizing. → Heating Load, Heat Pump Sizing

Surface heating and emitters

Underfloor and wall heating are sized from the required heat flux per square metre and the permissible surface temperatures; supply temperature, pipe spacing and floor covering determine the output. → Underfloor Heating, Infrared Wall Heating

Ventilation, cooling and summer comfort

Ventilation concepts follow DIN 1946-6, cooling loads are computed from solar and internal gains, and summer heat protection (DIN 4108-2) limits overheating via the solar transmittance of glazing, shading and thermal mass. → Ventilation, Cooling Load, Summer Heat Protection

Hygrothermal simulation

Where the simplified methods reach their limits — internal insulation, half-timbered walls, thermal bridges — transient FEM simulation resolves temperature and moisture fields in the component. → Hygrothermal FEM