U-values are generally used to describe the thermal performance (heat loss) for a section of construction - such as a walls, roofs, windows and doors. U-value is used to measure how effective elements of a buildings fabric are as insulators.
U-values measure how effective a material is an insulator. The lower the U-value is, the better the material is as a heat insulator.
A windows thermal performance is a windows’ whole U value not just the value of the centre pane U value. U values are determined by reference to EN14351-1 and window type is a single frame and fixed sash
Simplified heat loss through any given surface is calculated using:
Heat loss = U x A x dT
U = U-value (W/m2K) Thermal transmittance
A = Area of surface (m2)
dT = Temperature difference inside to outside ( K )
Units of heat loss = Watts
The formula Heat Loss = ∑ ( U x A x dT )