(Only available in german)
Due to its lighter construction and high insulation values, vacuum glass is increasingly used – especially for the renovation of old buildings and in the field of monument protection. The new WINSLT add-on takes this fact into account. It makes it possible for the first time to carry out an exact, fully automatic calculation of vacuum glazing based on existing ISO/FDIS standards.
Further information on the calculation of vacuum glazing:
The U-value of a glazing, called Ug value, indicates the heat transfer through the undisturbed, central area of the glazing and is based on DIN EN 673.
DIN EN 410 – Glass in construction – Determination of photometric and radiation physical parameters of glazing: specifies the calculation method for determining the photometric and radiation physical parameters of glazing.
DIN EN 673 – Glass in construction – Determination of the heat transfer coefficient specifies the method of calculation for determining the U value of a glazing.
The heat transfer coefficient depends on:
- Gas filling
- Mounting position
This takes into account:
- Thermal radiation
- Heat conduction
The U-value indicates the heat transfer through a homogeneous solid. It depends on the boundary conditions of the thickness and the conductivity of the material. With the layer thickness (d) and the conductivity (l) the heat transfer resistance Ri = d / l is calculated for each individual layer. The sum of the internal resistances (Rsi), outside (Rse) gives the total thermal resistance (RT).
The U-value is now calculated from the reciprocal of RT = 1 / RT and is expressed in watts per square meter and Kelvin (W/m2*K).
The most important parameters are:
- Transmission τ (tau)
- Absorption α (alpha)
- Reflection ρ (rho)
τ + α + ρ = 1 or 100%