# FOSTA

Apart from ventilation heat losses, transmission heat losses are essential for calculating the heating energy demand of a building. For today's usual stationary calculations, the transmission heat loss is calculated with the U-value equation and the thermal bridge addition under constant static boundary conditions. The calculated heat quantity is used to determine the year-round heat quantity of a building released by transmission, which is compensated by a heating system. Heat gains due to internal loads and ventilation heat losses are included in the balance, as are solar gains due to transparent components. Here too high energy inputs are compensated by a ventilation system. However, through these rough calculation processes with static calculation methods, considerably higher heat losses may occur compared to transient calculation processes. Buildings with a frame construction in particular experience significantly greater fluctuations in external surface temperatures and heat flux density due to solar radiation than buildings with a solid construction. For example, on cold but radiant winter days, high surface temperatures are reached on sandwich-wall or -roof elements. If less heating energy has to be provided at precisely these times, this effect can be specifically exploited. It is only possible to calculate a realistic energy savings for this case through transient calculation approaches. Consequently, considerable savings in insulating materials can be achieved in the construction of framed buildings where no cooling energy is required in summer due to increased ventilation.