NSB 2011 9th Nordic Symposium on Building Physics vol:3 pages:1177-1184
Nordic Symposium on Building Physics edition:9 location:Tampere, Finland date:May 29 - June 2, 2011
A new quasi-steady-state assessment method of mechanical night cooling for calculating the cooling demand of non-residential buildings is developed. In accordance with the calculation methodology proposed in the European standard EN 13790, the impact of night cooling is calculated by a ventilation heat transfer coefficient which is, on its turn, determined by the heat capacity of air per volume and the air flow rate alongside a temperature adjustment factor, a time fraction of operation and an adjustment factor for dynamic effects. Dynamic simulations of a generic small and large office building and a school building determine these adjustment factors. The time fraction of operation is function of the losses to gains ratio. The temperature adjustment factor is constant and equal to 1. The adjustment factor for dynamic effects depends on the accessible thermal mass of the building structure. Comparing the new calculation method to dynamic simulation results of the same buildings, shows a non-linear and uncertain correspondence. The dynamic effects, which are essential for night cooling, are insufficiently considered in the new assessment method as described in EN 13790. Therefore, further research is needed to assess the effect of night cooling on the cooling demand in a quasi-steady-state calculation method.