Single Skin Glazed Office Buildings - Energy Use and Indoor Climate Simulations

Sammanfattning: Modern office buildings have high energy savings potential and potential for indoor climate improvements. During the nineties many office buildings with glass facades were built, in several cases with double skin glass facades. The advantages of buildings with double skin facades (compared with single skin glazed ones) are considered to be the reduced heating and cooling demand, the increased sound insulation towards the outside and the efficient solar shading. Glazed office buildings are considered to be airy, light and transparent with more access to daylight. However, there is insufficient knowledge concerning the function, energy use and visual environment of glazed office buildings for Scandinavian conditions. Therefore a project was initiated in order to gain knowledge of the possibilities and limitations of glazed office buildings regarding energy use and indoor climate issues. This means further development of calculation methods and analysis tools, improvement of analysis methodology, calculation of LCC, compilation of advice and guidelines for the construction of glazed office buildings and strengthening and improving the competence on resource efficient advanced buildings in Sweden. The first part of this project involved establishing a reference building with different single skin glazed alternatives, choosing simulation tools and carrying out simulations for the determined alternatives. As the reference building, an office building representative of the late nineties was chosen. Different possible glazed alternatives were determined for this building. For the simulations the dynamic energy simulation program IDA ICE 3.0 was chosen. It is already obvious that some improvements of the simulation tool are desirable. Further development of simulation tools allows simulation of more precise models. Parametric studies can then be more detailed and additional aspects can be examined. This report presents the building alternatives studied, the methods and the results of the parametric studies made for office buildings with 30%, 60% and 100% glazed area. Interesting results were obtained through varying the building’s orientation, the interior plan type (open plan and cell type offices), the type of glazing and solar shading devices and the HVAC strategy. The different building models are compared with different indoor environment classifications and a sensitivity analysis is presented regarding the occupants’ comfort and the energy used for operating the building. Highly glazed office buildings risk having a higher energy use for heating and cooling and at times poorer thermal comfort, compared with a building with conventional facade. However, it was shown that energy reduction is clearly possible with improved window types combined with proper shading devices, but the energy use is likely to still be somewhat higher than for the conventional building. Studying indoor climate in a highly glazed building, where the external skin is much more sensitive to the outdoor climatic conditions than a conventional façade, is a complicated task, since many parameters influence its quality. It was shown that an improved indoor environment with low energy use can be obtained if a detailed study for each building design is carried out, involving proper combination of control set points and choice of widow and shading devices, used for certain occupancy and function of the building.