Ventilation heat loss in a multifamily building under varying air density

: Standards related to calculation methods used in building energy performance simulation tools usually impose constant volumetric heat capacity of air. However, this simplification may result in errors if the actual conditions differ from the assumptions made. The paper presents the problem of dry air density and specific heat capacity variation and their influence on calculated energy use for space heating in a multifamily building. The monthly calculation method of PN-EN ISO 13790 was used. Simulations were performed in five cities, each in one climatic zone according to PN-EN 12831. Variation of the air density caused by air temperature and elevation resulted in differences in calculated heating demand from -4.5% to 4.5% in relation to that at constant volumetric heat capacity assumed in PN-EN ISO 13790. specific heat capacity. But varying outdoor conditions cause these parameters to change. This paper presents an assessment of the impact of the air density on the ventilation heat loss and resulting heating demand of a multifamily residential building in five cities, each in different Polish climatic zone. Calculations were performed using the monthly method of [10]. The ventilation heat loss was determined at capacity of of 1200 3 ∙ K, imposed in that and comparatively at monthly outdoor air temperatures from monthly weather data.