Ground contact heat losses: Simplified calculation method for residential buildings

Heat loss through building elements in contact with the ground plays an important role in a building's thermal behaviour, therefore its estimation and management is relevant when assessing a building's energy performance. The EN ISO 13370 standard provides a method for calculating heat loss through the ground that takes into account steady state heat loss as well as heat loss due to temperature variations throughout the year (on a monthly or seasonal basis). It is based on calculating thermal transmittance for floors and walls in contact with the ground and differs greatly from the method established in the Portuguese building regulation codes. The EN ISO 13370 method requires a large input of data. This paper presents an alternative simplified version of the method that is more suitable for general building energy performance calculation procedures since it requires fewer calculation parameters and steps. The proposed method is mainly conservative and overestimates slightly heat transfer via the ground when compared to the EN ISO 13370 standard method.

► Heat loss via the ground is of growing importance in thermal behaviour of buildings.
► The current Portuguese building regulation codes differ greatly from EN ISO 13370 method.
► A simplified version suited for seasonal energy performance assessment is presented.
► In general, the proposed method slightly overestimates heat transfer via the ground.