The effect of shallow depth horizontal ground loop clearance on the heat loss of a single family residential dwelling

Abstract

Using solar energy stored in the ground to preheat incoming fresh ventilation air with ground loops is a renewable energy system strategy which is becoming more frequently used in new residential developments. The purpose of this research was to examine the effect of ground loop to foundation wall clearance on building heat loss. Additionally, the thermal properties of the soil were examined to determine their impact on the ground loop's effect on heat loss. A simulation-based research approach was conducted using HEAT3, which is a three-dimensional transient heat transfer software. This study found that ground loop clearance had a larger impact on building heat loss for sites with low thermal conductivity soils than for sites with high thermal conductivity soils. On average, ground loop clearances of 10 cm, 50 cm, 100 cm, and 200 cm resulted in increased building heat losses of 20%–83%, 19%–55%, 16%–35%, and 12%–15% (high conductivity - low conductivity), respectively. It was also found that at a ground loop clearance of 200 cm, the correlation between soil thermal conductivity and building heat loss decouples and the soil thermal properties become less influential on the building heat losses observed. This provides a key result to organizations such as PHIUS, who intend to provide guidance to designers on minimum recommended ground loop clearances.