Slab-on-grade thermal bridges: A thermal behavior and solution review

[Display omitted] •This study presents a state-of-the-art on thermal bridges focusing on slab on grade TB, including calculation methods, norms and software summary.•A numerical study of possible technical solutions to decrease slab on grade TB’s effect is presented.•Different external insulation solutions to renovate existing building were compared.•The study highlights the effect of soil thermal properties on slab on grade TB calculation.•Improving insulation thickness and depth does not necessarily reduce the thermal bridges effect. The building industry is responsible for considerable energy consumption and the production of large amounts of greenhouse gas emissions worldwide. Hence, reducing the building heat losses that occur through the building envelope, especially through the floor foundations, is important. This paper provides an up-to-date review on thermal bridges (TBs), mainly with respect to slab-on-grade TBs. First, different thermal bridges types are defined; then the standards used to evaluate TBs are presented. Common approaches to evaluate TBs are discussed, such as the U-value method, the equivalent method approach, and the three-dimensional dynamic method. This latter focuses on heat loss through the foundation and soil in existing buildings. Soil’s effect on thermal bridges is described and our case studies showed that thermal bridges heat losses are inversely proportional to soil thermal conductivity. This analysis is involved in the present paper. Finally, exterior insulation solutions at ground level are presented among those the trapezoidal double insulation type can reduce TBs up to 65% compared to no insulation case. As conclusions, directions for further works are suggested to fill current literature gaps.