Attempt predicting slab-on-ground temperature for bioclimatic buildings
Abstract The prescriptive approach of the Moroccan Building Thermal Regulation (2015) provides for the insulation of buildings ground in almost all climatic zones of Morocco. This work demonstrates that it is an unnecessarily expensive constraint for most climatic zones of this country (only 8.6% of the cold semester days with slab-on-ground temperatures below 19°C and only 22% of the hot semester days above 26°C). This work shows also that the ground floor of a building is subject to (i) a slow mono-dimensional vertical heat transfer (outdoor ambient temperature long-term extrema delayed for – 22 days), (ii) a faster bi-dimensional horizontal heat transfer (outdoor ambient temperature singularities delayed for – 2 days for five meters from the edge of the building). To limit this, the authors recommend lateral insulation the first 50cm of the building foundations, with any adapted insulating material. In addition, building thermal simulation software need better site-specific models of the seasonal evolution of buildings slab-on-ground: a solution is proposed to obtain the seasonal variation of building slab-on-ground temperatures directly from the evolution of outdoor ambient temperature. It shows that this slab-on-ground temperature under cover varies almost like the at 1.6 m depth underground temperature of a non-covered soil.