Basements benefit considerably from the insulating properties of
the surrounding soil. However, that alone is insufficient to satisfy
the typical requirements for wall and floor U-values of 0„35 and
0„30 W/m^2 K, respectively.
Refurbishment of existing basements may include insulation within
dry lined walls and under the floor screed or particle board
overlay. This should incorporate an integral vapour control layer
to minimise risk of condensation.
External insulation of closed cell rigid polystyrene slabs is
generally applied to new construction. These slabs combine low
thermal conductivity with low water absorption and high
compressive strength. The external face of insulation is grooved to
encourage moisture run off. It is also filter faced to prevent
clogging of the grooves. Backfill is granular.
Tables and calculations to determine U-values for basements are
provided in the Building Regulations, Approved Document L and in
BS EN ISO 13370: Thermal performance of buildings. Heat transfer
via the ground. Calculation methods.
Insulation of Basements