Energy savings and risk of mold growth in apartments renovated with internal insulation

This article presents a project for renovation of a large residential area, where the focus is on moisture-safe internal insulation measures and the energy saving potential. Parts of two three-story houses were renovated with different combinations of capillary active insulation measures, including mechanical ventilation with heat recovery in one house. For two years, energy use for heating was measured, as well as temperature and relative humidity in the internal insulation, indoors, and outside. The insulation was dismantled in two apartments after 2 years, to test for mold growth at the original wall surface. Furthermore, the indoor climate and energy use for heating was measured in nine reference apartments. The inspection and mold measurements after the removal of the insulation material did not show signs of mold growth. Apparently, the used insulation material can be used in these specific cases without risk of mold growth. However, the relative humidity behind the insulation was measured at up to 90% in the first winter and decreased to 70% relative humidity in the next winter. There was good agreement between measured and calculated energy savings for heating; up to 24% savings was documented for the house with more far-reaching measures.