The preponderant number of multistorey buildings constructed in Denmark in the period between 1850 and 1930 were built with masonry walls incorporating wooden floor beams. Given the nature of this construction, it is supposed that significant energy savings could be achieved by simply insulating the facades of such buildings. To maintain the exterior appearance of the facade, the only possible means of installing the required insulation is placing it on the interior of the wall. However, the installation of insulation on the interior of the wall assembly reduces the overall drying potential of the wall, and this in turn may lead to increased freeze–thaw damages and moisture problems at the beam ends embedded in the masonry, when the masonry facade is subjected to driving rain. This article presents a method to investigate retrofit measures of interior-insulated masonry walls having wooden floor beams based on a failure mode and effect analysis combined with hygrothermal simulations. The method was first used to determine the potential for failure in retrofitted walls and their effects and causes, and thereafter, the expected hygrothermal performance of the retrofit measures was further investigated using both thermal and hygrothermal simulation software. The results show that the risk to incurring moisture problems at the wooden beam ends can be resolved by not insulating that portion of the wall directly above and below the floor division. Additionally, this proposed retrofit measure would reduce the heat loss of the original wall structure by half.

This paper presents at project for renovation of a large residential area, where focus is on moisture safe internal insulation measures and the energy saving potential. Parts of two three-story houses were renovated with different combination 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 two 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 up to 90% in the first winter and decreased to 70% relative humidity in the next winter. There was a good agreement between measured and calculated energy savings for heating; and up to 24% savings was documented for the house with more far-reaching measures.

This article presents a method for the design of retrofit actions with focus on energy savings that permits a systematic and thorough assessment of potential failures, anticipated maintenance and the expected durability of the retrofit actions. The proposed method combines the use of failure mode and effect analysis (FMEA) to permit identifying likely failure modes from which maintenance actions could be planned and the limit states (LS) method to assess the durability of the given retrofit action. One case study was completed to illustrate the application of: (1) the FMEA and LS method and (2) the proposed method for a retrofit action of an internal insulated solid wall of masonry bonded with lightweight aggregate concrete and floor division of concrete. It was evident that FMEA is useful regarding failure-mode identification and maintenance planning, and the LS method has its strength in durability assessment. Combining the use of both the FMEA and LS methods allowed improved design of new energy-saving retrofit actions, given that a thorough risk assessment was possible that included a decision-making process on maintenance planning, durability assessment and decision on potential redesign of retrofit actions.