Low-Energy Retrofitted Homes from their Occupants’ Perspectives: Indoor Environmental Quality and Satisfaction with Heating and Mechanical Ventilation Systems

This study aims at obtaining feedback from occupants of low-energy retrofitted houses concerning the indoor environmental quality (IEQ) and the building systems in their homes. A questionnaire study was carried out in a social housing complex consisting of 2007 single-family houses, of which 1305 were retrofitted between 2014 and 2019. The different retrofitted houses were equipped with two types of heating systems, as well as balanced mechanical ventilation with two inlet locations. The questionnaire was sent to both retrofitted and non-retrofitted houses, and focused on four aspects: (1) thermal comfort and indoor air quality, (2) perception of the usability of the heating and ventilation systems, (3) adaptive actions in case of discomfort, and (4) interest in obtaining information about IEQ and building systems.
The results show a large improvement in satisfaction with IEQ in the retrofitted houses compared to the non-retrofitted houses, apart from overheating in summer and drier air. The type of heating and mechanical ventilation does not show a significant influence on the occupants’ adaptive actions in case of thermal discomfort, but occupants of retrofitted houses air out less frequently in winter. Occupants express a lack of sufficient knowledge about heating and ventilation systems in retrofitted houses. Floor heating is seen as more difficult to control than radiators. Mechanical ventilation with inlets placed on the top part of the walls generates more noise and draft issues than when the inlets are placed on the floor under the radiators. Finally, occupants of retrofitted houses are largely interested in receiving information on IEQ, energy use and systems’ status. This study highlights the need for more communication and guidance regarding the operation of technical installations in private homes. The usability and transparency of these systems should be major attention points in future residential retrofit projects.