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This paper focuses on the indoor climate in new Danish low-energy houses and discusses the issue of overheating in relation to evaluation methods and user satisfaction. The user satisfaction has been evaluated among 370 owners of new low-energy class 2015 detached single-family houses based on a questionnaire survey. The survey evaluated overall satisfaction, and more specifically satisfaction with the indoor climate parameters temperature, draught, air quality, noise and daylight, and also technical installations of the house. The survey showed satisfaction with living in new low-energy houses and more than 90% perceived the indoor environment as satisfactory both in summer and winter. The majority perceived the various indoor climate parameters to be better in their new low-energy house compared to conditions in their former house. Compared with earlier studies on previous generations of low-energy houses, problems with overheating seem to have decreased, as only 12% found temperature conditions to be unsatisfactory in summer.

The need for renovation and energy retrofitting of Danish social housing from the 1960s and 1970s is substantial. Such energy retrofits often include the installation of mechanical ventilation systems with heat recovery to fulfil the current standards for energy efficiency. These systems typically ensure a more constant and higher ventilation rate than previous systems. Therefore, there is potential for residents to perceive a higher air quality and a reduction in problems due to condensation on cold surfaces and mould growth after retrofits. The purpose of the present study was to evaluate if this potential is realised for residents in social housing complexes. A questionnaire survey was performed among residents in dwellings with ventilation categorised within one of the five ventilation principles: natural ventilation, bathroom fan, exhaust fans in the kitchen and bath, decentralized balanced mechanical ventilation and centralized balanced mechanical ventilation. Compared with residents without balanced mechanical ventilation, residents having such systems perceived less often problems with unpleasant odour from their own apartment and less visible mould, but more often perceived the air as dry. Residents with decentralized mechanical ventilation tended to experience more often problems with noise from their ventilation system. However, results show that nuisance are avoidable with correctly designed decentralized ventilation. The purpose of the present study was, among other things, to evaluate how tenants perceived the indoor environment in renovated and energy-retrofitted social housing erected in the 1960s. Tenants answered a questionnaire to quantify problems and satisfaction with the indoor environment before and after the renovation work. A majority of tenants perceived the indoor environment improved for all parameters: temperature, draught, air quality, noise and daylight, after the renovation work. In particular, the tenants experienced fewer problems with too low temperature and draught during the winter, noise from outside and too little daylight. The evaluation shows that it is possible to achieve a win-win situation, with both energy savings and improved perceived indoor environment. The evaluation also reveals that careful attention is needed to avoid introducing annoying noise from new technical installations.