Evaluation of the indoor environment in 8 Danish passive houses

In correlation with the increasing demands for energy savings in the residential area, the building envelope has been improved and made more resilient to heat loss, both with regards to utilisation of more insulation and by making the building more air tight. With less infiltration and less heat loss the indoor environment is more sensitive to the operation of the building, with regard to both thermal and indoor air quality. In 8 passive houses (the Comfort Houses) built in a Danish context measurements of the indoor environment have been conducted, where 5 minute values have made it possible to analyse the comfort level in detail. In this article especially problems with the thermal and atmospheric indoor environment will be in focus. Both overheating and inadequate heating have caused problems for the inhabitants during the three years of measurements in the houses. The overheating problems have clearly shown that even though the houses are built in a colder northern context than typical passive houses, the solar shading must be an integrated part of the project. Examples and effects of different solar shading solutions are included in the paper.

Evaluation and design of thermal indoor environment have typically not been at the top of the ranking scale when buildings are designed. Typically the main focus is on the energy consumption and optimisations regarding energy are much higher rated than optimisations regarding the indoor environment.

Several design tools includes the indoor temperature as a parameter considered as an average value for the entire building, but due to the southern orientation of the main window openings the southern rooms have a tendency to overheat while the northern rooms stay colder. The results from detailed measurements are included to illustrate the need for further attention to these critical zones.

The atmospheric indoor environment also needs to be in focus. As the houses become more air tight, the comfort level depends on proper designed ventilation systems. In the 8 houses demand controlled mechanical ventilation is installed, since all the houses have exemption to ventilate less than the requirements set by the Danish building regulations. The control of the systems is based on the individual demands in the houses, where systems have several ventilation steps to accommodate the demands.

The CO2-levels in the houses were very different depending on ventilation rates and internal gains. Bedrooms and children’s rooms often showed levels outside the comfort criteria set in the project, which revealed a need for higher ventilation rates in these rooms.