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The impact of over-tempered air on the perceived indoor climate was evaluated by questionnaires filled in by the users of the first office building with passive house standard in Norway. In this building, the heating demand is covered entirely by warm air supplied into the rooms through the ventilation system.
On the coldest days of January 2014, warm ventilation air was supplied into the rooms at a constant temperature during half an hour. Each user of the building was exposed to 3 different supply temperatures (around 21.5°C, 24°C and 26°C) under the minimum ventilation rate according to the Norwegian standards (17 l/s). Questions related to both perceived thermal comfort and Sick Building Syndrome-symptoms (SBS; feeling tired, headache, etc.) were answered by all the occupants on a scale of 0 (unsatisfied) to 10 (satisfied). The data from the questionnaires were then analyzed using a random effect linear regression model.
The regression analysis did not report any significant relationship between the supply air temperature, and perceived thermal comfort and SBS. It enables to document with a 95% certainty that increasing the difference between supply air and room temperature by 1°C would cause a maximum reduction of the SBS score of 1.02 points on a scale of 190. The impact of an increase of the supply temperature on the perceived SBS seems therefore very limited.
Using air heating to completely cover the heating demand therefore appears to be a relevant solution for office buildings in cold climate with passive house standard.