A new ventilation strategy for humidity control in dwellings - a demonstration project.

A demand controlled ventilation system with humidity as the control parameter was tested in an experimental demonstration project in 16 apartments. In the same housing complex 16 identical apartments with a constant exhaust airflow rate were included in the test as a reference group. The purpose of the study was to investigate whether satisfactory physical health conditions could be reached in the humidity-controlled in apartments, while at the same time reducing the use of energy for heating. In the apartments with humidity-controlled ventilation the air supply was regulated so that the humidity in the indoor air in all rooms was kept at a level which was below the limit for the growth of house dust mites and just sufficient to prevent condensation on all indoor surfaces of the building. The airflow could increase up to a maximum to the requirements as stated in the Nordic Committee on Building Regulations and in the Danish Building Code. The airflow in the reference apartments was at a constant level, according to the requirements. In the humidity-controlled apartments the total outdoor air change, the mechanical exhaust airflow rate, and the energy consumption for heating were significantly reduced compared to the reference apartments, at mean temperatures per day below 9°C and at the same time the humidity criteria were met. In addition to the technical study, a resident indoor climate satisfaction study was carried out in the housing complex. The main purpose of this study was to gain knowledge of the residents' appraisals of the indoor climate.