The report deals with an energy saving and cost effective ventilation plant which is an important element in the Norwegian project ``Reasonably-priced low energy houses``. The energy saving measures which are both easy and safe in operation with a minimum of maintenance, are to be integrated into the building structure in the planning phase. The plant is equipped with a noise reducer, and a system design for the operation control, is shown. The report shows the alternative methods of plant design, which include the location of an heat exchanger and a system of soil-covered pipes. A cost quotation for the plant is given. A new project with the aim of developing a ventilation aggregate with natural circulation, is briefly dealt with. 4 refs., 24 figs., 5 tabs.