Decentralized ventilation unit for window frame integration

Abstract

Swedish National Board of Housing, Building and Planning reported in “Energi i bebyggelsen” that 80 % of the detached houses in Sweden were under-ventilated, and had a flow of 0.23 l/(s·m2) on average instead of, by the code, required 0,35 l/(s·m2). Well known concerns here are lacking indoor environmental quality and a risk of moisture problems in certain rooms and in the envelope. The naturally ventilated houses have a higher airflow at low outdoor temperatures which increases the energy use for heating. Adding proper ventilation to all Swedish detached houses could according to Besmå’s pre-study “Potential för energieffektivisering i småhus (2019)” increase the annual energy need by 5.5 TWh. Many of these use electric heating resulting in a heavy pressure on the electricity production and distribution. One way to solve this problem is to install mechanical ventilation with heat recovery. Installing such system in older houses is however often costly and often carries technical and practical problems. Ducts must be installed in every room in the building, requiring space which often leads to reconstruction of walls and ceilings. Another way to solve this is reinforce the existing ventilation in the house with a decentralised ventilation unit with heat recovery. The technical solution is to mount several smaller ventilation unit with heat recovery in the building skin in order to ventilate individual rooms. The solution does not require any ducts to be installed. This simplifies the installation and reduces the maintenance. In this report we study a decentralised ventilation unit with heat recovery intended to be installed in window frame to lower the cost of the combination of ventilation and window renovation. In this report we measure draft, short-circuiting between inlet and outlet air, air mixing in the room, noise and heat recovery efficiency of the ventilation unit. The results show that no draft and no short-circuit occurs and that the mixing of the air in the room is high and an efficiency of the heat recovery of approximately 70 %.