Solutions for MVHR in existing dwellings

For retrofitting of existing dwellings MVHR is seldom applied, despite the potential in energy saving and improving thermal comfort and indoor air quality. Major barriers and limitations for application are lack of space, especially for the supply ducts and the MVHR units as well as the complexity of execution. Also initial costs are an important barrier. Limiting supply ducts could be beneficial for application in single family dwellings. In a study some configurations with simplified air supply with MVHR in single family dwellings have been investigated. The main principle is supplying air only on the first floor and internal air transport by overflow provisions to the exhaust points. Simulations with COMIS show the CO2 levels in habitable rooms for different configurations and the Low Ventilation Index (Lvi) in relation to a reference situation with natural supply and mechanical exhaust. Good quality overflow provisions are crucial in this concept. Simulation show a Lvi < 0.005 which is equal (and in some cases even better) then the reference situation. In a number of field experiments ventilation efficiency of different configurations have been measured with tracer gas. In collaboration with the company Agpo BV some industrialised prefab solutions for simplified air supply have been developed and tested in retrofitted dwellings.