chromaticmind

Hello all! We're considering installing dMVHR units in our Victorian ground floor flat in London. We do not have a roof/loft or space in the ceiling to do a centralized MVHR system. The flat is currently very well ventilated with high ceilings and original vents in all the rooms, and we have no damp or condensation problems. We are lucky to have a decent size garden at the back of the flat, overlooking greenery and trees. There is a train that passes behind the garden about 25 meters away. Our living room, kitchen, and bathroom face the garden. However, both our bedrooms face a busy main road (lots of cars and buses) which is 6 meters away. My wife suffers from respiratory issues and is allergic to pollen, dust and mold. All the literature we've come across so far mentions that MVHR systems 'extract stale air from inside the home while pulling fresh air in from the outside'. Given that the air outside our home is pretty polluted we have the following question: If we install dMVHR units in our flat (initially in the bedrooms, and two years later, in the living room), while this may filter out pollen, will it bring in more polluted air, including vehicle emissions or harmful gases from the busy road inside the home? And, if the system is running 24/7, will it bring more of the outside air at a faster rate than the flow that comes through the current vents? In other words, are we going to save on heating bills but increase the pollution in our home? Many thanks!