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Following on from some discussion in my blog: we are experiencing some fan noise transmission through our radial ducting to individual room valves, only really noticeable on normal ventilation rates at night when the house is silent, but certainly noticeable during the day when the MVHR is on boost. Experience of other members suggest a silencer would greatly assist in reducing the transmission of any fan noise, and I'm pleased to say having contacted my supplier (BPC) they are going to send me a silencer. I'm also planning to build my own using some acoustic foam that I've purchased. I'll do a comparison test in due course to see which silencer works best. One of the things Gary from BPC suggested was that there may be an air imbalance in the MVHR unit, and I thought it would be helpful to explore how we all go about balancing our systems. I borrowed and airflow LCA301 meter (with hood) from my builder and used that to measure the air flow at each room terminal, adjusting each individual room terminal as required to meet the flow rates specified by BPC. I know some members have distribution boxes that allow the adjustment to be made by way of restrictor rings in the distribution box. I balanced the system and set fan speeds so that the supply and extract air flow rates were the same. The cumulative supply / extract rates were equal to each other (or at least as close as I could get them to be). However, thinking back to previous builds and advice, and one which was professionally commissioned, there was always a difference in the supply and extract air flow rates of up to 10%. Has anyone else done this? I'm not convinced this is the best approach as you end up over or under pressurizing the house.