I've finally got round to balancing the MVHR and am more than a bit worried by the figures I'm getting.   I've followed @JSHarris excellent write up (and spreadsheet) and am using a Testo 405i in a 1m length of 100mm diameter straight duct with a cone to go over the inlets/extracts. The system is a Vent Axia Kinetic High Flow (max flow rate 666m3/h) and the house has a floor area of about 305m2 with high ceilings upstairs - I'm guessing at a total volume of about 1000m3.   Bu