Do I actually need someone like BPC to design my MVHR ducting system?    For my new-build bungalow, it seems really simple. I have designed the ducting plan myself following the basic rules: equal number of supply and extracts across the house (5x of each) double pipes to every terminal so it is quiet supply to bedrooms and living room (x3 & x2) extract from bathrooms, kitchen, utility room and plant room (x2, x1, x1, x1) room terminals as far fr