My planned Potton is a 200 sq/m house. I think the longest duct run will be from the loft space to the far end of the living room. This will be 15 metres as best as i can estimate it.
A previous quote and design ( from a company i dont intend to use) said i need a house total of 60 litres/second.
Will a single 90mm duct be sufficient? If its good for the living room run then it should be good for everything else.