Hi, im looking at self installing an MVHR system into my house, it is a 3 bedroom detached house with 1 kitchen and 1 bathroom roughly 130sqm, early next year we will be adding a side extension which will add 1 utility room, 1 bathroom and an office which will take the house to 170sqm. the unit will be placed in the loft which is boarded out and well insulated and i have a good idea where the ducting can run to be able to reach each room. i am wanting to do the design calculations myself to select the best unit and correct size ducting and looking for a good spreadsheet to start off with, i thought this forum would be the best place to start, thanks
