I have added a Beam MHRV system to my house last year (not a new build, renovation / extension of old terraced house). House is only about 110 sqm, so using the at the time smallest Axco C75 unit. Three extracts (bathroom, utility, one in open plan livign/kitchen/diner above kitchen island), 5 inlets (one each bedroom, one living room, one kitchen/dining area). No other ventilation at all. House is reasonably air tight, triple glazed windows. Works very well, would never again go without it in Ireland. IMO, money well spent (was about 4500 including planning and installation). filter replacement ever 6-12 months, filter is about 25 euro. Had some limitations in terms of placement of inlets and extracts, and some of the piping as it wasn't a new build, but all in all very happy.