I have installed a Blauberg Komfort Ultra D105-A and on medium fan speed it is keeping the internal CO2 level below 600ppm, despite having 2 adults (and a 1 year old baby) in a 4 bed house (I know this is a single room unit, but is more than adequate in substitution for two tacky noisy extract fans it replaced). It also means we don't have to open windows for fresh air that helps resolve external noise ingress, cold drafts and spider visits (I like them but my wife doesn't). Even on cold days the fresh air supplied into the house is pleasantly warm (as it recovers heat from the exhaust stream) and the house always smells very fresh. The unit has to overcome the resistance of 3 grills (2 extracts from wet rooms and 1 supply into the landing) as well as 20m of 125mm⌀ insulated flexible ductwork. Despite this the power consumption is even less than technical specs (actual values are 23.5/33/56 Watts at fan speeds 1/2/3). I leave the unit on fan speed 2 at night (to get fresh air for 2 adults and a baby) and speed 1 at daytimes when I am the only one working from home. Point of interest: I have arranged for the intake air to be from my ventilated loft space to take advantage of a slightly higher loft air temperatures in winter. The pulley in the photo is to lift the unit comfortably for annual filter replacement. A beautiful, quiet and efficient product. Every house should have one.