1.5 must have a house with ventilation... The smaller the n50 value, the better. So it is sufficient (but good is something else) At 1.3 there would already have to be proper openings letting air in. Would have expected better for such an “expensive“ house :-/ But it is simply the case that the GU only has to make improvements until the value is just barely undershot. For comparison: - As a Passive House, a value under 0.6 would be necessary. - Our house (a lot of own work and with trades via architect) had a value of 0.7