Abstract: The invention relates to a ventilation unit (1) for providing supply air (SA), preferably outside air (OA) or fresh air, to an apartment or parts thereof and for removing return air (RA), preferably exhaust air (EA) or used air, from said apartment or parts thereof. The ventilation unit comprises a bypass valve (BV; BV?) having a plurality of elongate members (EM; EM?) extending across a bypass duct and arranged in parallel next to each other, thus forming an arrangement of a plurality of elongate members next to each other as a one-elongate-member-thick layer. At least some elongate members (EM; EM?) of said plurality of elongate members (EM; EM?) are rotatably mounted around an axis of rotation (AR) parallel or identical to a longitudinal axis (LA) of said elongate members (EM; EM?). At least some elongate members (EM; EM?) are rotatable between a first rotational position or closed position (CP) and a second rotational position or open position (OP).