A greenhouse includes housing walls delimiting a growing space for growing plants, an air mixing chamber for conditioning of air, air distribution for distributing conditioned air from the air mixing chamber into the growing space along the plants, a re-circulation air connection connecting the growing space to the air mixing chamber for having used air flow from the growing space back into the air mixing chamber, an ambient air inlet connecting the environment to the air mixing chamber for having ambient air flow from the environment into the air mixing chamber, and a heating unit for heating of air. The heating unit is located at the ambient air inlet for heating ambient air before it gets mixed in the air mixing chamber with used air.
