Freezing ventilation duct MKD

When accepting an apartment for the last. On the 17th floor of the MKD (without a technical floor), a thermal imager detected severe freezing of the walls of the ventilation duct in the bathroom (at 0 C outside) 14 C below the temperature in the room. Supply and exhaust ventilation from nature. prompting. At the same time, neighbors in the ventilation duct a few floors below noted reverse draft. The house is new, not inhabited, double-glazed windows (cold season, I think the windows are closed everywhere). In the layout of the apartment there are 2 ventilation ducts (everything is ok with the second one) and interior partitions have not been erected, just in the area of ​​the ventilation ducts. Question: is it possible to solve the problem by insulating the roof outlet of the ventilation duct (to prevent freezing and its consequences), as well as by installing a check valve on the ventilation grills throughout the ventilation stack. It is clear that the plus should be provided with air flow, but it is not clear how to solve this issue in the whole house (a house with a ventilation facade made of porcelain stoneware)?