Temperature of Communal Hallways in Block of flats

Hello,i need some advice please. Today my landlord sent letters to each flat saying communal windows in the hallways cannot be opened if the temperature is below 18°c,its raining,snowing,hail or excess wind. No one lives in the communal areas,we all live in our flats. They even installed thermometers on each landing. Sometimes the communal areas stink & when they are cleaned,how can the floors dry if the windows arent open. Plus gov says open windows because of the virus. Can a landlord enforce this? Is this legal?? Thanks in advance.