Unfortunately, in most cases in rental properties it is the lifestyle of the tenants which determines whether condensation and black spot mould become a problem. You can of course try to educate the tenant regarding sufficiently ventilating the property, particularly the kitchen and bathroom areas, as well as avoiding using radiators to dry clothes and to use the heating system correctly. However, experience will tell you that tenants will continue with their bad habits, saving on their personal energy bills, also not being able to open windows on ground floor properties due to security. it’s not always your tenant’s fault.