YOU ARE NOT RESPONSIBLE FOR LIVING IN A COLD, RICKETY HOUSE... It is a law that landlords must have things as serious as improper air ventilation "Professionally" taken care of... not at the cost of the tenant!!! Have a city building inspector come by to look at it free of charge to address your concern. He will also see if there are any other violations in your house that have been over-looked such as faulty electrical wiring, asbestos, other in-adequate ventilation, non-working appliances such as your dishwasher and/or refrigerator, washer/dryer . If the ventilation issue hasn't been taken care of, or anything else he finds, he will formally write a letter to the owners/landlord and tell them that they have a certain amount of time to have it professionally fixed or else they will be penalized and their business shut down until it complies with housing/building code regulations. Also, if they choose not to have these things "professionally" fixed... document the before and after with photos, or keeping a journal so you have grounds to sue them in Small Claims Court.
You also have a right to get out of your lease if the landlord fails to maintain the property and have your deposit given back to you "no questions asked".... if they refuse to, you again, have legal grounds to sue.
Your well-being is what matters here, don't feel sorry for your landlord, you are paying him money every month. Obviously something is array, or else you wouldn't be upset. Call City-hall if you cannot find the number for the Building inspecter in the govt. section of the phone book.
Hope things get straightened out for you ~ Sorry this is happening ... :(