I find that any issue worth addressing is best done in person! However, with that being said with the situation of the windows it’s a behavior although there are several indirect ways to address! Once you set up how you will communicate I would ask if texting is acceptable? If yes, I would text them a picture of the windows open with $$ signs and kindly remind them that if this doesn’t end they will see an increase due to utilities bill jump! In addition, then you have a time, date, stamp of how many times you’ve had to address and frequency.
It’s very easy to get yearly print out and if heating costs have increased it is not unreasonable for you to expect more in renewal increase- if renewing is an option.
Finally, smells. . .
It’s best to address at time of incident instead of assuming anything once you notice it - knock on door and address. That is a situation whereas; it’s best done at time of incident so that there are no accusations just facts. I smelled this at this time do you have a minute for you to come and see what I’m talking about so we can resolve!
Just my two cents!