After living in so many drafty houses while growing up, I figured there was little you could do to improve the situation once a house had become leaky enough to present temperature issues.
You assume that there are just too many open holes either inside the attic or within your own walls that it would be foolish to address the issue with any sense of urgency. Sure, I knew that windows are a huge factor for a home’s energy efficiency, and since it’s obvious to anyone with a brain that most of the time they can be swapped out and replaced—that implies there is something a homeowner can do to mitigate a drafty house. And of course there is the weatherstrip foam that you can put inside the creases of your doorways leading into your house. This becomes a second factor in addressing drafts and poor insulation. But, there was one example I saw recently that genuinely surprised me. While reading through maintenance tips for central heating and cooling systems, I spotted a post about getting your ductwork resealed from the inside out. You can have an HVAC tech coat the inside of your ducts with an adhesive that hardens and fills any air gaps, leaks, cracks, or holes. A different product called Aeroseal is sprayed inside of your ventilation system and bonds to the inside surfaces of the ductwork. The second method costs more money and requires more product to achieve the same results as having a technician do it by hand. Regardless, if you have drafts due to leaks in old metal ductwork, this could be a gamechanger in addressing your home’s energy efficiency.