Keeping baby warm

It’s starting to get very cold out. How do you keep your baby warm enough? My boyfriend refuses to turn the heat up past 65 because we’re really tight on money right now. But it just doesn’t keep our baby warm enough at night or even in the day in the house. I usually keep him in a sleeper since we don’t leave the house on my days off, but when I got to change him he still feels a little cold. At night I put his ticker socks on his hands but I can’t do that I’m the day because he chews on his hands all the time now. He also doesn’t stay swaddled anymore.