I have three small glass windows in my basement from 1900s. They barely let in any light, can't be opened, and I noticed a little bit of ice is forming on them. I want to insulate over them and I don't care if they get blocked. I know they are leaking heat.

What do you suggest besides complete replacement. I want to make sure no matter what I do, there won't be any water or condensation collecting there. I'm open to anything as they can't serve as an exit, don't let light in and are condensating water that's turning to a bit of ice.