Mark this: you can have all the fancy kit to heat your van and water, but if you ain't warm, you stand a good chance of having a stroke or heart attack if you push it too far in the cold. All the thermals/gloves etc won't help when you're breathing in freezing air.
If you are in any doubt about your physical ability, don't go out there. Especially if you're an old git, and especially if you are an old git with circulation issues.
I think it's a matter of time before we hear of windows dying from being in the cold, not because they was on a ladder.
Think I'm wrong?