Hi I have a question, I am currently painting a room and I have come across something I have not seen before. The room has paint peeling off due to humidity and possible moisture. The owner has said a there was a roof leak prior to this happening then he pointed out one off the walls in particular that gets very hot which had caused the most damage. We have scraped and skim coated (plastered) all defects and sanded plaster. The other 3 walls are straight forward but this one wall in particular I am unsure of what type of 'sealer' to use to prevent heat from breaking the protective paint film. Can anyone help?

Moisture behind the wall, possibly from water leaking down behind a gutter or soffit or fascia, or even a roof leak dripping down the roof to the wall, can't be cured by any kind of paint. But if the leaks are all truly fixed and the wall is truly dry, I see no reason to use Kilz or any other special paint.
The owner needs to tell YOU why the wall is hot. Is it exterior or interior? Ask him what pipes go through it. I don't see why latex paint isn't OK, if the heat isn't unbearable. If it is, something is very wrong with this house.
I would write a disclaimer for the owner to sign, about both moisture behind walls and the heat. No guarantees at all about the longevity of the paint, just the neatness and cleanup.

Thank you for your reply and advice taken. Many thanks.