Spoke to Zinsser earlier about switching to all coat for the sash windows. They cleared up some doubts I had.
Firstly Allcoat has an adhesion resin similar to the 123 so adhesion to glass shouldnt be an issue. It also has some anti mould/ fungal agent and can be used on the inside of windows so should help resist mould build up from condensation on the internal glazing bars.
Perma satin/ semi gloss has longer exterior expectancy, and has better anti fungal but it doesn't have any adhesion...
Zinsser Allcoat Technical info
Firstly Allcoat has an adhesion resin similar to the 123 so adhesion to glass shouldnt be an issue. It also has some anti mould/ fungal agent and can be used on the inside of windows so should help resist mould build up from condensation on the internal glazing bars.
Perma satin/ semi gloss has longer exterior expectancy, and has better anti fungal but it doesn't have any adhesion...
Zinsser Allcoat Technical info