D
Doctor Drivel
It's illegal to fit a noncondensing boiler![/b]
It isn't as long as the exception is met. Not sure about se and u-ducts coming into it. Worth looking.
I know there were boilers which USED to be fittable to U ducts! They aren't any more!
I think they still are.,.,.it needs some more research.
As the flat on the top floor, how about feeding a plastic flue and air pipe up the se-duct. Is it accessible from the roof? Then the se-duct is by-passed. It is being used a duct for the flue pipes. Or a two pipe flue with exhaust into the se-duct and fresh air taken from elsewhere.