Mike Mitchell wrote in message . ..
Are Crittall's steel-framed windows of yore that much worse for
insulation than cheapo plastic-framed double-glazed units?

Certainly. But more to the point theyre also much worse than
traditional single glazed wood windows. The steel frame is an
excellant conductor of heat: not a shred of insulation there. I've
experienced them in 2 places: in one the room with the metal window
was horrendously cold, and when the window was replaced with something
modern, suddenly the place was warm and comfortable.

The other place had an enormous area of 1930s steel windows, but was
not cold. But then it had an equally vast area of radiator running the
whole length of the windows. Extremely wasteful. Must have been
something like 3x or 4x the normal amount of radiator area in that
room.

Not recommended!


What if the steel-framed windows are furnished with secondary
double-glazing? Doesn't this make them equal to uPVC?

No but it would help hugely.


Regards, NT