Thermally broken vs non thermally broken windows - an insulation question

… thus is my entry for forum’s Most Boring Title award.

So we are thinking of getting steel crittall doors for the rear doors of our house (have two large sections) - although it’s looking like the cost is quite prohibitive and we’ll probably settle for bland bi-folds.

Looking into it, one difference is that some are thermally broken frames, some are not, although they all use 18mm double glazed glass panels.

Googling says that thermally broken frames offer many times greater insulation. I was just wondering if anyone had experience of these types of windows/doors to say how much practical difference it makes - given that the framed area is a relative small part of the overall surface.

Why wouldn’t you have frames with a thermal break given the choice? Is there a cost difference?

Yes, forgot to mention there is one, although it’s a little complicated:

Out of two quotes we’ve had, one firm is 1/3 more expensive - but the difference in price between TB and non TB is about £2-3k.

The cheaper firm only does non thermal break. We could just about afford the cheaper firm but I wouldn’t do it if it’s going to be very poor insulation wise.

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We have non thermally broken aluminium double glazing dating from the 70s and they are a pain for condensation (on the frames only) in rooms with higher humidity (kitchen, bathrooms and bedrooms)

Seem fine elsewhere though.


Interesting, thanks.