Simon Gardner wrote:

Whilst I understand that old-style single or double glazing may be
direction of heat-transfer neutral - what about the newer glasses now
compulsory in double glazing? Does this in any way act in a one-way manner
so as to exacerbate the heating effects of a lot of sun as compared with
older glazing?

I don't think there is anything directional about the glass, but you may
get some directionality if the sun is shining in through the window as a
result of the "greenhouse effect".

--
Cheers,

John.

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