"Janet Baraclough.." wrote in
message ...
The message
from (Nick Maclaren) contains these words:

This is something that we have discussed before, but I still don't
understand the mechanisms, and so am asking for clarification and
cross-posting. Here is what I understand the situation to be.

The annual peak intensity of the sun in the UK is perhaps 70% of
the daily, clear sky, peak intensity in the tropics, perhaps less.
The ultraviolet levels are a LOT less, but I haven't been able to
find what they are - let's take them as 40%. (snip)

The ozone layer (or lack of it) plays a significant role in
screening
UV. In Scotland the ozone layer is seriously depleted, May usually
has
clear skies, and even when the temp is only 60 to 70 F, skin can
burn
within minutes. It's not uncommon in that month for people here to
burn
seriously enough to require hospital admission. Scotland has the
highest
incidence of skincancer in the UK.

A couple of years back we were in Darwin Australia in May, also
clear
skies, 90 degrees, sun much more direct, no burn sensation at all. I
met
an Australian doctor there who had just arrived back from Scotland,
and
remarked on the same thing. Her caucasian skin which never blistered
at
home in Darwin,was burned in Scotland.

I believe that the problems caused by sun through glass are mainly
surface heating, because it is typically associated with slow air
movement, is much more serious close to the glass than a distance
away, and 1/2" air gap K glass double glazing does not seem to
cause
the effect much. Can you confirm or deny this?

In the 80's when I was being treated for multiple malignant
melanoma,
I asked about UV transmission through glass. The reply was that
single
glazing,(car windows for example) and standard double glazing at
that
time, offered virtually no protection at all.

I don't believe that. Most glasses have quite a sharp cut-off just
beyond the visible blue end of the spectrum. If not, the near-UV
photodetectors which I used for decades would not have had to be
constructed with fused silica windows.

Franz