You can overcomplicate these arguments. All aircon units consume electric
power. This power is turned into heat and this heat is absorbed by the
outside air, whatever the type of unit. Power stations with their carbon
load are therefore being used to heat the atmosphere, again whatever the
type of unit and some would regard differentiating betweend them (in terms
of environmental impact) as nit-picking!

Yes, but the efficient units are pumping out less heat and carbon dioxide.
Probably by several times over.

It is true that an insulated box with no ventilation, cooled by a split
unit
will need less power but most air conditioned areas have ventilation as
well
and ingress and egress of people, much reducing this efficiency.

The ventilation will be a tiny fraction of that provided by a portable
unit's extractor. Of course, for air con to work efficiently you have to
close the windows. However, hot weather is normally associated with calm
winds, so natural ventilation will actually be quite low. Of course,
insulation and reducing ventilation down to the minimum comfortable level
(or better still providing plenty of heat recovery ventilation) is the way
to go.

Far better to design houses and clothing appropriately and get used to it.

Indeed. However, I like to think of the entire picture. Whilst I am very
interested in environmental affairs, I'm not some Greenpeace nut. Having
everyone work at 50% efficiency because they are too hot is not
environmentally friendly, in my book, as it wastes resources.

Christian.