Dick LeadWinger wrote:

If one were going to build a home today in an exclusive (multi-million
$) housing area between 6,500 and 7,000 foot altitude, what would be
considered state-of-the-art in heating systems?

Solar heat from a sunspace :-) Higher altitudes have more sun, and thinner
air makes insulation work better: each 1000' reduces the heat loss by 5%.

Nick