PBS's World Focus had a little ditty on Denmark energy efficiency -- $15
per YEAR heating bills! Holy shit....
ROI on these systems seems to be about 10 years, whose initial cost is about
10% of the house value -- which was either $60,000 or 10% of 60,000 -- heh,
just a zero....
But inyway, one method was a heat pump/AC that uses buried coils (3 feet
underground) as the heat exchanger. I don't know if it's a formal heat pump
as in a minisplit ($15 wouldn't go very far, even with inverter technology),
or if the underground is just a passive equalizing heat resevoir, with water
as the transfer medium.
One home-moaner smartly distinguished "solar heating" from "solar cells",
and uses the solar heating for direct heat transfer for hot water, and solar
cells/panels (photovoltaics) for electricity -- a separation that allows
much bigger bang fer yer photonic buck.
The diff between Denmark and the US in all this is that there seems to be
much more government interest, ergo more apparent development and
progress -- depending on the PR spin. It's not clear whether this stuff is
in the "every man's" home, or still for experimenting arkytecs.
Rainwater is collected in underground tanks, as well, for less critical
You might be able to catch archives on pbs.org.
The construction methods (laws) used in those northern countries make a
house just about airtight. The environmental air system exchanges heated
fresh outdoor air (in cold weather) to maintain oxygen levels for the
Their construction methods aren't new.. I saw a program over 30 years ago
where the airtight methods were the only way new homes could be constructed,
as a matter of government regulations/laws.
Air leakage and infiltration are a major sources of heat loss. Caulking is
the most cost effective heat-saving product you can buy. Sealing air leaks
isn't particularly hard work, but commonly ignored.
When a hundred feet of cracks are added up, it can represent a fairly large
hole to the outdoors. Many homes probably have many hundreds or thousands of
feet of leaks.
If I ever get a heat pump I've always thought it would be good to use
the normal air cooled condensor with the last few yards of heat
exchanger/pipe underground to cool it below the air temperature. The
water from the evaporator would flow to the underground heat exchanger
to help keep that effective.
A hundred or so years ago we had cisterns that stored rain water
underground. It's not anything new. We just got lazy.
Last summer my family toured Northern Europe visiting here and there.
Europeans are much more green conscious and they do practice it.
New airport in London collects rain water and it fills 70% of utility
water needs for the terminal building. Even tiny country like Estonia,
people actively talk about global warming, energy conservation,things
like that. Their attitude is correct and commendable.
My son looked into the type of system you are describing, but 3 feet is not
deep enough. It needs to be well below the frost line. In Iowa the system
is so expensive that it would take much more than 10 years to recover the
cost in savings. More like 50 years, much longer than you can expect the
system to last. Also, in 10 years you are looking at buying a new system,
negating the cost savings.