Ideas could include advanced cold climate
heat pumps, integrated
heat pump solutions
for space conditioning and hot water,
alternative HVAC solutions not requiring a compressor that lower the cost of installing a ground
heat exchanger associated with a geothermal
heat pump system.
It has been suggested by Alan Rushforth that
for some of the very wide collectors that DIYers tend to build
for space heating that an
alternative in which the «risers» run horizontal (hisers?)