Image from CMX-CIPHEX, Lloyd Alter
27% of North America's greenhouse gas comes from the production of electric power, so it makes sense to use as little of it as possible. That is why I am not as enthusiastic about ground source heat pumps as many others are; they run on electricity. If you are in a temperate part of the continent and can live without air conditioning, then there are perhaps better alternatives.
One might be the NTS Matrix; Martin Holladay at Green Building Advisor includes it in a list of "magic boxes" that combine water heating, space heating and heat recovery ventilation. It packs five functions into one very efficient natural gas burning unit, using 30% less fuel overall compared to discrete units. The manufacturers claim that it has a lower carbon footprint than a ground source heat pump.
The Matrix "incorporates a Condensing Water Heater, Condensing Furnace, Condensing Boiler and Heat Recovery Ventilator, and which is already pre-wired for air conditioning. All of these functions are contained in one powerful system that requires less energy to operate than competing products."
The water heater can heat both domestic water through a heat exchanger, and also be used for radiant floor heating. The forced air furnace includes a heat recovery ventilator with 72% efficiency. Total cost is under $ 8,000, but the manufacturer suggests that there are big labour savings compared to plumbing and ducting four different pieces of equipment. It also takes up a lot less space.
One might worry about so much technology in one box; Putting all the components together into one unit is sort of like the comparison of notebook computers to desktops; you get a smaller, more efficient unit but if one component goes down the whole thing is knocked out and the repairs cost more.
They are a bit over the top with their marketing, with tag lines like "saving our planet for the children we'll never meet."- It's a furnace. I really could do without the polar bears and cute kids. But if you are in an area with natural gas delivery this might be a more economical way to go than a heat pump system. More at NTI Matrix
More on ground source heat pumps
Are Ground Source Heat Pumps (AKA Geothermal Systems) A Good Choice?