Passive, low-tech geothermal?
Many years ago, I saw a television special about a house that (in addition to other features) used underground pipes (and some solar-operated blower fans) that circulated air that was then used in the house. The air was supposedly a fairly stable 55 degrees, so that really made heating and cooling the home much more efficient. My recollection is that this was lower tech than modern geothermal systems.
My house is almost 100 years ago and originally had a gas gravity system (now gas forced air and central air). I would love to find out if there is any way that I could incorporate something that basic and simple to augment my current system.
Thanks in advance.