One of the most important components of a tightly sealed house or a super-sealed Passive House is a fresh air system. Often they are heat recovery ventilators, and others have used earth tubes running under the home or in the garden. Japan's Geo Power Systems has turned it into a clever system. They call it a solar geothermal system, preheating the air from the solar heat trapped in the ground. The ground is a constant temperature and a comfortable one, so it warms in winter and cools in summer. It has a number of components:
(1) Hot-air ventilation A fan in the attic automatically ventilates hot air when the temperature reaches a predetermined point.
(2) Air circulation unit Air below a certain temperature is sent back to the Geo Pipes.
(3) Ceramic charcoal Ceramic charcoal placed in the floor and attic naturally reduces odors, helps control humidity, and emits far infrared rays, which may be beneficial for health.
(4) Fan unit The energy-saving design includes a brushless DC motor for energy efficiency during the 24-hour programmed circulation.
(5) Cobblestone layer The cobblestone layer stores natural coolness and helps keep indoor temperatures from rising during the summertime.
(6) Geo Pipes The Geo Pipes transfer heat from the hot outside air to the ground. Moisture in the air condenses out, controlling humidity and removing pollutants.
The temperature is a lot more even below the ground than it is above.
This is a lot more sophisticated than a typical ground pipe or HRV; it conditions, cleans and deodorizes as well as bring in fresh air. The designers claim:
- Moderates temperature differences up to 50 degrees F
- Lowers heating and cooling bills
- Purifies indoor air, removing 95% of dust and 99% of pollen
- Includes automatic air circulation and ventilation
- Naturally controls humidity
- Operates in an entirely chemical-free environment
- Reduces CO2 emissions
This just makes so much sense; like natural light and opening windows, it is free cooling and warming when needed, and lots of fresh air that every house needs. In much of America there should be a check for Radon emissions, that rubble layer could be an effective collector of the stuff. But we love solar and we love free. More at Geo Power System