A few feet down, the ground stays a steady temperature all year. Earth tubes — also called a ground-to-air heat transfer (GAHT) system — are buried pipe that draw fresh air through that stable ground, pre-heating it in winter and pre-cooling it in summer before it ever reaches your home or HVAC.
The standalone planner is still in development
The on-lot planner — size the home, place it, mark the intake, price the trench — is built, but its cost model is still calibrated against one soil type. A trench price is mostly a guess about what's under the yard, and we'd rather not publish a number we'd have to walk back.
Earth tubes on a Sophab are available now. Run under the patio of a Sophab Solarium they're a costed add-on in the sizing tool today — tick earth tubes + patio and the estimate includes them, because there the dig is shared with work that's happening anyway.
Air is pulled through pipe buried below the frost line, where the earth holds a near-constant temperature year-round. By the time that air reaches your home it has already given up its summer heat — or picked up winter warmth — for free.
Bitter outdoor air is pre-heated by the ground on its way in, so your furnace or heat pump starts from a much milder temperature.
Hot summer air is pre-cooled underground, taking load — and cost — off your air conditioning, sometimes replacing it outright.
The ground does the tempering. All it takes is a small fan to move the air — a fraction of what heating or cooling that same air would cost.
Earth tubes can pre-condition the fresh air for any home, on their own. But paired with a Sophab — run under a patio, or feeding a GreenPhab greenhouse or a Solarship — they close the loop on a fully solar-passive, low-energy system.
We size the run, depth and layout to your soil, your lot and the air volume your home needs — then hand you a plan you can build to.
