A fresh look at earth-to-air heat transfer

Added on 19 February 2024

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A fresh look at earth-to-air heat transfer

This rendering shows piping below ground for Ceres’ Ground-Air-Heat-Transfer (GAHT) greenhouses, such as Rob Lyle’s greenshaus in Ontario, Canada. Photo: Ceres Greenhouse Solutions

Half an hour west from Parliament Hill, Ottawa, behind a private driveway and out of sight along a pleasant, forested side road at Almonte, Ontario, sits Rob Lyle’s little-but-high-tech, net-zero passive solar greenhouse, known as greenshaus inc. It was growing heads of lettuce, a thousand a week, in hydroponic solutions in frosty January 2023.

An Ottawa-area winter can be harsh and cold; summer can be hot and humid. Last January, outside temps topped out at 20°F and plunged to -5°F; inside, with a bit of propane heat, the lettuce stayed crisp, cool, and quickly growing in healthy, disease-free, pest-free hydroponic nutrients, at around 45°F to 60°F.

A former investment management specialist for large financial institutions, Lyle entered the horticulture business in 2019 with a 2,100-square-foot greenhouse as a prototype for a larger project. The greenhouse was supplied by Ceres Greenhouse Solutions, headquartered in Boulder, CO.

According to Ceres, hundreds of the patented GAHT (Ground-Air-Heat-Transfer) greenhouses have been sold in North and South America and in Europe in the past 10 to 12 years. They range from residential scale to multiple modules measuring 60×100 feet each. GAHT is coupled with other equipment to reduce energy bills.