Surface geothermal science

The Canadian well is a geothermal technique that takes advantage of the inertia of the immediate subsoil and the slight variation in its temperature throughout the year, to preheat or cool the fresh air used to renew buildings, depending on the season. Cooling mode is also known as puits provençal. This relatively old technique has recently been rediscovered with the construction of HQE (high environmental quality) buildings, where it is now favored for its low cost. It reduces heating costs in winter (up to 40% of air renewal costs) and provides natural comfort in summer. Canadian or Provençal wells can be installed in all types of building (primarily new), from single-family homes to commercial buildings.

Since the end of the 1990s, heat pumps for heating single-family homes have been enjoying a marked revival, particularly those with buried collectors. The main advantage of ground-source heat pumps over air-source heat pumps is that they use an external heat source (the ground) whose temperature remains virtually stable throughout the year. What's more, this temperature is generally higher in winter than the ambient air temperature, and lower in summer, so the coefficients of performance achieved are better. The rising cost of fossil fuels and growing public awareness of the effects of global warming should encourage the development of these heating techniques, which can now be considered among the least expensive in terms of operating costs and greenhouse gas emissions. It is estimated that by 2020, a third of new single-family homes built in France could be equipped with such systems (source ADEME).

For load-bearing reasons, some buildings have to be built on foundations. Foundations, which can be piles, concrete walls or slabs, are underground structures designed to ensure the static stability of a building by transferring its weight into the depths of the ground. The principle behind thermoactive foundations or geostructures, for example, is to incorporate an energy collection system at the manufacturing stage, consisting of a network of polyethylene tubes embedded in the pile and reinforced with iron reinforcement, through which a heat-transfer fluid (water with glycol added) can circulate in a closed circuit. The energy collection system is connected to a heat pump. This concept is relatively recent (the first projects date back barely ten years). It is an integral part of the approach adopted in recent years to reduce energy requirements in buildings, with the corollary of reducing environmental impact (limiting greenhouse gas emissions). Several hundred projects using thermoactive foundations are currently underway in Europe. In France, a number of projects have recently been launched.