Construction instructions for the Sí-BoFe-1000 geothermal drilling field for air temperature control

The Sí-BoFe-1000 is a blueprint for a vertical ground-air borefield for passive air tempering. The system uses the relatively stable ground temperature of about 8–12 °C found a few meters deep to preheat outside air in winter and precool it in summer.

The construction is based on a DN200 drilling pipe with a continuous dividing plate. This creates two separate air channels within the same pipe: the supply air flows down the first channel, is redirected at the end of the pipe, and rises back up through the second channel. This creates an air path of about 10 m in the ground per borehole.

Multiple boreholes are combined to form a compact borefield. This allows for stable air tempering even on small properties – without a heat pump, without a compressor, and without complex technology. Typical applications include supplying air to buildings, greenhouses, animal stables, or technical rooms, as well as pre-tempering the intake air for air-source heat pumps.

Integrated condensate management ensures that any resulting condensate is drained via a hose at the lowest point of the pipe. This eliminates the need for additional holes in the pipe, and the system remains permanently sealed.

The blueprint describes the complete system setup – from the drilling scheme and pipe string to the connection to collectors and air mixers. The system is modularly expandable and suitable for DIY projects, agriculture, greenhouse projects, and energy-efficient ventilation solutions.

Borefield

Multiple boreholes form a common borefield.

Typical sizes:

Borehole spacing approx. 1.5 – 2 m

Construction Cost Concept

System as a kit + drill rental (https://si-climate.com/products)

Example costs

As of March 15, 2026, plus VAT + transport:

Material per borehole: approx. €100 – €150