Horizontal Collectors
The effectiveness of a horizontal collector depends on the local ground conditions. This means both the type of soil (loamy, sandy, etc.) and the moisture content. In general wet, loamy soil will have better heat transfer properties than dry sandy soil. Much of the energy recharge of the ground at shallow depth comes from rainwater passing through the soil.
It's important therefore that the area above a horizontal collector remains permeable, meaning it can't be covered by paving or a building.
Horizontal collectors require a good amount of space to be available near the building. For a new build the area needs about 1.5 to 2.5 times the heated living area. The pipes are buried at a depth of 1-1,5m, generally in an area that will be grassed or covered with another permeable material like gravel.
On some sites, particularly for a new-build, all the top-soil is removed and the pipes are then easily laid prior to final landscaping. More commonly the pipes are buried in shallow trenches. In many cases these is insufficient space for this type of collector and vertical boreholes are used.
