Not all ground conditions are the same, what Lambda value (Wm/K) are the length of collectors based on?

The Lambda value is a measure of the heat conductivity of a material, in this case the ground in which the collectors will be installed. The lower the value, the lower the conductivity of the ground. For the purpose of our RHI calculator tool, we have assumed a generic 1.7Wm/K for horizontal collectors and 2.4Wm/K for vertical (borehole) collectors.

Our RHI calculator tool exists to provide an estimate of costs and benefits of installing either ground or air source heat pump in your home, which is why we use default values.

In accordance with MIS 3005, we would advise a full geological survey in advance of installation to ascertain the correct size for the ground array and to work out the Lambda values. MIS stands for microgeneration installation standard, and MIS 3005 is the standard for heat pumps. Our MCS heat pumps are designed and installed in accordance with this standard.