Ground Source Heating

Ground source heat pumps can be a good solution for many vicarages located outside areas with district heating.

Which buildings are suitable?

The building should be reasonably well insulated and have normal density for it to make sense to install a ground source heat pump. To keep costs down, it is very important to keep the flow temperature as low as possible. Underfloor heating in most of the building is preferable, but not a requirement.

If there are radiators, it is important that they are sufficiently dimensioned. This will normally be the case in an older building, which is renovated and reinsulated by newer standards and where the old radiators are preserved.

It is fairly easy to test whether the radiators are large enough compared to the insulation-related condition of the vicarage. The test is best performed in winter in cold weather in a span of 7-14 days. Turn the flow temperature to 60° C (or lower: down to 45 - 50° C, if the boiler can handle it. If necessary, contact a plumber). If the temperature stays at a comfortable level, it is likely that a heat pump can be installed without problems. The “test" is more reliable, the lower the outdoor temperature is.

If the vicarage gets too cold in the test period, it will either require more insulation, better sealing of the building or larger radiators. Perhaps it is even necessary to do all of the above, in which case it is worth considering whether a ground source heat pump is the right solution at all.

Water tubes (ground collectors)

A ground source heat pump requires a ground area of some size for placing the water tubes. This can in some cases be a challenge. A rule of thumb is that about 50 m of tubes corresponding to an area of 60 - 70 m2 land per installed kW heat pump must be installed. The recommended tube length also depends a lot on the soil conditions.

Be aware of any large trees often found in vicarage gardens and avoid damaging their roots, which can be fatal for the trees and increase the risk of storm damage.

If the vicarage is located close to the church, there may be particular challenges. Water tubes may not be buried in a cemetery, so there must be an appropriate area available outside the cemetery. Please note that the local museum must always be informed before starting digging work. It is likely that there may be remains of archaeological or historical interest in the area close to the church, if it is a medieval church. If the museum wants to make excavations, this will delay and increase the cost of the project.

Permission

Before the establishment of a ground source heat pump a permission from the municipality is always required.

Inspection

An annual inspection is mandatory.

Economy

Cost savings are typically 50 - 60% if replacing oil-fired heating with a heat pump. If the heat source is pellet heating or district heating, there are normally no savings.
The investment of course depends on the heat pump's size. A small ground source heat pump in "single family-size" typically costs about 150.000 kr. In large, old vicarages investments may be up to 250.000 kr.

Example

A listed vicarage south of Aarhus with a heated area of about 500 m2 is heated with an older oil-fired boiler. The vicarage is from the late 1700s and is only insulated to a limited extent.

Before replacing the boiler, it was necessary to insulate the ceiling and rooms of the first floor and seal doors and windows. The old oil-fired boiler was replaced with a ground source heat pump.

The investment in the new heating system was about 250,000 kr. with a payback time of 7-10 years, depending on the current oil price.