The Hill Fort

The Fort is a Grade II listed property perched on top of a hill in Gloucestershire. Built on the site of many other historic buildings that had gone before it was first constructed in 1764 with various extensions added over the years. A restoration programme has begun with the new owners restoring the various buildings making it comfortable and sustainable.

The owners of the fort contacted The Renewable design Company to provide a proposal for a renewable solution to reduce the cost of heating the property, reduce carbon emissions and to protect themselves against future fossil fuel price rises. The existing heating was run by LPG gas boilers from an external plant room. The owners prepared for a low temperature system by installing underfloor heating throughout the ground floor covered with tiles which radiate the heat efficiently. The upper floors were fitted with smartrads which are fan assisted radiators, ideal for low temperature heating with in-built fans that can be used to push more heat into a room if required, increasing the temperature in a room by up to 30%.

After studying the property and its location it was decided that the most suitable technology would be a heat pump system using the adjacent field as the heat source. The existing boilers were left in place to create a bivalent system to back-up the heat pumps as a precaution against any future severe climatic conditions, also the building is very exposed to cold winds from all sides being on top of the hill. Constructed of thick stone walls, these will act as a thermal store for a heat pump, holding the heat and keeping the body of the building at a constant temperature. The house is well insulated in the roof space and has some double glazing, attempts to reduce heat losses have been made where possible. The heat pump will operate in a different way to a traditional heating system, the constant low levels of heat build up the thermal mass in the building, most oil or gas systems pump heat out at 70 degrees in short bursts resulting in the heating of the air in the room only, not allowing the building to hold the heat.

An internal assessment of the building indicated that a 50kW heat pump system would comfortably provide sufficient heat and a 500L hot water cylinder was added to provide sufficient hot water for the family and guests.

The ground loops were laid in the field. An investigation into the geology of the area showed that as the field was on top of a hill the topsoil was thin, with a shaley sub-soil filled with rock. For this reason instead of using individual trenches it was decided to excavate an area wide enough to accommodate the pipes, spread out across a 100m section of the field. The pipes were then laid and covered with sand to protect them from any damage from rocks after which the pipes were then laid and covered with sand to protect them from any damage, after which the entire system was covered and the field returned to its original status.

The only evidence in the field is the manifold pit at one end, which is a metal drainage cover and will soon disappear in the grass. The flow and return pipes from the manifolds were then installed and connected to the plant room, and heat pump.

Once all external pipework was in place, the heat pump was connected to the existing system and now has control of the back-up gas boilers, calling on them only if weather conditions result in temperatures in the house dropping to the pre-set point.

The system was designed to be eligible for the domestic RHI and is receiving payments for 7 years.