RIver House - Kensa Heat Pumps
Kensa James Standley


With UK government making a clear commitment to the rapid decarbonisation of heat with the introduction of a future homes standard mandating the end of fossil-fuel heating systems in all new build homes from 2025, James Standley, Managing Director of Kensa Heat Pumps explains how to get the best efficiencies from ground source heat pump technology in retrofit installations in particular at the lowest cost possible.


Addressing common misconceptions

It is not only new-build properties that can benefit from ground source heat pump technology; retrofit projects can also enjoy lower carbon emissions and running costs compared to fossil fuel technologies.

A concern about the widespread roll-out of heat pumps into existing properties is the misconception that they won’t operate effectively without the very high levels of fabric efficiency that you would expect to see in a new-build, for example with an EPC band of C or better, and underfloor heating throughout. In fact, the vast majority of Kensa’s very successful large-scale ground source heat pump retrofit works are in properties with an EPC of D or lower!

And Delta-E, in its December 2018 study into the Technical Feasibility of Electric Heating in Rural Off-Gas Grid Dwellings’, reported that ‘based on average peak winter day temperatures, around 84% of homes can be electrified at their current level of insulation. This increases to around 93% if all suitable homes have loft & wall insulation installed’.

Obviously not all retrofit buildings can be as well insulated as a new build, especially in the case of barn conversions or where a property is listed or historic. However, what isn’t widely understood, is that improving insulation in a property containing a ground source heat pump typically results in a ‘double-win’ in comparison to a boiler, for example.

Extra insulation reduces the amount of energy required to heat a building, and means that this energy can be delivered at a lower flow temperature, because the emitters need to emit less heat. This actually improves the efficiency of a ground source heat pump – by roughly 2% for every 1*C reduction – and a more efficient heat pump will result in lower running costs.


Project example: Orchard House

Orchard House barn renovation ground sourceOne such retrofit project in rural Somerset involved a Kensa 15kW Hybrid ground source heat pump combined with a Solar PV system installed into a converted barn called Orchard House. As the barn was converted in the mid-2000’s to current building specifications, the heat pump was integrated with the barn’s existing heating system of radiators and underfloor heating to provide efficient space heating and sufficient hot water temperatures, covering 100% of the property’s requirement.

The 6kW solar PV array on the roof of the barn provides the customer with further self-sufficiency; generating electricity throughout the day, supplementing the electrical use of the ground source heat pump and providing an additional source of income through the Feed-in-Tariff.


Project example: River House

Ground Source Review River House ǀ Heat Pump 3When Keith Clarke and his family moved into a spacious Grade II listed farmhouse in Cambridge, he replaced the old, inefficient gas boiler with a Kensa ground source heat pump. As River House had a high heat load, Kensa’s 24kW Twin Compact, the largest single phase ground source heat pump on the market, was chosen to meet the demand for heating and hot water. To improve the property’s energy efficiency, extra insulation was added in the floor and roof. Many of the existing radiators were already oversized and simply needed upgrading from single to double panels. As the building is listed, the Clarke’s had to seek permission for the upgrades, which was easily granted, however unlike air source, planning permission isn’t needed for ground source heat pumps.

Project example: Llanishen House

Ground Source Review Llanishen House aerial viewFormerly a Medieval Inn, Llanishen House in Monmouthshire was renovated by it’s owner into a modern and spacious family home. Llanishen House was a large 500+ sq/m property and as such the demand for heat was high – so Kensa’s 24kW Twin Compact was ideally suited to provide the required amounts of heating and hot water. As the building The original building was part Medieval and part Victorian with some solid sandstone walls, and prior to the refurbishment project it was cold and draughty; this was improved by adding double-glazing windows and wall insulation, modern features with traditional styling in keeping with the property’s history. The house has mostly underfloor heating throughout which increases the efficiency of the ground source heat pump.



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