Preserving our heritage properties


04 June 2021

Preserving our heritage properties

Mark McManus, Managing Director of Stiebel Eltron UK, discusses how heat pumps have been used to significantly improve the sustainability credentials of two historic Yorkshire properties.

The UK boasts some of the world’s most spectacular heritage buildings. Yet when it comes to energy efficiency, owners are often under the impression that installing modern sustainability measures are out of reach for their older properties.

Improving the energy efficiency of the UK building stock is an integral part of the UK’s journey to improved sustainability and ultimately a net-zero economy.

The average EPC rating for a house in England and Wales is D, meanwhile the median energy efficiency score for new flats and houses is a B.

Many initiatives and strategies have been introduced over the years to improve these ratings. From the Clean Growth Strategy’s targets to upgrade all fuel poor homes to an EPC band C by 2030, to the ongoing proposals to ensure all private rented homes meet a minimum energy performance standard of EPC Band C by 2028.

Heritage properties, traditionally defined as those built before 1919, make up 21 per cent of all homes in England, and 500,000 of those homes have a listed status according to Historic England. Because of their status, improving the energy efficiency of these homes and the thousands of other heritage properties – from hotels to office buildings – is not as simple as modernising windows and doors, or installing renewable energy generation technologies like solar panels, because those doors and windows are part of the historic fabric of the building and those panels would not be in keeping with the setting.

This attitude is of course led by a need to protect the UK’s heritage architecture. Not least because figures from the Historic Houses Association show that 81% of inbound UK tourists state that historic houses and castles are the reason they come to the UK.

Making any improvements to a historic building’s energy efficiency using modern renewable systems, cannot therefore compromise their historical fabric. For owners of heritage properties – particularly those with a listed status – complicated planning restrictions also means that making energy efficient upgrades become a much more challenging process. But it’s not impossible.

Modernising Yorkshire’s heritage buildings

These considerations were all in play when we were approached by Grantley Hall, a Grade II* listed five-star hotel in North Yorkshire.

The hotel was undergoing a £70m restoration project and wanted to introduce a renewable hot water system that would provide energy efficient and reliable water to the hotel’s 47 guest bedrooms and hotel kitchens. 

As well as being a listed building, Grantley Hall is also located in a conservation area. This meant that any system installed would need to comply with all the conditions for visual impact that implies.

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Working alongside the hotel’s owner, we decided that an extensive water source heat pump system was the best approach. The 520kW system installed, made up of eight individual 66kW heat pumps and based on 0-degree source water temperature, is fed by a subterranean aquifer, situated 90m below the surface. Using underground pipes and wellheads, we could utilise the flow for the heat pump system. This approach means that there are no visible flues required, minimising the visual impact on the property, which now provides a constant a constant supply of 14-degree source temperature water.

With the source water achieving 14-degrees and not 0-degree, the actual heat pump power achieves almost 90Kw each – or almost 700Kw across the entire eight-pump system. A property like Grantley Hall would require, at most, 500Kw of energy to run comfortably, giving the hotel owners more than enough power.

The renewable system supplies 12,500ltr of hot water capacity for the hotel and heating through an extensive underfloor heating and radiator network – making it a fundamental part of Grantley Hall Hotel’s sustainability strategy.

What’s more, Stiebel Eltron’s internet service gateway system offers the ability for maintenance teams to monitor the installation remotely, meaning any problems can be proactively prevented before they impact the day-to-day running of the hotel.

Welham Hall, a large countryside property situated between the North York Moors and Yorkshire Wolds, also benefitted from the use of pumps.

Two Stiebel Elton WPF13S ground source heat pumps were installed, which provide heating and hot water to the property using a nearby lake as the location of the collector loop. The lake supplies a natural source of energy that can power the system with minimal impact on the environment, saving money while improving the property’s sustainability credentials.

A core component of this restoration and retrofit was to avoid changes to the original buildings and minimise any visual impact on the wider estate. This prerequisite led to the design teams’ decision to use the existing lake as an energy source. It meant that trenches for a ground loop system, which would provide power to the system, were not required with the end results being a system that causes minimal disruption to the historic landscape of the property.

While the heat pumps have so far provided a consistent performance in a range of weather conditions, a back-up boiler was also installed as a fail-safe during spells of particularly low temperatures. It ensures that a system can operate reliably in a range of situations with no loss in performance while vastly improving the sustainability of the site.

Since completion, the system has been monitored using our Internet Service Gateway, which has revealed a Seasonal Performance Coefficient of 3.36, gaining the project widespread recognition from the industry.

The common thread between both projects are the benefits of upgrading to low flow temp heat systems. Utilising heat pumps with low flow temp heating, where the heat pumps run for a longer period of time and at low temperatures, can significantly benefit the fabric of historic properties.

Negating the need to use high flow temp heating systems that can often encourage issues like damp or condensation, means Grantley Hall and Welham Hall can protect the historic fabric of their properties while maintaining a constant warm temperature throughout.

Both these projects are evidence that historic buildings do not need to compromise on their sustainability to maintain their original architecture and design.

While preserving our older properties is crucial for the history of the UK, it no longer needs to come at the detriment of our environment. And when more than a fifth of the UK’s housing stock is considered a heritage building, harnessing technologies like heat pumps will be crucial if the UK is to meet its net zero ambitions.