Climate Change Adaptation Case Study: A 'Whole Building' Approach at a Medieval Chapel: Becket’s Chapel, Norfolk
This case study shows how a Grade I listed chapel in very poor condition was made more energy efficient during works to save it.
About the property
Becket’s Chapel is a rare survival of a medieval independent chantry chapel. It is a Grade l listed building, located in the centre of Wymondham, South Norfolk. Since the mid 16th century the chapel has been in the ownership of the town. It was used as a library from the late 1940s until a new library was built in 2009. Since then, the previous owners struggled to find a permanent use for the building, letting it under annual summer-only licence to Wymondham Arts Forum. The chapel was at risk of becoming completely redundant and in 2018 was placed on the Heritage at Risk Register, before being purchased by Historic Norfolk in September, 2022.
What happened during the planning process?
Historic Norfolk received grants for phase one of the works. They worked with a conservation architect, a retrofit specialist and heritage consultants to guide them through the planning and listed building consent process.
The Trust was granted listed building consent and planning permission from South Norfolk Council for adding roof insulation, raising the height of the roof, and installing underfloor heating in addition to the essential repairs, which included roof repair and recovering. Given this requirement Historic England requested an energy assessment that took a holistic approach but focused on insulation options for the roof. The assessment concluded that if all recommended measures were implemented, total energy demand may be reduced by over by 30% in the chapel.
The building was in poor condition with urgent intervention necessary to prevent further deterioration. The proposed changes did not negatively impact its character or appearance, so the application was viewed favourably.
About the adaptation
This is a trailblazing project based on the ‘whole-building’ approach to reducing carbon emissions. This approach considers all the factors that affect energy use and building energy efficiency so that an optimum solution can be recommended. Historic England worked with Historic Norfolk and other funding partners to save and repair the building using traditional repair methods, combined with measures to reduce dampness and reduce its carbon footprint. This is the first phase of the Becket’s Chapel project with further energy efficiency measures planned to be implemented in the second phase.
The floor of the chapel previously had concrete flooring installed in the 1940’s. Concrete is not a breathable substance and this was exacerbating damp issues. This presented an opportunity to remove the concrete floor, address damp issues and install under floor heating, wiring and insulation.
In October, 2022 the concrete floor was removed, the ground was insulated using foam glass gravel, underfloor heating was installed along with modern wiring and a replacement limecrete floor was laid on top. The foam glass gravel is a moisture managing, insulating flooring material that is breathable which, it is hoped, will along with the installation of a new French drain, eliminate the damp problems. The limecrete floor was later laid with Ancaster Weatherbed limestone tiles sourced from a local Lincolnshire quarry. This material was considerably more expensive than many imported alternatives, but considering the carbon costs of transporting such heavy materials, the Trust considered this the most carbon friendly option.
Internal scaffolding was erected in November, 2022 so that the repairs to the internal timber roof structure and repair of the render on the external walls could start. The walls were covered in acrylic paint which had to be painstakingly removed and replaced by specialist mineral paint to allow the walls to breathe. Other energy efficiency measures were undertaken as part of the ‘whole building’ approach, including installing energy efficient lighting.
In January 2023 the external scaffolding was erected, so that the roof tiles could be stripped, the underlying wooden boarding could be repaired and treated, and 120 millimetres of insulation could be added. Works were completed to the roof by September 2023. Various insulation options were assessed by the retrofit specialist, including one with both internal and external insulation. Internal insulation was rejected by the Trust since there was an increased risk of condensation causing timbers to rot and this would be hard to identify if the internal roof timbers were not visible.
The installation process
The owners, Historic Norfolk, found the addition of the carbon reducing measures was well managed by the professional team and did not negatively impact on the project in any way. In fact, the support and funding Historic Norfolk received allowed them to make more improvements to the building in the first phase than was originally envisaged.
Results and lessons learned
- The works undertaken were the first phase of wider works to repair and further improve the energy efficiency of the chapel. Further phases will include secondary glazing to the windows, an air source heat pump and photovoltaic panels to generate electricity.
- Figures relating to energy savings are not yet known, as the chapel has only been open for a few months at time of writing, however the Trust has already observed improvements. For example, the building is already much dryer and comfortable to be in and the underfloor heating allowed a chamber music concert and two literary events to take place in late October which would have not been possible previously.
- The roof and floor insulation has also made a difference to the thermal properties of the chapel.
- Furthermore, the new lighting makes the chapel work well as an exhibition and concert space which has improved community use for the space and is energy efficient.
Find out more
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Historic Norfolk: Beckets Chapel Restoration Diary
A month by month illustrated diary of the restoration work.
