Energy Audit Case Study for Historic Religious Buildings
Energy audits for heritage and religious buildings across England
Project Overview
e‑mission Ltd. was commissioned to carry out detailed energy audits across two religious estates to better understand rising energy costs, improve comfort for occupants, and support the early stages of carbon reduction planning.
The estates included a mix of chapels, residential accommodation, guest rooms, and community spaces, all of which remained in full operational use throughout the assessment period. While the estates served similar functions, the buildings themselves were very different, and this strongly influenced both energy performance and the range of suitable improvements.
Due to the historic nature of the buildings, the audits required a careful balance between improving energy efficiency, respecting heritage constraints, and ensuring any changes were practical for day‑to‑day operation.
The Buildings
Estate One – Grade II Listed
The first estate consists of historic buildings with statutory protection due to their architectural and historic significance. As a Grade II listed site, there are clear limitations on how the building fabric can be altered.
The buildings feature traditional construction, older windows, and limited existing insulation. Heating systems have been added and adapted over time rather than being designed as part of the original structure. Any recommendations for improvement therefore needed to avoid intrusive changes that could compromise the building’s character or heritage value.
Estate Two – Mid‑19th Century with 1960s Extension (Not Listed)
The second estate was originally constructed around 1850, with a substantial extension added during the 1960s. Unlike the first estate, it is not listed, allowing greater flexibility when assessing potential fabric improvements.
The combination of older stone buildings and later extensions resulted in noticeable variations in thermal performance across the estate. In particular, the 1960s extension exhibited lower insulation standards and higher heat loss, presenting clearer opportunities for improvement.
The Challenge
Across both estates, energy consumption was higher than expected, particularly during the winter months. Despite differences in age and constraints, several shared challenges were identified:
- Large open chapels with high ceilings that are difficult to heat efficiently
- Heating systems with limited zoning and manual controls
- Rooms being heated when unoccupied
- Frequent use of portable electric heaters to address cold areas
- Draughts caused by ageing or poorly performing windows
- Inconsistent insulation levels due to multiple phases of construction
Analysis of utility data showed that heating demand was the primary driver of energy use, costs, and associated carbon emissions.
Our Approach
We took a practical, building‑led approach to the audits, combining energy data analysis with detailed site inspections and discussions about how the buildings are actually used.
A fabric‑first approach was adopted where appropriate, recognising that reducing heat loss is often the most effective long‑term way to lower energy demand and improve comfort. However, the extent to which fabric improvements could be applied varied significantly between the two estates.
For the Grade II listed estate, the focus was on non‑intrusive measures, optimisation of heating systems and controls, and operational improvements that could deliver benefits without impacting the building’s historic character.
For the non‑listed estate, particularly in the later extension, greater flexibility allowed for a wider range of fabric‑based recommendations, alongside system and control improvements.
Energy consumption analysis involved a review of twelve months of gas and electricity data to identify seasonal trends, elevated baseloads, and anomalies, with performance compared against similar religious buildings.
On‑site assessments included inspections of walls, roofs, floors, and windows, reviews of heating systems and controls, observation of occupancy patterns, and identification of everyday behaviours contributing to higher energy use. This ensured recommendations were grounded in real‑world building use rather than theoretical assumptions.
Key Findings
Heating Performance and Controls
Heating was found to be the largest contributor to energy use across both estates. In many areas, air‑based heating systems struggled to serve large open spaces effectively, with warm air rising rapidly and limited comfort at occupant level.
A lack of effective zoning meant heating was often supplied to rooms that were not in use, while predominantly manual controls increased the likelihood of systems being left on unintentionally. These factors contributed to higher fuel consumption and inconsistent comfort.
Supplementary Electric Heating
Electricity data showed noticeable increases during winter months. Site inspections confirmed widespread use of plug‑in electric heaters and fixed electric heaters to compensate for areas where central heating was insufficient.
While these heaters improved local comfort in the short term, they significantly increased electricity costs and carbon emissions and masked underlying system and fabric issues.
Building Fabric Performance
Both estates exhibited heat loss through the building fabric, although the causes differed.
Draughts from older window frames were common, insulation levels varied across buildings and extensions, and junctions between original structures and later additions created cold bridging. Fabric improvements were more feasible on the non‑listed estate, while the listed estate required a more cautious and limited approach.
Constraints Affecting Decarbonisation
There is a strong desire across both estates to reduce carbon emissions, but a number of real‑life constraints shaped what could sensibly be achieved at this stage.
The cost of major works such as large‑scale fabric upgrades, full heating system replacement, or electrical infrastructure improvements would require a level of investment that is not currently available. With limited budgets, the focus needed to be on measures that make a meaningful difference without placing unnecessary financial strain on the estates.
Disruption was also a key consideration. These are busy, lived‑in buildings that support daily routines, worship, residential use, and guest accommodation. Extensive construction work or long periods of shutdown would have caused significant disruption to normal activities, so highly invasive measures were not appropriate in the short term.
Taking these factors into account, a phased and realistic approach to decarbonisation was adopted. A ground‑mounted solar photovoltaic system was recommended as a practical and low‑disruption way to start reducing carbon emissions and energy costs. This approach allows progress to be made now, while keeping open the option for more substantial upgrades in the future as funding becomes available and circumstances allow.
Energy Efficiency Recommendations
We developed a prioritised improvement plan tailored to the specific constraints and opportunities of each estate.
Short‑term measures focused on aligning heating schedules with actual occupancy, improving zoning and system control, reducing reliance on supplementary electric heaters, introducing heritage‑appropriate draught‑proofing, and providing clear guidance to occupants.
Medium‑term improvements included upgraded heating controls, improved time and temperature regulation, targeted insulation upgrades where feasible, and window repair or replacement where permitted.
For large worship spaces, radiant heating systems were identified as a more suitable long‑term solution, offering faster warm‑up times and improved comfort without the need to heat large volumes of air.
Renewable Energy Opportunities
While full electrification of the heating systems was not viable at this stage, both estates demonstrated strong potential for solar photovoltaic generation as a practical and effective step toward decarbonisation. In each case, the aim was to maximise on‑site electricity generation and reduce long‑term reliance on grid supply, while avoiding unnecessary disruption or constraints linked to the buildings themselves.
For the first estate, which is Grade II listed, a 49.5 kWp ground‑mounted solar PV system with approximately 60 kWh of battery storage was recommended. A ground‑mounted solution was selected to avoid any impact on protected roof areas and the historic fabric of the buildings. This configuration provides a strong balance between generation capacity and on‑site consumption, with battery storage improving self‑use of generated electricity. The proposed system is expected to deliver estimated annual savings of £11,527, with a projected simple payback period of approximately 3.7 years.
For the second estate, a 46 kWp ground‑mounted solar PV system with around 60 kWh of battery storage was recommended. Although the estate is not listed, available roof space was limited and would have constrained the size and effectiveness of a roof‑mounted installation. A ground‑mounted system was therefore identified as the most effective way to maximise generation potential and reduce grid dependency. The proposed system is estimated to achieve annual savings of £5,474, with a projected payback period of approximately 6.4 years.
Across both estates, the recommended solar PV systems provide a low‑disruption and financially viable route to immediate carbon reduction. They also establish a strong foundation for future low‑carbon upgrades as funding opportunities, technology, and infrastructure capacity continue to develop.
The Outcome
The energy audits provided clear explanations for elevated energy use, identified immediate opportunities to reduce costs and improve comfort, and set out a realistic pathway towards lower‑carbon operation. All recommendations were aligned with the buildings’ heritage status, construction type, and operational needs.
Why This Matters
This case study demonstrates that even complex, historic religious buildings can take meaningful steps toward improved energy performance. By understanding how buildings are built, used, and constrained, practical and achievable improvements can be delivered without compromising their character or purpose.
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