Here’s where heritage meets performance

A church is a landmark, a record of craftsmanship, a place of memory and, in many communities, a familiar point of continuity across generations. Yet many historic churches and cathedrals now face a practical challenge: how can buildings created for another age remain comfortable, affordable and useful today?

Heritage buildings have always evolved. The challenge is to guide that evolution carefully, using evidence to distinguish between changes that strengthen a building’s future and those that risk diminishing its monumental value.

Deerns is undertaking research for the Cultural Heritage Agency of the Netherlands (Rijksdienst voor het Cultureel Erfgoed) to help provide initial direction. The study uses building performance simulation to assess how different improvements could affect churches of varying sizes, locations and usage patterns.

Preservation depends on continued use

The greatest threat to a historic building is not necessarily change. It’s the risk of becoming irrelevant.

A church that is used only occasionally can become increasingly difficult to maintain. Congregations may be smaller than they once were, while energy and repair costs continue to rise. Without sufficient activity or income, maintenance may be postponed. Over time, the very attempt to preserve a building unchanged can therefore contribute to its decline.

More intensive use can offer a way forward. Across Europe, churches are increasingly accommodating museums, concerts, exhibitions, conferences, rehearsals and community events alongside their traditional religious role. In many cases, to accommodate these functions, changes to the comfort and energy efficiency of the buildings are needed.

Knowing where to begin

The aim of this study is to assess the current energy performance of three reference churches, evaluate potential energy efficiency measures, and model a range of scenarios that provide building owners with an evidence-based foundation for informed decision-making and targeted investment in future improvements.

The 3 reference churches represent small, medium and large church buildings:

• Waalse Kerk in Delft – 210m²
• Sint Martinuskerk in Weert – 1,260m²
• Sint Laurentuiskerk in Alkmaar – 2,180m²

The simulations examine how each size of church performs in a dense urban environment and in a more rural setting, as well as under different levels of use. These range from a traditional Sunday service pattern to weekday activities and more intensive occupation as a museum, conference or cultural venue. In total, 108 simulations provide a broad evidence base from which more general guidance can be developed.

Improving comfort without erasing character

The study focuses on several building envelope measures, which include:

• insulating the full vault
• insulating only the more accessible upper section of the vault
• adding a secondary layer of glazing inside existing windows
• insulating the lower part of internal walls

The measures are assessed against an uninsulated baseline, considering both energy use and thermal comfort. Comfort is studied not only in the centre of the church but also near external walls, where cold surfaces and draughts are often most noticeable.

This distinction matters because energy efficiency is about more than reducing energy consumption. The success of any intervention should also be measured by how it improves the building for the people who use it. A solution that significantly reduces heat loss but does little to enhance occupant comfort may have limited overall value. A carefully targeted intervention can deliver meaningful improvements in comfort and usability without requiring the most extensive, costly or intrusive retrofit.

Every building offers a different opportunity

A plain plastered wall may allow a reversible internal lining. A wall with historic paintings, timber work or decorative finishes may not. In one church, access above the vault may make insulation straightforward; in another, the geometry and construction may make the same measure impractical. Moisture movement, material compatibility, ventilation and local heritage requirements must all be understood before work begins.

The most effective strategy depends on 3 key factors:

• the architectural and cultural value of the existing fabric;
• the way the building is used now and how it may be used in future;
• the relationship between energy savings, comfort and available budget.

Simulations do not remove the need for building specific investigation. What it can do is give owners a more informed starting point.

Engineering a future for living heritage

The future of churches and cathedrals will depend on enabling their future use. That requires a more nuanced understanding of conservation: one that accepts thoughtful adaptation as part of a building’s history rather than as a break with it.

By combining respect for the past with a realistic understanding of present-day needs, Deerns helps churches remain comfortable, viable and valued. In this way, sustainable engineering becomes both a technical exercise and a means of keeping heritage alive.