Project name: St Mary’s Episcopal Cathedral, Edinburgh
Technology: Energy system options appraisal
Location: Palmerston Place, Edinburgh
CARES funding: £2,125 grant funding
Date installed/operational: December 2020


St Mary’s Episcopal Cathedral is a prominent building in the West End of Edinburgh. Built in the nineteenth century in the Gothic style, it is now a category A-listed building serving the local community and providing a venue for civic events. It is also a notable visitor attraction.

Heating the building to a comfortable temperature is challenging because of its vast size and its current heating infrastructure. Finding a solution to the building’s heating issues is a pressing concern for the church community, who wish to develop the building’s community use and reach. Modelling the ways in which renewable heating can be used even in challenging and large-scale contexts such as the Cathedral was also desired.

Project aims and objectives

The project aimed to commission a feasibility study from qualified building engineers, to determine possible heating solutions and the likely cost implications. Five building engineering firms were asked to tender for the project, and two submissions were received. Harley Haddow were asked to fulfil the brief, which it did through a site survey and computer modelling.

CARES supported the project by providing 50% of the feasibility study costs.

Outcomes and achievements

The Cathedral was presented with a detailed report setting out potential options to renewing the heating within the cathedral and the other buildings on site. The report presented useful modelling of the heat required and how that might be delivered.

It revealed that a ground source heat pump, although technologically possible, had high capital costs associated with it. There would also be potential architectural and geological obstacles to contend with. The savings that a ground source heat pump would provide did not outweigh these initial costs.

Instead, an air source heat pump, either by itself or within a cascade system, was revealed to be adequate for the building’s heat demand, and cheaper to install too. The running costs of such a system, however, would not provide any savings when compared to the current gas boiler heating. It would also require new underfloor heating to be installed in the main part of the cathedral. Installing underfloor heating is challenging in a Grade A* listed building, as well as an additional expense.

The report highlighted, therefore, the further work required to fundraise for any new heating system, and the required permissions that would be needed to proceed. It has provided the Cathedral, however, with a useful template and detailed information as it continues to explore how to renew, and decarbonise, its heating system.

Lessons learned

A spokesperson from St Mary’s Episcopal Cathedral said:

“The project itself was straightforward, and the building engineers were easy to work with. The conclusions offered in the report provide considerable challenges for us moving into the future, but we are now armed with much more information than we were previously.”

Find out more about St Mary’s Episcopal Cathedral.