Considerations for Solar and ASHP in heritage buildings

If you’ve decided to install renewables in a listed building, you likely already know that this

may require a Heritage Statement as part of the planning process. Our most successful clients are those who have a clear idea for their property and seek to build a robust, evidence-based case to ensure a straightforward path to consent.

A successful project is often defined by an ability to anticipate and solve a series of complex, challenges. This guide is designed to illuminate those details that are frequently overlooked.

Fabric first: You have chosen your technology, but its performance hinges on a principle that cannot be skipped: the "fabric first" approach. Before any new system is installed, an expert assessment will always begin with the building's existing performance. Reducing energy demand at the source by improving loft insulation, managing draughts, and ensuring the building's fabric is in good repair should always be the starting point - finding the easy-wins. This ensures the system you have chosen is correctly sized.

These are examples of issues that have influenced projects we’ve seen:

• Vibration Transfer from ASHPs: A point often overlooked is that an air source heat creates a constant, low level vibration. If the unit is improperly mounted directly to the building's structure, these vibrations can transfer through the wall and cause delamination and cracking in fragile historic plasterwork. Professional siting can involce the use of separate ground based plinths and anti vibration mounts.

  
  

• Acoustic profile with historic glazing: The gentle hum of a heat pump that would be unnoticeable through modern double glazing can become a persistent and intrusive presence when transmitted through thin, single paned historic glass.

  
  

• Asymmetric loading on old rafters: Historic roof structures have often settled over centuries into a state of equilibrium. Placing a concentrated, asymmetric load of PV panels on one slope can distort this balance, creating subtle twisting forces in old timber rafters that were never designed to handle them, and an engineers report may be required to calculate if this would present a risk.

  
  

• Dynamic wind uplift: Undulations in the slates or tiles of a historic roof can create complex airflows. In high winds, these can exert a powerful "uplift" force on a solar panel, putting immense stress on its fixings and the historic roof fabric it's attached to. The mounting system must be specified to withstand these dynamic, site-specific forces.

  
  

• Capacity (The DNO Application): A heat pump, solar panels, and a car charger can easily exceed the capacity of a standard domestic electrical supply. A crucial, early diligence step is to investigate whether a supply upgrade is needed from the Distribution Network Operator (DNO). This is a formal process that can take many months and discovering it late in the day can halt a project in its tracks.

  
  

• System Intelligence: The project must include a clear control strategy that allows the heat pump, PV array, and any battery storage to "talk" to each other, ensuring that you are making smart use of the free electricity you generate.

  
  

• Archaeological implications of groundworks:  The grounds of a historic property can be as sensitive as the building itself. Any excavation, whether for a ground source heat pump loop, or simply a trench for an armoured cable, carries the risk of disturbing archaeological remains, and an archaeological assessment may be required within a planning application

  
  

The Heritage Statement

You already know a Heritage Statement may be required. Its role is to serve as the document that brings together the solutions to all the complex issues outlined above.

A professionally authored Heritage Statement can demonstrate your expertise to the local planning authority. It proves that you have considered all of the relevant requirements and potential risks and harms, giving the conservation officer the confidence they need to support your application. It shows them they are dealing with a well advised project, making the path to approval smoother.

A successful renewable energy project in a historic setting is defined by foresight. It requires an appreciation for the subtle complexities that lie beneath the surface. If you are ready to move forward and need to build a robust, evidence-based case that demonstrates this level of expert consideration, get in touch. Let's discuss how to structure a Heritage Statement that effectively addresses these critical details and paves the way for a successful consent.