Hierarchy of Responsible Retrofit

16 November 2022
Purcell have developed a Hierarchy of Responsible Retrofit, which is founded on the principle that the most sustainable, greenest, and cheapest energy is the energy we don't use.

Escalating energy prices, coupled with the increasing effects of human induced climate change, is rightly drawing focus to the energy efficiency of our existing buildings.

Retrofitting our old, leaky and fossil-fuel reliant building stock is essential if we are to cut carbon emissions, reduce energy bills, and build energy security. The urgency of the climate crisis means we cannot waste time.

The word retrofit means to add to something that did not originally have it when it was first built or manufactured. In recent times, retrofit has been used to describe the introduction of new materials, products, or equipment into an existing building, with the aim of reducing its energy use.

However, a rush to retrofit carries many risks, particularly when it comes to older buildings, and the consequences of getting it wrong could cause lasting damage, unnecessary expenditure, and put people off retrofitting entirely.

© Purcell
Purcell transformed unused lightwells and space within the National Gallery into a retrofitted workspace: The Accommodation Hub

There is no 'one size fits all' solution to retrofitting older buildings and what works on one property, may not work on its neighbour. The Sustainability Traditional Buildings Alliance (STBA) published a report in September 2012 titled “The Responsible Retrofit of Traditional Buildings”.

The report identified significant challenges in traditional building retrofit because of the uncertainty of data and research; the complexity of interactions; and possible conflicting priorities and values. It instead champions a ‘whole building approach’, one which considers the building as a system of interconnected materials, functions and users, and understands the effect of external and contextual influences.

Stoke-On-Trent's Centre of Refurbishment Excellence (CORE), where Purcell led the final two phases of the high profile regeneration of this Grade II listed former pottery works.
Stoke-On-Trent's Centre of Refurbishment Excellence (CORE), where Purcell led the final two phases of the high profile regeneration of this Grade II listed former pottery works.

We have developed a Hierarchy of Responsible Retrofit which is based on this ‘whole building approach’ and founded on the principle that the greenest (and cheapest) energy, is the energy we don’t use.

Reducing carbon emissions is more than simply insulating and adding solar panels: much can be achieved by changing behaviour, avoiding waste, using efficient controls and equipment, and managing the building to its optimum performance.

Purcell's Head of Sustainability, Laura Baron, breaks down this hierarchy of responsible retrofit below. You can view the full infographic on Issuu.

The greenest and cheapest energy is the energy we don't use: how we can sustainably use and adapt existing buildings through retrofit


The first and most important step is knowledge.

Understand the context of your building: its surroundings and situation; its history, construction, and condition; its energy use and impact; its occupation and patterns of use. Understand the financial context of the project, what is the budget, are there grants or funding opportunities available?

Allowing time to properly understand the building, how it is used, and where energy is being wasted will save time and money later.

Purcell transformed three disjointed buildings into the award-winning Story Museum in Oxford


Next, seek to eliminate unnecessary energy use.

Addressing issues like damp, draughts and other defects can be a cost-effective way of saving energy. Look at how a building is used: is a space constantly heated but only occupied once a week for example?


Your plan should then mitigate the impact of things that are unavoidable.

For example, lighting and electrical appliances are essential items, these should be as efficient as possible (LEDs etc). What is the most efficient way of using the spaces?

Sustainability measures with the Common Ground in Sacred Space at Newcastle Cathedral included the installation of air source heat pumps, making St Nicholas' one of the first Grade I-listed cathedrals to have the pioneering technology


Next, improve the existing buildings fabric to reduce energy use further through passive means.

For example, upgrading windows, insulating the roof, walls, and floors, looking at air tightness and cold bridges. Traditional buildings were constructed to be ‘breathable’ using vapour-permeable materials. Incorporating materials that enable this permeability is crucial to avoiding unintended consequences like moisture buildup and damp. A risk-based approach will help effectively manage this. Consider occupant comfort, effective ventilation and minimise risks of overheating.


And last but not least, introduce appropriate ‘active’ energy technologies that are zero carbon and renewable.

This could include solar panels, heat pumps, district heat networks etc. This final measure is an essential part of addressing the climate emergency but jumping to this step too early could risk implementing the wrong solution. If you don’t take steps to reduce energy demand first, the new energy source will need to be larger and work harder, and ultimately cost more to install and to run.

In collaboration with MCW Architects, Purcell were appointed to introduce design solutions to upgrade the external envelope of a fire-damaged engine shed to meet BREEAM excellent and accessibility standards, creating a new facility for the University of Northampton

Read more about our approach to sustainability here.