Retrofitting homes in the UK

Historically, the UK’s approach to home energy efficiency has been less than optimal. Understanding why is key to the home retrofitting process.

The challenges the UK faces with home retrofitting and energy efficiency aren’t a recent phenomenon. They are rooted in past practices and a lack of foresight. Historically, with fuel being relatively cheap, the impetus to insulate homes was low. Furthermore, the repercussions of fossil fuel usage on the climate weren’t as widely acknowledged. Most historic UK homes were therefore constructed with uninsulated walls, and single glazing was the norm.

The change began in 1985 when building regulations introduced a U-value of 0.6 for walls, making insulation mandatory for new homes. By 2022, this standard had tightened to a U-value of 0.26 or better. However, it’s important to note that a staggering 75% of homes in the UK were constructed before these 1985 guidelines, resulting in a persistently energy-inefficient housing stock.

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Why the UK must prioritise retrofitting homes to meet net zero goals

The built environment is directly responsible for 25% of the total UK carbon footprint. Most of this figure is due to space heating using fossil fuels. We must therefore retrofit our homes to reach net zero emissions by 2050. A low-energy retrofit is crucial for every project that we work on – because the homes that we refurbish now are unlikely to be refurbished again before 2050. If we don’t reach a low energy standard, every project is a lost opportunity.

In addition to the environmental implications, there’s a compelling economic rationale. Investing in home retrofitting can pave the way for considerable savings in future energy bills. If homeowners and landlords understand the long-term benefits, they’re more likely to invest in these improvements.

How to retrofit for energy efficiency

Addressing energy inefficiency involves a multifaceted approach, and the right approaches can make a significant difference. Insulating the entire thermal envelope is of the utmost importance, as is triple glazing, airtightness, and MVHR (Mechanical Ventilation with Heat Recovery). By adhering to the Passivhaus standards, homeowners can achieve a comprehensive and effective retrofit. Once a home’s foundational energy inefficiencies are addressed, transitioning to renewable energy sources can open a pathway to net-zero.

However, it’s crucial to strike a balance between efficiency and preserving the UK’s architectural heritage. Especially with listed buildings or homes in conservation areas, retrofitting can pose aesthetic and conservation challenges. Yet, with advancements in retrofitting technology, it’s becoming increasingly feasible to integrate efficiency without compromising a building’s character.

Retrofit insulation

External insulation performs better than internal insulation for home retrofitting. We tend to use this where possible on less important facades – usually at the side and rear. To maintain a character front elevation, we often insulate internally at the front and accept the slight compromise on the U-values and performance that can be achieved here. Wood fibre of around 60mm can typically be used internally.

This does, however, require any cornices to be removed and potentially new ones reinstated afterwards. With a listed building, where plasterwork is protected, we often use very thin aerogel insulation on the internal walls, leaving the cornices and skirting in place.

We have to accept that double and triple-glazing will change how traditional-style windows will appear. However, there are now excellent products from Bewiso and others, including Passivhaus-rated, triple-glazed, airtight sashes. In listed buildings, we should consider slimline double glazing, or, where conservation issues dictate, at least replacement single glazing from Histoglass, which has improved U-values over the original glass.

Retrofitting listed buildings and older homes

There are currently many conservation issues with listed buildings and those in conservation areas. We believe that planning policy needs to be relaxed, particularly when dealing with the side and rear facades of heritage buildings, which are usually of little architectural interest or importance.

Cost is certainly a consideration, although a low-energy retrofit can be achieved for as little as 5 to 10% extra over the cost of a standard refurbishment. This cost will, of course, be repaid in future lower energy bills.

Political will also seems to be a major issue currently. Could the government simply offer all homeowners and landlords low-interest loans to pay for retrofit works? The interest on the loan could be repaid out of the future reduction in energy bills; therefore, possibly have no net cost to the owner.

In conclusion, the path to a more energy-efficient UK housing landscape hinges on effective home retrofitting. Balancing historical preservation, economic considerations, and environmental imperatives will be the key to success.

This article formed the basis of Architecture for London’s contribution to the Dezeen feature ‘Effectively retrofitting UK housing requires compromise between performance and heritage’.

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