Fabric right: Why low-carbon technology needs a good foundation to perform effectively

Technology cannot compensate for poor foundations

Heat pumps, solar panels and battery storage are essential tools in our decarbonisation toolkit, but we should not see them as silver bullets that can compensate for decades of underinvestment in building fabric. We know that we have some of the draughtiest homes in Europe. This means a high-efficiency heat pump installed in a poorly insulated home with existing draughty windows and poor ventilation will not perform to its potential. The system will struggle to maintain comfortable temperatures, running costs will remain stubbornly high, and residents will likely question whether the disruption was worth it.

However it is not the technology’s fault. It cannot perform to potential if the fundamentals are not in place to support it. But residents will likely see it as the technology as having failed to deliver, when this is probably not the case.

The building envelope as the foundation for performance

The building envelope - the walls, roof, windows, floors and how these all meet and interact with each other, creates the conditions in which the heating system has to operate. It is the canvas that technology has to work with.

When we talk about the home, we need to take a holistic view. Energy efficiency is very important, but it is not the sole measure of success. This is personal for residents. These are the places where people work, sleep, raise families, recover from illness and spend an increasing proportion of their time. It is said we will spend more than 90% of our lives indoors. This means we need to pay specific attention to the health of the home and its subsequent impact on the health of residents. 

Ventilation and air quality must not be an afterthought

Ventilation and indoor air quality should be central to our thinking. We can no longer afford for them to be afterthoughts. If we improve the airtightness of a home to reduce heat loss, we must make sure we do not create just a sealed box. We must ensure that fresh air enters and that stale moisture-laden air can exit. If we get this wrong, the consequences are serious: condensation, mould growth, poor air quality, and the respiratory and mental health impacts that can follow.

The social housing sector has learned hard lessons about the health consequences of damp and mould recently. We therefore cannot allow retrofit activity to inadvertently create new problems whilst it is reducing carbon emissions. The homes the sector provides must support residents’ health and comfort all year round, not just be able to keep them warm in the winter.

Moving beyond the fabric versus technology debate

Presently though there seems to be an unhelpful debate and narrative emerging that pits fabric improvement against technology deployment as if we must choose between them. It will not surprise you to hear that we think this is a false dichotomy that benefits no one. In essence, both are essential and both are interdependent.

Insulation, airtightness, and appropriate ventilation combine to create the stable thermal environment that allows heat pumps to operate efficiently and to achieve their designed coefficients of performance. A home which has a good fabric foundation means their need is for smaller, less expensive heating systems that cost less to run. This means that homes can stay comfortable for longer when the heating is not in use. This means it helps residents and their energy bills.

Therefore, we need building fabric and technology to be working together in harmony for the best possible outcome.

The risks of getting it wrong

If we don’t get building fabric right for low-carbon technologies, then there are a number of associated potential risks. The first is under performance of heating systems against modelled predictions eroding trust in those technologies. Added to this poor fabric can lead to oversized systems being installed which brings with it higher capital and running costs.

There are also possible health consequences with inadequate ventilation in sealed homes creating the potential for condensation, mould and poor indoor air quality. Retrofit is invasive so separate visits for technology and fabric interventions can prove disruptive, expensive and will potentially undermine resident confidence. A lot of retrofit is delivered on trust, trust from residents that the intervention will improve their lives, so those who endure poor experiences will oppose further change.

Finally, if we cannot get the right volume of homes engaged then public and organisational funds risk being deployed on technology that cannot perform optimally representing poor value for money.

Designing homes that work all year round

But perhaps the most complex challenge we face is creating homes that regulate temperature, humidity, and air quality across all seasons, effectively helping them to operate comfortably all year round. We have to balance underheating in the winter and overheating in the summer.

This would require a holistic approach to building design including the choice of insulation that considers thermal mass, orientation and seasonal patterns. It is the introduction of appropriate glazing to balance heat retention, solar gain and natural light coupled with ventilation that provides controllable, adequate fresh air without the risk of excessive heat loss. It means consideration of thermal bridging that prevents cold spots where condensation forms. And to tackle the issue of overheating there is the requirement to look at the question of shading to help prevent overheating of the home.

This requires moving beyond checklist compliance to one of genuinely understanding building performance management viewing the home as an integrated system. This requires true collaboration between assessors, designers, installers and housing providers who understand how residents live and what they want from their homes.

A foundation for the Warm Homes Plan to succeed

The Warm Homes Plan is a great opportunity to help transform the social housing stock in the UK. But we need to do this in a measured way, one that does not pitch one technology against another, or against a fabric approach. It is about the right solution for the challenge it needs to overcome. That requires a clear understanding of the building, a clear understanding of what the resident wants, a clear understanding of what the landlord needs and an environment and foundation in the home that allows technology to perform to its best ability.