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The quietly emerging debate on the embodied environmental footprint of retrofit

An installer fits insulation in the roof of a house
22 February 2024

While home improvements can make homes operate at net zero, it takes a lot of energy to make those necessary changes.

Our energy system is changing rapidly. With the continued plummeting costs of renewable energy, the national grid predicts that grid electricity will be zero, or very nearly zero carbon by 2035.

This has interesting implications for how we should think about retrofit. Once homes are renewably heated, they will effectively be zero carbon in operation however thermally efficient they are.

It also means that over time the operational energy used in homes will be less important in terms of carbon emissions. Instead, the ‘embodied’ carbon – the carbon associated with making, transporting and eventual disposal of the materials we use – will become more important.

Is this the end of the fabric first mantra?

Should we stop bothering to insulate or retrofit our homes, switch everyone over to heat pumps, stick solar panels on their roofs and get on with our lives? 

The natural performance of a building, a balancing act.

There’s a couple of reasons why we’d say no.

Firstly, emissions aren’t the only consideration. Cold, damp, and poorly insulated homes cost more to heat and make people ill and miserable. At CSE we see the fallout from this in human suffering every winter. As do the NHS in increased admissions and premature deaths. To be liveable, homes need to be safely and appropriately insulated, adequately ventilated, cheap to heat, dry and in a good state of repair.

Secondly, by 2035, 80% of vehicles on the road could be electric, and 41% of households could use electricity as their energy source for heating. This will significantly increase electricity demand. Additional challenges and costs arise to configure our electricity network and generate all the energy we need from renewable energy.

We need to make our buildings as energy efficient as safely possible. Not only will this reduce the additional demand for electricity generation from households. But it’ll improve the performance of the heat pumps installed in them (assuming they’ve been appropriately sized and installed). Tackling our carbon emissions requires improving both the thermal performance of our homes and making the source of our electricity renewable. We need to reduce demand.

Embodied energy in retrofit

It’s important to consider embodied energy when improving or redeveloping our homes. There’s a trade-off between the operational carbon saved by making a building more energy efficient and the carbon embodied in the retrofit itself. 

If we’re trying to reduce emissions, it doesn’t make much sense to cover every single building in the UK with fossil fuel-derived insulation or other high embodied carbon material. We should be measuring heat loss first to understand, through accurate data, how energy efficient a building is. Then we can take appropriate steps to improve it.

We should be focusing efforts first on those buildings, which are thermally inefficient and have poor standards of air tightness. To overcome some of the problems, we’re piloting heat loss surveys in CSE’s retrofit projects. Problems can occur with incorrect heat pump installations and assumptions about energy efficiency and heat pump suitability in different types of homes.

Similarly, demolishing an existing inefficient building doesn’t always make sense. The carbon already spent in its construction would be lost, even if it’s replaced by a new zero-carbon structure. 

Image showing the balancing act of low carbon buildings

Campaigners are making these arguments. And if Part Z – a proposed amendment to building regulations – does come into effect then we will all be required to balance the initial embodied impact of retrofit (and construction more widely) against any potential reductions in a building’s operational footprint (heating, etc.).

This idea of considering whole-life carbon is already written into the PAS2038 for non-domestic retrofit where it is required for buildings over 1000m2.

Sure, it’ll make things a bit more complicated but it’s a necessary change.

7 responses to “Debate on the embodied carbon of retrofit”

  1. locker Avatar

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  2. Mike Jenn Avatar
    Mike Jenn

    This is a very ‘electricity-centric’ article which makes no reference to natural gas, the source of the big majority of domestic heating. Its comparitively insignificant if electricity reaches near net zero by 2035 if most homes remain gas heated.

    1. CSE Avatar

      You’re right of course that there’s an urgent need to get rid of gas central heating. Our article is really talking about how once grid electricity is decarbonised and assuming that buildings are electrically heated, we’ll need to start changing how we think about retrofitting, and the carbon embodied within retrofit projects.

      The phasing out and replacement of gas boilers can’t happen fast enough, but efforts are being made. Regulations will stop new gas boilers being fitted from 2035, and heating contractors are being required to fit a higher proportion of renewable heating systems each year. Perhaps of greater significance, householders can apply for a £7,500 grant to fit a heat pump. With falling costs from installers this means that increasingly it costs no more to fit an air source heat pump than a gas boiler.

  3. Hugh Barton Avatar
    Hugh Barton

    Your response to the question about embodied energy in retrofit is of course correct. There are compelling social/financial reasons to insulate buildings and manage ventilation well. The embodied energy in extra renewable energy provision is also a major reason. But the argument goes beyond that to consider the environmental and land use impacts of all those panels, turbines, and so on, and the need for increased energy storage (with currently use of rare metals in batteries from countries we may not want to be dependent on.) The sheer pace of growth in energy demand worldwide as medium and low income countries moderate and then reduce fossil fuel demand means that reducing heat demand and cooling demand (an often ignored but growing factor) is absolutely critical.

  4. CSE Avatar

    We agree. There’s a common assumption that renewable energy is a panacea for climate change, but all this infrastructure has its own environmental footprint, and land use impact. In fact, as important as increasing renewable energy provision is reducing our energy demand, and increasing energy efficiency. As the adage goes the cheapest energy is that we don’t use.

    The majority of retrofit materials used today are derived from fossil fuels themselves though and have their own carbon footprint. So once heating is electrically powered and electricity is fully decarbonised, the trade-offs will be become a bit more nuanced. By the way, Dan Stone, Policy Officer at CSE and your old college student, says hi!

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  6. Edwardo Paige Avatar

    The post resonated with me on many levels. Thank you for writing it!

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