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Does retrofit pay off the embodied CO2?

Whether you like it or not, every action we take to improve the UK housing stock comes with a carbon cost. So how do we know that the carbon savings promised by retrofit will counter the emissions we create in doing the work?

At Parity, we’ve analysed over 20 million homes, created 13 million net-zero plans, and identified millions of tonnes of CO2e savings by creating cost-effective retrofit plans.

This has allowed our clients to report not just on their carbon emissions but provide answers to questions like:

  • “How will our planned works affect tenant fuel bills?”
  • “How do we get our stock to Net Zero by 2050?”
  • “What’s the financial payback on our 5-year strategy?”

And now we’ve developed a way to estimate the embodied carbon for home-improvement works alongside the savings.

Which energy-efficiency measures pay off their embodied CO2?

Whether it’s insulation, solar PV, or swapping out light bulbs, every measure has embodied CO2. Generally speaking, most retrofit measures will easily cover their carbon cost within their lifetime. The retrofit measures least likely to deliver carbon savings are window replacements, particularly when the existing windows are already double glazed.

There are some wider considerations to take into account though, meaning that even considering the embodied carbon of retrofit and the savings are not the whole story:

How to measure embodied carbon cost

To measure embodied carbon costs, you can use a home energy modelling service or software. These are important to model the costs, benefits and carbon savings for every energy-efficiency measure applied to a home.

The first set of measures to model will be those in your planned works, which is the list of measures you already plan to implement at each home.

Including planned works is also important because you can also include them in modelling calculations for the second step, running an investment scenario.

The second set of measures are from “Investment Scenarios” which calculate a tailored, cost-effective, whole-house plan for every home in your stock that’s based on your housing goals.

The housing goal could be as simple as “get all homes to EPC C by 2030” or a more advanced combination of heat demand, carbon and fuel bill targets on properties that meet filtered criteria.

Here’s an example of an Investment Scenario’s results, which include all the required measures and their costs. (Note: This example isn’t based on real housing data)

the results from an investment scenario, showing a total investment of circa. 3 million pountds

Summarised results from an investment scenario


The investment breakdown for the scenarios

A breakdown of the measures for an investment scenario

With all the measures available for analysis, you can see the estimated embodied carbon with every Investment Scenario.

How to interpret the results

If you’re already one of the 130+ social housing providers or local authority clients using our platform, you can head straight to the Embodied Carbon page.

The calculations include 3 different payback periods to account for the variation in embodied carbon costs, so you can decide how optimistic/pessimistic you’d like to be.

Years to payback scenario embodied CO2

Years to payback scenario embodied CO2

There are several ways to view the data, but one of the clearest to interpret is the “Years to payback scenario,” which includes both the carbon and financial payback periods.

In the case of this scenario, we can see that even with the most pessimistic assumption, a three-million-pound investment into heating, fabric, photovoltaics and lighting might only take two years to payback the embodied carbon and deliver real carbon savings.

Surprising when you see how much longer it takes for the financial payback.

This shows that carbon-saving payback times tend to be much shorter than financial payback times, especially where fossil fuel heating is being decarbonised with heat pumps or other electric heating.

What can I do with embodied carbon emissions reporting?

Embodied carbon reporting can be used to help steer several strategic discussions. We can provide you with the figures above for any investment scenario so you can:

  • Compare different retrofit strategies’ effectiveness based on the combined operational and embodied carbon.
  • Evaluate retrofit plans against your calculated costs of demolition.
  • Present a stronger case for retrofit to your stakeholders.

Is it a legal requirement to reduce embodied carbon emissions?

At the time this article will be published, there aren’t any mandatory requirements to report on or maintain embodied carbon targets. The UK’ government’s “Code for Sustainable Homes” or “Environmental Profiles” have voluntary reporting. For more information, check out UCL’s fact sheet on embodied carbon in social housing


Other steps you can take to improve your housing stock

Embodied carbon is just one of many measures that can be used to evaluate your housing decisions. It quite quickly illustrates payback periods and the benefits of upgrading ageing stock.

Ready for the next step? Parity’s data analytics services have been used to analyse over 26 million homes across the UK and have identified the potential for billions of pounds in savings for their residents.

Whether you are a local authority performing area-wide analysis to develop your supply chain or a landlord just starting their net zero plans, we can help.