Upfront carbon: doing nothing is not an option

Upfront, or embodied, carbon is the trickiest of problems in the built environment.

Whenever we build anything we add to the carbon tally and as ‘now’ is a problem, this is not ideal. At the same time Australia has 10.9 million homes of which ~10 million (our guess) need retrofitting for health, comfort and resilience.

Much of the approach to retrofit has been governed by financial payback which only seems to apply to thermal performance of homes, not kitchens, bathrooms, cars or anything else in life. Depressingly, when it comes to payback, the best bang for your buck, the answer has always been ‘put as much PV on the cheapest building you can build’.

This has proven to be good for the hip pocket of many Australians yet has not delivered on health or comfort, something that some (us included) see as critical to home! In the renovation space, this translates to doing nothing to improve thermal performance while making future upgrades slightly harder by putting PV on a poorly performing roof.

So we have jumped into the rabbit hole that is upfront/embodied carbon to see what this means from a carbon perspective, surely PV panels on a terrible building wins over deep retrofit…..

The graph below shows lifetime carbon for three scenarios for the same house (120m2) in a cold winter, warm summer non-coastal location of NSW. The key assumptions are a deep passivhaus retrofit with and without PV as well as a non-renovation option.  The unrenovated version gets double the PV system in an attempt to power a 16kW air conditioning system that may or may not be able to keep you warm in a house that leaks like a sieve when it is -5ºC outside. The passivhaus retrofit has just an 8kW system (more about distribution than capacity) and just a 6kW PV system.

The unrenovated cottage having a higher starting point is initially counterintuitive but is driven by the additional carbon associated with the extra photovoltaics and larger air conditioning systems. The (mostly) bio-based retrofit (woodfibre insulation, local triple glazed windows) happens to have a similar upfront carbon impact as the extra PV and air con. The take away from this being that the carbon associated with retrofit, at least in this case, is similar to that needed to overpower the poor performance.

An energy efficiency measure making long term sense is not news and nor, so history shows, a motivator for systemic change. In the world we have collectively constructed, the power of money drives everything and while many do not love this, it is the reality in which we exist and, as architects and built environment professionals, must successfully operate if we wish to see change.

The graph above shows a difference of 42 tonnes of CO2 between the ‘do nothing’ and ‘do it well’ options. As Australia decided to abandon logic and abolish the carbon tax, we’ll translate that figure into dollars via the European carbon price. At current values, 42 tonnes of carbon is worth $5,000. It is safe to say that is not sufficient to fund the retrofit.

The graph below comes from the Infrastructure Guidelines Supplementary Guidance on Measuring & Valuing Changes in Greenhouse Gas Emissions in Economic Appraisal, an Irish government document. It is their guidance that is used for calculating the cost benefit ratios on projects, it gives an assumed carbon price for every year out until 2055. The graph clearly shows a huge rise in the assumed carbon price since they last issued the guidance in 2019, this is a reflection of the lack of global progression on carbon reduction hence a greater need for reductions and therefore associated cost.

If we value the retrofit using those government carbon prices, we arrive at a carbon equivalent cost of $52,400. Once we start to view the benefits of carbon prices at those levels, the cost of retrofitting starts to make more financial sense and sheds light on the quantum of financial support being offered in most other developed countries.

There is so much more detail within these analyses of carbon; assumptions about the carbon intensity of the grid, maintenance cycles, building operations especially as the weather becomes more varied. We can safely say that all of the assumptions are wrong (modelling always is) however, it is what we have right now and it is significantly more sophisticated than it has ever been before. While some will dedicate their professional lives to improving the accuracy of this, others will focus on the actions to reduce the emissions themselves. All of these tasks are of critical importance as they have feedback loops between themselves. The current inaccuracies should not be used as a reason to delay action but as a reason to move faster, evaluate, improve and repeat.

Once again, a rationale analysis of our relationship with energy efficiency, carbon and our national commitments to carbon dioxide emissions reduction shows that deep retrofitting of existing buildings remains fertile ground. Are we about to see the needle shift? I am unsure but remain optimistic (as it is the only viable option).

The ‘throw more PV on’ attitude is not ticking the boxes that need to be ticked, just making the real changes harder and slower.

There is an immediate need for serious government action to drive the retrofit market, not only for carbon reasons but also for the health benefits that will flow too. Passivahus is arguably the only sensible approach as it remains the only global building standard that actually does what it says on the box!

It should not go without reinforcement that the unrenovated option while financially appealing today also fails to deliver on the concept of ‘home’, a place of safety, comfort and healthy for those in it. While putting a dollar value on those is useful in some contexts, I prefer to keep with Mastercard take on the lived experienced; “priceless”.

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