September 25, 2023

When you look at the world through the lens of upfront carbon, it changes everything

Times have changed, and so has the way we look at saving existing buildings.

The Toronto chapter of the Architectural Conservancy of Ontario invited me to a panel discussing Heritage and Housing: Responding to the Climate Crisis. It was a fascinating day full of wonderful presentations. Here is a bit of mine; It is hard to distill my thoughts down to 15 minutes and harder still to put them into a Substack, but I thought I would try to post the main thoughts here with the help of a pile of graphs and charts.

25 or so years ago, nobody worried much about what was then called the “embodied energy” of materials; we heated leaky buildings with gas and made electricity with coal, so operating energy overwhelmed it. Studies showed that “the energy of operation was between 83 to 94% of the 50-year life cycle energy use.” And any time someone wanted to knock down an old building, they would claim it was wasting energy, and the replacement would be LEED certified.

But a funny thing happened as our buildings got more efficient; it started taking longer and longer for the operating energy to overtake the so-called embodied energy. The concept of embodied energy was still so obscure in 2009 that MIT had to explain it:

"As the world struggles to reduce energy consumption and greenhouse gas (GHG) emissions, much attention is focusing on making buildings—both existing and new—operate more efficiently. But John Ochsendorf, associate professor of building technology, thinks mostly about another, less-recognized aspect of the built environment: the “embodied energy” of buildings, that is, the energy consumed in construction, including the entire life cycle of the materials used, from the extraction of raw materials to the manufacture, transportation, and installation of products at the building site."

With the Paris Agreement and the understanding of the importance of reducing carbon emissions, we switched from talking of “embodied energy” to “embodied carbon,” which is a terrible name; the dictionary definition of embodied is “include or contain (something) as a constituent part.” The carbon is not embodied; it’s in the air, and every tonne of it is banging up against the carbon budget.

This is why, from hereon in, I will be using the term “upfront carbon” because it is emitted upfront before a building is occupied, a car is driven off the dealer’s lot, or an iPhone is removed from its fancy plastic-free box. You could also call them “now” emissions vs “later” emissions; as architect Larry Strain noted in The Time Value of Carbon.

“When we evaluate emission reduction strategies, there are two things to keep in mind: the amount of reduction, and when it happens. Because emissions are cumulative and because we have a limited amount of time to reduce them, carbon reductions now have more value than carbon reductions in the future. The next couple of decades are critical."

Forgive my terrible graph, but another funny thing happened as our electricity decarbonized, and we got heat pumps and electric cars: the upfront carbon emissions swamp the operating emissions, the reverse of the first graph. This led to what I called the Ironclad Rule of Carbon:

The best demonstration of this is from architect Evelyne Bouchard, with this wonderful graph of total carbon emissions from her all-electric Passive House in Quebec: total flatline, with the decisions about upfront emissions from insulation being the difference between the lines.

A focus on upfront carbon instead of operating carbon requires a completely different way of thinking from our days when we worried about energy consumption. If, as in Bouchard’s house, all of our emissions come upfront, then if we want to minimize them, the first thing one tries to do is build nothing. The next thing is to build less and maximize use of existing assets. And this is where we return to the issues of housing and heritage, the topic of my presentation. As Jim Lindberg of the National Trust for Historic Preservation wrote in "The Reuse Imperative":

“The urgency of reducing embodied carbon emissions inverts common perceptions about older buildings and climate change. Rather than outdated structures that we hope to replace, older buildings should be valued as climate assets that we cannot afford to waste.”

In the UK there is a major battle over the preservation of the Marks & Spencer store on Oxford Street; as architect Julia Barfield noted in the report on the building, our thinking has to change.

“She highlighted that the IPCC told us in 2018 that we have 12 years to avoid a catastrophe, and we see growing evidence all around the world that it is happening – with floods, droughts, fires and melting ice caps. Instead of acting as if there is an emergency, by proposing to throw a huge carbon bomb unnecessarily into the atmosphere, the scheme misunderstands the urgency of our situation. What the science tells us is that what we do in the next 8 years is critical. The brief here was clearly to maximise the site’s potential and the architects have fulfilled their brief well – creating a building minimising operational carbon that 5-8 years ago would have been considered fine. However, now that we understand the upfront impact of embodied carbon it really isn’t.”

So here we are in 2023. and the tables have turned, the dial has moved, the shoe is on the other foot, although here in Ontario, the thinking on carbon is way more than 5-8 years out of date.

Where it used to be argued that our existing buildings were energy hogs, we now know that with the right mix of insulation and heatpumpification, we can fix them and have lower carbon emissions than we would if we knocked them down and replaced them. As the carbon consultants at Preoptima write:

“When looking at existing buildings, the three magic words are retain, retain, retain. Think critically as to whether building more or building new is the answer. Do we need to use new materials at all? Remember that building nothing eliminates the potential for embodied carbon emissions.”

It was bizarre, presenting all of this in the Ontario Science Centre, which the Premier of Ontario wants to knock down and replace with a lite version on the waterfront on top of a 2118 space underground parking lot, next to the new Therme Spa I wrote about recently; the man is a walking carbon bomb. My last slide summarized it:

Come 2024 you can read a longer version of this in my upcoming book, The Story of Upfront Carbon.

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