The Preservation of Existing Buildings Is Climate Action

Two things change everything: upfront carbon and heat pumps.

Monument and courthouse in Brockville, Ontario
Monument and courthouse in Brockville, Ontario.

Lloyd Alter

A decade ago, I was president of Architectural Conservancy Ontario, an organization that "encourages the conservation and reuse of structures, districts and landscapes of architectural, historic and cultural significance." I spent much of my time talking about embodied energy, a controversial subject back then, noting in a 2012 post on Treehugger that it was considered by many to be "water under the bridge–Energy spent 2, 20, or 200 years ago to build a building simply isn't a resource to us today."

Much has changed in the last decade, with many of those changes documented on Treehugger. I was recently invited to speak at the Ontario Heritage Conference in Brockville, Ontario, where I tried to explain how two developments of the last decade should change the way we think about existing buildings. What follows is a summary of my presentation about these two things that change everything: embodied carbon and heat pumps.

Ten years ago, we were often told an old building had to be demolished because it wasted too much energy and would cost too much to retrofit but would be replaced with a "green" building that would be LEED certified. We also watched attempts to make old buildings as energy-efficient as new ones, often with thick layers of spray foam that turned out to have its own set of problems.

Every tonne adds to global warming


Then we got the Paris Agreement in 2015 that set limits on carbon emissions, and the realization that every tonne of carbon dioxide (CO2) emissions add to global warming. We got carbon budgets needed to stay under 2 degrees Celsius and soon after, to aim for 1.5 degrees Celsius.

After 50 years of worrying about energy conservation in buildings, suddenly we had to pivot to worrying about carbon instead, which involves different approaches. While it may have been difficult talking about the embodied energy in an existing building, there is no question that renovating and retrofitting a building has significantly lower upfront carbon emissions than demolishing and replacing a building.

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.”

Lindberg also understands we don't have a lot of time for discussion, noting "the best way to avoid embodied carbon emissions right now, when our carbon budget is shrinking fast, is to conserve and reuse as many existing buildings as possible."

Or as architect Larry Strain wrote in "The Time Value of Carbon" on the University of Washington's Carbon Leadership Forum: "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."

Lindberg and Strain, and I suppose myself, are voices in the wilderness in North America, where almost nobody takes the argument of embodied carbon seriously and where many consider historic preservation to be NIMBYism for the rich.

Architects Declare
Architects Declare

However, in the United Kingdom, the building professionals are taking the issue of demolition very seriously indeed. In 2019, a group of award-winning firms established Architects Declare: "For everyone working in the construction industry, meeting the needs of our society without breaching the earth’s ecological boundaries will demand a paradigm shift in our behaviour."

Their stated goals included:

  • Upgrade existing buildings for extended use as a more carbon-efficient alternative to demolition and new build whenever there is a viable choice.
  • Include life cycle costing, whole-life carbon modeling, and post-occupancy evaluation as part of our basic scope of work, to reduce both embodied and operational resource use.
Development stages

World Green Building Council

The World Green Building Council, in its document Bringing Embodied Carbon Upfront, developed a set of principles, the first of which is to prevent—to "question the need to use materials at all, considering alternative strategies for delivering the desired function, such as increasing utilisation of existing assets through renovation or reuse." 

This report was also the first to use the term upfront carbon, which I have promoted as a way of making it more comprehensible. It is not embodied in the building, but released upfront, and ends all the silly discussions about water under the bridge.


ACAN / Finbar Charleson

The Architects Climate Action Network, in its report on the carbon footprint of construction, came up with a number of recommendations, with the first being to "reuse existing buildings: pursuing a strategy of retrofit, refurbishment, extension and reuse over demolition and new build." 

All of these arguments are playing out in the U.K. now, most notably in the fight to save the Marks & Spencer store on Oxford Street in London, where British architect Julia Barfield noted:

"We all need to get Carbon literate and understand the carbon consequence of demolition. How can it possibly be justified? Further reason why embodied carbon needs to be regulated and made a meaningful part of the planning system."

Retrofitting and renovating has become a public issue with the campaign led by Will Hurst of the Architects' Journal. He writes:

"Demolition is the construction industry’s dirty secret. Despite all the declarations of climate emergency and talk of a green recovery, it is propped up by outdated rules and taxes and great swathes of our towns and cities are currently earmarked for destruction. If the government really means to 'Build Back Better' it must recognise that conservation of buildings is now a climate issue and introduce reforms to ensure that bulldozing buildings is an absolute last resort."

The problem, as Australian architect Jennifer Crawford puts it so succinctly, is that it is everybody's dirty little secret. Building nothing doesn't exactly pay the bills, and it is in everyone's financial interest to build as much new stuff as possible. She tries to crack this nut by consulting.

Fist Pumps for Heat Pumps

I noted earlier that a decade ago we saw many attempts to do deep energy retrofits on existing buildings that were problematic. In almost every case, it involved gutting of the interior, was incredibly expensive, caused deterioration of the structure because moisture couldn't get out of the walls, and when done with spray foam insulation, actually ended up with a bigger carbon footprint than if nothing had been done at all because of the high embodied carbon in the foam.

All of this was done to save energy when energy meant burning fossil fuels, either directly with natural gas or indirectly with electricity, which was mainly generated with coal and was very expensive.

But everything changes when you think about carbon instead of energy. Some suggest that if your electricity source is clean, you can use as much as you want! I was initially appalled at the idea—that groups like Rewiring America, promoted by entrepreneur and inventor Saul Griffith, would say we could have our cake and eat it. "We build a model of future household energy use, which assumes that future behaviors will be similar to current behaviors, only electrified."

The model was basically: electrify everything. I was not impressed at first, suggesting we had to reduce demand first, as well as clean up electricity and electrify everything.

Where the heat goes
How homes lose energy in cold climates.

Harold Orr

My thoughts about the "electrify everything" gang were that we don't have enough electricity and we should still be reducing consumption first. But where? And how much? Building pioneer Harold Orr of Saskatchewan Conservation House fame had some thoughts:

"If you take a look at a pie chart in terms of where the heat goes in a house, you’ll find that roughly 10% of your heat loss goes through the outside walls.” About 30 to 40 % of your total heat loss is due to air leakage, another 10% for the ceiling, 10% for the windows and doors, and about 30% for the basement. “You have to tackle the big hunks,” says Orr, “and the big hunks are air leakage and uninsulated basement.”

Reading that, I wrote, "Doing an Energiesprong or complete rebuild of every house in North America would take forever and cost the Earth; cutting energy use by 50% or even 80% is achievable by following Harold Orr's prescription. Once you are there, it is not a stretch to switch to an air source heat pump and electrify everything, and you are no longer emitting carbon."

This is where I make my peace with the Electrify Everything and Fist Pumps for Heat Pumps crowd. Air source heat pumps that work well at low temperatures are relatively new, but they change everything. In places with clean electricity, they already eliminate the carbon from heating and cooling, and they reduce it everywhere else.

Heat pumps with wind and solar
The future we want: Heat pumps powered by renewables.

ewg3D / Getty Images

More recently, there have been others making a more persuasive and logical case than I did, with scientist Richard Erskine writing in a wonderful post—Insulate Britain! Yes, But By How Much?—where he questioned the need for deep retrofits in an all-electric world.

"The ‘retrofit community’ generally have established an article of faith that ‘deep retrofit’ is essential. This is a belief that has very deep roots and predates concerns about the climate emergency. Key organisations in the public and private sector promote this belief."

He noted also deep retrofits "are not achievable for hard-to-treat homes at reasonable levels of cost and disruption," adding: "For Britain’s housing stock, this is not achievable on a timescale commensurate with the climate emergency. This point seems to be lost on advocates for deep retrofit."

His article was picked up by engineer Toby Cambray, who wrote in PassiveHouse Plus, inventing the words heatpumpification and heatpumpify—two words I have incorporated into my vocabulary. Cambray writes, "Installing a heat pump does not preclude a subsequent deep energy fabric retrofit, especially if it’s planned in advance. A rapid growth in heat pumps would quickly stimulate the investment in the infrastructure needed if we're to shift away from gas in the medium term, and with appropriate forethought, we can go back and reduce the demand of those properties later." We do that with "fluffy stuff" or insulation.

I didn't entirely agree, concluding that we needed a bit of fluffy stuff now to reduce the need for electricity, especially in the U.K. where they get so much electricity from burning trees in the form of wood pellets imported from the U.S. and Canada. I wrote: "I continue to say the first thing to do is Reduce Demand! with a lite retrofit, Orr-style, and then Electrify Everything! insulation before heatpumpification. Fluff before forests."

The Role of Preservation and Heritage

I concluded my presentation in Brockville by noting that looking at carbon instead of energy changes everything for us in the heritage community in two important ways. 

  1. It means a complete repositioning of why we retain buildings instead of replacing them because there are far fewer upfront carbon emissions that matter now in renovation than there are in new construction.
  2. It means we should stop chasing deep energy retrofits on a few buildings, but should go after the big chunks with low-carbon insulation and make up the difference with heatpumpification.

Our problem is carbon, and our existing buildings are a big part of the solution. Preservation is climate action.

View Article Sources
  1. Lindberg, Jim. "The Reuse Imperative." National Trust for Historic Preservation, Preservation Leadership Forum, 16 Mar. 2022.

  2. Strain, Larry. "Time Value of Carbon." Carbon Leadership Forum, 18 Apr. 2020.

  3. Griffith, Saul and Sam Calisch. "Household Savings Report: No Place Like Home: Fighting Climate Change (and Saving Money) by Electrifying America's Households." Rewiring America, Oct. 2020.