Why fabric remains first

From the proceedings of the 27th International Passive House Conference in Innsbruck, my attempt at an academic paper.

Trying to explain why heatpumpification means we need a lot more electrification.

“Fabric First!” is a cri de coeur in the efficient building world, a statement that the building envelope or fabric (both words that often don’t make sense to outsiders but mean the exterior that keeps the wind, rain and cold out) should be fixed before we do anything else. Some have challenged this notion in the last few years for renovation and retrofit, suggesting that if we have heat pumps and clean electricity, we can have our low-carbon cake and eat it, too.

I first became aware of the issue with engineer Toby Cambray’s article in Passive House Plus, in which he notes, “A basic fabric retrofit is relatively expensive, and heat pumps are getting better and cheaper; therefore we should do a bare minimum of fabric work and focus on deploying heat pumps.” I was impressed with Toby’s argument. (Hear an interview with Toby on the Zero Ambitions podcast.)

Others went further. Nigel Banks (second from left during a presentation in London) goes so far as to write “Fabric Fifth,” calling for 1) heat pumps, 2) smart controls, 3) measure, 4) solar and storage, and finally, 5) fabric.

I am impressed with Nigel, too, and he is not alone. But I became convinced that he was wrong in his ordering of things.

When I was invited to speak at the International Passive House Conference in Innsbruck, I thought I would compete with the academics and submit a paper, “Why Fabric Remains First.” After my talk in Paris about sufficiency, I changed my lecture, relegating fabric to a few slides. But for those who are interested, here is my attempt at academia from the proceedings of the Passive House conference. In it, I try to challenge those who say that the upfront carbon emissions of deep retrofits are a problem (they are not if you are aware of the issue and make appropriate choices), why retrofits matter, and why we still have to think “fabric first!”

Abstract

Our existing building stock is a significant source of operating carbon emissions, the greenhouse gas emissions from burning fossil fuels to operate buildings over their lifetime. However, demolishing and replacing them with more efficient buildings would create a massive “burp” of upfront carbon emissions (UCE) from the mining, manufacturing, and transportation of materials and the construction of the building. Retrofitting existing buildings can reduce operating carbon emissions with significantly reduced upfront carbon emissions compared to new construction. With the decoupling of electricity production and carbon emissions, it has been suggested that upfront carbon emissions can be reduced even further by relying less on reducing energy demand with deep “fabric first” retrofits and more on heat pumps running on “zero carbon electrons.” However, in an increasingly all-electric world, it remains critical that we maximise building efficiency to reduce demand, particularly at times of peak load. We still need a “fabric first” approach.

The Importance of Upfront Carbon

In his book Architecture: From Prehistory to Climate Emergency, Barnabas Calder writes, “The history of architecture is shot through with the remarkable ingenuity and adaptability shown by humans in meeting the challenges of their natural environment and in improving human lives in the most unpromising circumstances.” The climate crisis is a challenge like none our industry has faced before, and our buildings must adapt. It’s not a case of “we must reduce emissions by 2030 or 2050” or whenever; the 1.5°C or 2°C thresholds are based on carbon budgets that are rapidly diminishing.

Fifty years ago, we had an energy crisis caused by an oil embargo, and our preoccupation was reducing operating energy consumption. There was little concern about the energy consumed in making building materials because it mainly came from plentiful coal. It was also swamped by the operating energy; In the 90’s(Straube, 2010) it was estimated that “the energy of operation was between 83 to 94% of the 50-year life cycle energy use.”

Figure 1 John Ossendorf

But as buildings became more energy efficient, the picture began to change, and what was then called “embodied energy” became more significant. As explained in MIT Energy Initiative:  (Stauffer, 2009)

"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."

Oschendorf’s graph made it very clear that as the efficiency of buildings increased, the embodied energy came to dominate the total energy use of the building.

Energy vs Carbon

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 CO₂ is not embodied; it is in the atmosphere. Many people also use embodied energy and embodied carbon interchangeably, and they are not. This is why many now prefer the term “upfront carbon.”

The estimates of the proportion of upfront carbon in buildings’ life cycle keep climbing. By 2020, Stephanie Carlisle of Kieran Timberlake Architects wrote, (Carlisle, 2020) “When we look at new buildings anticipated to be built between now and 2050, embodied carbon, also known as “upfront carbon” because it is released before a building is even occupied, is projected to account for nearly half of total new construction emissions.” In their 2021 report, Architects for Climate Action noted that "the embodied carbon of a building can be up to 75% of its total emissions over a typical 60-year lifetime." 

Figure 2: Upfront and operating emissions/ Lloyd Alter

However, with the proliferation of affordable, low-temperature air source heat pumps and the continuing decarbonisation of the electrical grid, one gets to the point where upfront carbon emissions approach 100% of total carbon emissions.

Figure 3: Total carbon emissions/ Evelyne Bouchard

As Evelyne Bouchard (Bouchard, 2023) of Tandem architecture écologique demonstrated with her all-electric heatpumpified Passivhaus dwelling in Quebec, which has zero-carbon hydroelectricity, 100% of the carbon emissions from the 50-year lifecycle of the building are upfront emissions. Bouchard concludes that material choice becomes critical; in her building, insulating to the Passivhaus standard with fibreglass would have higher total carbon emissions than insulating to the building code minimum. Her actual design with cellulose insulation was the lowest. In an all-electric, heatpumpified, upfront carbon world, the choice of materials matters and the amount of materials matters.

Why Retrofits Matter

This is the driving force behind retrofits and renovations rather than demolition and new construction; retrofits use less material and produce fewer upfront carbon emissions.

FIGURE 4: LARRY STRAIN, CLF 1

Studies and tools such as the Carbon Avoided: Retrofit Estimator  (CARE, 2023) have demonstrated that “Renovating an existing structure usually has a much lower carbon footprint than building new because renovations typically reuse most of the carbon-intensive parts of the building — the foundation, structure and building envelope.” 

The World Green Building Council, in its Bringing Embodied Carbon Upfront (Adams, 2019) document, suggests strategies to reduce Upfront carbon, the first being 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 favours the preservation of existing buildings, as does Principle 2, Reduce and Optimize, to "apply design approaches that minimise the quantity of new material required to deliver the desired function."

Will Arnold of the Institution of Structural Engineers distilled it all down to three words: “Use less stuff.”

Electrify Everything!

For fifty years, we have had a preoccupation with energy consumption, but I have written: “When you look at the world through the lens of upfront carbon, everything changes.” With the proliferation of heat pumps and the rapid expansion of renewable energy, some have begun to question whether we might be better off worrying less about energy consumption and more about upfront emissions.

 Consultant Richard Erskine (Erskine, 2021) asks, "Some experts say we need to insulate our homes so well they will hardly need any heating! Others say we must get off gas as fast as possible by installing heat pumps. Who is right?" Erskine suggests deep energy retrofit “isn’t a realistic strategy for reaching net zero in the fastest time possible”.

Architect Kelly Alvarez Doran (Doran, 2023) notes that deep retrofits use more material and have higher upfront carbon emissions and suggests that “the case for 'higher performance' systems is strong in cold-climate-dirty-grids and very weak in the greener grids.”

(Eyre & Rosenow, 2023) claim, “Heat decarbonisation is necessary to deliver zero-carbon goals. In many cases, no additional fabric improvement is needed to decarbonise heating; a heat pump, or other zero-carbon heat supply, will be enough.” 

Others note that “For retrofit, fabric changes are a huge cost, upheaval and carbon burp” and suggest instead a ”lite” renovation, patching the fabric, tightening the building envelope to reduce air infiltration, insulating the easy places such as lofts, and making up the difference with heat pumps.

Some have even suggested that deep retrofits could be counterproductive; Zach Semke and Skylar Swinford (Swinford & Semke, 2023) describe what they call the “backfire” misperception:

If you’re not careful, Passive House practice will do more climate harm than good; that the extra insulation and triple-pane windows on a Passive House can backfire, adding more upfront carbon emissions than the operational carbon emissions that they reduce, particularly if your building is powered by (what are assumed to be) “zero carbon electrons”.

There are several reasons why this is not true and why, even in a zero-carbon, heatpumpified world, we still need a fabric-first approach. We cannot take our eye off the ball and focus only on carbon emissions; energy efficiency still matters.

1.    There does not have to be a backfire. As Evelyne Bouchard demonstrated, we can choose materials with low upfront carbon emissions and size our windows appropriately.

2.    There are no such things as “zero carbon electrons.” As (Swinford & Semke, 2023) demonstrated, electricity is bought, sold and crosses borders. There are upfront carbon emissions from building turbines, solar panels, and nuclear plants to be accounted for. Even in Quebec, with 100% hydro-electric power, it still makes sense to build to the passive house standard because, as Bouchard explained, “Freeing up some of the electrical grid’s capacity by making buildings more efficient makes it possible for other sectors, such as transportation or industry, to switch from fossil fuels to electricity. In places that are still working to decarbonise their electricity system, energy-efficient buildings can help to make the challenge of scaling up renewables and grid capacity more manageable.”

3.    Most grids are not anywhere close to zero carbon. While electric grids are generally decarbonising, there are still significant carbon emissions from using fossil fuels for power generation. Austria is at 158 grams of CO2 per kWh generated; Germany is at 385; the UK is at 485, and the USA is at 533. Even with a heat pump, reducing energy consumption through deep retrofit still means reductions in CO2 emissions. It will be decades before these reach zero carbon.

FIGURE 5: ELECTRICITY IN EUROPE

4.    Electrifying everything means demand will grow significantly. Converting transportation from gasoline and diesel, heating from natural gas, and industry from coal will create a vast demand for electricity while powering it all with renewables and zero-carbon sources will limit supply. Reducing demand in every form of electricity consumption should be a priority.

5.    With buildings, it is the peak demand that matters. The electrical grid must be designed around peak demand under the worst conditions. Skylar Swinford and Zach Semke (Swinford & Semke, 2023) noted, “envelope-first” building energy efficiency is uniquely suited to address this winter heat load.” A study published in Nature (Buonocore, 2022) found that in the USA:

“All of our building electrification scenarios resulted in substantial increases in winter electrical demand, enough to switch the grid from summer to winter peaking. Meeting this peak with renewables would require a 28× increase in January wind generation or a 303× increase in January solar, with excess generation in other months. Highly efficient building electrification can shrink this winter peak—requiring 4.5× more generation from wind and 36× more from solar.”

Dr. Wolfgang Feist (Feist, 2024) found that in Germany, “the consistent application of energy-efficient component renovation” would result in a significant reduction in peak demand. “The power requirement is reduced by a good 50%, even during peak heating times, i.e. to only around 27.4 GW.” He also notes that “the temperatures also fall less quickly and to a less low level with possibly lower heating outputs.”

6.    With renewables, we must design for resilience and intermittency: Passivhaus can work as a “thermal battery”, excluding or retaining heat when electricity is lost due to weather or lack of renewable energy. A network of “smart” Passivhaus buildings might well be controlled by utilities and controlled remotely at peak times, as water heaters often are, to shave the peak.

7.    With Passivhaus, heat pumps are smaller. Many heat pumps are charged with refrigerants that are serious greenhouse gases; the commonly used R134a has a global warming potential of 1400 times that of CO2. Heat pumps leak; estimates in the UK are 6% per year. Since the heat pump's size is based on a building's heating and cooling demand, a Passivhaus design will get by with a significantly smaller unit, leaking less refrigerant. However, perhaps more critically, smaller heat pumps can be charged with hydrocarbon refrigerants like R-290 (propane,) which has a GWP of only three times that of CO2. For safety reasons, these units are limited in size. The efficiency of a Passivhaus design could make the difference between two heat pumps with two very different refrigerants.

8.    Comfort and health still matter: Uninsulated walls and poor-quality windows significantly lower the mean radiant temperature, reducing comfort levels. They make humidity levels challenging to control, resulting in either uncomfortably dry air or the possibility of mould growth.

Conclusion

The geologist Simon Michaux (Michaux, 2022) has written: “The logistical challenges to replace fossil fuels are enormous. It may be so much simpler to reduce demand for energy and raw materials in general. This will require a restructuring of society and its expectations, resulting in a new social contract. Is it time to restructure society and the industrial ecosystem to consume less?”

This applies to everything in our lives, but especially in our buildings. We cannot just knock down and replace buildings; we need to retrofit what we have. A new social contract might mean smaller homes, denser communities, fewer cars, and careful retrofits that minimise upfront carbon emissions. But we must also reduce the demand for low-carbon electrons as much as possible so that there is enough for everyone and everything in an all-electric world.

Works Cited

Adams, M. (2019, September). Bringing embodied carbon upfront. Retrieved from World Green Building Council: https://worldgbc.s3.eu-west-2.amazonaws.com/wp-content/uploads/2022/09/22123951/WorldGBC_Bringing_Embodied_Carbon_Upfront.pdf

Bouchard, E. (2023, August 17). Embodied carbon in a Passive House. Retrieved from Tandem architecture ecologique: https://en.tandemarch.ca/post/embodied-carbon-in-a-passive-house

Buonocore. (2022). Inefficient Building Electrification Will Require Massive Buildout of Renewable Energy and Seasonal Energy Storage. Nature.

CARE. (2023). Carbon avoided retrofit estimator. Retrieved from caretool.org: https://www.caretool.org

Carlisle, S. (2020, January 3). I’ve been polluting the planet for years. I’m not an oil exec—I’m an architect. Retrieved from Fast Company: https://www.fastcompany.com/90435650/these-are-the-last-years-of-design-as-we-know-it

Doran, K. A. (2023, March). Less is Less. Retrieved from Linkedin: https://www.linkedin.com/posts/kelly-alvarez-doran-475a3720_lower-carbon-lower-cost-it-was-an-honor-activity-6980988090093867008-0mj0/

Erskine, R. (2021, January 17). Are Air Source Heat Pumps (ASHPs) a Silver Bullet? Retrieved from Essays Concerning: https://essaysconcerning.com/2021/01/17/are-air-source-heat-pumps-ashps-a-silver-bullet/

Lindberg, J. (2022, March 16). The Reuse Imperative. Retrieved from National Trust for Historic Preservation: https://savingplaces.org/stories/the-reuse-imperative

Stauffer, N. (2009, July 30). Innovative buildings: Prudent use of energy and materials. Retrieved from MIT Energy Initiative: https://energy.mit.edu/news/innovative-buildings-prudent-use-of-energy-and-materials/

Strain, L. (2017, May). Time Value of Carbon. Retrieved from Carbon Leadership Foundation: https://carbonleadershipforum.org/download/9171/

Straube, J. (2010, September 10). BSD-001: Why Energy Matters. Retrieved from buildingscience.com: https://buildingscience.com/documents/insights/bsi-012-why-energy-matters

Swinford, S. (2023, March 3). New Tool for Assessing upfront and operational Emissions. Retrieved from Passive House Accelerator: https://passivehouseaccelerator.com/articles/new-tools-for-assessing-upfront-and-operational-emissions-no-passive-house-emissions-backfire-found