Not so Zero Carbon buildings. Why we need to make embodied carbon count.

Image: NYC's daily carbon emissions as one tonne spheres. Credit: Creative Commons  

Image: NYC's daily carbon emissions as one tonne spheres. Credit: Creative Commons  

This piece is taken from our newsletter "Force of Nature" see more and subscribe here.

The simple fact is that our buildings are a climate change catastrophe (PDF). If we don't change how buildings are made then we will not meet the green house gas targets we need to to address climate change. The good news is that great strides are being made around the world to push for better buildings. We've reported on the Living Building Challenge, and other certifications like LEED and Passive House. Increasingly the news is about an exciting initiative often named "zero carbon buildings" or "Zero emission" buildings. In fact at least ten countries (including Canada) have now committed to recognize zero-carbon emission buildings.

This is a strong step forward. However, it is important to note that few if any of these "zero" certifications are really net zero. Some will not be even close. There is a very key term here and that is the word "emissions." These standards are targeting an important goal (operational emissions) but are missing in their metrics the embodied carbon from the building materials. This approach has some dramatic and surprising negative results in terms of carbon emissions that come from buildings. 

This month the Canada Green Building Council (CaGBC) announced the Zero Carbon Building Framework (PDF). As the CaGBC says, this "is the first stage of a broader CaGBC Zero Carbon Buildings Initiative to champion the move to lower-carbon buildings in support of Canada's efforts to reduce GHG emissions by 30 per cent by 2030." The CaGBC says "The Framework facilitates broad participation across a range of building types and sizes, provides a clear definition for zero carbon buildings, and establishes five key components for the evaluation of building carbon footprints." 

The Framework is calculating operational energy/carbon, not the embodied carbon that goes into buildings. While the Framework acknowledges the importance of embodied carbon, and says that "the zero carbon building framework should require or encourage building designers to note the embodied carbon in building envelope and structural materials" it also states that "embodied carbon should not be used in calculating a building’s progress toward a zero carbon balance."[emphasis added, Zero Carbon Building Framework, page 43].

In other words, zero is not zero. 

This is (currently) true as well for Vancouver's ground-breaking "Zero Emissions Building Plan." (PDF). The plan states "The City of Vancouver’s green building and community-wide greenhouse gas emission reduction targets do not account for embodied (also referred to as upstream) emissions that occur as a result of energy used and GHGs emitted from building material resource extraction, production and transportation."[emphasis added, Zero Emissions Building Plan, 2016, page 11). Like the CaGBC, Vancouver's plan recognizes the importance of embodied energy: "In anticipation of the near term importance of measuring and reducing the embodied emissions of building materials, it is essential that the City 11 begin collecting data from new developments on their estimated embodied carbon in order to inform future incentive, policy, and potentially regulatory mechanisms targeted at reducing the embodied emissions of new buildings as these become an increasingly significant portion of overall building lifecycle emissions." [ibid].

Still, under both systems, it seems one can declare a building "zero emissions" or "zero carbon" when it simply is not. With both the CaGBC and Vancouver system, the case is made that operational carbon emissions greatly outweigh embodied carbon and that, for now at least, we should focus on reducing operational emissions. As operational emissions are reduced, the argument goes, the importance of embedded carbon increases and in the future more emphasis can be put on embodied emissions. The trouble is that the assumption that embodied carbon emissions are low doesn't seem to be holding up to scrutiny. Many new buildings are using materials with a lot of embodied carbon and therefore even a building with low operating emissions can be responsible for a tremendous amount of carbon emissions.

Furthermore, calculating the operating emissions of a building is based on modeling which has its own problems, including the variations of construction quality and the energy source used in a building. What is crucial to understand about operational energy is that the energy use of a building depends dramatically on the behavior of the occupants. Different thermostat settings in the cold months can have significant impacts on energy use. This month reported that many LEED buildings in Vancouver are failing to meet energy targets "due to gaps in oversight and poor operations management." These buildings are not meeting the operational standards they are certified to have met. 

Because of this failure Vancouver is working on policies to require reporting and monitoring. As one consultant put it in the article, “If you want to evolve and continue having a community of interests and a truly green building, it requires cooperation of the tenants and it requires green behaviour, as opposed to just green building systems.” According to natural builder, author and research Chris Magwood  a Passive House Institute report in 2007 found deviations of +- 50% from the average consumption value in identical houses based on occupant behavior. Notably embodied carbon is fixed and measurable and as Magwood observes, reductions in embodied carbon have an immediate affect and are not dependent on behaviour, building energy source or quality of construction. 

Magwood has done important work on the issue of embodied carbon in construction including through his pieces "The Carbon Elephant in the Room" and the "Carbon Elephant in the Room, Part 2". As he writes "Every time we make or renovate a building, there is a carbon footprint as a result of the harvesting and manufacturing of the materials as well as the transportation involved. If we think this carbon footprint is negligible, we’re ignoring the elephant in the room!" 

In the chart below Magwood compares the embodied carbon of different building approaches. He researched different sample homes in two different climates. His comparison included a high-performance house that was insulated with spray foam, a conventional home, a conventional home built with low carbon materials, and a high-performance (energy efficient) home with natural (low-carbon materials). Note the effect of using low-carbon materials, both in the conventional home and in the high performance natural building. The shorter the yellow bar, the less carbon the building is emitting.

Based on Magwood's calculations we are not talking about an insignificant amount of carbon here, in fact, quite the opposite. The research had some surprising results. For example, if the homes were using low-carbon energy sources the "conventionally-built example with low-carbon materials can have a lower 35 year carbon footprint than the high performance house" even in a cold climate. And again with low-carbon energy sources his home with natural materials had lower embodied and operational carbon combined than just the embodied carbon of the high performance house. This was in a cold climate and true "even if the owner's energy use is double the predicted amount." This is big news. 

In fact as design and engineer consultants Engin Ayaz and Frances Yang show "that for structures taking on popular approaches to carbon reduction (lowering operational demand, sourcing cleaner energy, facade and MEP refurbishment, or rebuild), embodied carbon can account for up to 50 percent of the total carbon emissions (Smith, 2008)." The chart below is from a presentation by Ayaz and Yang (along with Scott Simpson and Fiona Cousins). It shows how different studies have estimated embodied energy and embodied carbon in a project. In this case "embodied energy" does not include energy sources, chemical processes or transportation fuel types, but "embodied carbon" does. One study showed that up to 80% of the life-cycle carbon emissions in a building is embodied carbon!

Magwood's illustration below shows embodied carbon (EC) emissions cumulatively that different building approaches can mean (based on U.S housing). There is a 24% reduction in tons of carbon if we build with natural (carbon sequestering) materials compared to just 'building with better materials."

While the different studies on embodied carbon show different impacts, all are significant. For more reading, see this research piece from the University of Bath (PDF). The fact is that you will get a lot closer to "net zero" carbon if your building materials are sequestering carbon. 

We can't control what people do in a building, but we can encourage and reward green behaviour (as Vancouver is seeking to do with LEED). Good building design will help. Good buildings also require good energy and we need to move to 100% renewables now. This is especially true in terms of the operational energy of a building. 

Again, the initiatives that aim toward "zero emissions" are to be applauded, including the recognition of the need to track embodied carbon (and perhaps require its accounting in the future). Many builders and designers are aware of the need to reduce embodied carbon and are paying more attention to materials. Evidence of this includes the journal of Energy and Building who is planning a special issue entitled "Embodied Energy and Carbon Efficiency: The Next Major Step Towards Zero-Impact Buildings."

However, given where we are now, with green building standards focusing on operational emissions largely based on modeling, we need to ask in terms of public education and public policy what does it mean to call something "zero emissions" when it is not? Perhaps the standard, for now, should be  "low carbon" or "near zero" (though in some cases that simply isn't true). 

When it comes to buildings, mistakes last decades, even centuries. Short-term decisions we are making now around building codes and standards can lead to serious long-term effects. We can control the amount of carbon we put into building and how much it sequesters. If we want to succeed in making buildings that properly respond to climate change we need to account for and reduce embodied carbon as well as account for and track energy efficiencies. There are more and more tools available to track both, including the Swiss building standard, the Minergie A (PDF), that attempts to do this very thing. We can too. The climate depends on it. 


Short video on European research into bio materials to reduce embodied carbon:

Biomass materials offer 20 percent better insulation than traditional ones. And data shows that by reducing the energy and CO2 emissions needed to create and transport construction materials, the total “embodied energy” across the whole lifestyle of a building could be cut by up to 50 percent.