Embodied carbon is responsible for 11% of global GHG emissions and 28% of global building sector emissions.
Embodied carbon is the carbon emitted in the making of building products and construction. According to Architecture 2030, it is now estimated that embodied carbon will be responsible for almost half of new construction emissions between now and 2050. It is time to recognize the scale of this problem, but this is a tough fix.
It never used to be considered a big deal, because as recently as 20 years ago, one study found that "the energy of operation was between 83 to 94% of the 50-year life cycle energy use." Ten years ago, smart people were complaining that we should just focus on operating energy because "scientific life-cycle energy analyses have repeatedly found that the energy used in the operation and maintenance of buildings dwarf the so-called 'embodied' energy of the materials."
But as buildings get more efficient, and their operating carbon emissions are reduced, the importance of embodied carbon goes up. As Architecture 2030 notes,
...as we trend toward zero operational emissions, the impact of embodied emissions becomes increasingly significant. It is therefore crucial to address embodied emissions now to disrupt our current emissions trend, and because the embodied emissions of a building are locked in once the building is constructed and cannot be taken back or reduced.
Most of the industry is still ignoring it, or actively dismissing and challenging it, but the issue is popping up on on the radar; Paula Melton of BuildingGreen wrote about it recently, and now the Architecture 2030 is making a really big deal about it. Beside their jazzy website that explains embodied carbon, they are promoting the Carbon Smart Materials Palette to help builders separate the high-impact from the carbon-smart materials.
There is interesting stuff in the palette, though I have a few serious bones to pick. They contort the English language to say that "Using less cement is the most impactful way to reduce the carbon footprint of concrete." This isn't even true. The best way to reduce the carbon footprint of concrete is to use less concrete.
They put wood up at the same level of high impact materials but when you look at the information, it is clearly better than concrete and, if you follow their recommendations, it is a lot better. Like their section on insulation, the material can be all over the carbon map, depending on what choices you make.
In fact they treat insulation differently than wood, putting one down in the carbon-smart section -- sheep's wool. This is arguable; sheep have a huge carbon footprint. The Environmental Working Group (EWG) reports that “lamb meat tends to have higher net GHG emissions because lambs produce less meat in relation to live weight than cows.” There are many sources that claim that raising sheep (and using wool) is not good for the climate because of their carbon footprint. And it doesn't scale; how much insulation can we actually get from sheep?
The Carbon Smart site puts wood up on top because not all wood is good, but doesn't say baaaa about the problems of wool, or recommend that it all come from sheep that were not subject to mulesing. It is just all wonderful.
In the small print at the bottom, Architecture 2030 says that "the Carbon Smart Materials Palette is a living resource that reflects the best available knowledge and resources at this time. The palette will be updated as new technology, research, and data becomes available." That's good to see, because this is certainly a work in progress. Their general principles are terrific, but their specific recommendations need work.
This is such a difficult problem, and the solutions are complex. The calculations of embodied carbon are difficult and subject to serious disagreement; just look at Paula Melton on wood in her article. Or me about wool right here.
But it is important, it is significant, and this Architecture 2030 initiative is a great start.