I wanted to make this for a while because I found Net Zero Carbon and Carbon Neutral so confusing. I left it for a while until the recent UN report saying there was no ‘credible pathway’ to 1.5°C limit.

I was trying to relate this to the built environment and there are two main reasons for it:

1. Too many projects are still releasing large amounts of greenhouse gases now when we’re at the turning point in the climate.
2. Too many projects rely on offsets, most of which will take time to grow or be available at scale to have a significant impact.

I’ve taken most of the definitions from the great work by LETI, WLCN and RIBA in their “Carbon Definitions for the Built Environment, Buildings and Infrastructure” and had to make up a few that were missing.

Climate Denial Design: Carbon emissions are not considered or measured during design or construction. These projects are continuing as if nothing has changed since we declared a climate emergency and really should have stopped by now.

Carbon Neutral: All carbon emissions are balanced with offsets based on carbon removals or avoided emissions. The emissions from the project are not limited so can be as high as climate denial design. It also relies on offsets to balance the carbon emissions, which don’t take effect straight away. It could still take several decades for the emissions from the building are offset with carbon being captured and in the meantime, the carbon in the atmosphere continues to lead to global warming.

Net Zero Carbon: All carbon emissions are reduced in line with the Paris Agreement 1.5°C trajectory, with residual emissions offset through carbon removals or avoided emissions. This is the highest all projects should now be. The offsets will take time to balance the emissions, but the emissions now are limited and those limits will get progressively lower.

Absolute Zero Carbon: Eliminating all carbon emissions without the use of offsets. Over the life of the project the emissions are zero. An interpretation is that the emissions stay at zero over the life of the project. I find that difficult to imagine practically and think the emissions will be negative at times, but will eventually reach zero.

Carbon Negative Design: Carbon emissions are eliminated without the use of offsets and remains negative. This would include timber self-build, where the material stores carbon, it remains stored and processes used are carbon neutral or negative.

Carbon Capture Design: Carbon emissions are eliminated without the use of offsets and carbon is captured and stored. This is the real aim, architecture that doesn’t contribute to the climate emergency and also helps address it. There are very few examples of this, but might involve the building developing over time using locally grown materials, using a facade system that grows algae or uses carbon capture technology once available.

Hopefully this makes it a bit easier to understand the different terms, see the importance of reducing emissions now and the urgent need to move to much more carbon negative forms of construction.