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CA32 - Low Carbon Envelopes
The hidden reality of modern envelopes, especially poorly insulated ones.
THE TOPIC - WHOLE LIFE CARBON
Last week I had the privilege of presenting at the BC Building Envelope Conference on the importance of considering whole life carbon when designing building envelopes. I was honored to be alongside many very smart people who had incredible insights. Here is a summary of my presentation:
WHY IT MATTERS
A great presentation always starts with WHY and this one was no different. Why talk about carbon anyway? I’ve been learning the importance of relating the changing climate to generations and focusing on specific timelines. You can find projected future climate data in Canada from climatedata.ca where I presented the changing number of days above 30C over my children’s lifetime. If we fail to reduce our emissions here is a summary of what our climate could hold:
When I was born - 1 day/year
When my children were born - 2-5 days/year
When my children are my age - 5-25 days/year
When my children are 70 - 15-75 days/year
Why are we talking about this? Because we need to change.
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WHOLE LIFE CARBON
Traditional envelope design has focused on thermal conductivity, durability, moisture management, and constructibility. The future of envelope design takes into account the carbon emissions, but we need to make sure we aren’t just looking at a single metric like operational or embodied carbon. We need to look at the carbon impact of our decisions through the life of the building. Let’s look at three theoretical examples.
House 1 - Code construction, standard embodied carbon, clean energy
Operational Carbon = 175.5kg/year
Embodied [upfront] Carbon = 37,000kg
Whole Life Carbon = 39.2t [10yr] 42.7t [30yr] 48.0t [60yr]
House 2 - Code construction, low embodied carbon, dirty energy
Operational Carbon = 6650kg/year
Embodied [upfront] Carbon = 7,500kg
Whole Life Carbon = 73.8t [10yr] 197.4t [30yr] 405.3t [60yr]
House 3 - High performance, high embodied carbon, clean energy
Operational Carbon = 58.5kg/year
Embodied [upfront] Carbon = 77,250kg
Whole Life Carbon = 77.8t [10yr] 79.0t [30yr] 80.7t [60yr]
The important thing to note here is simply that if we focus on either embodied carbon or operational carbon we don’t get the full picture. By looking at whole life carbon we can see that House 1 is better after 10, 30, and 60 years. We need to think more like this.
So how much of an impact does the envelope have on embodied carbon? Well according to LETI, it’s around 14-17% third on the list following the substructure and the superstructure. The City of Nelson looked at this for residential construction and found that number to be closer to 35% primarily due to residential construction being primarily wood based. Either way, the envelope is a big part of the problem, and the solution
The Ha/f research studio headed by Kelly Doran studied a series of envelopes to understand the embodied carbon impact of their assemblies in comparison to their R-value. They range from 46.3kg/m2 for a typical brick-insulated assembly to over 209kg/m2 for an aluminum curtainwall. The sad part is that the assembly with the highest embodied carbon also has the lowest R-value (aluminum curtainwall).
The Ha/f Research Studio, out of the University of Toronto, completed an LCA on a project that showed the brick cladding as contributing twice as much as any other material. At first the conclusion was that the additional carbon was from the far transportation distance from Nebraska to Toronto, but upon further research, it was the fact that the brick was fired with an electricity grid that is primarily powered by coal.
The conclusion for our envelopes is:
We need to have a whole life carbon perspective that focuses on both short and medium-term emissions
We need to use less metal and use more plants
Geography is a large driver of emissions, we need to consider this
1 PERSON TO FOLLOW
Ryan is the founder and CEO of Mantel Developments. Helping to create a resilient, low-carbon future. He specializes in building embodied carbon life cycle assessment, green building consulting and certification including LEED and Zero Carbon Building Standard.