It was a nicely polished presentation.
They are claiming that pre-fab could reduce significant embodied carbon amounts by reducing material waste and then using renewable energy to power assembly building.
A4 & A5 seems to represent a pretty small slice of the embodied carbon pie.
It seems to me like the other benefits from pre-fab are more valuable, like controlled assembly construction resulting in better continuous insulation and air tightness.
Thoughts?
I did not attend, but I’ve been curious about this topic.
A question that comes up frequently for us is cast-in-place PT concrete podium vs precast podium (in the case of a 1-2 story concrete podium under 4-5 stories of light framed wood residential construction). We design a lot of both types of podiums, and historically the decision is driven by economics and owner/contractor preference.
There are certainly some benefits of precast along the lines that you mentioned, but there are also drawbacks - for example, we historically have exerted less control over the concrete mix used by the precaster, as it is a delegated design, and they often use a very high cement content so the concrete gains strength quickly and they can cycle through their forms quickly. The structural design of the two systems is also fundamentally different, so there is an inherent difference in material quantities, but I don’t have a definitive comparison yet.
Has anyone done a proper study they can share comparing the embodied carbon of a precast vs cast-in-place podium or some other common prefab vs non-prefab design alternative? Otherwise, this is on my eventual to-do list…
We (UMC, Inc.) do think that pre-assembly reduces embodied carbon in the construction process as well as in the overall efficiency of the building’s operations over time. That’s important to us, since as a mechanical contractor, it’s the place we can offer the most decision-making to set up the building for long-term low-carbon operation.
But we’re still learning! Eager for your input and expertise. Open conversation here, or directly at bhemphill@umci.com. Thanks and onward together,
Bonnie Frye Hemphill
Director, Policy & Partnerships
UMC, Inc.
Hi @bhemphill
Pre-assembly has the potential to add a lot of value, no arguments there.
I think the argument that it could make a big or even significant impact on reducing embodied/upfront carbon is up for debate.
Generally speaking (and obviously project dependent), from what we’ve seen on our LCAs, carbon emissions relating to transportation (A4) and construction (A5) have a pretty small impact on the total carbon footprint.
At the end of the day, if we are trying to shave every piece of unnecessary carbon, then this is what we will have to do!