Use of concrete, foam, and other high embodied carbon materials in buildings
Please help me here. I am having difficulty following all of the advice on helping reduce our environmental impact through the use of foam and concrete and steel in buildings. This seems very contradictory to me. Data I see says concrete produces between 7 and 10% of GHG’s that cause climate change) and foam has a pretty heavy embodied carbon data sheet as well.
I don’t understand why the Green Building Advisor is not recommending approaches that will sequester carbon . For example Chris Magwood seems to have some pretty credible research….’http://endeavourcentre.org/’ and Project Drawdown….has 10 Solutions to Reverse Global Warming.
https://www.drawdown.org/.
Number 10 is – Build with wood
’10. Build with Wood
With the Industrial Revolution, steel and concrete became the main materials for commercial construction. Wood use declined, relegated to single-family homes and low-rise structures. But that is beginning to change with high-performance “mass timber” technologies, namely glued laminated timber (glulam) and cross-laminated timber (CLT). In cities around the world, they are being used to construct tall buildings that are strong, fire safe, quick to put up, and aesthetically appealing.
Building with wood has a double climate benefit. First, as trees grow, they absorb and sequester carbon. Dry wood is 50 percent carbon, so a building can become a longstanding carbon sink. Second, the process of producing glulam or CLT generates fewer greenhouse gases than manufacturing cement or steel, each roughly 5 percent of global emissions. To be a true climate solution, wood must be sourced through sustainable forestry, and the less transport the better. Check out: http://www.metsawood.com‘
Cellulose, wood fibre and even Hemp batts make a great alternative to foam.
Please help me.. What am I missing.
Thanks, Rick
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Replies
These issues seem like they are discussed frequently on this site. Here's a big article on the subject from not too long ago: https://www.greenbuildingadvisor.com/article/embodied-carbon-emissions-in-buildings
What do you find contradictory?
Reducing concrete, foam, etc. is good and is often recommended on this site.
Sometimes practical concerns prevent folks from using cellulose for everything, so reclaimed rigid foam is often suggested.
Sometimes (especially in renovations) spray-foam is the only way for some to achieve their energy/moisture performance goals within the constraints of their project (budget, HOA rules, code, etc.), and in this case folks on GBA typically recommend the newer generation of HFO blown closed-cell foam that is significantly less bad than previous generations. Cellulose is still better of coarse, but buildings are full of competing requirements and compromises.
Reducing concrete use is frequently brought up when concrete is discussed!
Read a little more, and I think you'll find a wealth of useful information.
If you you are struggling with specific contradictory ideas, ask some questions about them!
As to your question "what am I missing", if I was being catty, which I guess I am, I would say you are missing actually spending some time reading the content on GBA!
Try this: write a post saying you want to insulate your house completely with extruded polystyrene. Report back here how the commenters respond.
Read the Q&A Spotlight from Dec 30, Do Concrete Houses Make Sense? As always, there are differing opinions, but the general consensus of the GBA community seems to be, not really.
There are other issues to consider too. Using concrete as an example, a concrete foundation can be expected to easily last 50+ years, with many examples of 100 years or more. Wood isn’t going to be able to do that. If the foundation fails, so does the house from a practical standpoint. What this means is that while concrete may have a bigger initial impact, over the life or the structure it will actually use fewer resources than alternatives that may have a lower initial impact.
It’s important to think of the structure as a system and not be overly focused on one or two components. It’s a “miss the forest for the trees” sort of problem. A very easy to understand example is insulation. Using NO insulation has NO initial impact in terms of resource consumption! But when you look at the life of the structure, no insulation means MUCH more overall energy use so you’re actually worse off than if you’d expended resources to insulate the structure in the beginning. You want the lowest OVERALL impact for your structure.
I can tell you that wood is NOT capable of replacing steel too. Commercially, fire codes very nearly prevent the use of wood in many types of structure. You also don’t have the load bearing ability or rigidity or connections that you can get with steel. Another thing with steel is that steel is nearly entirely recyclable and industry generally recycles most of it. When a steel frame building is demolished, the steel is usually sold as scrap, reprocessed, and then used to build new steel things. Wood frame buildings are usually trashed since there isn’t an easy way to reuse old framing lumber in most cases.
These are complex issues with no easy answers.
Bill
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