The LightHouse Sustainability Society recently produced a pair of studies that focus on “design for disassembly” and construction waste diversion. Spoiler: There’s not nearly enough of either.

Light House works to create regenerative built environments that nurture ecological and human health. Recently, in connection with Vienna House, BC Housing asked the organization to produce a pair of studies that explore how the industry can reduce its waste footprint and design and build buildings with their “end of life” in mind. We recently spoke with Brenda Martens, Light House’s managing director of research and collaboration, for the scoop.

Martens worked on these Light House research studies with project manager Christina Radvak and regenerative building coordinator Shijie Wang.

What is design for disassembly?

Design for disassembly, or DfD, is the consideration of what will happen to either a product or a building at its end of life, and over the course of its life. It takes into consideration how easy it is to repair that product or building, to maintain, or to replace parts of it. For a building, it looks at flexibility and adaptability as well.  And then, at the very end of its usefulness, it considers how easily it can be  disassembled into its component parts so that they can be reused or recycled.

Other than waste reduction, what are the benefits of the approach? 

One of the most important co-benefits is economic. For example, at the moment, I am sitting in a high-performance office chair, and one of the arm pads has worn out, just the top surface under my elbow, so the underlying material is showing through. But the chair is cradle-to-cradle certified, and therefore designed for disassembly and not made of mixed materials that are difficult to separate and by extension difficult to recycle. I don’t need to send this chair to a landfill and buy a new chair, I’m just going to purchase arm-pad replacements for it, and they’re only about $50. So that’s the economic benefit of design for disassembly—you can repair products throughout their life, you can replace just the parts, and therefore you don’t need to purchase a complete replacement prior to realizing both the full utility and the full value of the product. At it’s end-of-life, you may also be able to capture any residual resale value the materials may have!

What are the climate implications of DfD?

Design for disassembly is part of circularity in the built environment. Ideally, everything that you take out of a decommissioned building, you should be able to use either in another building, or in some other use. Reusing this salvaged material reduces the amount of new materials coming into a construction project, which can represent a huge savings in greenhouse gas, especially with wood. Wood is filling up our landfills more than any other single construction material, because it can’t be compressed. It shortens the “life” of the landfill, and then when it eventually anaerobically decomposes in the landfill it emits methane. Additionally, if you reduce the need for new wood in a project, you’re sequestering that carbon in the forest.

But there are reasons why salvage isn’t mainstream practice in construction. Tell us about the constraints.

Everything that you use for the structure of a building needs to be verified to be structurally capable of performing to the specifications set out by the project designers. And if you’re reusing something out of a decommissioned building, all of that material has to be re-graded to determine its structural capabilities. This might seem odd because when you’re pulling out old growth wood, it’s much denser than new wood, its structural capabilities are much higher in terms of compression. 

So every piece of structural wood would need a new stamp on it. That sounds very expensive.

Indeed, it can be because it’s time consuming. The other thing that can be expensive is that you need to pay a lot more attention to the design details. When you’re designing and building, you have a lot of connections in that building between materials, and if those connections haven’t been designed so that you can reverse them without destroying the materials in that process, then obviously design for deconstruction doesn’t work. So there’s additional design time spent in the detailing of buildings for design for disassembly.

What are the best materials and the worst materials for this approach? You mentioned old growth wood, but what else lends itself to disassembly, and what does not?

You want to specify simple materials that are not mixed with other materials. Structural steel, wood, stone—those, to an extent, can all be salvaged at the end of life. As soon as you start getting into composite materials, it becomes less viable. There are a number of panel products that have multiple layers in them. Anything with spray foam is difficult to take apart or, if you can take it apart, the end product isn’t really reusable. It might be recyclable at that point, but not really reusable. Surprisingly panel manufacturers, who you would think would jump on this, do  not make their products to be disassembled.

I’m sensing there may be some clashes in the sustainable building practitioner community around priorities. Can you have it all in a structure?

Not right now, with the building products currently on the market. The product manufacturers haven’t stepped up on DfD, but they probably haven’t stepped up because they haven’t seen the demand for it.

But demand is often driven by regulation. Are there jurisdictions that are on the right track when it comes to enabling demand for disassembly?

To the best of my knowledge, there’s no jurisdiction anywhere in North America that requires design for disassembly.

Okay. What’s it going to take for that to happen?

Awareness, for one, and public sector leadership. If we look at what happened in [British Columbia] with LEED. In 2007, the provincial government stated that any project it funded had to achieve LEED certification. That single step caused an astounding increase in the number of green buildings in British Columbia. It increased the capacity of the industry to provide those buildings, from the perspective of both design and construction. It entirely changed the waste industry’s reporting, because it required identification and measurement of the waste that these projects generated. 

So that was basically an incentive approach.

Yes. “If you want our funding, you have to comply.” I think that that would work wonders for design for disassembly if the federal government, or the province, or even a municipality said that anything built with public money has to be designed for disassembly, because governments are owners for the life of the building, right? This is not a developer that is going to “walk away.”

If that were to happen, would the industry push back?

Yes. They wouldn’t be able to fully comply at this point in time. It would have to be some sort of phased approach where you would have  specifiers saying to their manufacturers or their product suppliers “This is what we’re looking for, can you meet this?” And right now, they’re going to say no. But just like LEED, the manufacturers will respond to demand.

That sounds like a chicken-and-egg market transformation challenge.

Right. But you can create the demand gradually, building up the capacity for industry to deliver. And remember it’s not all dependent on “products,” it’s also design-based. So you can design a building such that you’ve minimized the number of kinds of products in it, and  that you’ve detailed the connections for DfD. That can be done now. 

We haven’t mentioned Vienna House yet. I am certain that the team will divert construction waste from the landfill, but would the project also be an opportunity to try some of these DfD practices?

I’m actually more hopeful for Vancouver House [the corresponding project that will be built in Austria in 2022]. There are so few products available here that would support a design for disassembly approach. But in a recent online meet-up of the two teams, the Vancouver House group spoke specifically about that piece of it.

Finally, I want to ask you about the other piece of research on the quantity of construction materials that end up in landfills. What did you learn there?

The work that we did for BC Housing was based on a database that we compiled of 678 projects that went through LEED certification and had, therefore, recorded all of their waste. The waste number that is sometimes quoted for Canada’s construction industry waste is four million tonnes annually. Our research indicated that that’s not even close. It has been underestimated by at least half, it’s likely nine million to twelve million tonnes nationally per year. So as bad as we think construction and demolition waste is, it’s even worse.

Wow. And again, that’s a regulatory fix, right?

The projects we looked at are all across Canada, and while many of them are urban, some of them are rural, but they all averaged 88 per cent diversion. The industry-wide average is between 15 and 20 per cent. And so there doesn’t seem to be any geographical restriction to builders getting to these high percentages of recycled content. So regulatory agencies could certainly demand that contractors go higher in their percentage of recycling. 

Check out the Light House research studies here:

Design for Disassembly for Residential Construction

Mid- and High-Rise Construction Waste Calculator

Residential Construction Waste Analysis