Construction Waste
MALCOLM TAYLOR
| Posted in General Questions on
I often see proponents of different construction methods, like pre-fabrication or SIPS, using the efficiency and reduction of waste as part of the appeal. Can someone explain the rationale behind that claim?
All of the materials I buy, like dimension lumber, sheet goods, pipes, wire etc, are manufactured in certain sizes. Whether I cut them to length on the site or in a shop doesn’t alter that. Where are the efficiencies?
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Replies
Malcolm,
You're right that "reduction of waste" calculations are notoriously difficult to perform.
You're also right that manufacturers' claims about "less waste" are often greenwashing, and need to be taken with a grain of salt.
The idea is that precut SIPS can be installed relatively quickly leaving you with an insulated shell. We spent January and February framing a home in subzero weather; as soon as the roof was on and the windows in we set up a construction heater to complete the framing & sub work. A SIPS shell (ideally scheduled) would have shortened the job by a month and allowed the crew to work in relative comfort. The waste panels would be at the manufacturer, and there would be much less construction waste at the site. The downside is the increased cost. We've also tried prebuilt stud wall panels, but insulated panels are the ideal solution. In terms of just framing, a stud wall panel manufacturer will save and reuse all the plywood and 2x scraps, instead of being tossed into the dumpster when you're framing on site. In Europe they have been preassembling house parts for years; we're just starting to get serious about it in the US. The shortage of young carpenters entering the field may change this dynamic.
Bob, I can understand the first argument, you may move the waste from the site to a manufacturing facility, it's the second part I don't get. On site I never cut down large dimension materials to get blocking or small pieces. The waste occurs because of the difference between their nominal lengths and what I need. What gets used up is always less than what is generated. There isn't much point in moving the scraps or storing them for the next project, because the same thing will occur - and that surely holds true of building in a factory.
The only way I can see of reducing waste is to design and build using modular dimensions that correspond with those of the materials. Otherwise someone ends up with it. You just don't see it on site.
I've never seen the inside of a SIP or panelizing facility but I have toured several window factories and I think it's fair to say that a large scale manufacturing facility is capable of doing waste management very efficiently indeed, whether that means more complete use of offcuts or an effective recycling process. The relative gains over a well-run construction site though might be hard to quantify, as Martin aptly points out, and on the other side of the scale is the sustainability benefit of using local labor and helping preserve local skills. Support your local farmers' market? Support your local craftspeople too. Building skills are indispensable to a vibrant, sustainable local economy.
If you've got a real production manufacturing operation you really can reduce waste: For example, you can order lumber in the actual sizes you need. And you can keep the scraps dry and organized much more easily than you on a construction site.