The Efficient Materials Trap
Efficient materials can sometimes seem to be the ideal path for green building. If we can find a way to more efficiently produce the materials we need to build our buildings, it would seem that we would be well on our way to reducing our impact on the planet.
For example, rather than using lumber sawn from old growth forests, engineered lumber and I-joists make more efficient use of lumber resources and can take advantage of smaller trees. Instead of needing to find trees old enough and large enough to produce a piece of 2 x 12 lumber, an engineered I-joist can be made that uses chipped wood and glue manufactured wood board (like oriented strand board) and narrow, laminated strips of wood (again, made of smaller pieces of wood and glue). These engineered joists are lighter, straighter, and less prone to warping, cupping and twisting than even kiln dried sawn lumber is.
Engineered joists would seem to be an ideal solution. They are made from small, rapidly renewable trees, which can be farmed, rather than requiring the logging of large trees. Builders and carpenters like them because they are more regular, and they make for flatter floors, straighter walls, and truer roofs, with less variability when they are installed and less likelihood to move and twist over time.
But there are downsides to these more efficient materials.
While a house built with 2 x 12 floor joists may be able to be disassembled and those pieces of wood re-used, recovering engineered I-joists - which are more fragile - is a much harder task. It is much more likely that the engineered joists will end up in a landfill at the end of their life.
Efficiency also means that they are suited only for the purpose they are designed for. If you needed to cross a 15-foot wide stream, you could lay down a 2 x 12 on its side and walk across it; it would bend in the middle, but it would be strong enough to hold you even if it was lying on its side. An engineered wood I-joist of the same length, if laid on its side, would likely drop you in the water when you reached the middle; it doesn’t have any strength other than the direction in which it is designed to be used. So while it saves on material, it also reduces the flexibility with which it can be used.
Similarly, do highly efficient vehicles make it easier for people to do more driving? If even more people were driving fuel guzzling SUVs, the constricting supply and spiking prices for gasoline would be forcing even more people to take a closer look at their driving habits and trying to reduce their overall use.
The increase in efficiency has helped to make it possible to build the overblown tract houses that are sprawling across the landscape across the country. Without the development of these materials, lumber availability and costs would make it much harder to build the numbers of oversized houses at such relatively inexpensive prices. If solid sawn lumber was the only building material available, the growth of “lawyer foyer” houses (as one friend refers to them) would be much more constrained.
A little bit more efficiency sometimes becomes a license to be a lot more wasteful with the materials we consume. Efficiency can provide significant benefits, but alone, it is not the entire solution.
“So while it saves on material, it also reduces the flexibility with which it can be used.”
So, the high efficiency vehicle encourages the wasteful to drive more than if they owned a gas-guzzling SUV. Maybe it does, maybe it doesn’t. However, what the U in SUV does for the owner is allow the flexibilty of the 2 x 12 in lieu of the rigidity of the engineered I-Beam. U = UTILITY, right! As such, one can use an SUV to accomplish all of the usual getting around tasks but he can also add towing, hauling, and improved comfort to the list. The SUV can tow the livestock trailer, the tool trailer, or maybe the boat on the weekend. It can make a run to the lumber yard and haul thousands of pounds of materials in one trip instead of multiple trips. It can take half of the soccer team to practice in one - instead of 5 - vehicles. Sure they use a bit more fuel, but the econo-car’s limitations may not suite every buyer.
Good post, Philip.
Terrific post.
I also worry about how long they will last before the glues dry out and they fall apart under your feet. A properly framed house with real lumber will last hundreds of years; I doubt these things will last thirty.
Interesting post. I am reminded of the debate concerning the estimated energy wasted making plastic silverware vs. washing your fork when you’re done.
On a side note, I have to disagree about the “properly framed house with real lumber” lasting longer. These glues are probably NOT going to break down when used appropriately. For all we know they could be like styrofoam and in fact take longer or never break down.
As far as structural integrity, it is widely known man-made boards shrink and expand less than dimensional lumber. If you ever check out the joist system of an old home, you’ll see countless areas where the nails have started pulling out from joists due to the shrink/expand cycle, causing gaps at nailed intersections, and inevitably failure. These engineered products help reduce the damage due to repeated climate change and wind racking.
On the other hand, these engineered joist systems place an extra burden on both architects and flooring installers. Herein we lose that efficiency; the design limitations caused by increased deflection, unacceptable/unconventional joist spacing, and added preparatory work for conventional flooring make for a troublesome and increasingly expensive installation.
The I-beams do make handy wheelbarrow ramps though.
Having designed many house additions w/ both traditional lumber and engineered lumber, I (and our field management) are quite happy with engineered lumber. It’s dimensionally stable, easy to place, and very reliable. On my end, there’s no extra design time required for engineered lumber. As a practice, we will use engineered lumber and pre-manufactured trusses as often as possible.
I would tend to agree with the theory that traditional lumber may be more adaptable for future use, and it especially makes good sense to contemplate what may happen to all building materials at the end of it’s life in a house, but a good deconstruction crew will be able to salvage a tji just as well as a piece of 2×12 (usually the plywood gets torn up by the adhesive, not the tji). The bigger problem is the adhesive. Wouldn’t it be nice to have a good zero VOC adhesive which could be dissolved in a ecologically humane way, once it’s useful life was up? Traditional Japanese wood joinery techniques with post & beam construction doesn’t even use metal fasteners, and it can last hundreds of years if well maintained. I’m sure we could come up with a way to build with the end-use in mind.
Regardless, as was mentioned, I am currently much more concerned about all the perfectly good lumber being thrown into our landfill on a daily basis as a result of houses being torn down to make way for a new mcMansion.
Thanks for the post - and the general reminder that efficiency is a double edged sword; and must be used properly if it is to both help us and our future generations.
Matt Dirksen
Case Design/Remodeling, Inc.
Have any of you ever toured an industrial-type sawmill, a plywood mill, or an OSB manufacturing facility? If not, you would be amazed at the speed and efficiency of the tree-to-product processes. You always leave these factories wondering how they grow enough trees to support what goes on in just one of those places. I have watched large timber blanks go into a computer-controlled rip saw and come out the other side as dimensional lumber in a grouping of different sizes that make the most efficient use of the board. It happens in seconds. I have seen log-sized lathes peel the thinnest of skins from a log for use on the outer layers of plywood. I have watched the hot-oil stack presses cure both plywood and OSB sheets in minutes. The rip saws and gang saws make quick work in taking the oversized sheets down to the standard 4′ x 8′ pieces we see at the lumber yard.
So, why mention any of this? The other side of the coin is the completeness of the processes. Absolutely nothing is wasted. Bark is used to fire boilers. Chips get sold to paper mills. Sawdust becomes particle board or MDF. It is truly amazing. And even more amazing is the industry’s committment to replanting more than is used to guarantee its future.
BTW, I also spent two years in a large paper mill. It is way cool, too.