Is engineered lumber more “green” than solid sawn?
Anyone reading this website will be familiar with the green angle for engineered lumber, using wood more efficiently. And of course there are technical advantages to I-joists, especially for longer spans. However I feel some influence by Mr. Riversong to steer toward low-tech solutions. Solid sawn lumber is certainly lower tech, and free of added glues or other chemicals. Should be better for IAQ. A solid wood joist may or may not last longer than the 3/8″ wide OSB web of an I-joist. It would certainly last longer in a fire or if it got wet. Does this add up to a more environmentally responsible choice, or does the I-joist win with the smaller trees argument?
This question is primarily about floor joists. Please share your thoughts.
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Replies
Thomas,
This question is discussed at length in the GBA Encyclopedia, on these pages:
Roof Framing Choices
Engineered Lumber
Among the points made in the Encyclopedia:
"The 2x10s or 2x12s that are often used for rafters come from big trees and represent more raw material than alternatives such as roof trusses, I-joists, or structural insulated panels (SIPs). Yet the use of 2x10 or 2x12 dimensional lumber for roof framing may still make sense in regions of the country that have local sawmills. Delivery distances for dimensional lumber from local sawmills are short, saving transportation energy."
"Engineered lumber is usually more expensive than dimensional lumber. And connections between engineered framing members are made with metal connectors, which adds to the cost and may require special ordering. ...
"Rafters made from dimensional lumber can be nailed in place quickly, but I-joists must be fitted with web stiffeners to accommodate metal hangers. Similarly, cutting the bird’s mouth in rafter tails may take a jig or two, although the technique is basically the same as working with sawn lumber. ...
"The commercial use of small-diameter trees is not always an environmental plus. By creating a market for small-diameter trees, the manufacture of engineered lumber can promote the harvesting of trees which might otherwise have been left alone. In some areas, this increases the pressure to clear-cut forests rather than engage in selective logging."
When talking about how benign or damaging building materials are we need to understand their origins, what the impacts of producing the materials are and also what sort of "world" the use of these materials contributes to.
I'm skeptical of the reasoning that using engineered wood is better for the environment because it can use smaller dimension trees and wood scraps. I think because of the demand for these materials their production uses as much virgin material and has as much impact on forest ecosystems as sourcing larger dimension lumber.
The correct mindset is to support forest management practices that maintain a healthy forest ecosystem that supports the livelihood of the local residents that make a business of selling the wood. In my opinion only forest certified by the Forest Stewardship Council (FSC) represent these practices. This is akin to 'organic' farming. So in this contest producing larger dimensional lumber can be done without degrading the overall forest. The supply might be limited but our economy needs to transition to work within limits that don't destroy ecologies that took millennia to develop.
Engineered lumber is as much glue as wood. It is easier for me to imagine the forests, mills, warehousing and freight that produce and distribute solid lumber. I have less an understanding of manufacturing glues. Where do the materials come from? 3M is a large presence in my area and in our local lakes their chemicals tend to turn up so we don't eat the local fish.
Concerning larger spans, solid wood trusses are as common as engineered lumber. Older housing stock were designed without spans that require anything over 2x8 lumber. Its the desire for more (and not the need for more) that pushes the use of more engineered solutions in most cases.
What! Live within limits? That's downright Un-American!!!!!!!!!!!!!!!!!!!!!!
It's speculated that one of the reasons that island nations rank high on the Happy Planet Index (health and happiness of the population divided by the per capita ecological footprint), is that island people live their lives within finite boundaries and obvious limits - and build a successful life within those constraints. By the way, "undeveloped" Latin American nations also ranked high, largely because of the emphasis on strong local community.
Happy Planet Top 20
1 Vanuatu
2 Colombia
3 Costa Rica
4 Dominica
5 Panama
6 Cuba
7 Honduras
8 Guatemala
9 El Salvador
10 Saint Vincent and the Grenadines
11 Saint Lucia
12 Vietnam
13 Bhutan
14 Samoa (Western)
15 Sri Lanka
16 Antigua and Barbuda
17 Philippines
18 Nicaragua
19 Kyrgyzstan
20 Solomon Islands
150 United States (out of 178)
Bottom line is that a healthy ecology is maintained only by healthy communities, and that people and place are inextricably intertwined. It's insane, for instance, to "conserve" wild forest regions by evicting the native populations, as some international conservation groups are advocating. But it's equally crazy to try to save the environment without creating a just and equitable social order.
And, Chestnut is quite right that the FSC label is like the "organic" label (once the gov'mnt got hold of it) - each a good idea partially perverted by the scale of the program and insufficient oversight. A number of prominent environmental organizations have withdrawn or questioned their support of FSC, and FSC-Watch documents numerous and quite serious violations of sustainable standards within the program: http://www.fsc-watch.org/
The "Happy Planet Index" is skewed toward poor countries, because a country's ecological footprint is the most important criterion. Poor people don't have much impact on the planet. And human rights abuses are largely ignored by the Index.
Garbage in equals garbage out.
What I'm considering is to use glulam beams at 8' to 10' centers and then span between them with dimensional lumber, maybe 2x8 joists. The alternative would be running all joists the other way at the longer span (i.e. the beam span). It would be relatively impractical to use dimensional lumber for the longer span (too far for a 2x12), but easy to do with an I-joist. If the goal is to choose solid lumber wherever practical, then maybe this is the strategy, finding a way to make dimensional lumber work for the spans and loads.
"In matters of style, swim with the current, in matters of principle, stand like a rock"
- THE Thomas Jefferson
If it's decidedly more green to use locally-sourced sawn lumber than factory-manufactured "engineered" lumber, then that's a principle worth standing firm upon. In residential applications, I consider any need for greater spans than what sawn lumber can manage as a design flaw - putting form (or vanity) before function and putting quantity above quality.
If you can't span a floor with 2x12s to a center bearing wall or built-up beam, then the house is too large. Go back to the drawing board or Just Say NO!
I guess the above response is what I was looking for, to begin with the limitation of a certain size of board and design around that.
The span in question is 18'-6" clear, which is across the width of the house at this point. It would be possible to have interior columns and reduce the span that way, but the columns would be a little awkward. I'm going to get pricing on this with glue-lams making the longer span and light joists spanning between the beams. Of course it's also true that quirks such as a column in the living or dining room can become a favorite feature in the design.
For what it's worth, Thomas Jefferson is my actual name.
Better that than Richard Nixon ;-)
Are you a descendant of Sally Hemings?
Aside from the environmental impact of using engineered joists etc. ; we have no direct knowledge the glues and binders will last for a very long time.Whatever long means to the viewer. In other words,do we really want to depend on the life cycle of glue to hold our buildings together ? ?
Actually, we do. The adhesives used are pretty well understood. The automotive industry has been using adhesives where they used to use welds in many places because the adhesive actually performs better.
We’re not talking about Elmer’s glue here folks :-) modern construction adhesives do a good job.
Bill
Fred,
In for a penny, in for a pound. Unless you want to use solid wood for subfloors. roof, and wall sheathing, you end up relying on adhesives for much of the structural integrity of the building.
Even if you forswear those products, and also find a substitute for gypsum board as an interior surface, and sheet goods for cabinet carcasses, you still need to figure out how to plumb, air-seal and ventilate without similar adhesive reliance.
You can certainly go that route, but it seems a bit extreme to limit the use of certain materials in the absence of any evidence their reliance on adhesives is a problem.
The earliest three buildings constructed from laminated timbers in the mid-eighteen hundreds are still in use.
Fred, my team forswore those products; used solid wood for subfloors, roof, and wall sheathing; identified a few superior options to "gypsum" board as an interior surface; and plumbed, air-sealed, and ventilated without similar adhesive reliance. It's challenging, and I couldn't be happier. I suggest, nevertheless, you take the hint from Malcolm and Zephyr7 and get with the program - they're relentless with their logic, and the distorted market and fiat-money forces make it a no-brainer to go with petrol-based everything at the moment. The earliest cars constructed using adhesives from the mid-eighteen hundreds are still in use... okay, I made that one up - but still...
Yep, us fiat-money guys lurking just over the edge of the flat-earth.
Now you're conflating, Malcolm. Oh, well... it was a good run. Just don't run over the edge!
Greg,
Well we are either having a serious discussion or we are not. Fred thinks the adhesives in laminated wood products won't have a long lifespan. That what we were talking about, not the evils of twenty-first century capitalism.
Touché, mon frère - point well taken: You nailed the subthread, while I kept going on the overall question of whether it's "green" (a point on which I keep pounding away, for better and worse).
My 50 year old house uses glu lam beams and glued up t&g decking for floors and roof
The beams extend out of the house to support the deck. In repairing I found that the glue effectively separated the layers limiting rot to the top layer of the beams. Similar houses with solid wood beams have had their entire decks permanently cut off due to the rot in the beams.
Of course if they had used metal flashing originally.....
Similarly the small amount of rot on the roof was usually limited to the top layer
Glue works, you can have other related questions, but I think the lifespan is not in question.
WE started using plywood sheathing, when?
dunno bout 9 year old thread resurrection
I think plywood came out a bit after World War II during the reconstruction boom.
The auto industry started using more adhesives in the 80s. It’s not a new thing. People tend to not trust what they don’t understand, but modern materials are often superior to the “natural” products when used correctly.
Don’t even get me started on the socialism stuff. Talk to anyone who’s ever lived under that type of system and you’ll know it’s a miserable failure.
Bill
Bill,
I think the more discussions we can steer clear of the shoals of potentially divisive and distracting political debate the better. People are free to use the techniques and knowledge they find here to create whatever housing forms they think make sense. If they can't find somewhere else to discuss the broader unrelated issues they think are important, they aren't trying very hard.
Yes, I agree with you. Best to stick with construction related stuff and leave the other stuff elsewhere. Other stuff does seem to creep in occasionally which I suppose is human nature, but I’ve never seen it get out of control here which is a good thing.
It does seem there have been more posts as of late questioning some of the more modern materials but maybe I’ve just been paying more attention lately.
Bill
It makes a lot of sense to me to look at materials for their environmental impact, but I think a lot of the questions around new methods of building comes from a deep and understandable unease with how people see the modern world unfolding right now. However, I don't think the problems assailing us are solved by a retreat to the past or nostalgia for some "purer" form of building.
I’ve always said everything is a tradeoff. The older building methods tended to be very energy inefficient in terms of heating and cooling the structure. Newer methods are much better about that. You could still build a stone castle, for example, but you’re heating bills would be huge, and the labor to build the place would be unaffordable.
A lot of the decisions about which tradeoffs to make will come down to what is important to any particular builder. Materials that may require less energy to produce may be less efficient over time in regards to ongoing energy use of the structure. Any building is really a pretty complex system with a lot of interacting parts so there is a lot to think about.
Bill
I'm still waiting for that AI level algorithm to inform us of the precise methods and materials to best build with (for the health of the planet and its inhabitants).
Of course things start feeling very 'down the rabbit hole' when one starts thinking like this, for the parameters to the discussion are all but gone.
In lieu of this, I'll echo what J Chesnut said in 2010; that using smaller trees isn't necessarily better if we can manage our forests for larger growth, which has other implications on the ecosystem as well.
This still gets real complicated real fast, as there are many hard-to-quantify values involved with forests (playing roles of farm, habitat, CO2 sink, recreation land, etc).
To echo Bill; for every choice we make, it should be weighed against alternatives. Engineered lumber might be considered quite green if used in place of steel (mass timber applications).
It would seem to make some intuitive sense to use glued lumber in applications where the forces we are resisting and sealing goals we are after are best dealt with by 'sheets' of material. Trees don't grow as sheets. They do, however grow as long (tall) structures (beams).
If only we could get our economics to somehow more closely track real value and eliminate the innumerable externalizes we currently deal with. That'd be the algorithm.
I really don't think tree size has anything to do with anything
The larger the dimension lumber you need, the more waste there is. You are cutting rectangles out of a circle, more complicated a tapered cylinder. The waste is huge. Pick up that pile of smaller lumber and what to be turned to pulp can be structural lumber. The glulams above my head are over 20 foot long 4x12. They are made of 8 foot long 2x4. They are actually smaller than the equivalent solid beam because they are significantly stronger, due to not having to account for flaws or non parallel grain.
20 years ago my designer told me they won't use 2x12 anymore, the TJI are stiffer, stronger, and don't shrink and cause creaks and sags.
"I really don't think tree size has anything to do with anything"
It may or may not.
You make great technical points, though there's more to the story in regards to forest management and the economic demands which dictate said management.
In other words, if there is demand for larger trees (which are indeed needed for solid-sawn lumber, not sure how one could argue otherwise?) then there would be economic incentive for growing more mature forests.
On the other hand, if manufactured lumber was the norm, then the demand is more or less for pulp/chip only, and an entirely different sort of management may be employed (one that is arguably worse, though there's a whole other debate to be had here).
The middle ground (and reality) exists where one still saws lumber from a tree and then uses tops, limbs, offcuts, etc for engineered lumber and other products. Modern saw mills do a decent job of maximizing cuts, though there is always waste.
Perhaps the point is made that very large structural members are not the best use of solid lumber, but there is a lot of other in-between applications.
If we could sustain the building industry with limited farm-style crops (using mostly engineered lumber perhaps) and still maintain large healthy forest ecosystems (perhaps managed under different economic incentive) then that would seem like a win to me. Whether that's feasible, I'm not sure.
As a Mainer, I can attest to seeing how a region with significant forest land can still have a fairly significant want for forest maturity. It is cut with enough regularity that one truly feels 'in the sticks' in more than a few places.
Remember that the original forms of engineered lumber were intended to better deal with waste. Particle board used sawdust, for example. There is always an economic incentive to be as efficient as possible, so a lot of the waste from the sawmill is going into products like particle board and MDF. That’s a good thing!
Remember also that modern lumber is generally farmed — they’re not out cutting old growth forests. They’ll cut land (a harvest), then replant. The only downside is that the lumber companies tend to favor fast growing species since that shortens their time to harvest, but those fast growing species don’t make as dense of wood so the resulting lumber isn’t as strong.
Bill
" a lot of the waste from the sawmill is going into products like particle board and MDF. That’s a good thing!"
couldn't agree more.
"Remember also that modern lumber is generally farmed"
Yes, that is the crux of the issue. How we manage (or farm) is related to what forest products are in demand (coupled with other economic values of the forest).
One could maybe (loosely) liken it to mono-culture ag crops. Take corn for example. It is used so extensively in processed foods that growing large expanses of mono-culture apparently makes economic sense (let's ignore subsidy for the discussion). Some of this has simply to do with economy of scale of specialized processing.
Similarly with forests, if we focus entirely on processed goods, we are likely to start seeing management focused with processing in mind - something that changes the 'farm' management practices. To tackle whether these management changes are good or bad is to wade into deep water; but I think most people will be-able to look into this and see some of the potential issues involved.
To be clear, use of solid-sawn lumber does not absolve us of potential management issues; they are just a different set of issues with different solutions. I certainly see the path forward
involving use of all arrows in the quiver.
RE: local lumber..."the use of 2x10 or 2x12 dimensional lumber for roof framing may still make sense in regions of the country that have local sawmills. Delivery distances for dimensional lumber from local sawmills are short, saving transportation energy."
I used a lot of local dimensional lumber years ago working on barns; it came from a sawmill 3 miles away. It was much less expensive than the dimensional lumber from a standard builder's lumber yard. But it was hemlock, it was rough, and it varied widely in width and thickness, compared to dressed SPF imported from Canada. So cheaper and local, but much more work.
Bob,
As a substitute for the framing package you get from a lumberyard I agree. However, I've got three small sawmills within ten miles of my place that will custom cut any species to any size from trim to heavy timbers. Their mills are all computerized and cut to very exacting dimensions. The surfaces of the lumber is well enough planed that I often don't need to sand before applying finish.