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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.

Asked by TJ Elder
Posted Sep 9, 2010 3:45 AM ET


7 Answers

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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."

Answered by Martin Holladay
Posted Sep 9, 2010 5:40 AM ET


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.

Answered by J Chesnut
Posted Sep 9, 2010 9:06 AM ET


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/

Answered by Riversong
Posted Sep 9, 2010 9:44 AM ET


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.

Answered by TJ Elder
Posted Sep 9, 2010 3:58 PM ET


"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!

Answered by Riversong
Posted Sep 9, 2010 7:08 PM ET


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.

Answered by TJ Elder
Posted Sep 9, 2010 7:51 PM ET


For what it's worth, Thomas Jefferson is my actual name.

Better that than Richard Nixon ;-)

Are you a descendant of Sally Hemings?

Answered by Riversong
Posted Sep 9, 2010 8:05 PM ET

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