Wood: the Pluses, the Minuses, and the Neutrals

This blog is intended for anyone who’s interested in being more environmentally conscious and wants to further analyze how everyday things are made.

When we think about building materials we usually think about wood. It's one of the most sophisticated materials that has been around for more than 400 million years. Wood is a uniquely renewable resource because it requires almost no energy to make, but changing its form from a tree to a house requires taking a closer look at the process. 

The process of making a 2x4 starts way before hitting the shelves at hardware stores. The harvesting process consists of selecting mature trees to sustain forest health. The logs are then loaded into trucks and transported to a sawmill where they are measured to estimate the volume of lumber it will produce. A machine will remove the outer bark from the logs. That bark is mostly used for fuel or mulch while the log is being processed. A computerized band saw cuts through the log into thick slabs and edger machines remove uneven edges and trimmers cut the boards to standard lengths. There are other impacts to keep in mind other than energy. For example, there's almost no waste generated in the milling process but there's still some waste produced from the packaging material. 

The most challenging part of using wood for construction is its relationship with water. More than 50 percent of a tree is made up of water. Wood needs to be dried before it can be used for any purposes because the percentage of water in the wood affects its dimensional stability, durability, and strength. You don’t want a house to rot or fall down. As wood dries, it reaches the FSP (fiber saturation point) which is approximately 30 percent moisture content. Anything above this point, the wood is stable. Anything below it will cause the wood to warp or shrink. Wood's ability to bend and flex without breaking makes it different compared to other building materials. But a 2x4 piece of wood is not as strong as concrete or steel which is why it's not used as framing material for projects that have really high loads.

Engineered wood is a durable and stable material manufactured by gluing together thin layers of wood and offers moisture resistance compared to standard wood. Cross Laminated Timber (CLT) refers to a type of composite lumber technology by bonding layers of lumber boards in alternating grain alignment. Cross laminated timber panels are made of cross laminated large lumber which makes it strong, stable, and able to handle load on all sides. Engineered wood products eliminate knots found in solid timber and make the forest products industry more sustainable.

The good thing about wood is its ability to sequester carbon. Carbon sequestration is a natural process where trees remove carbon dioxide from the atmosphere through photosynthesis, converting it into biomass and storing it in their trunks. Approximately 50 percent of the dry weight of wood is carbon which remains stored even after the tree is harvested and converted into products. Using wood for construction can reduce the overall carbon footprint of buildings with wood framed buildings releasing 26 to 31 percent less carbon than concrete and steel alternatives. Overall, wood is a better alternative than the two because wood stores the carbon contrary to concrete and steel releasing massive amounts of carbon during production, making wood a cleaner alternative long term.

Works Cited:

Lesson 13: Forest to Lumber, BBE 1002, UMN

Lesson 14: Moisture and Strength Pertaining to Wood Use, BBE 1002, UMN

“The Wood Manufacturing Process: From Forest To Finish.” Duffield Timber, 22 Jan. 2024, https://duffieldtimber.com/the-workbench/timber-trends/how-is-wood-manufactured-and-processed.

Using Wood for Good – How Timber Can Help Fight Climate Change - Creating Tomorrow’s Forests | Restoring Biodiversity by Creating Habitats and Planting Trees. https://www.creatingtomorrowsforests.co.uk/blog/using-wood-for-good-how-timber-can-help-fight-climate-change#:~:text=Although%20all%20plant%20matter%20absorbs,How%20Do%20Trees%20Store%20Carbon.