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The Green Guide to Mass Timber Construction

By Mike Waltman,

The construction industry emits massive quantities of carbon. The estimate comes in at roughly 5.7 billion tons, which makes up 23% of the world’s yearly carbon emissions.

Whether it's constructing offices, infrastructure, or residential buildings, our addiction to development and expansion is one of the most environmentally destructive habits of our society. This hard reality makes finding ways to reduce the environmental impact of construction critical.

(Photo: Marshal Andrews - DPR Construction)

Enter mass timber onto the construction scene. Wood, one of the oldest building materials known to humankind, has made a big-time comeback over the last decade. Advances in technology have allowed manufacturers to produce fire-resistant, wood-based building materials on par with steel and concrete.

The big draw? Mass timber products represent an opportunity for businesses to reduce the carbon footprint of their construction projects.

Going green has become increasingly popular with businesses and governments these days. Organizations are looking at all options on the table when it comes to reducing carbon output.

So, when there's a need to plan that new corporate headquarters or residential development, incorporating mass timber provides the dual value of reducing environmental impact and being aesthetically appealing.

With any new technology, it's important to understand the realities that come with it. The more you know, the greater impact you can have on the environment, society, and your own life.

With that in mind, we’re going to take you into the current world of mass timber. We’ll look into:

  1. What is mass timber?

  2. How does mass timber promote sustainability?

  3. Environmental considerations of mass timber (and a heavy word of warning)

  4. What companies are using mass timber?

Mass timber is moving forward at a rapid pace. As it does, it becomes increasingly important to understand what it is, the opportunities its growth presents, and the information you need to ensure good intentions don’t lead to devastating results.

(Photo: BDP Quadrangle)

What Is Mass Timber?

Just because a building has wood elements doesn’t make it a mass timber project. In order for a building to be considered classified as a mass timber building, the load-bearing structure of the building must be made of wood.

Typically, steel or cement would be used to support the primary weight of a structure, but thanks to developments in the strength and enhanced fire resistance of wood constructed building material, mass timber is now seen as a viable alternative.

The two most common types of mass timber building material are cross-laminated timber (CLT) and glulam beams.

CLT is a large panel that is constructed from many small planks of wood that have been specially conditioned and pressed together using hydraulic pressure and adhesive. The finished product is then used for walls ceilings and floors

(Photo: Stora Enso)

Similar to the manufacturing process used by CLT, Glulam beams are constructed by binding together smaller, specialty panels of wood using mechanical force and adhesive. The final product is a load-bearing column or beam that is used to support the building.

(Photo: GC Lumber)

You won’t typically see CLT or glulam used in the construction of single-family homes. As things stand right now, apartment buildings, office buildings, and other institutional facilities are where you’re likely to find mass timber materials.

For many years, mass timber was only used in buildings with less than 12 floors. Now, with the increase in market demand and technological innovation to support it, mass timber projects are soaring to new heights. Setting the bar for this trend to the sky is the ‘Ascent’ project in Milwaukee, which will be 284 feet and 25 stories after construction is completed.

Across the country and around the world, mass timber projects are popping up with increasing frequency. Upon completion, these buildings proudly wave the green flag of environmental sustainability.

How does Mass Timber Promote Sustainability?

The driving factor behind mass timber’s rise in popularity is the environmental sustainability associated with its use.

No matter how you cut it, constructing a new building will use resources and emit carbon. The reality is we’re not going to stop building anytime soon. So, any measures we can take to reduce the impact of a fundamental function of society is a necessity.

Companies are moving away from primary building materials such as concrete and steel and are instead looking to mass timber as a way to reduce the inevitable environmental impacts of construction.

There are 3 arguments for the sustainability of mass timber as compared to steel and concrete:

  1. It represents a switch to a renewable resource.

  2. It significantly reduces the carbon footprint of a building project.

  3. It promotes the preservation of healthy forests.

A Switch to a Renewable Resource

Steel and concrete don’t exist in the natural world.

(Photo: Taleo Pan)

Steel is an alloy created by fusing carbon and iron. Concrete is a chemically fused mixture of stones and minerals. Extractive mining and industrial manufacturing, both of which require the heavy use of non-renewable resources and fossil fuels, is necessary at all stages of the raw material production of steel and concrete.

Trees, on the other hand, are a naturally occurring resource. Although the extraction process requires the use of some non-renewable resources (logging equipment and transportation burn fuel), it requires significantly less than what’s required for steel and concrete.

After trees are extracted they can be replanted and harvested again later down the line. The same can’t be said for the extracted stones and minerals required for concrete and steel.

Reduction of Carbon Emission

The core argument for the environmental sustainability of mass timber is its ability to reduce the carbon emissions caused by the current use of concrete and steel as primary building materials.

According to the International Energy Agency, when all factors of steel and iron production are considered, “The share of energy system CO2 emissions attributable to the iron and steel sector rises to 10%.” Concrete is used more than just about any building material and contributes to 8% of the world’s CO2 emission.

Mass timber presents an alternative to these two materials. The use of wood helps reduce carbon emissions of a building project in a handful ways.

Less carbon emitted in the extraction and production processes

Although the use of logging equipment, the transportation of trees to mills, and the manufacturing of materials into usable products does emit carbon, it's far less than the carbon produced in the extraction and production processes involved with steel and concrete.

It’s also important to note that steel and concrete require the extra step of manufacturing the raw material itself--a step absent in the use of wood that significantly reduces total carbon output.

Traps carbon that would otherwise be emitted into the atmosphere.

Trees are our greatest allies in reducing carbon in the atmosphere. While trees develop, they absorb large amounts of carbon to aid growth. As a tree gets older, its ability to absorb and store carbon decreases. At the end of the tree’s life cycle, it falls to the forest floor and begins to decay.

(Photo: Daniel Moqvist)

When a tree falls in the woods and no one’s around to hear it, it's unclear whether or not it produces a sound, but it's certain the dead tree will break down and emit carbon into the atmosphere.

When a tree is harvested for use as mass timber, a portion of the tree is left behind to promote healthy soil that is then used to grow more trees. Those new trees, now in the process of growing, increase the rate of carbon absorption and storage for the forest.

The portion of the tree hauled away for use in mass timber construction holds carbon within it and ultimately locks the carbon into the building project.

Lighter weight structure means less concrete

There's no substitute for concrete as the primary material of building foundations. This means heavier carbon emissions in the production of material for foundations is inevitable.

By switching the load-bearing structure of the building to mass timber products, you end up with a lighter weight building requiring a foundation with less concrete, and thereby, you further reduce carbon emissions.

Preservation of Healthy Forests

Deforestation is a pressing concern when it comes to the overall health of our environment. This raises the question of how exactly will chopping down more trees prevent deforestation and promote healthier forests?

In short, the more financially valuable trees are, the less likely it is that forestland will be sold off for destructive development projects.

North America currently boasts one of the most stable forest systems of any continent in the world having more trees being produced than harvested.

(Source: Mass Timber Report)

Logging practices are strictly regulated, and policies are made with the health of forestland, as a whole, in mind. As an additional incentive, it's in the best interests of logging companies to ensure the sustainability of the forests. No more trees mean no more business for the logging industry.

Clear cut development projects, on the other hand, are the biggest threat that exists to forests. Their projects require complete and permanent deforestation. When trees are cut down to make way for commercial and residential ventures, there will never be a forest in that area again. Additionally, the bordering forestland will be adversely affected by the encroachment of human development.

Mass timber products (CLT, glulam beams, etc.) are not the average 2x4 you can find at Home Depot. These are unique building materials that require expertise and specialized equipment to produce. Reading between the lines here, they’re not cheap. These are high-end products that are bought in bulk by contracting companies undertaking mid-to large-scale projects with bigger budgets. This is a far more lucrative and environmentally sustainable business model than selling mass quantities of low-value wood products.

(Photo: Jon Flobrant)

The more expensive and in-demand the end product, the higher the value of the raw material and the less likely the land the raw material exists on will be sold off for alternative use. This is especially true in developing countries where forest land is often looked at as one of the least productive land uses.

Moreover, as demand rises and forests are looked at as a high-value crop, it's possible to see efforts of reforestation undertaken by companies driven by the financial incentive.

The other important factor to consider is that old-growth trees are not typically used to produce CLT and other mass timber products. Small-diameter trees are the most commonly used raw material. This allows for the preservation of the largest foundations of the forest while also serving the necessary purpose of selective brush clearing typically undertaken by forestry management services.

Environmental Considerations For Mass Timber

(Photo: Steven Weeks)

Cutting down trees to promote environmental sustainability is treading a very fine line. While the arguments for how the adoption of this building material can positively benefit forests seem to add up, the whole operation only works well for the environment if sourcing is done the right way.

Whether or not you agree that mass timber construction promotes environmental sustainability is beside the point. The reality is, it's rapidly gaining in popularity and being supported by major companies with substantial financial resources. Like it or not, it's happening, and one of the most pragmatic things we can all do is keep an eye on the way it’s being done.

Forests are the most effective carbon removal systems we currently have. A rise in the demand for mass timber could ultimately help promote the preservation of healthy forests, but if trees are sourced irresponsibly, it could mean the destruction of our greatest allies.

The tragic irony of diminishing the planet's natural ability to remove carbon in an effort to reduce carbon emissions is unacceptable. That’s why we need to ensure the following sustainable forestry practices are being followed as the demand for trees rises.

Polyculture (not Monoculture) Reforesting

There are many logging companies that claim that for every tree they cut down, they plant one, or even two, in its place. Although replanting can be an effective technique, it's only beneficial to the forest’s ecosystem if the tree that's been cut down is replaced by another of the same species. Naturally occurring diversity in tree species is the foundation of healthy forests. It allows for the flourishing of plant and animal life and provides optimal conditions for carbon absorption.

(Photo: Luca Bravo)

When companies looking to reforest an area decide to plant only one tree instead of the naturally occurring diversity of species, it's known as monoculture reforesting. This is a technique used by some logging companies to cut costs. They plant fast-growing, quick harvest trees that will never help to regenerate a substantial forest ecosystem.

Perhaps the most disturbing aspect of monoculture reforesting, within the context of mass timber, is that monoculture forests are nowhere near as efficient at absorbing carbon as natural forests are.

In a worst-case scenario, we could see healthy, carbon-absorbing forests being replaced by monoculture plantations--barren of life and stripped of carbon-absorbing efficiency.

Sustainable Harvesting Practices

In order to ensure that the use of mass timber does the least damage possible to the forest, the logging companies involved in the sourcing of trees need to adhere to strict guidelines for sustainable harvesting.