All over social media, enthusiasts are celebrating “PSL” this autumn season. At SweisKloss, PSL isn’t about our favorite Pumpkin Spiced Latte. In architectural terms, PSL, or parallel strand lumber, is when parallel wood strands are joined together using structural adhesive. A timber revolution is sweeping the construction industry as wood’s sustainability and environmentally friendly attributes become a key tool in reducing waste.

Mass timber “is the name given to the various different types of engineered wood that can be used as structural building materials” (dezeen). Layers of wood are joined to form strong panels such as glulam (glued laminated timber); CTL (cross laminated timber) is most commonly used and often called super plywood; DTL (dowel-laminated timber), made from layers of softwood and used to construct floors or roof decks; and PSL usually used for long-span beams or columns that need to hold a lot of weight. (dezeen)

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With the built environment being responsible for 37% of the energy-related greenhouse gas emissions (cnn.com), timber’s small carbon footprint makes it increasingly popular. “Wood's ability to sequester carbon … means timber has a significantly lower embodied carbon than concrete and steel” (dezeen). Harvested through responsible and sustainable forestry, wood is a unique renewable building material. But the environmental impact does not stop there. Some lumber mills use wood byproducts as bio-fuel for their facilities reducing the fossil fuel emissions in the production process (wagnermeters.com).

Wood can also save time and money. Timber tends to be lighter than concrete and easier to transport. It also allows for quicker and cleaner assembly on site. Lasse Lind of GXN explains that because it is prefabricated, in theory, it is possible to be more precise and cut down on waste. In the full timber hotel extension in Bornholm, Denmark, GXN “even used offcuts from the CLT used for the building to create furniture and furnishings,” explained Lind (dezeen).

Photos of Green Solution House 2.0 Courtesy of Dezeen

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Mass timber + tall buildings = big business. Milwaukee currently boasts the world’s tallest timber tower, the 25-story Ascent MKE, standing at 284 feet (cnn.com). According to designer Korb + Associates Architects, “the timber in Ascent sequesters enough CO2 to be the equivalent of removing 2,400 cars from the road for a year” (dezeen). Mjøstårnet, built in Norway using locally sourced wood, is the second tallest tower and incorporates glulam columns and elevator shafts made from CLT. The third tallest, Vienna’s HoHo Wien, is a mixed-used building with “75% … made from wood, including walls, ceilings, floors and column” (dezeen). Coming soon to Perth, Australia, will be the world’s tallest hybrid timber tower in 2025.

Photos courtesy of dezeen: Ascent

Photos courtesy of dezeen: Mjøstårnet

Photos courtesy of dezeen: HoHo Wein

From acoustics to insulation, other attributes also make wood an appealing material for commercial and residential spaces. Timber is lighter than other construction materials, requiring less expensive foundations than needed for bricks or concrete. Additionally, wood has a higher insulation rating than steel and plastic, requiring less energy to maintain heating or cooling. Sound absorption is another characteristic of wood that makes it ideal (wagnermeters.com). Architects also cite the material’s ability to withstand low-intensity natural disasters such as earthquakes, storms and hurricanes (usframing.com). And of course, aesthetically, wood’s variety of grains, textures and tones can create a distinct character to any design.

Wood does have its drawbacks too, fire safety being a major concern. Timber is combustible and can also become a source of fuel for a fire. Additionally, “the external flames emitted from a burning timber building would be larger than those of a concrete structure, increasing the risk that the fire could spread to surrounding buildings” (dezeen). Climate and weather also effect wood materials. In wetter climates, wood needs protecting and treatment to prevent it from expanding, warping, and growing fungus.

What’s old is new again-- While timber has been around for ages, it is having a resurgence in urban architecture. According to Lasse Lind of GNX, “As timber buildings become more popular, …. as well as having an impact on carbon emissions, the material will also impact the way that buildings look, behave and feel” (dezeen).

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