Growing Good Homes
Learning Objectives:
- Describe how light-frame and mass timber construction can help meet health and safety goals in affordable housing.
- List some ways wood’s design elements can support occupant well-being in transitional housing.
- Discuss mass timber benefits for multifamily housing and single-family housing.
- List the ways in which wood’s carbon benefits help architects reach sustainability goals, while also serving the greater well-being of building occupants.
This course is part of the Wood Structures Academy
CARBON REDUCTION
The built environment is growing at a record pace: An estimated 3.5 million new housing units are needed to make up for the nation’s housing shortage. Buildings and their construction account for 39% of global carbon dioxide emissions. Twenty-eight percent of global emissions are from buildings in the form of operational carbon—the energy used to power, heat, and cool a structure—which can be reduced through energy efficiency measures. Policymakers, architects, developers, and engineers have made significant advances in this arena. The remaining 11% of global carbon emissions attributed to building construction are generated from building materials and construction. This “embodied carbon” can account for half of the total carbon footprint over the lifetime of the building. 40
To reduce the greenhouse gas (GHG) emissions associated with construction, specifiers and stakeholders need to act now to create embodied carbon strategies that reduce environmental impacts from buildings we’ll use well into the future.
The threats of climate change—which are already being felt across the globe—carry a greater weight for low- and moderate-income groups and communities of color. The solution for affordable housing, therefore, carries with it the environmental weight of constructing more housing. This section looks at how wood’s ability to store carbon makes it an ideal product for buildings when it comes to meeting sustainability goals while supporting the health, safety, and well-being of those who require affordable housing.
In the face of climate change and the most recent Intergovernmental Panel on Climate Change (IPCC) report, architects are seeking to decarbonize the built environment.
By now we know that climate change is one of the biggest threats to the planet. In the first installment of the 2022 IPCC report, the working group of scientists stated that climate change is widespread, rapid, and intensifying. Some of the changes are irreversible. However, strong sustained reductions in emissions of carbon dioxide and other GHGs can limit climate change. Building construction is a prime place to start.
One key area for change is the specification of building products with low GHG emissions, including the replacement of concrete and steel with wood. The IPCC confirms that expanding the use of wood in multistory buildings could help mitigate climate change because wood-based systems represent 10%–20% less embodied energy41 than traditional concrete systems.
Wood products are approximately 50% carbon by dry weight.42 The use of wood products in buildings provides an additional environmental benefit by storing carbon removed from the atmosphere. This ability to store carbon makes wood an ideal material for buildings, which are designed for long service lives. This storage of carbon is a unique environmental attribute that does not exist with other structural products.
Embodied carbon is determined by conducting a life-cycle assessment (LCA) of a product, assembly, or building throughout declared life cycle stages. Embodied carbon is measured for each stage of the product’s life cycle, allowing comparisons across any combination of stages. As buildings become more energy efficient, the upfront embodied carbon from materials begins to account for a higher proportion of a building’s carbon footprint.
Wood has other sustainable advantages beyond storing carbon: Unlike other building materials, wood is a renewable resource that can be harvested responsibly without diminishing its source. Data shows that global regions with the highest levels of industrial timber harvest and forest product output are also regions with the lowest rates of deforestation.43 Demand for forest products can actually increase the size of forests rather than decrease them. The annual rate of trees harvested for timber in the U.S. is less than 2% of the total available volume. Just a 1% increase in annual demand for industrial wood products could drive 77,000 square miles of new sustainably managed working forests.44
Forest management in the United States and Canada operates under federal, state, provincial, and local regulations to protect water quality, wildlife habitat, soil, and other natural resources. Training, continuing education, and certification for loggers and foresters support continuous improvement and the use of best management practices. Regeneration practices ensure forests have enough natural seeds, seedlings, and tree sprouts to grow for the future. Active forest management, or forest thinning, mitigates wildfires and cuts carbon emissions. It replenishes area waterways, expands wildlife habitat, and creates jobs in rural areas. And, finally, harvesting and replanting increases carbon sink abilities as younger trees sequester more carbon.
For young people moving into multifamily residences, the appeal of wood is a product of a concern for the environment but also a matter of quality of life and personal identity. In the face of climate crisis, younger generations want to occupy buildings that are sustainable in order to act as part of the solution to mitigate climate change. But they also want to inhabit a space that aligns with their philosophy at an aesthetic level, signaling sustainability through exposed beams or other wood interior elements—a design that’s in alignment with their values and where they can enjoy feeling at home.