Energy Efficiency

For the Bethel School District, energy efficiency is an objective because of the cost savings. However, it underscores wood’s benefits from a thermal performance perspective.

Between 2004 and 2011, the district reduced its energy use by more than 7.⁶ million kilowatts and saved $4.3 million in utility costs—equivalent to the cost of electricity for 15 of its elementary schools for one year. It reported an 81 percent ENERGY STAR rating overall, and several of its 17 elementary and six junior high schools had a rating of between 95 and 98 percent. All of these schools are wood-frame.

Wood-frame building enclosures are inherently more efficient than steel-frame, concrete, or masonry construction—because of the insulating qualities of the wood structural elements, including studs, columns, and beams, and because wood stud walls are easy to insulate.⁹ Options also exist for insulating wood-frame buildings that aren’t available for other construction types. For example, while requirements for lighting systems or mechanical systems do not change based on structural material, wood’s versatility related to building envelope configuration gives designers more insulation flexibility.

Continuous insulation is often specified as a stand-alone prescriptive requirement or, alternatively, in conjunction with nominal insulation (e.g., between wood studs) in order to achieve higher effective R-values. Continuous insulation is necessary in structural systems using concrete and steel, which have high rates of thermal bridging, but is often avoidable in wood-frame envelopes.¹⁰

Environmental Performance

School boards, whether they receive funding from public or private sources, often include environmental performance in their objectives for school design.

In addition to the fact that wood grows naturally and is renewable, wood has a lighter carbon footprint than other common building materials.

As trees grow, they absorb carbon dioxide from the atmosphere, storing the carbon in their wood, roots, leaves or needles, and surrounding soil, and releasing the oxygen back into the atmosphere. When trees start to decay, or when the forests succumb to wildfire, insects, or disease, the stored carbon is also released. However, when trees are harvested and manufactured into products, the products continue to store much of the carbon. In the case of wood buildings, this carbon is kept out of the atmosphere for the lifetime of the structure, or longer if the wood is reclaimed and manufactured into other products. In any of these cases, the carbon cycle begins again as the forest regenerates and young seedlings once again begin absorbing carbon dioxide.

The fact that manufacturing wood into products requires less energy than other materials (and very little fossil fuel energy) also contributes to its relatively light carbon footprint.¹¹

Life-cycle assessment (LCA) studies consistently show that wood outperforms other materials in terms of embodied energy, air and water pollution, and global warming potential.¹² LCA is an internationally recognized method of evaluating the environmental impacts of materials over their life cycles, from extraction or harvest of raw materials through manufacturing, transportation, installation, use, maintenance, and disposal or recycling. It is increasingly being integrated into green building rating systems as a way to compare the impacts of alternate building designs.

Health and Well-Being

Most people in North America spend approximately 90 percent of their time indoors, either at home, at work, or in other spaces like retail stores, restaurants, schools or other public buildings. Because we spend so much time indoors, the spaces we inhabit can affect the way we act and feel, and even our health and wellbeing.

Interior design may prove to be just as important as diet, sleep habits or exercise routine. This is the premise behind biophilic design – the idea that incorporating natural elements into buildings, such as exposed wood, natural light or plants, can actually improve overall health. Research on the effects of wood as an interior element of classroom design is a relatively new area of study. In Japan, government officials have found that the use of wood in schools has a positive impact on students. The Japanese Wood Academic Society conducted a three-year study of 700 schools and reported reduced incidence of influenza outbreaks in schools featuring wood interiors vs. ``non-wood” schools.¹⁴

A one-year Austrian study observed 36 high school students, aged 13-15, who attended either fully wooden furnished classrooms or standard classrooms with plastic equipment and plasterboard walls. By the end of the year, students who were taught in wood-based environments daily had significantly lower stress levels, blood pressure and heart rates, as well as increased productivity compared to the opposite group of teenagers who didn’t have contact with wooden items. (Kelz, C. & Moser, M. 2011).¹⁵

As green building objectives have come to embrace human health issues, researchers are increasingly looking to quantify the impact of the built environment on occupant well-being. The results may hold promise for healthcare facilities, schools and offices to improve performance, productivity, and occupant well-being.

Conclusion

If there is a generalization to be made about the design of educational facilities, it is that architects are often called upon to achieve many objectives with limited budgets. This may be wood’s greatest strength in the context of schools—that it typically costs less, while performing structurally and offering benefits that cover the gamut from design flexibility to carbon footprint to occupant well-being. This may also be the reason we see more wood schools over the next decade, as U.S. designers seek to satisfy the needs of a growing student population.

End Notes

¹spaces4learning 2020 Facilities Construction Brief, https://spaces4learning.com/research/2019/01/facilities-construction-brief/asset.aspx?tc=assetpg

²National Center for Education Statistics, Projections of Education Statistics to 2024, http://nces.ed.gov/pubs2016/2016013.pdf

³Case Study: Bethel School District, WoodWorks, http://www.woodworks.org/wp-content/uploads/CS-Bethel2.pdf

⁴Case Study: El Dorado High School, WoodWorks, http://www.woodworks.org/wp-content/uploads/CS-El-Dorado.pdf

⁵Acoustical Considerations for Mixed-Use Wood-Frame Buildings, WoodWorks, http://www.woodworks.org/wp-content/uploads/Acoustics_Solutions_Paper.pdf, Acoustics and Mass Timber: Room-to-Room Noise Control and its accompanying Inventory of Acoustically-Tested Mass Timber Assemblies https://www.woodworks.org/wp-content/uploads/wood_solution_paper-MASS-TIMBER-ACOUSTICS.pdf, Acoustically-Tested-Mass-Timber-Assemblies-WoodWorks.pdf

⁶2015 National Design Specification^® (NDS^®) for Wood Construction, Section 2.3.2.1, American Wood Council

⁷ASC Steel Deck Floor Deck Catalogue, http://www.ascsd.com/files/floordeck.pdf

⁸ASCE 7-16: Minimum Design Loads for Buildings and Other Structures, Table C3.1-1a

⁹Guide for Designing Energy-Efficient Building Enclosures for Wood-Frame Multi-Unit Residential Buildings in Marine to Cold Climates in North America, 2013, FPInnovations

¹⁰2018 International Energy Conservation Code, Table 402.1.3

¹¹A Synthesis of Research on Wood Products and Greenhouse Gas Impacts, FPInnovations, 2010

¹²Werner, F. and Richter, K., Wooden building products in comparative LCA: A literature review; International Journal of Life Cycle Assessment, 12(7):470-479, 2007

¹³Back to Nature: Can wood construction create healthier, more productive learning environments, Building Design + Construction, 2005

¹⁴Back to Nature: Can wood construction create healthier, more productive learning environments?

¹⁵Wood, Housing, Health, Humanity. Page 6.

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