Trends in Green (Sustainable Innovations on Campus)
Building With Wood
- By Joseph Mayo
- August 1st, 2014
College and university campuses across the country are seeing a resurgent interest in wood frame construction for all building types. While light wood frame construction can certainly offer significant cost savings and streamlined construction schedules when compared to concrete and steel, it also boasts several sustainable attributes beyond what alternate structural systems can provide. These sustainable features are driving wood’s resurgence and proving that in many cases, it can exceed expectations for sustainable campus buildings.
A Renewable Resource
Wood is one of our few domestic and truly sustainable structural materials. As a renewable material, it is capable of offering yields for generations to come through the sustainable forestry practices now used across the U.S. and Canada. Common building materials emit greenhouse gasses during extraction, processing and transportation. The natural growth of wood in our forests sequesters large amounts of carbon naturally from the atmosphere. Once harvested, wood products typically sequester more carbon than is used in their processing, equating to a net negative carbon building material. Wood’s low thermal conductance properties also means that it is a natural insulator and is able to meet ambitious energy performance goals without complicated envelope detailing or added project costs.
Wood is strong, having a similar strength-to-weight ratio as steel, can be shaped using simple tools, and is lightweight, aiding in transportation and erection. A strong, flexible and sustainable material, wood is well suited for a variety of building types and can offer many benefits to design teams, contractors and owners.
Wood Use on Campus
At the University of Washington (UW), for example, Mahlum Architects employed wood for the West Campus Student Housing Phase I project to create a series of five seven-story buildings (668,800 square feet), adding vital student housing capacity to their Seattle campus. Known as “5-over-2” construction, the UW Phase I buildings have a two-story podium of concrete construction on which five stories of wood construction sit above. The use of wood allowed the design team to create a high-performance exterior façade with large openings for generous daylighting. Interior walls were designed to be the primary load-bearing system, allowing the exterior brick clad walls to have studs spaces typically at 24 inches on center to allow more continuous insulation and reduce thermal bridging. The design team also carefully detailed the façade to minimize air infiltration, ensuring the project meets the 2030 Challenge (requiring 60 percent reduction over baseline fossil fuel energy consumption) with the purchase of green power.
The entire project was constructed for $177 per square foot, uses 208,320 cubic feet of wood — which stores 4,466 metric tons of CO2 in the wood structure — and avoids 9,492 metric tons of CO2 emissions by using wood instead of higher CO2-emitting materials. Calculated to current forest production levels, the volume of wood used in these five buildings grows in approximately every 17 minutes in U.S. and Canadian forests.
While light wood framing provides many benefits, an emerging type of wood construction known as mass timber (using materials like cross-laminated timber [CLT]) is opening new possibilities to wood use for campus and institutional buildings. CLT construction uses large-dimension engineered wood panels that provide structural and safety characteristics similar to concrete and steel, yet with greatly reduced on-site labor and construction schedules. Developed and adopted first in Europe, with gaining popularity in the U.S. and Canada, CLT offers many of the sustainability benefits of light wood frame construction with greater structural flexibility often only found in highly reinforced concrete construction. These attributes can be especially suited for larger multi-story campus buildings.
Mahlum has just completed a feasibility study exploring the use of CLT in a ten-story building application. Comparing the costs of CLT with conventional concrete and steel construction, wood offered a four-percent cost saving, indicating the material is cost-competitive and could be even more competitive in the future. Mahlum is also exploring the use of a hybrid system of mass timber and conventional light wood frame construction, maximizing the benefits of both systems, in Western Oregon University’s new School of Education building.
For college and university campus facilities, wood construction continues to meet the structural, schedule and budgetary needs while supporting the ever-increasing sustainable initiatives.
This article originally appeared in the August 2014 issue of College Planning & Management.
Joseph Mayo, LEED-AP is a member of the team at Mahlum Architects (www.mahlum.com).