Innovative, Affordable Studless Wall System Can Change the Industry
An affordable, studless building and delivery system for residential construction could be a “game changer in the industry.”
Developed by University of Minnesota researchers, “this system is designed to be better, faster, stronger, and less expensive than conventional building methods,” says Patrick Huelman, associate extension professor and Cold Climate Housing Program coordinator in the Department of Bioproducts and Biosystems Engineering.
Testing has shown that a house built using the studless panel system is as airtight as any in the country while providing outstanding moisture protection and energy performance.
It has an approximate 40% energy savings over the current Minnesota Residential Energy Code and a 30% savings over an ENERGY STAR Version 3 certified home. Measured airtightness has been as low as 88 cubic feet per minute or 0.26 air changes per hour (ACH) at 50 Pascals pressure difference. A Minnesota code home must be less than 3.0 ACH at 50 Pa. Additional monitoring is being conducted on energy use, temperature, relative humidity, and moisture content.
The NorthernSTAR Building America Partnership team, led by Huelman, is the group that is developing and testing the system in partnership with the U.S. Department of Energy and three affordable housing developers in Minneapolis and Denver. The team is comprised of faculty and researchers from BBE and the Center for Sustainable Building Research in the College of Design. The University of Minnesota researchers have been working on this concept since 2001 in partnership with the Wilder Foundation and U.S. Department of Housing and Urban Development at the time.
The main goal of their current study is to validate the performance and costs of this building system. First, Huelman and his team will compare the modeled and actual performance of this system to two more traditional construction methods. In a second series of tests, they will evaluate the means and methods to further optimize the system design and reduce the costs through multiple builds.
By the end of the study in 2019, a total of 20 “real world” houses will be built. These houses will be occupied by qualified owners and their families.
“We are focusing on the affordable housing market because the need is so great,” Huelman says. “Keeping the cost down is important, but having an efficient, durable, and healthy home is critical for this segment of the market.”
Huelman and his team will also show that this innovative stud-free panel wall structure can easily facilitate the “perfect wall” design. A “perfect wall” is one that places the four critical protection layers on the outside in order to keep the structure on the inside warm and dry all year long in any climate. These control layers include a moisture barrier, air barrier, vapor retarder, and thermal insulation.
Building the studless “perfect” wall
The main piece of the studless “perfect” wall has two layers of large, cross-laminated wood panels or structural engineered panels. To build a house, the panels are joined together at the corners. This monocoque-style technique requires no studs and creates a very rigid structure.
Then, a single heavy-duty peel-and-stick membrane is wrapped around the outside of the panels and is integrated with windows, doors, and penetrations. This serves as the robust water, air, and vapor control layers.
Then, two layers of rigid insulation are added on top of the membrane. Furring strips are fastened through these layers to the structural panel, which will support the final siding and trim.
“The idea of exterior control layers and the ‘perfect wall’ certainly isn’t new. It has been tried for many decades from Canada to Texas and from New England to Alaska,” Huelman says. “However, the approach has been perceived as both complicated and costly, and therefore, failed to gain significant market share. The excitement with this innovative system is that it is much simpler and can actually reduce the costs of achieving such high levels of durability and performance.”
Potential for performance and affordability
“Right now, the homebuilding industry is between a rock and a hard place,” Huelman says.
The market has improved dramatically, but the labor force simply isn’t available to meet the demand.
“The builders who have reviewed the system are telling us this building and delivery system could solve three critical nationwide problems in new home construction,” Huelman adds.
First, the house can be framed-in, secured, and water-protected in a just few days. This reduces exposure to the elements, provides quicker and better access for other trades, and ultimately reduces overall construction time and carrying costs.
Second, with the housing downturn and recent rebound, there is an incredible shortage of skilled carpenters, framers, and trades. This system requires less skilled framing labor. Furthermore, this system facilitates a new approach called a single enclosure contractor. This further reduces the number and skill level of the other trades needed to complete the building enclosure.
Third, framing lumber prices are increasing. This system uses less lumber than traditional wall construction methods. Two layers of solid, cross-laminated, engineered wood panels are used for the walls. Although the panels use more wood fiber overall, composites generally have a much higher yield than solid sawn lumber. And since they are produced domestically, their price has been far more stable.
“With our building system innovation, houses in the future will be more energy efficient, durable, and resilient to wind and other natural disasters while providing a more comfortable and healthier indoor environment,” Huelman says.
This project is funded by the DOE through its Building America Program. Project partners include Twin Cities Habitat for Humanity, Urban Homeworks, City of Minneapolis, Thrive Home Builders in Denver, Building Knowledge, Huber Engineered Woods, and Cobalt Creed.