Looks aren’t everything, in life and certainly not in construction. Performance counts, and construction management teams work closely with owners, designers, engineers, subcontractors and testing resources to determine that buildings meet expectations for a range of considerations, such as energy use, safety and security, mechanical equipment commissioning, and of course, the onslaughts of weather. These days, quality assurance efforts can include building and testing building methods and materials in a lab setting to identify and correct vulnerabilities prior to landing at the job site.
Vertical construction of H.Q., the KA Block’s 17-story apartment tower, is now underway in downtown Minneapolis. To test the building methods and materials for both aesthetics and performance, recently a full scale replica of the 16th floor exterior walls of the apartment tower was created and tested in a lab environment for performance under extreme weather conditions. Members of the KA Block project peeled back the layers of this intensive testing process. Watch the test.
Q: What is the purpose of mock wall testing?
JON PORTER, KRAUS-ANDERSON QUALITY MANAGER: A Performance Mock Up (PMU) is used to validate the performance (air-tightness, water-tightness, resistance to wind loads), design, workmanship, and material selection of an exterior wall assembly, and to gain the approval of Clients, Architects, Contractors and Consultants. A PMU can help the project team detect any potential deficiencies in the design, fabrication, and installation of the wall system before the system is put into use.
The intent is not much different than when you want to try out a recipe for the first time on a very large dinner gathering – sometimes it’s a good idea to make a trial batch before you commit to the larger effort. The H.Q. Apartments will have over 120,000 s.f. of wall surface standing up to wind, rain, and seasonal temperature and humidity swings, and so we are looking at 500 square feet as that trial run to make sure that we understand beforehand how the building’s wall system will perform once it is put into use.
Q: What portion of the building is the mock wall designed to simulate?
JON PORTER: The PMU closely approximates the west-facing exterior wall condition at the 16th floor of the H.Q. apartment building.
Q: Why was the west wall chosen for replication and testing?
JON PORTER: The west wall will overlook a courtyard and has exterior balcony doors that are in the same plane as the exterior wall, with balconies extending out; so it is more exposed to the elements.
Q: Where was the mock up wall created?
JON PORTER: It was built at ATI (Architectural Testing, Inc.) in Saint Paul.
Q: How big is the mock up wall?
JON PORTER: The wall is 37’-0” long by 13’-6” high.
Q: Who are we working with to design/engineer the mockup?
JON PORTER: It’s been a joint effort with multiple contractors and Kraus-Anderson. The PMU simulates the wall design provided by the design consultants, ESG Architects and MBJ Structural Engineers. The test chamber is a five-sided box engineered and provided by ATI, with the sixth side being the mockup. Engineering of specific elements (such as steel studs, aluminum framing systems, and fiberglass windows) within the PMU wall section is provided by our subcontractor partners.
• ATI provided the basic outline of the test chamber
• Olympic Companies- installation of steel studs and poly iso sheathing
• Braxton installed the blocking the wood blocking around the openings in the wall
• Crossroads installed the Pella window (which is more optimized for locations where wind load isn’t as extreme)
• WL Hall is doing the aluminum framed opening and patio terrace door (optimized for more wind load)
Q: What materials are being used in the construction of the wall?
JON PORTER: Steel studs, wood blocking, rigid insulation sheathing, spray applied and adhered flashing, a mechanical (furnace/AC) unit with a wall louver, a combined dryer/bathroom vent, a fiberglass window, an aluminum window, an aluminum patio/terrace door, and metal paneling over everything else.
Q: Are we incorporating mock ups on our Kraus-Anderson office building? Why or why not?
JON PORTER: In addition to small scale individual material mock ups or samples, we will have a visual mock up for the office building. In contrast to a performance mock up, a visual mock up does not undergo any specific testing; it is used primarily for visual review and approval of finished appearance. Using a performance mock up on the apartments project is more advisable than it would be on the office building, due to the nature of the project.
Q: How standard or unusual is this process as part of KA’s Quality effort?
JON PORTER: Visual mock ups and small scale individual material mock ups or samples are very common, and often prescribed in a project’s specifications. Performance mock ups are less common, perhaps occurring on a project once every several years.
Q: How are the new energy code requirements incorporated into this building?
JON PORTER: To address new requirements of the energy code that went into effect in 2015, we are using a wall system that eliminates typical sheathing (such as plywood or gypsum board) and replaces it with a combination of rigid insulation board and spray-applied insulation. This system provides a consistent weather resistive barrier and an air barrier without the need to apply large areas of sheet material (such as Tyvek wrap or poly sheeting) across the entire wall surface.
Q: Does the wall present varying materials/methods for comparison? Or is it one consistent treatment?
JON PORTER: The visual treatment will be consistent. However, minor details in the termination and sealing of the weather barrier will be varied to study if certain treatments perform better than others.
Q: What have you learned from this exercise? Are any changes being implemented as a result of the performance testing?
JON PORTER: Yes. The system we were originally using was a more industrial type product that you would typically see on warehouses or distribution centers with a vast expanse of uninterrupted wall. It didn’t lend itself well to a building with a lot of openings; a lot of windows, doors, vents and louvers, which characterize this building. As a result of the testing the team a change in the exterior panel, switching to a higher-quality composite aluminum panel that provides the desired weather performance plus a higher finish and aesthetic appeal; while actually at a lower field labor and installation cost.
Q: From an owner’s perspective, what is the benefit of investing in a mock up wall test?
JACI BELL, DIRECTOR OF DEVELOPMENT, KRAUS-ANDERSON DEVELOPMENT: It is fantastic to see a mock up of this magnitude being leveraged to preview the materials and application. Testing the form and function like this is meaningful because it allows us the opportunity to confirm any performance assumptions, and also discover any methods and materials that may not have served us quite as well down the road. We benefit from zeroing in on tiny details that can be perfected before they are performed. Not only can we be more confident in the final result, the investment will pay dividends down the road.