Air barrier material resists air leakage and is designed to prevent uncontrolled air movement in and out of the building envelope. It is typically installed along exterior sheathing of some sort, behind a finished product such as metal, stone, brick or wood.
If penetrated by outside weather, interior finishes can be damaged and clients forced into uncomfortable environments. It can overwork building HVAC systems and throw off their warranty and maintenance cycles as well. The importance doesn’t stop with just the air barrier itself, but also the adjoining systems and tie-in points that create a continuous outer shell of the building.
“I think the most challenging learning opportunity we had was realizing that, although on paper the air barrier can seem fairly simple, there are so many ins-and-outs that can be overlooked that only come to fruition when the installation occurs,” Hastings said.
One highlight of this project was the coordination and completion of a substantially complicated truss wrap system. The team was faced with the challenge of building a weatherproof box within a small amount of space several feet in the air at multiple locations. With exterior columns, the trusses spanned from one exterior to another exterior, penetrating the exterior walls on both sides of building.
It was not clear where or how the weather barrier would terminate at these truss wraps, so it was decided a completed mockup-to-scale on the ground could provide a look and feel of the products, ultimately gaining a solid comfort level of the system.
Superintendent on the project, Tony Kouba, noted the increased self-perform work required due to the size and complexity of design. “This is a large scale, complicated concrete structure with a great deal of complex details. Our team placed over 52,000 yards of concrete which included 8-foot elevation changes in monolithic decks and over a half mile of 30-foot-tall foundation walls.”
Looking back, Hastings said he can think of three larger lessons he has taken away from the project.
“First, schedule all systems of your exterior enclosure as tight as you can in order to eliminate exposure to exterior elements because some air barriers have a specific weather tolerance that should be considered,” he said. “Second, understand the air barrier is not just one product as there are multiple sealants and detailing strips required to make it a complete system. Along those same lines, request or perform adhesive and compatibility tests between systems to ensure there will not be any issues down the road.”
The initial approach was to have one manufacturer own the entire package of exterior weather membranes, being the roofing, underground waterproofing and air barrier. This project was designed to have a metal panel rain screen that covers the air barrier that required several fasteners attaching to the stud framing, penetrating the air barrier.
With this in mind, they intended to have a self-healing membrane so to not have concerns with all the penetrations. This was initially thought to have been a fluid applied system; however, the curtainwall system was in place and concerns arose about damage to the glass without a massive effort in protecting it. The plan evolved to coordinate a sheet applied good and stress the importance of sealing the metal panel fasteners individually.
“I enjoyed the team effort we had when driving home a lot of the complex details with the exterior skin,” Hastings said. “I had a small part in this large project and I have a high level of respect for the guys in the lift out there actually putting the plan into place. It’s eye opening for me when I get to put my harness on and go up in the air to see the work up close.”