This month, I had the privilege of sitting down (virtually) with Adrian Lowenstein, who is responsible for national business development at Skyline Windows. I got his take on the challenges of implementing high-performance fenestration in New York City (NYC) renovations and beyond. He identifies major themes: the criticality of quality control in both the field and shop; the importance of creating fenestration systems that are easy to retrofit into existing buildings; and the need to think about the maintenance of windows in the same way we think about car maintenance.
Meet Adrian Lowenstein
Lowenstein is a licensed professional engineer (P.E.) with an MBA and a background in both manufacturing and building envelope consulting. While working with Vidaris for over four years he had first-hand experience with quality-control inspections of fenestration assembly in-shop and on-site during construction. His orientation to, and passion for, high-quality came through clearly during our conversation. Now at Skyline Windows, a window fabricator and installer specializing in historic preservation and rehabilitation, he is focused on educating the national community on how to effectively execute high-performance replacement fenestration.
Credit: Skyline Windows
Quality control and durability
Lowenstein asserts that quality control of fenestration fabrication in both the shop and the field is critical to delivering long-lasting field performance. Many issues with gaskets or seals cannot be seen once the curtainwall is in place (e.g. joinery seals, insulation, chicken head gaskets), so it is critical that in-shop quality is monitored and controlled. He believes that manufacturers need to take ownership of the quality of the delivered systems. For example, Skyline pulls one in every 100 units built to undergo extensive air and water testing.
He emphasizes the importance of educating the factory team about what is critical about every step of the fabrication process. He says that getting buy-in from the factory team on the significance of their work, its complexity, and the impact on the performance once it’s in the building is key. One of the best factory quality systems he has witnessed was one in which photos of each process step were posted at each fabrication station with an explanation of its importance.
While the large, unitized curtainwall fabricators seem to have built good quality management systems into their processes and are scrutinized closely by curtainwall consultants, Lowenstein observes that “the majority of the country doesn’t implement this level of quality.” When asked why, he says he believes it is due to lack of education and lack of enforcement.
In NYC, he is used to seeing a level of third-party in-shop and in-field inspection and testing of assemblies imposed by regulation that is not typically required elsewhere. In NYC, he explains, “a third-party inspection agency must certify that assemblies are in compliance.”
The devil is in the interfaces
One of the biggest issues that degrades fenestration performance is the perimeter details on the installation. He says, “While you can design and specify fenestration perfection on paper, the perimeter interfaces to the wall can degrade performance significantly.” He adds that flashing choice, sealant compatibility with both the fenestration and the connecting masonry wall, and the execution of those joints can have a big impact on the resulting thermal, air leakage and acoustical performance and need to be carefully detailed and implemented.
The path of least resistance for air and heat is at the perimeter interfaces. He predicts, “Air leakage and thermal performance degradation will be the new water leakage” with the focus of installed performance moving from water mitigation to air-leakage and thermal bridge mitigation.
Credit: Skyline Windows
Fitting the window within the glove
Upgrading old, leaky windows in the existing installed stock is a significant lever for addressing carbon emissions in buildings. Existing building performance standards, like NYC’s Local Law 97, are proliferating in cities and states around the country. They typically begin by requiring energy disclosure, followed by labeling, and then a requirement to hit a specific energy use intensity target.
Lowenstein identifies several challenges with renovation including managing the installation while the building is still occupied and minimizing the difficulty (cost) and risk of the installation process. He mentions the challenge of pulling the old window out completely and with it the old drywall and the inherent risk of “not knowing what you’ll find, especially in old buildings.”
Lowenstein describes a “fitting the window within the glove” strategy, which works especially well in landmark buildings where historic replication is needed. This process involves preserving the existing frame and inserting the new window inside that frame. Often the old frame is shaved down, a flashing membrane installed to overlap it, and new sealant joints are made. In this way, disruption to occupants and installation risk is minimized, and the cost of installation significantly reduced, since the general contractor no longer must employ drywall installers and painters. The process minimizes sightlines, preserves the historic look, and uses existing materials that help reduce waste to landfills, which is a more sustainable approach.
While Lowenstein says NYC’s construction industry has mastered this style of the window replacement process, other installers in different cities have yet to recognize the cost-benefit of “fitting the window within the glove” and tend to resort to a full tear-out approach.
Treating windows like cars
Design for serviceability and maintenance is a key attribute of sustainable design as it extends the useful life of the fenestration assembly. Lowenstein asserts, “The construction industry rarely views fenestration as an area that needs ongoing care.” He says that we should think about window maintenance in the same way we think about car maintenance. It should be expected and planned for to ensure the same high level of thermal performance is delivered over a full (and extended) service life.
For example, the locking and opening mechanisms and the seals of operable windows need regular maintenance to extend service life and maximize thermal performance.
He also recommends that windows should also be designed for serviceability. In particular, the glazing pocket should be exposed to the interior so the insulating glass unit (IGU) can be replaced with minimal disruption from the interior, eliminating the need for a building maintenance rig for access to the exterior.
Lowenstein also believes that architectural specifications should consider the maintainability of fenestration assemblies to maximize the building’s useful life and that of their components. Most do not currently.
To be continued…
My conversation with Lowenstein will be continued at a later date. We have only scratched the surface of installation quality control and durability topics and have yet to dig into his thoughts on new innovation.