Why Polymer (uPVC)?
Throughout his presentation, Kintzele emphasized that glazing often gets most of the attention when talking about window performance, but frame material can also have a dramatic impact on durability, recyclability, fire-resilience, structural strength, and thermal performance. This is what led INTUS to take an interest in Polymer, also known as unplasticized polyvinyl chloride (uPVC). As the name suggests, uPVC does not contain plasticizers. Plasticizers make windows more flexible and, usually, non-recyclable. In contrast, Polymer windows are far more rigid, thereby making them suitable for high-rise construction, and they can be recycled after use. In facta portion of INTUS’ windows are composed of recycled Polymer.
Another benefit is that Polymer windows do not off-gas, are non-toxic, and can pass the ASTM E84 (Steiner Tunnel test), which measures how fast flames and smoke spread in a high-rise setting over 10 minutes. Kintzele also noted that Polymer contains far less embodied carbon than even aluminum and that it is significantly less conductive than aluminum-fame windows, as well.
Polymer Performance at Commercial Scale
A key takeaway from the session was that high-performance windows no longer require sacrificing design flexibility. INTUS’s polymer systems can achieve commercial-scale structural ratings while supporting large expanses of glass. Kintzele highlighted fixed windows up to 70 square feet with no mullions and operable units up to 32 square feet, allowing architects to maintain ambitious design goals while meeting rigorous performance requirements.
As Kintzele explained, those performance requirements center on thermal insulation and airtightness. To meet Passive House standards, walls need to possess robust thermal resistance values (R-values) in the range of R-30 to R-60 (depending on climate). However, windows are typically the weak point in a wall assembly (typically ranging from R-2 for a single-pane window system and up to an R-10 for a top-tier, triple-pane window) and tend to drag down performance. Moreover, they can be a weak point for airtightness, too, which is why high-performance windows systems contain sophisticated gasketing systems. Why is airtightness important? It’s like walking around with a high-end coat that’s unzipped, Kintzele said. All those R-values in the wall assembly become meaningless if unconditioned air can move freely through gaps in the building envelope.
Without well-insulated, well-sealed, thermally broken, and multi-pane windows systems, it is not possible to reach the level of performance necessary for certification through Phius or the Passive House Institute.
