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To double glaze, or to triple glaze — that is the question. Well, that’s been the question until recently, when some window manufacturers have stepped up their games and began offering quadruple-glazed window options. This multilayered window trend has begun to grow in Nordic countries where the climate is significantly colder; hence, building insulation needs to be of maximum efficiency. Think of window glazing in terms of men’s razors: the more blades, the better the shave; the more panes, the warmer the interior.
Projects are now popping up around the world outside of freezing cold regions that plan to use not two or three, but four panels for glass-enclosed façades and basic window applications. This rise in heavy-duty glazing brings up another serious question: If manufacturers are already stepping up to meet the growing demand for quadruple-glazed windows, how long until they become an industry standard?
SHoP Architects’ design for Uber’s headquarters in San Francisco consists of a multilayered glazed façade.
To dive into that, we must know why multilayered glazing is so popular and how it actually benefits a structure. Per the Passive House Institute, for a building to achieve the highest levels of efficiency, it must be fitted with low-e glazings filled with argon (most common) or krypton gas (most expensive) in order to combat heat transfer. In some cases, this requires the U-value — which measures a material’s insulation capabilities — to be 0.80 W/m²K or less. If this sounds technical, that’s because it is. Building an air-tight, highly insulated glass façade requires incredibly careful detailing and exactly the right materials.
Zola Windows is a manufacturer from Colorado that crafts European-style standard window systems. Among their triple-glazed window offerings, Zola features a product called ZNC, which includes three glazing layers, two low-e coatings and five seals and is now available in a quad option. This state-of-the-art window was actually the first on the market to achieve both Passive House Germany and Passive House U.S. certifications.
Typical triple-glazed window section; via FineGlaze
On an even more niche note, Klearwall, a New York–based manufacturer, specializes in designing super-energy-efficient windows for retrofits of landmark buildings in Brooklyn. Their product, aptly named Landmark, simulates double-hung style windows with a fixed sash on top and tilt and turn below, with triple-glazed panels and a center pane U-value as low as 0.088. Klearwall’s other PassiV products, which achieve next to the same levels of competence, come in quadruple-pane options, as well. Scottish company Enviro Windows bred the first quadruple-glazed window from the U.K. with a U-value of 0.35.
Comparison between typical triple- and quadruple-glazed windows; via Maven
Companies likes these are increasingly making quadruple-glazed windows a standard in the industry, and the physics surrounding the creation of such uber-insulated window systems are what makes the product an easy sell. Essentially, the goal is to keep the surface of the most interior window pane from reaching a ridiculously cold temperature.
For example, if the internal air temperature is just under 70 degrees Fahrenheit, then a single-glazed window should be around 34 degrees. In a double-glazed window, it should be 52 degrees. For an ultra-efficient double-glazed window with a U-value no less than 1.6, it should be 61 degrees. A triple-glazed window in those same conditions should hit 64 degrees.
Left: Zola’s Arctic quadruple-paned window system; right: interior applications of the product; images via Zola
It’s easy to imagine how warm a quadruple-glazed window will be, even in a severely cold climate such as the Arctic. Some argue that the best triple-glazed windows also slightly reduce heat absorption, further adding to the overall efficiency of the structure in desert-like settings.
But one drawback for increasing window glazing is major: weight. The more window panes, the heavier the window is and the harder it is to install. So, as we begin to see triple-glazed windows taking a back seat and quadruple glazing rising to the top of the building-product specification list, we’re sure to also see manufacturers coming out with stronger framing systems and ways to lessen the extra mass.
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