Windows- Residential versus Commercial

In a previous post, I looked at window performance and the Performance Grade (PG) metric.

We have also looked at the cost of windows from residential/ light commercial and from heavy commercial manufacturers. Light commercial windows will be familiar to many people: they are the windows Marvin, Jeld-Wen, Pella or Andersen makes, and you see them in houses and smaller commercial buildings. These windows are called residential/light commercial because they have acceptable performance when installed in a house or small commercial building. On recent projects, we have seen these windows come in at about $25-30 per square foot for double glazed fixed units.

designers interested in fine-tuning window performance have a wide range of options with commercial windows.

Residences and light commercial buildings are usually between one and three stories tall. They are usually located in dense areas, and their windows tend to be small. These three factors protect building windows from the effects of high winds. High winds are the cause of driving rain and structural stress. Window performance grades are a direct measure of a window’s ability to withstand driving rain and wind-induced structural strees. As buildings get taller, as they tend to stand out from their neighboring buildings (in height, for instance), and as their windows tend to get larger, the effect of high winds gets worse. These buildings require better windows.
Those better windows- windows with heavy commercial performance grades- have frames made out of extruded aluminum, instead of wood with aluminum cladding, or just wood, or vinyl, or fiberglass. There are some thermal performance considerations to think about, but for now let’s just realize these are pieces of glass held in a substantial metal frame: not for the faint of heart. Typical manufacturers here are Kawneer, EFCO, and Wasau. As with the residential window market, there are smaller manufacturers in this space, too.
Do they cost more? Yes. Unit prices appear to be closer to $45 per square foot. They also appear to be more labor intensive to install.
Looking at RS Means cost data, metal-clad windows are about $32 per square foot to install, while commercial aluminum windows are about $48 per square foot to install. These numbers need to be corroborated. The true cost of window replacement also includes the cost to finish or trim the window, and this will add significantly to the overall project cost.
Commercial aluminum windows are significantly tighter and stronger, which means they can resist higher structural wind pressures, and resist driving rain better. Commercial aluminum windows can use a very wide range of glazing. Where residential window manufacturers might offer five or six different glass options, commercial windows can be specified with any type of glass that is available, and that number runs into the hundreds. So, designers interested in fine-tuning window performance have a wide range of options with commercial windows.
We are looking at several glass options for a school window replacement project. Our goal is to reduce solar heat gain on south-facing windows, and provide reasonable night-time U-values. Commercial windows allow us to look at dozens of options. It may be that a residential window manufacturer offers the option that’s best for us, and this is something we will need to consider.
I plan on updating this post as more information on window cost and performance comes my way.

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Principal at Sealander Architects, Ellsworth Maine. Revit guru. Married with 3 children. Avid gardener. Lived in San Francisco for nine years. Master in Architecture from Columbia University Bachelor of arts in religious studies, Wesleyan University. Graduated Staples High School, Westport CT. Hope to spend some time in Hokkaido before all is said and done.