Published: March 3, 2016


In essentially every climate, good façade design begins with good glazing design. For the cold winters of the upper Midwest, it is particularly important to keep the overall façade insulating value (U-value) as low as possible to slow the transfer of heat through it.

This starts with selecting the right amount of glazing. Limiting the amount of glazing is important because even the highest performing glazing has a much higher U-value (U = 0.2–0.3) than a typical wall assembly (U less than 0.064). In addition to not insulating as well as a wall assembly, glazing adds solar heat to the space, contributing to the cooling load.

Keeping building occupants happy and productive is crucial, so ample daylight and access to good outdoor views is important. Optimal glazing design, therefore, is a balancing act that provides adequate daylight, minimizes direct sun exposure and reduces energy use.

Fully daylighting a space does not require a 75 percent glazed façade. Careful attention to glazing placement can provide plenty of daylight while minimizing the amount of glazing needed. Selecting the appropriate glazing product will minimize solar heat gain, keep the building well insulated, and allow natural daylight into the space. Then well-designed wall assemblies round out the façade for a well-insulated daylit building.

Impact of WWR on comfort: Payette,

COMFEN tool:

Window property ratings: National Fenestration Rating Council,