At some point in the life of your building, the windows will have to be replaced. Moving parts will wear out, materials will deteriorate, and technological improvements will render them obsolete. Before a window replacement project is considered, have the condominium by-laws reviewed to determine ownership responsibilities.

We have seen cases where windows, caulking, and flashings have been classified as a combination of common, limited common, and privately owned elements within the same window opening.

There is much to consider when selecting replacement windows, but nothing is more important than performance. A major consideration is the design pressure (DP), as it represents the maximum wind load that a window can undergo without sustaining structural damage (e.g., breaking, deforming, etc.).

Washington, D.C., and the metropolitan area is located in a 90 mph wind design region.

The design pressure an engineer specifies for your windows depends on many factors. Building type (e.g., hospital, office building, school, etc.) and geographic location (coastal vs. inland) play a major role. Washington, D.C., and the surrounding metropolitan area is located in a 90 mph wind design region according to the current Building Code. The nearby Atlantic coastline is in a 120 mph zone due to hurricane potential.

Proper design also requires higher DP values for windows located higher above ground, as well as those near building corners where swirling wind pressures increase.

Another important rating is the Performance Class (PC), certified by the American Architectural Manufacturers Association (AAMA). Performance Class designates resistance to water infiltration, air infiltration, ease of operation, and forced entry, and incorporates Design Pressure. AAMA classifications range from “R” (lowest) to “AW” (highest).

Specifying windows is a complex undertaking and is best left to professionals. That said, if you proceed directly with a contractor, there are a few things to watch for:

• It is not enough for a window to carry a Performance Class designation. It should also be AAMA-certified, meaning the manufacturer submitted current production samples for testing. A rating may have been granted years ago, but materials and processes can change over time.
• AAMA ratings do not include thermal performance. Even the best windows have limited thermal resistance, but improvements can help. Low-emissivity (Low-E) coatings reflect heat and improve efficiency. Modern windows are double- or triple-glazed, and gas fills such as argon improve insulation by reducing convective heat transfer.
• Windows come in a variety of materials (wood, aluminum, steel, vinyl, fiberglass, etc.), and each has advantages depending on the application.
• Installation methods vary depending on whether the building is new or existing. Replacement windows can sometimes be installed within existing frames, which is more economical but reduces opening size. Proper flashing and sealing are critical to prevent leaks.
• In-place testing by an accredited laboratory is recommended to ensure the installed system performs properly and remains watertight.

The two most frequent comments we receive after window replacement projects are that new windows significantly reduce outside noise and improve energy efficiency. This article is not exhaustive, but it provides an overview of key considerations and highlights the complexity behind what may seem like a simple window replacement project.