New York's Cooperative and Condominium Community

Habitat Magazine Insider Guide



Replacing Old Windows

I'm on the board of a six-story, 39-apartment cooperative in Brooklyn Heights, and after many months of discussion, we've decided to replace the badly deteriorated original wood windows in our 71-year-old building. The windows are the standard double-hung wood types, except on one floor that has arched-topped double-hungs facing the street. We plan to replace each type of window with its original style. What things should we be looking for when selecting new windows, and how long should the project reasonably take?


Replacing old, deteriorated windows can be lengthy, expensive, and disruptive, but the result will be better thermal insulation, energy efficiency, and noise reduction as well as an improved aesthetic appearance. Your main considerations will be selecting the type of window material and performance rating that best suits your needs and architectural design. It is also important to understand the expected timetable for the installation of the new windows.

Choice of Materials. The two most common window materials for residential use are aluminum and wood. Each material has distinct advantages and disadvantages; your choice will depend on your budget, aesthetic preferences, and building location.

Aluminum windows are popular because of their durability and low maintenance. Aluminum doesn't peel, crack, or warp, it doesn't require painting, and it's easy to clean. Aluminum windows can be expected to last between 20 to 30 years, and they require little care beyond periodic caulking and replacing miscellaneous hardware as needed. In addition, aluminum windows are less expensive than wood. The first generation of aluminum windows from roughly 35 to 45 years ago did not have the high-performance properties, such as thermal insulation, of today's offerings. Because of the material's strength, flexibility, and lightness, the windows can be designed to open and close easily. Tilt-in aluminum windows also make the outside face of the glass more accessible for cleaning. (As a result, tilt-in wood windows are now typically offered as well.) One drawback to aluminum is that, because of its thermal conductivity, it is cold to the touch. In addition, choosing a custom color beyond the standard white or bronze adds to the cost.

Compared to aluminum, wood offers much more design flexibility, but it also requires greater maintenance. Matching the look and feel of the original windows, especially those with distinct detailing, curves, or special features, is easier done with wood than with aluminum. This is of particular importance with landmark-district buildings, where historical characteristics must often be preserved. In addition, wood can be stained or painted any color, giving it a warmer appearance than aluminum.

The life span of wood windows largely depends on how well the wood is constructed, prepared, and cared for. Wood tends to warp, crack, and chip if not maintained, which means scraping, painting, and caulking every five to ten years. Wood (and for that matter, aluminum) windows also need a special finish and require more frequent maintenance in harsh environments, such as those with an ocean exposure or high humidity.

In addition, installing new wood windows usually entails more disruption and demolition than installing new aluminum because in a wood installation the original wood frames usually have to be ripped out.

Replacement windows also come in two other common types of construction. In the first, aluminum-extrusion cladding is fitted over the exterior details of a wood window. This hybrid window retains the aesthetic qualities of wood on the inside of the apartment but has the durability and low maintenance of aluminum on the outside.

In another type of configuration, the wood sashes are replaced with new wood jamb liners in the existing wood frames. This type of replacement window, however, often doesn't work properly because the old frames may be warped or deteriorated, providing inadequate support for the new sashes.

Some buildings benefit by installing a combination of aluminum and wood windows. The less expensive, more resilient aluminum is used in the windows that have a basic, straightforward design. The more costly, higher-maintenance wood is saved for selective windows, i.e., those with special features or detailing that wood can better mimic.

Vinyl windows are also a popular option, chiefly because they are considerably less expensive than either aluminum or wood. Vinyl, however, does not withstand structural wear and tear very well, so it is not recommended for windows in multi-dwelling buildings.

Glazing. Single-paned glass is rarely used in new windows any more. Most high-performance windows have double-paned, thermally insulated glazing. The two pieces of glass with vacuumed-sealed air or gas in between provides the best energy efficiency-better retention of cool air in summer and less loss of heat and reduced condensation in winter-as well as greater noise reduction. Low-emittance (often referred to as low-e) coatings can be applied to glazing to minimize glare and ultraviolet ray transmission.

Performance Ratings. The American Architectural Manufacturers Association (AAMA) rates and certifies window performance through independent laboratory methods. Window manufacturers cite these ratings on their products so consumers can compare different types of windows by the same set of standards.

AAMA-certified windows are tested in several categories, including structural pressure, water resistance, and air infiltration. Based on the results of these tests, windows are placed in one of the following five performance classes (from lowest performing to highest): Residential (R), Light Commercial (LC), Commercial (C), Heavy Commercial (HC), and Architectural (AW). Each class of window also has a performance grade number, which corresponds to the pounds per square foot of minimum design pressure used for the performance tests.

The recommended performance class for aluminum windows in multi-family buildings is commercial or higher, with a minimum performance grade of 45, which would be designated as C-45. Anything lower will probably not be durable enough to provide long-term reliability.

Project Timeline. Window replacement projects, from the initial decision to move ahead until completion of the installation, can take up to a year or more. A typical replacement program would probably include the following steps and timeline:

Window survey. Since your building is replacing all its windows, a survey isn't necessary. For some buildings, however, the existing windows are in varying condition and of different styles, so a survey would determine which ones can be repaired, which need to be replaced, and which can stay as is. (Allow six weeks.)

Site work and construction documents. The engineer or architect performs site work to determine and analyze the condition of the windows, takes measurements, and prepares drawings and specifications. (Allow 12 weeks.)

Competitive bid process and contract negotiation. The owner reviews the specifications and drawings, and the approved documents are sent out for sealed bid to qualified window contractors. The engineer or architect reviews the bids and makes recommendations, and a contract is negotiated with the selected contractor. (Allow eight to ten weeks.)

Sample installation. The shop drawings (installation details from manufacturer) are reviewed and a sample of each type of window is installed and or tested to verify that it meets the specified AAMA-certified performance ratings. (Allow eight to ten weeks.)

Window fabrication. The windows are assembled in the factory. (Allow eight to twelve weeks, depending on the number of windows.)

Installation. The quality of any window replacement project depends on proper installation. The installation for each apartment (up to say, 18 windows) takes about one to one-and-a-half days; custom installations or special finishes may take longer. (The total installation time for all windows in the building will obviously vary depending on the building size; in your building it should take about 12 weeks.)

Knowing that the entire window replacement project will take up to a year to complete, your board should plan the project accordingly. Actual installation should take place in the spring, summer, or fall rather than in the winter, when the cold temperatures create an additional inconvenience for residents.

Fire-Rated Windows, Permits. Windows in fire-egress hallways, stairwells, corridors, or mechanical rooms may require a fire-rated assembly. Fire-rated windows have steel frames, wire-reinforced mesh embedded in single-paned glass, and fusible links (i.e., the window seals itself off when heat reaches a certain temperature so that a fire will not spread as quickly to adjacent apartments and properties). Windows on a property line (except those facing a street facade) also usually require a fire-rated assembly.

Unlike most repair and installation work, window replacement projects do not require a permit from the New York City Department of Buildings if the openings holding the existing window frames are not altered. Buildings that are landmarked or situated in a designated New York City historic district, however, require prior approval from the Landmarks Preservation Commission (LPC). If the replacement windows mimic the detailing and styling of the original windows, and the glazing area is only minimally reduced, then the replacement program has a much greater chance of getting LPC approval.

Even if no permits are required to replace the windows, a sidewalk shed will still be necessary for windows facing the street, courtyard, or other space accessible to pedestrians. Finally, an environmental consultant should be brought in to test for lead and asbestos that may be disturbed during the window installation.

By carefully considering your building's needs and planning accordingly, you and your fellow residents will enjoy the benefits of new high-quality windows for decades to come.


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