Window replacements fuel energy efficiencies.
Cutbacks in services, dramatic rate increases, and a battening down of hatches are obvious short-term solutions, but these can prove to be long-term mistakes. Instead, a prudent investment in a more efficient plant can offer long-range dividends, either by attracting new income or by decreasing operating and maintenance costs.
A building's windows can be viewed as such a plant system, offering both kinds of revenue boost.
Replacing old windows can reduce operating costs by increasing energy efficiency. It also can lower maintenance costs and help to improve the competitive "rentability" of available space. Thus, especially when windows are more than 15 years old, window replacement certainly deserves a careful cost-benefit analysis.
To do so, managers must first understand how various window features deliver cost-cutting or revenue-enhancing benefits. Windows are quite complex, and a range of choices is now available. Managers should consult with architects, particularly in large jobs, for appropriate window specification. Window manufacturers or contractors also can provide useful advice.
Following are a few of the factors managers should consider when deciding whether to replace windows.
Windows have no direct operating costs, but they do exert a major influence on one very significant operating cost: energy. Old windows with mediocre insulating value or air leakage around warped, deteriorated, or damaged frames can as much as double heating and cooling costs.
Energy-efficient replacement windows, on the other hand, provide insulating glass, thermally insulated frames, and precision, tight-fitting construction that minimizes air leakage.
* Glass choices. Insulating glass is a manufactured unit consisting of two or three separate panes (or "lights") of glass, separated by an insulating air space and hermetically sealed around the edges. The space between the two lights may be dry air or a special, inert gas, such as argon. Use of the gas is a relatively new development, and now it is used in 15 percent of the windows made for non-residential construction.
A recent study conducted by the American Architectural Manufacturers Association, a trade group based in Palatine, Illinois, shows that five out of six window units sold for replacement or remodeling purposes in 1990 were insulating glass units, compared to three out of four units five years ago.
Triple glazing, employing three lights of glass, improves energy efficiency even more than the standard double glazed variety, but can cost up to 25 percent more. Thus, the higher price tag of triple glazed windows should be carefully weighed against the cost savings offered.
Windows today also offer more choices in glass type than those available only a few years ago.
Coated or tinted glass, which helps reduce unwanted solar heat gain, gradually is replacing clear glass; according to the AAMA study, it represented 85 percent of the windows sold for non-residential replacement and remodeling in 1990.
Coatings may be reflective, featuring a bronze or silver mirror-like exterior sheen, or low-emissivity, known as "low-E." Low-E is a thin, transparent coating that helps reduce heat build-up; it is showing increasing popularity and was used with 19 percent of the glazing in new non-residential construction in 1990 and with 11 percent used in remodeling.
Tinted glass, which is colored like a pair of sunglasses, is still quite popular. It was used in half of the non-residential glazing in 1990.
Glass available today is annealed, tempered, or laminated. As the most common practice, annealizing is used to produce inexpensive, general-use glass; it allows the glass to cool slowly after heating. When broken, annealized glass can shatter into large, potentially dangerous shards.
In contrast, tempered glass is cooled rapidly. It is four times stronger than annealized glass and breaks into small, safe cubes. For this reason, tempered glass is used extensively in cars.
Finally, laminated glass sandwiches multiple layers of glass between thin layers of clear plastic, such as polycarbonate or urethane. Laminated glass exhibits the highest level of strength of the three types of glass currently available and will not shatter.
Recently, certain plastics like polycarbonates have come into use, representing 2 percent of 1990's non-residential glazing. These plastics offer light weight and high resistance to breakage.
* Framing choices. Because a window frame can reduce leakage of heat and air, it is critical to energy efficiency.
A wide variety of framing materials is available: aluminum, wood, and vinyl, or combinations like vinyl-clad wood and aluminum-clad vinyl. Steel framing is rarely used today, except in industrial applications that demand a high degree of structural strength.
For non-residential uses, particularly multi-story applications, aluminum was the framing material of choice in 1990, accounting for 86 percent of the total. Aluminum combines structural strength and stability, and can support highly durable exterior finishes.
In addition, more than 70 percent of the aluminum-framed windows ordered in 1990 were "thermally broken." This feature provides insulation that breaks the high thermal conductivity of metal and is highly effective in energy efficiency.
A thermally broken aluminum framing member actually is composed of three pieces: an outer extruded frame, a central core of insulating material and an inner extruded frame. Because the inner and outer metal components do not touch, heat transfer between the interior and exterior is greatly reduced.
The central core of an insulated window frame typically is made up of strong, durable, high-density polyurethane or rigid vinyl (PVC). Polyurethanes form a structural bond with the aluminum to create a strong composite structure. In contrast, PVC frames incorporate rigid PVC inserts that are used to form a mating fit with the inner and outer extrusions.
While not quite as strong as aluminum frames, vinyl frames are natural insulators, and so do not employ thermal breaks.
One advantage of aluminum and vinyl framing materials is their ability to be precision-formed into tight-fitting frame assemblies. Close tolerances can be maintained to keep air leakage to a minimum. Further, aluminum exhibits relatively high dimensional stability over time, so the precision fit won't deteriorate due to warping, swelling, or rotting.
An additional benefit of thermally efficient windows is that they reduce moisture condensation on the inside surfaces during the winter. At best, this can be annoying; at worst, condensate can damage surrounding trim and wall materials. Although regulating indoor humidity is the only way to completely control condensation, insulating window designs which keep the inside surfaces at or near room temperature will all but eliminate the problem under most conditions.
In addition to energy savings, one of the primary advantages of replacing old wood or steel windows with those made of aluminum or vinyl is the reduction of maintenance costs.
Properly specified windows with good structural properties and high-performance sealants, gaskets, and hardware can, with reasonable care, be expected to perform well for years. Thus, building managers should work closely with the architect to choose window types and features that will minimize the frequency and difficulty of maintenance, including washing, repairing hardware, and replacing parts and glass. Specially, property managers should choose designs that permit easy replacement of the hardware, gaskets, or glass from the inside.
* Finishers. Maintaining frame finish can be especially costly on old, deteriorated windows. However, new windows will require varying degrees of finish maintenance, depending on the type of finish and its bond with the underlying framing material.
Vinyl (PVC) windows usually have no separately-applied finish, as the exterior color and texture are an integral part of the framing material. Thus, modern PVC formulations demonstrate excellent resistance to color fading and rarely need cleaning. Painting, with its labor-intensive scraping, sanding, and priming, is eliminated.
Among aluminum windows, mill finish aluminum, which has a natural, silvery appearance, is being replaced by frames featuring the variety and improved economy of anodized or painted finishes.
Anodized finishes, found on 55 percent of the aluminum windows purchased for non-residential use in 1990, are applied with an electrochemical process that enhances the formation of aluminum oxide, a chemical that forms naturally in a thin surface layer on aluminum. The result is a durable and attractive finish that is available in a full spectrum of colors.
Painted finishes or coatings, used on 42 percent of the architectural grade windows sold in 1990, are baked on at the factory much like automotive finishes. Available in virtually any color, these finishes also are very durable and will not crack, peel, or fade over many years of exposure.
Both anodized and painted finishes on aluminum frames require virtually no maintenance beyond washing.
* Washing. The degree and difficulty of exterior washing required depends primarily upon window configuration. Windows that may be washed from the inside of the building can reduce maintenance costs substantially.
In some cases, windows with outside surfaces accessible from the inside (like double-hung units with tilt-in sashes) can be cleaned by the custodial staff rather than by specialized contractors further reducing maintenance costs.
A less quantifiable benefit of window replacement is its potential for attracting revenue-producing tenants. Some features that are popular with tenants are listed below:
* High energy efficiency appeals to tenants who must pay their own heating and cooling bills. Also, eliminating annoying or uncomfortable drafts and consideration keeps tenants satisfied.
*Modern tinting, coated glazing, and colored framing can improve the building appearance dramatically, making it more attractive to tenants.
*Sound transmission can be reduced through the same insulating characteristics of energy-efficient windows that reduce heat transmission. This provides better indoor quiet.
*Operable windows give tenants the option of natural ventilation on mild days, often a pleasant alternative to artificial indoor environments.
*Windows that offer an extra measure of security, including forced-entry-resistant construction, will appeal to safety-minded tenants, especially in low-rise structures.
The range of windows available has increased markedly over recent years, offering architects and building owner/managers a number of new options. In addition to the more traditional styles (double/single hung, sliding, casement, fixed, awning, or hopper), the selection includes projected, top-hinged (swinging), and pivoted styles.
In 1990, 60 percent of the architectural windows purchased for non-residential new construction and remodeling were of the fixed type. Of the remaining operable windows, 43 percent were single or double hung, 35 percent were swinging or projected, and 22 percent were sliding-type.
Among the most popular new styles, however, are greenhouse and dual-action windows.
Greenhouse windows are a popular addition to multi-unit housing, particularly those buildings with a shut-in feeling. Because they project outward from the building, these windows allow in an abundance of light, and so are well-suited for tenants who wish to grow plants and vegetables inside.
Dual-action windows, originally developed in Germany, are rapidly increasing in popularity in the United States, and offer two modes of operation. The bottom-hinged windows may be tilted in from the top for indirect ventilation, and the side-hinged variety may be swung in from the side for easy cleaning and maintenance. Both employ a single control handle.
It is important to note that local safety considerations may dictate the choice of styles and features, particularly for windows located at or near ground level. Thus, managers must evaluate all local restrictions before making any window improvements.
Foe example, many building codes require that windows in certain locations provide for escape in case of fire or other emergency. In some cases, the same window must allow firefighters or other emergency personnel to get in, a provision that in some cases may conflict with requirements for break-in resistance.
In addition, the use of highly impact-resistance glazing in some areas may have to be accompanied by special fire-protection design features. Also, operable windows must not place a building occupant in any danger of falling out when the window is opened.
Regardless of the construction, finish, glazing, or other features, quality manufacturing and installation are critical if replacement windows are to deliver the expected benefits.
The American Architectural Manufacturers Association (AAMA) offers voluntary performance standards for manufacturers of aluminum and vinyl windows. The AAMA standards are reviewed and approved nationally by the American National Standards Institution (ANSI) and cover the basic performance factors of structural strength and resistance to air and water leakage.
The AAMA also conducts periodic, unannounced inspections, performed by an independent, accredited firm. All conforming products receive a certification label and are listed in the AAMA Certified Products Directory. The AAMA also implements a Thermal Performance Standard, which rates products according to tested "U-value", a measure of heat conduction, and"Condensation Resistance," as well as a Forced Entry Resistance Standard. Both ratings are included on "tabs" added to the basic AAMA certification label.
Recently, thermal performance labeling of windows has become a more important issue nationwide, and federal legislation has been proposed. Locally, 27 states are in various stages of implementing, adopting, or considering their own thermal performance requirements, including testing, rating, and labeling provisions.
To keep builders and managers informed of these changes, several industry associations, states energy code directors, and utility and consumer representatives have formed the National Fenestration Rating Council. NFRC now is working to develop a National Uniform Rating Classification for window thermal performance, beginning with a standardized procedure for determining U-values.
With the assortment of attractive, energy-efficient replacement windows available today, property managers can upgrade their buildings' windows easily to allow for more efficient use of maintenance dollars. Thus, as an intelligent plant investment, windows can be a viable part of a long-term management strategy that both contains today's costs and allows for increased rental income in the future.
John Gurniak, P.E., has been technical director of the American Architectural Manufacturers Association, Palatine, Illinois, for the past seven years. Before joining the AAMA, he held a variety of engineering, marketing, sales, and general management positions.
Mr. Gurniak is a member of the American Society for Testing and Materials, the American Society of Heating, Refrigeration and Air Conditioning Engineers, the American Society of Mechanical Engineers, and other organizations. He holds several U.S. patents and has authored numerous technical papers.
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|Title Annotation:||Operating Techniques and Products Bulletin 411|
|Publication:||Journal of Property Management|
|Date:||Nov 1, 1991|
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