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By James Piper
January 2004 -
Windows & Exterior Walls
A window replacement project can reduce operating and maintenance costs, improve the indoor climate and comfort for building occupants, and enhance the overall appearance of the facility. But window replacement projects should not be entered into lightly. They are expensive, costing between $25 and $50 per square foot. They are disruptive, forcing the temporary displacement of occupants. And the choices made must be lived with for a long time, anywhere from 30 to 50 years.
For these reasons, facility executives must carefully decide on the best options. What type of windows should be installed? Should they be operable? What is the best frame material to use? Should special glazings be installed? While most of these options are considered in window replacement projects, one question is frequently overlooked: Should the windows be replaced, or is it better to repair the existing ones?
No single answer fits all facilities. In determining the best option, facility executives must look beyond first costs to evaluate which one best meets the economic, comfort and aesthetic needs of the facility.
The repair-or-replace decision must be based on the needs of the facility and the actual conditions of the existing windows, not on assumptions about those conditions. While needs will vary with the application, there are many common factors to be considered when evaluating the repair or replacement decision.
Many of the items that need to be evaluated require a close inspection of the window. In larger facilities, particularly those with a large number of windows, it isn’t practical to inspect every window. Instead, a sample of the windows can be inspected. The sample should look at 10 to 15 percent of each type of window being evaluated and should include windows from each building exposure.
Even minor changes in window construction can make a significant difference in how the building looks. The type of frame, the color of the frame, the tint of the glazing all affect how the window and the building appear.
Look closely at the existing windows. The appearance of any window will deteriorate with time and exposure to the elements. In some cases, routine and preventive maintenance can restore them to their original appearance. In other cases, the cost of restoration will add up to a significant portion of the cost of replacement windows. In evaluating the appearance of the windows, consider whether window components detract from the appearance of the building, what it would take to restore their appearance, and whether it would it be a one-time effort.
If new windows are being considered and are determined to be the best option for the building, consider having one of the new units installed as a test case to determine how it will affect the building’s appearance.
Caulking is used to seal the gap between the window frame and the building wall. Failed caulking allows moisture to enter the building, penetrating wall and window components and causing them to deteriorate.
To be effective, caulking must seal the gap between the frame and the wall. Closely examine the caulking for splits and areas where it has cracked or pulled away from either the wall or the window frame. Although failed caulking is a relatively minor item when considering repair or replacement, it can indicate possible hidden damage. If a large number of the windows are found to have failed caulking, the window’s structural components must be evaluated before deciding to repair or replace the windows.
The promise of improved energy efficiency is one of the most often-cited reasons for replacing windows. Increasing the number of glazings, reducing the rate of air infiltration and using a heat-reflective coating will all improve energy performance. But replacing the window is not the only way to improve energy efficiency. Storm sashes can be added to reduce the thermal conductivity of existing windows; weatherstripping can reduce the rate of air infiltration; and reflective film can reduce heat gain. Interior insulating windows can reduce heat transfer and air infiltration.
Evaluate how and where energy efficiency improvements can be made to the existing windows. How do those improvements compare to those that would be achieved by replacing the windows? What is the cost differential between upgrading and replacement?
As windows age, their components wear and deteriorate. Some components shrink and dry out, resulting in gaps that can allow air to infiltrate into the building. The looser the fit, the greater the infiltration. It doesn’t take much of a gap to allow infiltration to become a problem. Here’s a simple way to test the gap between surfaces in operable windows: close the window on two dollar bills placed on top of each other. If the bills can be pulled easily from between the surfaces, the gap and infiltration rates may be excessive.
Frame materials can deteriorate as the result of rot, corrosion, physical damage, weathering and other factors. As they deteriorate, more air and water can infiltrate into the occupied space. Severe deterioration can result in the structural failure of the window.
In most cases, only wood frames can be repaired. Deterioration of all other frame materials beyond surface corrosion will usually require the replacement of the entire window.
An important factor to consider when evaluating the repair/replacement option is how much light should be allowed to enter the occupied space. In buildings with large areas of glass, the solar heat gain through the windows can make spaces near the windows difficult to cool, even during the heating season. Facility executives have the option of installing new windows with a solar control glazing, or they can apply a solar control film to the existing windows.
Solar transmissivity in new windows is controlled through the use of tinted or coated glazings. Glazings in use today can eliminate as much as 80 percent of the solar heat gain while allowing nearly 90 percent of the sun’s visible light to pass through. These glazings have the same appearance as clear glass so they can be added to a building with no significant change in its appearance.
Existing windows can have a film applied to the inner surface of the inner glazing to control solar transmissivity at a much lower cost. Although these coatings can produce similar savings, they do not have service lives comparable to that new glazings. When considering which solar control option is best-suited for a particular facility, consider the overall condition of the windows and the other performance characteristics needed.
Window hardware is subject to wear from normal use. Locks, springs and other hardware can be replaced on an as-needed basis. If maintenance requirements for the window hardware are increasing as a result of the age of the windows, or if the existing hardware is not adequate for the application, then replacement might be the best course.
One of the most common building occupant complaints concerning windows is that they are difficult or impossible to operate. Over time, window components can swell or warp, causing them to bind. Similarly, paint can seal windows shut. The cost of restoring these units to operable condition can exceed the cost of a replacement window. If the survey determines that a high percentage of the windows cannot be easily opened and closed, and that operability is a desired feature for the application, then replacement may be the best choice.
Painting is a significant factor in determining the cost of ownership of a wood window. Over the service life of the window, the cost of painting will exceed the initial cost of the unit. Look at the maintenance records for the windows. If windows are being repainted on a five- or six-year cycle, replacement with a unit that does not require painting may be more cost-effective.
Finally, no matter how good the windows are, if they do not meet the needs of the building occupants and the tasks being performed inside the facility, they will need to be replaced. Even if the windows met the needs of the occupants when the building was constructed, changes in the facility may have altered things to the point where the windows are no longer suitable.
For example, fixed windows were often installed in facilities on the assumption that they were required to meet the security and energy use requirements of the space. Over time, if the functions performed in those spaces changed, fixed windows may no longer be a requirement. In fact, it may be that installing operable windows would improve the energy efficiency of the space.
Consider the needs of the space and determine if operable windows would best meet the space requirements. If the existing windows cannot meet those requirements, then replacement may be the only alternative.