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Condition Survey

The next planning step in almost every window study is to evaluate the condition of the windows by undertaking a detailed survey. Peeling paint, broken glass, loosely fitted windows, and apparent sill rot are not necessarily solid evidence that windows are beyond repair. For a majority of older buildings, failure to examine the existing window conditions closely precludes an objective evaluation of repairing and upgrading the existing windows versus partial or total replacing.

The surveys are often conducted by a window consultant, although some architectural firms have benefitted by having a staff member develop the skills to perform the survey. Without an objective and detailed condition survey (along with the window assessment) it is difficult to weight accurately the rehabilitation alternatives to ensure that the most appropriate window treatment is chosen. Too often the contractor is expected to give repair and replacement costs with little guidance from the architect. There are inherent problems in such an approach. Most contractors will not examine the windows carefully because it is a time-consuming process, and instead will bid close to replacement cost for repair work. Replacing windows admittedly is easier to plan and budget for, but in the final analysis it is not necessarily most cost-effective or appropriate.

If the window condition survey and the window significance assessment clearly support retention of the historic windows, then the next planning step is to examine the numerous options for repairing and upgrading the existing units. Often the assessment will prove inconclusive, thus requiring examination of other alternatives, including replacing many or all of the windows with others offering matching features and enhanced performance. Based on the window assessment, there may be cases where replacement windows could appropriately match only the overall appearance of the historic window rather than the exact design. This makes possible the use of modern commercial windows that have been adapted to the historic rehabilitation market, yet that consist of different materials. Once the options are identified and preliminary cost estimates are derived, other factors may influence final decisions about window work.

An energy study of the overall building — not just the windows — coupled with cost-payback analysis may lead to the conclusion that, for a particular building, double glazing (retrofitted either to existing windows or in replacement units) is simply not cost- effective. Such findings are not necessarily confined to geographic areas with mild climates. Taking steps to reduce air infiltration, however, is usually always cost-effective where older, poorly maintained windows are involved.

Fisher, Chuck. Rehabilitating Windows in Historic Buildings: An Overview (GSA 08500-03), Historic Preservation Technical Procedures, U.S. General Services Administration


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