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The Repair and Thermal Upgrading of Historic Steel Windows
Park, Sharon C. AIA. Preservation Briefs: 13 The Repair and Thermal Upgrading of Historic Steel Windows, National Park Service, 1984.


    Table of Contents

        1. Contents
        2. Historical Dervelopment
        3. Evaluation
          1. Historical and Architectural
          2. Physical Evaluation
          3. Rehabilitation
        4. Typical rolled steel windows available from 1890 to the present
        5. Routine Maintenance
        6. Repair
          1. In Place
          2. In Workshop
        7. Weatherization
          1. Weatherstripping
          2. Thermal Glazing
        8. Window Replacement
        9. Summary
        10. Bibliography

    The Secretary of the Interior's "Standards for Rehabilitation" require that where historic windows are individually significant features, or where they contribute to the character of significant facades, their distinguishing visual qualities must not be destroyed. Further, the rehabilitation guidelines recommend against changing the historic appearance of windows through the use of inappropriate designs, materials, finishes, or colors which radically change the sash, depth of reveal, and muntin configuration; the reflectivity and color of the glazing; or the appearance of the frame.

    Windows are among the most vulnerable features of historic buildings undergoing rehabilitation. This is especially the case with rolled steel windows, which are often mistakenly not deemed worthy of preservation in the conversion of old buildings to new uses. The ease with which they can be replaced and the mistaken assumption that they cannot be made energy efficient except at great expense are factors that typically lead to the decision to remove them. In many cases, however, repair and retrofit of the historic windows are more economical than wholesale replacement, and all too often, replacement units are unlike the originals in design and appearance. If the windows are important in establishing the historic character of the building (see fig. 1), insensitively designed replacement windows may diminish--or destroy--the building's historic character.

    This Brief identifies various types of historic steel windows that dominated the metal window market from 18901950. It then gives criteria for evaluating deterioration and for determining appropriate treatment, ranging from routine maintenance and weatherization to extensive repairs, so that replacement may be avoided where possible. (1) This information applies to doityourself jobs and to large rehabilitations where the volume of work warrants the removal of all window units for complete overhaul by professional contractors.

    This Brief is not intended to promote the repair of ferrous metal windows in every case, but rather to insure that preservation is always the first consideration in a rehabilitation project. Some windows are not important elements in defining a building's historic character; others are highly significant, but so deteriorated that repair is infeasible. In such cases, the Brief offers guidance in evaluating appropriate replacement windows.

    (1) The technical information given in this brief is intended for most ferrous (or magnetic) metals, particularly rolled steel. While stainless steel is a ferrous metal, the cleaning and repair techniques outlined here must not be used on it as the finish will be damaged. For information on cleaning stainless steel and nonferrous metals, such as bronze, Monel, or aluminum, refer to Metals in America's Historic Buildings (see bibliography).


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