By: Elizabeth McTigue Wanga
A buildingas windows are one if its most important features. In addition to their aesthetic qualities, they provide natural light, ventilation and a barrier to the elements. As the key functionality of the window degrades, owners must make a decision regarding restoration, repairs, partial replacement and full replacement. Through a series of articles on windows, we will examine how to maintain windows. We will also discuss what solutions are appropriate once maintaining the windows is no longer a viable option.
To start our window series we will discuss rolled steel windows. These windows were most popular from the 1890s through the 1950as. The strength of steel allowed for the mullions to be significantly thinner than those of wood windows, allowing for sleek design. The ability to create large window openings with minimal structure was attractive for industrial, commercial and some residential buildings. These windows provide character to the building and a small investment in there restoration can greatly impact their longevity. Unfortunately, these windows are often associated with energy inefficiency and air and water infiltration. This often leads to their replacement. However, there are methods to increase there efficiency and maintain the beauty of the steel windows.
The longevity of steel windows can be increased by routine maintenance. This is the key to preserving all components of the building, and is essential for extending the service life of windows. Remediate signs of deterioration as soon as they become apparent. Light rust and any loose paint should be removed and the windows should be primed and painted. Any cracked glass and all glazing compound should be replaced. The connections, pivots and hinges should be inspected, and any missing or loose components should be replaced. In addition to maintaining the window itself, care must be given to the surrounding area in order to reduce water infiltration. The caulk joint between the window and the surrounding masonry or frame should be maintained. Additionally, lintels, parapets and roofs must also be well maintained to avoid any excess water entering the window system.
If the window has deteriorated beyond the point of routine maintenance, it may require a more extensive repair campaign. The sashes or whole window, including the frame, may be removed and thoroughly cleaned of all paint, rust and debris. Any bowed or pitted sections of steel must be repaired or replaced, and all broken or missing hardware should be replaced. The window should then be shop painted, re-glazed and reinstalled.
Low efficiency can be addressed by proper weatherizing of the steel windows. The appropriate method and approach for weatherizing the windows depends on the window configuration. Weather-stripping around the operable portion of the window may be warranted and should be designed to work with any operable panels. Thermal glazing may be an option; a design professional would need to evaluate if the steel frame, hinges or pivots could geometrically and structurally accommodate the additional load of double paned glazing. It is also possible to add a storm window; the design of the storm window would be dependent on the operation of the steel window and the resulting visual impact.
Although window replacement is not encouraged, there may be situations that warrant full replacement with another material or modern steel window. Any replacement considered should complement the buildings aesthetics. For more information on the restoration of steel windows, please read Preservation Brief B: The Repair & Thermal Upgrading of Historic Steel Windows.