Conforming to Standards

Colonial sills pitch at a modest four or five degrees and are therefore more likely to collect moisture-trapping soot and dirt. Today's sills are usually pitched at a steeper 11 degrees and higher. The bottom rail on the lower sash is also likely to be more impaired because of its exposure to weather. The most deteriorated windows on houses are most likely to be found on the top floors. In the eastern U.S., west-facing facades take the brunt of wind-driven winter storms and rapid temperature drops after afternoons of baking winter sun.

Even if a building has been conscientiously maintained window deterioration occurs. The Georgian Federal landmark Pennsylvania Hospital in Philadelphia-the first hospital in the country-has reached a point where, after 250 years, one more coat of paint will not suffice. Termite damage, dry rot, powder beetles, and all kinds of conditions are under the paint, reports Alvin Holm, AIA, who is fund raising chair for the preservation of the original Pennsylvania Hospital building.

Preserving the original dimensions of muntins is a problem when replacing single panes of glass with thicker insulated panes. The widths of muntins have evolved from nearly one-and-three-eighths-inch during the Colonial period, one-and-one-eighth-inch during the Georgian period, seven-eighths-inch during the Federal period, to as little as one-half-inch during the Italianate period. One-half-inch was too thin for practical purposes, and muntins were often broken and removed, so that larger panes of glass could be installed, reports craftsman Torben Jenk, who has restored many buildings in the Philadelphia area. He notes that an important shadow-casting feature is removed when the depths of muntins are reduced to accommodate the thickness of double-glazing.

The Secretary of the Interior's Standards for Rehabilitation (www.cr.nps.gov) defines rehabilitation as "the process of returning a property to a state of utility, through repair or alteration, which makes possible an efficient contemporary use while preserving those portions and features of the property which are significant to its historic, architectural, and cultural values."

The critical paragraph reads: "The guidance that is basic to the treatment of all historic buildings-identifying, retaining, and preserving the form and detailing of those architectural materials and features that are important in defining the historic character-is always listed first in the "Recommended" area." This is summarized by every restoration architect as giving first preference to retaining and repairing original materials wherever possible, or replacing in kind.

Parc Rittenhouse, Philadelphia, PA, before conversion by HillierArchitecture Photo courtesy of HillierArchitecture

These Standards are the historic preservation gold standard for national, state, local, and district authorities and preservation bodies. But buildings must confirm first to local landmark criteria, which, on occasion, are stricter in their interpretation. This can affect the project cost and construction phasing. An example is the conversion of the 1926, 17-story Philadelphia Parc Rittenhouse, formerly the Rittenhouse Regency into residential condominiums by Hillier Architecture. Under the Secretary of the Interior Standards, the preference is for all the original 1,000 wood double hung windows to be replaced with a compatible unit or restored. But since the building is registered with the City of Philadelphia Historical Commission, explains James B. Garrison, AIA, Associate Principal, Hillier Architecture, the Philadelphia Historical Commission prefers to see windows from the second to the fifth floors either be replaced in kind or rehabilitated. For upper story windows, they will consider compatible units of a different material that also meet the Secretary's Standards.

In the world of practice, questions regarding restoration or replacement are not always argued over the condition and functions of the windows themselves. "The biggest issue we have to confront is clients or contractors who say they must be replaced, or there is no other option," says Skarmeas. "But past experience has indicated that there is rarely a case in which windows are beyond repair and cannot be repaired, restored, and reused. While the costs may be high, there are technology, products, and methods today that allow us to restore deteriorated windows without resorting to a replacement program. The costs may be higher is some cases, especially if there is severe deterioration."