The U.S. General Services Administration (GSA) is responsible for an inventory that includes over 400 historic buildings constructed between the early nineteenth and mid-twentieth centuries. Most were built during the 1930's, a period of high quality public building construction. Many retain original wood or steel windows that are character defining architectural features. In keeping with the Secretary of the Interior's Standards for Rehabilitation, GSA seeks repair and maintenance approaches that preserve original materials and design, repairing, and upgrading windows for functionality, energy efficiency, and improved security, as appropriate. For large and complex historic building projects, GSA often undertakes detailed analysis of alternative upgrade approaches to weigh cost, lifecycle, energy efficiency, functionality, and preservation tradeoffs.

This analysis guides GSA in balancing conflicting goals between setting a high standard for federal stewardship and reaching sound and cost effective decisions. Sometimes through this process, GSA architectural teams devise new solutions that achieve preservation goals at a savings to American taxpayers.

As a rule, GSA cost analysis has favored repair with replacement of irreparably damaged windows where the historic windows are large, multi-paned, and fabricated in steel or bronze. On the other hand, project-specific cost analysis has generally favored replacement in kind at buildings containing simple wood windows, such as the one-over-one double-hung windows at the Department of Interior (DOI) Headquarters Building.

For each project undertaken, GSA examines the arguments for repair or a combination of repair and in-kind replacement that offer the best value for GSA federal agency tenants, along with stewardship of the nation's public building legacy.

The Potomac Annex (Old Naval Observatory Campus) and the Department of the Interior Headquarters Building are both in Washington D.C., are listed on the National Register of Historic Places, and require review by the State Historic Preservation Officer for the District of Columbia under Section 106, National Historic Preservation Act (NHPA). Alterations must conform to the Secretary of the Interior's Standards for Rehabilitation, which give first preference to retaining and repairing original materials wherever possible. Necessary replacements, such as irreparably damaged windows, must match originals, including configuration, profile, dimensions, and detailing of sash muntins, mullions, meeting rails, jambs, and sills.

Potomac Annex (Old Naval Observatory Campus), Washington, D.C.

Constructed between 1843 and 1910, the site is a campus of small buildings. Specified work (not yet executed, as of 2005) is limited to repair of wood sash, repair and replacement of sash weights and cords, and caulking to improve weather-tightness. Estimated costs of repairing 438 windows in Building 2 (based on 1995 prices) are $122,041 ($279 per window)

Window retention advantages include:

• Lower lifecycle cost
• Preserving original materials, maintaining historic integrity, and original appearance.

Potomac Annex (Old Naval Observatory Campus), Washington, D.C., Architect: James Melville Gillis Photo courtesy of HABS/Library of Congress