Preservation Challenge: Windows
Windows can be one of the most challenging components of a historic building. Historic windows are integral to a building’s character, but are often in poor condition or lacking in modern comforts. Many building owners incorrectly believe that rehabilitating a historic building means sacrificing energy efficiency and functionality in order to keep character-defining historic windows. Other times, windows are replaced with incompatible modern windows that don’t compliment the history of the building. Taking the time to properly evaluate historic windows, and choosing an appropriate replacement, if necessary, goes a long way in maintaining the history and design of a building.
Depending on the condition of the windows, their contribution to the significance of the building, and the intended future use of the building, windows will either need be retained, repaired, or replaced.
Retaining Historic Windows
Retaining historic windows, where possible, is always preferred according to the Secretary of the Interior’s Standards for Rehabilitation. The Standards require that as much historic fabric be retained as possible, including the windows. However, historic windows can present several challenges, most notably, energy efficiency. Historic windows should be inspected for failing caulk and weather-stripping to improve efficiency. To increase the R-value of single pane windows, interior or exterior storm windows can be installed. Storm windows double the R-value of a single pane window, while protecting the historic window from wear and weathering.
Repairing Historic Windows
Generally, historic windows will need some level of repair. This can range from simple repainting to replacement of entire parts. Deteriorated sashes and frames can be repaired with like materials. Broken panes can be replaced with glass of the same color, reflective quality, and transparency. Where the width of muntins allow, sashes can be retrofitted with insulated glass to improve energy efficiency.
Depending on the level of deterioration, repairing, rather than replacing, existing windows can actually be cost effective. Replacement windows available today have a shorter life span than historic wood windows. Additionally, modern window cannot be easily repaired without replacing the whole unit. The life cycle cost of repairing a window, verses a replacement unit, should be considered before a final decision is made. While repair may be more expensive upfront, the shorter lifespan of replacement units may outweigh the initial savings.
Replacing Historic Windows
When windows are deteriorated beyond repair, or repair is cost prohibitive, windows can be replaced. Replacement windows should match original windows in size, design, number of panes, muntin profile, color, and reflective qualities. Replacement options range from insert unit replacements, full replacements, or custom replicates.
One, or several different options, can be appropriate in the same historic building. It may be possible to repair some windows, while others may be highly significant or in fair condition, necessitating retention or repair. In addition to the condition and significance of the windows, the requirements of the future building occupants need to be considered. Do the windows need to function? Are specific window sizes or types required by code?
A window survey will help determine the best option for each of a building’s windows. Window surveys outline the condition of each individual window, in order to assess which windows are candidates for repair and which require full replacement. If the majority of the windows in a building are deteriorated beyond repair, it may be acceptable to replace all the historic windows. Window surveys also assess which windows are highly visible or contribute greatly to the character of the building. These windows should be altered as little as possible to preserve the historic character of the building. Windows on secondary elevations and those further from street level may be better candidates for replacement than windows on primary facades or those with exceptional craftsmanship or architectural significance.
The pros and cons for the historic building and the future building users need to be weighed before an appropriate treatment is selected. With careful analysis, a solution for both the building and the future occupants can be achieved.
