In a typical facade rehabilitation project, windows will represent a sizable portion of the building's envelope and a significant relative cost. Some previous window rehabilitation strategies performed during the energy crisis are failing, and window rehabilitation has come under greater scrutiny by the preservation community.
Often the most difficult decision when repairing a building is determining if the windows should be repaired or replaced. Repair of existing windows may not prove durable, and window replacement may be the recommended solution. The window replacement solution on a landmark structure, however, could conflict with the Secretary of the Interior Standards for Rehabilitation which recommends “preserving windows … that are important in defining the overall historic character of the building.”
Technical, economic, and political reasons all drive the decision to repair or replace a window system. The technical and economic reasons can be weighed only after a comprehensive evaluation of the existing window systems is performed and rational techniques are followed to compare window repair to replacement.
The paper is in the form of a guideline. It establishes a background to understand window systems, describes an approach used to evaluate the condition of existing window systems, and discusses methods of comparison for interpreting the technical and economic data from the evaluation process. Existing guides, design aids, standards, and other references that establish pertinent criteria are listed.