Windows are one of the most important character defining features on a historic building. For example, sliding windows, with their sashes on staggered planes, side by side, present a significantly different face than a pair of double hung windows, while providing nearly the same amount of light and ventilation. Vinyl windows, with a second frame installed within the existing window frame significantly reduces the amount of glass in the window.

It is preferred that existing damaged or deteriorated window frames and sash be repaired rather than replaced. Under no circumstances will solid vinyl or vinyl clad windows be approved for replacement windows. Metal clad windows may be approved for basement egress window applications only.

Guidelines for Repair

When repairing or, if necessary, replacing window frames or sash, work must comply with these requirements:

  • New frames or sash should be made of matching material.
  • Repaired or new window frames and sash should match the pattern of the old members in every detail, including but not limited to true divided lights, profile of muntins and width of rails and stiles.
  • Existing balance mechanisms should be retained if operative. Metal jamb liners may be considered. Plastic or vinyl jamb liners are not recommended and will not be approved in existing windows because of a lack of structural stability and long-term durability. (An instruction sheet on replacing worn sash ropes is included on the inside back cover of this booklet.)
  • Deteriorated wood may be repaired with wood epoxy consolidants.
  • Rarely, the commission will consider wood to be covered with custom formed aluminum panning covers.

Guidelines for Replacement

If replacing the entire window becomes necessary, the following conditions shall be applied:

  • The dimension of the original window must be retained.
  • Muntins, sash, frames, exterior casing and brick molds must be of material and dimensions to match other windows in the house.
  • New windowsills must be extended to receive the nominal 4” wide vertical exterior casing.
  • Aluminum and vinyl clad windows do not meet the above requirements. Vinyl plastic windows are not acceptable because they are made of non-historic materials and do not comply with the Secretary of the Interior’s Standards for Rehabilitation. (CLICK to Secretary of the Interior’s Standards on this website).
  • Metal windows may be considered for some applications, such as basement windows if they match the dimensions of the original windows.
  • Decorative materials such as Palladian, oriel, bay, Gothic, round or segmental top cannot be removed.

See illustration #8 for window parts.

Lead abatement: Call the coordinator for more information 

Historic Preservation Standards: Window Components

Storm Windows

If storm windows are to be installed, they must be visually compatible with the historic windows over which they will be installed. The following requirements should be considered when planning storms and screens.

  • Wooden storm windows are the most energy efficient and most appropriate for historic wood windows.
  • Storm windows must match the overall design of the window. Meeting rails or dividers on the storm shall match the meeting rail on the primary window.
  • Gothic or other curved head windows may not have horizontal muntins or divisions added to the sash to accept regular storm windows. The window may not be “squared off” to accept a standard rectangular storm.
  • Storm windows shall not cover historic trim or molding.
  • Glass must be clear.
  • Screens for storm windows may be half or full frame design. Dividers in the screen shall match the meeting rail on the window. A wood screen frame is preferable to an aluminum or vinyl screen frame.
  • Aluminum frame “combination storms” must be painted or coated prior to installation. They may not be mill finish.

Historic Preservation Standards: Storm Window Standards

Historic Preservation Standards: Basement Screen