Topic: Windows, doors, skylights, solar systems and roof accessories
These guidelines apply to all exterior windows, doors, skylights, solar systems and roof accessories. For the purpose of these guidelines the term “skylight” Is defined as any opening in the roof of a structure for the purpose of introducing natural light. “Solar systems” is defined as any passive or active device or material which are intended to collect, store and/or convert energy from the sun. “Roof accessories” are defined as chimney caps, vents, or other mechanical additions placed on or adjacent to the roof of a structure, not including decorative items such as weather vanes, flags or lighting.
The Secretary of the Interior’s Standards for Rehabilitation and Guidelines for Rehabilitating Historic Buildings recommended against:
“Removing or radically changing windows which are important in defining the overall historic character of the building so that, as a result, the character is diminished;”
“Changing the number, location, size or glazing patten of windows, through cutting new openings, blocking-in windows, and installing replacement sash which does not fit the historic window opening;”
“Retrofitting or replacing windows rather than maintaining the sash, frame and glazing;”
“Installing new exterior storm windows which are inappropriate in size or color, which are inoperable;”
“Changing the configuration of a roof by adding new features such as dormer windows, vents or skylights so that the historic character is diminished;”
“Installing mechanical or service equipment so that it damages or obscures character-defining features; or is conspicuous from a public right-of-way;” and
“Locating solar collectors where they radically change the property’s appearance; or damage or destroy character-defining features.”
The following guidelines are provided to assist in the interpretation and application of the Secretary of the Interior’s Standards and Guidelines.
Window and Doors
Window and doors present a variety of problems due to period of construction, size of opening, method of operation, and other features. The guidelines will be applied with flexibility to allow for these differences. At the same time, windows and doors are often important historic features as part of the structure and in their own right. For that reason, every effort should be made to preserve or duplicate the unique features of the original windows and doors.
Wherever possible, repairing and retaining original windows and doors is preferred. There are various commercial products available and experienced local companies which can make possible the repair of even severely damaged windows and doors, often at less expense than comparable replacements.
When original windows and doors cannot be repaired, are missing or a new opening is added, it is normally possible to replicate existing windows and doors. A number of local and national sources are available for replacement windows and doors which are historically appropriate.
Specific issues considered by the Commission include the following:
Size, Shape and Proportion
Replacement windows and doors should fit existing openings and be consistent with existing trim and other features of the structure. Replacement windows should duplicate the appearance of the existing original windows in design, size, proportion, reflective qualities and profile including the profile of sash rails, stiles and muntins. Other design features reflecting the style of the structure should be considered, particularly original windows, doors, moldings and surface finish.
Appearance of the finished window or door is the paramount concern. Steel, vinyl, aluminum or fiberglass seldom match the appearance of wood, and they do not lend themselves to the application of added detailing. Window bars and metal security doors generally are not appropriate additions. Other security measures are less intrusive and equally effective. If the original windows are wood, then wood replacement windows should be used unless the specific alternative product is approved by the Commission.
Detailing, such as the use of inset panels, carving, bevelled glass and other features may be considered if consistent with the style of the structure.
Glass Block Windows
The use of glass block to fill window openings generally is not appropriate. Under the Secretary of the Interior’s Standards and Guidelines, replacing or blocking in windows is not recommended. Instead, the repair of existing windows features is favored. Wherever possible, this approach should be followed. However, there are circumstances, such as where original windows are missing or not repairable, which may lead applicants to desire to use glass block to close in openings. Such applications will be considered more favorably for locations such as basements where visibility is limited.
The use of glass block presents unique problems. Because the opening is sealed, ventilation is eliminated. In response, contractors recommended small vent windows set into the glass blocks, but there are particularly obvious and inappropriate in historic structures. Even where glass block may be acceptable, adding a vent destroys the symmetry of the glazing and adds a second inconsistent feature.
An approach more likely to be seen as appropriate is limited use of glass block in basements. One (1) or more openings can be left with original windows or like replacements to allow for adequate ventilation. This allows the use of glass block in other windows without obtrusive vents. It also allows the applicant to leave any windows visible from the street with original or like replacement windows.
Where glass block is approved, the Historic Preservation Commission may require additional measures to lessen the impact of the change from the original windows. Among such measures are the following:
- Recessing the glass block as deeply as possible in the foundation wall;
- Using block sizes and glazing patterns to follow as closely as possible other window styles in the structure;
- Placing a window screen or obscuring storm window over the basement window opening to obscure the glass block;
- Arranging landscaping to lessen the visibility of the glass block;
- Using textured, obscuring glass block rather than clear, reflective glass block; and,
- Not using glass block on windows visible from public rights-of way.
Storm Windows and Doors
The following issues will be considered in reviewing applications for the addition or replacement of storm windows and doors:
- Storm windows and doors may be of either wood or metal (aluminum) construction;
- The use of mill finished (unpainted) aluminum window and door frames will be not approved. Frames must be painted and the color of storm window sashes and frames shall match or be consistent with the house base, trim or sash color;
- The storm windows framing shall match or be aligned with the sash frame of existing interior windows including the center meeting rail in double hung windows and other similar features;
- Storm doors shall contain a maximum area of glazing and shall align with and be consistent in design with the interior door;
- Obscuring glazing material shall not be used for storm doors. Obscuring storm windows may be allowed over basement windows if the windows are not visible from the public right-of way.
The application should include at a minimum, a sketch or illustration, as from a manufacturers catalog, and preferably sample materials of the storm doors and/or windows to be used, along with narrative descriptions of the number, sizes, locations of windows to be installed, paint color of existing house trim , paint color of windows, door frames, and door.
Skylights, Solar Systems and Roof Accessories
The application of materials which will adversely alter the original roof line and/or physical character of designated historic landmark structures and structures within designated historic districts is discouraged. Owners of historic properties should explore alternative means of adding light or conserving energy before considering the use of installation of skylights and solar systems.
Where owners apply to install skylights or solar systems to the structure the Commission will evaluate each application on its merits. Factors which will be considered included the following:
- The historic character and architectural importance of the structure and surrounding environment;
- The intended purpose of the installation;
- Other alternative means explored for introducing natural light to the structure’s interior and/or conserving heat energy, and the reasons for their rejection;
- The visibility of the skylights and/or solar system from adjacent public streets and adjoining properties; and,
- The design and replacement of the skylight and/or solar system and their compatibility with the structure’s roof line, color, texture, and shape.
Generally, utilitarian roof accessories will be reviewed by the staff and given administrative approval. Where the proposed installation will have a significant impact on the roof line or other feature of the structure, such as the installation of large turbine vents or other obtrusive accessories, the proposal will be referred to the Commission.
These guidelines were approved by the Michigan Bureau of History as of October 25, 1995 pursuant to Section 5.(3) of Act 169 of 1970, as amended (Local Historic Districts Act).