Many apartment buildings built in cities in the 1930's "Art Deco" style were originally fitted with what are typically called "factory sash" casement windows. Single glazed, as were most windows prior to the 1970's energy crisis, with one inch deep steel frames and thin steel muntins, they are perfect heat sinks sucking heat out of the interior, and leaving condensation, damaged plaster and rotted wood sills behind. Yet they let in large amounts of light, and solar heat gain (insolation), that give modest rooms a spacious, airy feeling. The window openings are much larger than the punched openings of traditional masonry architecture and often turn the building corner to create the de-materialized corner that is characteristic of modernistic architectural styles. They are integral to the character of the Art Deco style and part of our architectural history.
All too often, with the objectives of reducing heat loss and maintenance costs, and of keeping first costs as low as possible, the windows are replaced with little thought to their positive qualities and to the integrity of the building's architecture. A common approach is to use vinyl double-hung sash, often without muntins, with wide sightlines at the sash frames. The double hung units are mulled together using clunky mullions between between them. Corners are boxed out and the plane of glass, which was originally uniformly four inches back from the face of the masonry, has a step at the meeting rail, so that the double hung sash can bypass each other. In addition, in order to allow depth for the sash to bypass each other, any reveal of masonry at the jamb is eliminated. In short, significant elements of the buildings character are lost.
Nevertheless, the original windows may be such a liability that they have to be replaced, so the question is what is the best compromise that saves energy and the architectural character of the building at a reasonable cost?
At a 1938 Art Deco apartment building in the Cleveland Circle section of Boston recently, Red Hawk Studio was faced with this problem. An easy choice would have been to use up to date steel casements, with insulating glass, that would essentially replicate the originals. These are available, but they are quite expensive. Instead, we selected thermally-broken aluminum casement windows, which provide good thermal performance, relatively narrow sightlines, and a reasonable price.
The sash sizes were laid out, first to meet Building Code requirements, but also to allow the same module (with minor variation) to be used in practically every window in the building, even though the window openings are of different sizes. A uniform module in the pattern of window panes was another characteristic of the original windows. However, because of the thicker size of the aluminum sash members, we could not hope to duplicate the original module (approximately eighteen by eleven inches) and maintain a light and airy feeling. Therefore, fewer divisions were used, both horizontally and vertically.
Aluminum casements allow a less deep frame than double-hungs, and by cutting back the interior jamb finishes and wood stool, the original setback reveal at the exterior masonry jamb is maintained (less about a quarter inch to cover the old caulking). An aluminum snap trim is used at the interior so that the cutting doesn't have to be particularly neat. In the process, about an inch of depth at the interior is lost, which is proportionally not noticeable, but may require relocating some window treatments.
The existing round tube corner columns are boxed on the interior rather than the exterior to provide insulation from conductive heat loss through the steel column, yet maintain the de-materialized appearance at the corner described above.
While absolute historic replication may be an ideal, these Art Deco buildings exist in enough abundance in most cities to allow some compromise in authenticity. The important thing is to maintain their livability through upgrading building components, such as windows, while not losing the architectural qualities that make them attractive in the first place.
If you have further questions about this case study, please feel free to contact Red Hawk Studio Architects,
Inc. by phone (978 369 2340) or e-mail (firstname.lastname@example.org).