Exterior Window Protection, Frames and Installation

Stained Glass windows are a tremendous asset to any congregation. Let Lamb Studios help protect your assets with expertly installed window coverings.

Our expert installers will carefully place protective window coverings into the existing window frames or will install a secondary framing system to place the window covering. We will install protective coverings in a manner that will minimize any obstructed view of the stained glass window and maximize protection. We will also carefully create venting in the protection glass or in the window frame to allow any moisture or heat to escape. An added benefit of protective window coverings is the reduction of heat loss through the window.

Stained glass and decorative arts studios have been dedicated to serving the artistic needs of churches and synagogues for many years. However, since 1973 it has become increasingly evident that a more pressing need is arising. Energy needs have taken precedence over artistic needs and studios are expanding their expertise into the energy field.

Even though energy losses are not limited to stained glass but occur through all single glazed areas, the insulation of a stained glass window poses more of a problem than does the typical window. By covering a stained glass window a church can save about 50% of the energy – either heating in winter or cooling in the summer – that is lost through the single· thick glass, a high conductor of heat and cold. There is also a greater loss when the windows are old, and the putty between the glass and lead strips hardens and cracks from expansion and contraction over time. A still greater heat loss takes place around an old steel ventilator which either does not shut tight due to sagging or corrosion, or which if it does close properly, is not weather-stripped. In the latter case, steel abuts on steel, which allows a great deal of energy to be transferred through these high conductors to the outside.

As for the problem of heat loss through steel ventilators, it is best to replace the steel ventilator with a modern aluminum unit that is double glazed, weather-stripped, and maintenance free. It should also be mentioned that it does no good to “sandwich” a piece of thin plastic covering against the stained glass in a ventilator. When it is an old steel ventilator that probably does not close tightly, the major portion of energy loss continues to occur. Furthermore, any thrown object will bend the plastic inward far enough to break the stained glass without being able to break the “space age” unbreakable plastic covering.

This standard energy loss, to which all unprotected stained glass windows are subject, is often further accentuated by failure to undertake certain relatively minor repairs. There is always the broken window which never gets repaired, either because the glass is irreplaceable artistically or because no one is available or capable of performing the needed repairs. Often some simple caulking is all that is needed, but due to the inaccessibility of some windows or just lack of awareness of this need, the caulking remains undone allowing a large amount of energy loss to occur.

A stained glass window can be covered with two basic types of material: glass or plastic. Different thicknesses of these protective covering materials are required depending upon the size of the window. Probably the most widely used plastics are polycarbonates, sold under the trade names of Lexan manufactured by General Electric and Tuffack manufactured by Rohm. General Electric guarantees its product unbreakable for three years. Rohm states that its product is “virtually unbreakable.” These products will yellow over time, so this is a major consideration. Also available are Plexiglas, acrylite, and lucite, which are plastics that can crack upon impact but are seventeen times stronger than 1/4″ plate glass. They will remain clear for a much longer period of time.

Plastics are easier to work with and install than glass. However, they often tend to have a slightly wavy appearance and sometimes a purplish cast when installed. Over time, they will scratch and accumulate dirt if not properly cleaned and maintained. This leads to an undesirable appearance from the exterior and gradually reduces the amount of light. This problem is especially severe in high pollution areas.

Glass, which was used exclusively until about thirty-five years ago when plastics became popular, is cleaned for the most part by rain and wind. It will withstand air pollution much longer, will not scratch, and can be cleaned very easily. Its great disadvantage, of course, is its relatively easy breakability.

An additional solution to this problem is the use of laminated architectural glass. With a polyvinyl butyral center layer bonded between two sheets of glass, laminated glass combines the clarity and clean appearance of glass with the damage protection afforded by plastics. Laminated glass may shatter upon impact, but it will break safely without glass splinters and will not allow flying objects to penetrate through the stained glass behind.

If re-caulking is needed, this should be applied around the perimeter of a window and at the horizontal joints. Old putty or dried caulking should be removed. It is worthwhile to apply a good grade of silicone caulking that will expand and contract with the changes of temperature and the movement of the building. A local commercial glass contractor can perform this work where it requires scaffolding. Once a good sealant is applied, one usually does not have to be concerned again about this problem. Use of inexpensive caulking is never advisable.

Whatever material is used as a protective covering for stained glass windows, it will provide the following advantages: reduction in energy loss, reduction in outside noise, deterrence of vandalism and damage due to accidents, and protection of the vulnerable lead strips and glass from corrosion due to pollutants in the air.

Key factors to consider when installing a protective covering for stained glass windows

  1. How accessible are the windows? Does scaffolding need to be used? How many windows are to be covered? What is the size of the window?
  2. What is the method of installation of the protective covering? Will it be cut to follow the window tracery or will it cover over the architectural details in a grid-like design (which in most instances is not aesthetically desirable)?
  3. What type of frame surrounds the windows (e.g., stone, wood, metal)? Which type of protective covering will be used and of what thickness?
  4. If the frames are wood, do they first need to be painted? Or even replaced, if the wood is rotting?
  5. How much traveling time is involved in getting to and from the church?
  6. If Laminated Glass is selected as the protective covering material to be used, need it be used for windows at a great height merely because it is also being used for street level windows? The danger of vandalism and breakage is much decreased for the more elevated window, and the less expensive Plexiglas can be used at that height.
  7. Will the ventilators be replaced? If there are many ventilators in the sanctuary, is it necessary to continue to use all of them, or can some be permanently sealed? If the latter, this will reduce cost.
  8. Will a protective covering conserve energy? The answer is clearly yes. Is it worth it? Yes, over time the installation depends on each church’s fuel consumption and conservation methods. Protective covering is an expensive proposition, ranging from a $500 project to a $75,000 project. However, it provides multi-faceted advantages for a church, making a full analysis of its real worth to a congregation somewhat difficult to evaluate.

As per recommended procedures set by the Stained Glass Association of America it is good to vent the air between the stained glass and the protective material. Typically, holes are drilled into the plastic and 1″ diameter aluminum screens are inserted. These are placed along the bottom and the top of a window. When using glass, either a soffit louver can be used along the top and the bottom or the corners can be cut off and screen mesh installed. It is important that air circulates along the entire surface of the leaded glass.