We live in a world where men build magnificent structures. Once one structure has been built, it is on to the next, and so our cities expand and age, and the buildings in them grow old and deteriorate. However, many older buildings are deemed historic and given a face lift that must hold true to their original architecture, and that requires them to keep their old wood windows or replace them with new ones. For many builders, this leaves only one option to increase the energy efficiency of the window and that is to add secondary glazing. However, there are problems that may arise as a result of secondary glazing and condensation.
For those who are unfamiliar with the term secondary glazing and do not know what it is, secondary glazing is an additional glazing panel added to the inside of an existing single glazed window. Typically a single glazed piece of glass, but sometimes a plastic film or shrink wrap, it is often surround by a metal frame which incorporates some sort of membrane or gasket to create a sealed interior air space between the new glazing and the old.
While some people are unfamiliar with secondary glazing, almost everyone understands condensation and how it generally occurs. For windows, since they are glass, it typically means that the exterior and interior temperatures are differing enough to cool the moisture that is in the air by the glass causing it to condensate onto the surface of the glass.
When it comes to wood windows, humidity and moisture are one of the things to avoid. They can cause warping and rotting, not to mention mold. Often times, problems are not identified until it is too late and the window has to be completely replaced.
Unlike double glazing, which is typically vacuum sealed in a moisture controlled factory, secondary glazing traps ordinary, moisture filled air, between it and the single glazed window. A drafty window can also allow moisture from the outside in. Given the right condition, that moisture will condensate between the glass and settle at the bottom of the window, increasing the chances of rot. This will also increase the humidity level between the two panes of glass, which will effect any wood exposed inside the seal.
The metal frame of the glazing panel also can be a culprit. Just like on glass, metal transfers temperature to the air and is likely to have moisture on it as well. While the moisture on the glass is easy to see, what is on the metal, especially between the panes, is much more difficult.
Wood windows that have failed due to moisture need to be replaced immediately. This can be very costly and labor intensive. So, when it comes time to look at how to weatherize windows, it is important to weigh all options available, looking at the positives and negatives, and decide which one is best.
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