Windows and Window Openings
Among the greatest challenges in designing and constructing weather-proof buildings are the design and installation or handling the windows' openings. Rather than a component separate and apart from the weather envelope, windows are an integral part of the weather envelope.
While they are an integral part of the weather envelope, the openings in which they are placed are penetrations in the water barrier. This viewpoint facilitates correct analysis of the design, construction, and installation of windows and openings.
If one were to consider the weather envelope of any building as an uninterrupted continuous membrane, such as a plastic sheet, for example, containing and protecting the interior space from the elements, then the problem of adding window openings into this membrane becomes clear--windows are actually glass panels or other panels framed with aluminum, steel, wood, or vinyl, inserted into openings made into this membrane, or water barrier, for purposes of aesthetics, ventilation, lighting, livability, or for some other purpose. In this light, how to make the window and all of its parts continuous with the water barrier, and with each other, is the essential challenge.
This continuity, if accomplished, must also be permanent. Windows are one of the major sources of problems in construction because this continuity is either not accomplished in the first place, or not accomplished with a reasonable degree of permanence. This problem is really two-fold, and failure in either area results in a defective installation:
The window unit or window assembly itself must have continuous permanent weatherproof integrity.
The method of installation of the assembly into the weather envelope must have continuous permanent weatherproof integrity.
Indeed, the marks of a correct window design, assembly, or installation are three:
1. Permanent
2. Continuous
3. Weatherproof
There are many different types, manufacturers, uses, and constructions of windows, with many variations among them. They are made of aluminum, steel, vinyl, wood, or combinations of these. They are fabricated in shops or in the field. However, they all have one thing in common—when installed, they must form a continuous unbroken barrier against the weather, continuous with the building's weather envelope. This is the area wherein the majority of construction defects occurs with windows.
