Vinyl windows are very popular. Their clean lines, no maintenance characteristics, and energy efficiency make them a natural for both new homes and older homes that need a facelift. However, not all vinyl windows are created equal. In fact, there can be vast differences in quality between windows that look identical.
The Raw Materials
Wood and aluminum windows have an advantage over vinyl windows in one respect. Wood and aluminum are stiffer and they don’t bend quite as easily as vinyl. This is just one reason why it is important to really do your homework when deciding which vinyl window to purchase.
Many homeowners who installed the first generation of vinyl windows were disappointed. Large windows or windows that faced direct, hot afternoon sunlight sometimes were the victims of sag. The vinyl would sag under the weight of large, heavy pieces of glass and/or would sag because the vinyl softened because of heat. The results were not pretty, as the vinyl would sometimes retain this new shape after the vinyl had cooled.
Other homeowners became disenchanted with vinyl windows because they would mysteriously change color after several years. Poor quality vinyl windows had a tendency to turn yellow. This color change was a result of poor quality ingredients in the vinyl.
What Makes Good Vinyl?
Vinyl windows are made using polyvinyl chloride (PVC). This is the same plastic that is used in plumbing pipes, electrical pipes and many other household items. PVC is made by combining several chemicals, fillers, plasticizers and pigments. As you might imagine, each of these ingredients is available in different levels of quality.
Those manufacturers who choose to make a quality product almost always purchase the highest quality ingredients. These, of course, are more costly. This, in turn, makes the cost of the materials higher than those being used by a competitor who wants to offer you a low price.
Let’s talk about color change as an example. The ingredients which make PVC stay pure white for many years are basically two ingredients: titanium dioxide (TiO2) and an organic form of tin. TiO2 is a pure white chemical used to tint the vinyl white. It is also used heavily by the paint industry to make pure white paints.
Anyway, these two ingredients are costly and they need to be used in certain minimum quantities to produce a high quality vinyl. Also, the grade of TiO2 must be a non-chalking grade, so that your windows don’t begin to dust after so many years.
Window manufacturers who do not use sufficient amounts or high quality forms of these two ingredients often must tint their windows a light blue color to buy time before they begin to yellow. If you see vinyl windows that are a polar blue shade of white, BEWARE! If in doubt,ask for a sample of the vinyl material and take it to another showroom. Hold it against the windows in the highest priced showroom in your town. Compare the colors of different samples. When seen by itself, a polar blue vinyl doesn’t really look blue. But, when held against pure white samples, the blue coloration is dramatic.
It is important to note that some certified manufacturers do manufacture a high quality vinyl which does have the blue shading. They have chosen to do this on their own accord, as some of them think the blue coloration is attractive. Your assurance of high quality is the presence of the American Architectural Manufacturers Association (AAMA) certification label on the frame of the window.
When you visit a window store, be sure to ask to see a cross section of the window frame material. Ask for a sample that you can take with you. You will notice that the frame is constructed of various sized chambers. Not only will the chambers be different sizes, there will be different numbers of chambers depending upon the quality of the manufacturer. The highest quality windows usually have the highest number of chambers.
The number of the chambers is important. The strength of the window and frame are a function of where the walls of each chamber connect to the walls of the other chambers. Yes, this sounds confusing, but it is important.
We already discussed that heat can make the vinyl soft. This softening can lead to deformation. The high quality vinyl windows have frames and sashes (that part of the window which frames the glass) that have been engineered to withstand the heat that causes the deformation.
During research and design testing, the stress points on a window frame or sash are identified. The good manufacturers then design the sashes and frames to have extra chambers to hold in shape those chambers exposed to the sun. These chambers are generally shaded and remain cooler. High quality window frames can have as many as fifteen different chambers!
How the windows and frames are assembled should be of great importance to you. After all, all joints need to be weathertight and the windows shouldn’t fall apart after five or 10 years.
There are two main ways that vinyl windows are assembled: mechanically fastened (screws), or heat welded. There can be, in some cases, a big difference between these two methods.
Mechanically fastened windows use screws, brackets and caulk to hold together the individual pieces of the window sash and frame. This method does work, as long as everything goes right from the time the windows are made until they are installed in your house.
Should a window be dropped, twisted or racked during shipment or installation, the caulked seams may break and leaks could develop. If a screw is slightly over-tightened it may strip out the vinyl. The caulk may not last the life of the window.
Welded frames, on the other hand, take advantage of the chemistry of PVC. PVC is really neat. The welding process actually creates one piece of vinyl.
There are advantages and disadvantages to using this process. Welded corners on frames and sashes usually look better. However, welded windows sometimes have hidden drainage chambers that allow rain water to drain to the exterior.
Sometimes it is difficult to block air movement in these channels and small amounts of cold air can drift into your home. The strength of the connection between individual pieces can be stronger. Leaks at the corners are practically non-existent.
The strength of a welded connection is a function of how much PVC from one piece is touching the PVC of another piece. This is often measured in square inches. The chambers we discussed earlier play a significant role in this area.
The more chambers that you have in a sash or a frame means that more PVC is available for the welding process. Manufacturers know this and many actually will tell you how many square inches of PVC are in contact at each corner. Look for a window that has the highest total.