In part 1 of this series I mentioned that a lot of people believe that I am against installing new windows as a way to make homes more efficient. My response was that I am actually not against new windows because sometimes the existing windows are a total disaster and replacing them would have a great effect on energy efficiency. That is as long as the other more cost effective methods are not ignored.
Now I am going to discuss the different components that make up quality energy efficient windows and the advantages and disadvantages of some of those components. The main components of a window are the framing material, the type and quantity of glazing (glass), gas filling between the glazing, what a thermal break is, weather stripping, and what low-e means.
First let’s look at the frame itself. Framing can be made of wood, metal, vinyl, fiberglass, or even a combination of these materials. My personal preference is vinyl because it needs much less maintenance than wood, is less conductive than metal, and less expensive. Also, many manufacturers have been able to create finishes that look like wood and come in a variety of styles so you can find one that will look great regardless of your home’s style. Here in Atlanta, look for a U-factor (materials ability to resist heat flow) of .35 or less. It differs by area of the country.
Second we look at glazing or the glass. The main concern here is the number of panes. Do you want double paned? Triple paned? Whatever it is, it’s definitely not single paned. Obviously, the more panes, the more they cost. Personally I believe for Atlanta, double paned is sufficient. There are some other options like tinting or even tempered glass, but that is usually based on building codes (for tempered glass anyway).
Next we look at filling the gap between those panes with gas. The most commonly used is Argon which is an inexpensive, non-toxic, colorless, nonreactive gas. The advantage of gas is that it is less conductive than air which slows down the transfer of heat between the panes. This helps to reduce that frozen piece of glass feeling during the winter. If the units are properly sealed you should not have any fogging between the panes either.
Fourth is the thermal break, also called a spacer. A thermal break is that little piece that fits in between the panes of glass to maintain proper spacing between them while reducing heat transfer at the edges of the panes. They used to be made out of aluminum but as most people know, aluminum is a very conductive material. Now they are made out of different types of less conductive metals or other non-conductive materials like silicone or extruded vinyl.
Next we look at weather stripping. The quality of weather stripping will affect how much air is able to leak around the window sashes. The more contact areas for the weather stripping, the less likely the unit is to leak air. Also the better the quality of weather stripping used, the less likely it is to fail over time. This is a common issue in originally installed builder grade windows.
Last but not least is low-e, which stands for low-emittance. This is actually a coating of tiny metal particles that is applied to the glass surface. It allows light through while reflecting solar heat which reduces the amount of solar heat gained through the glass. Ever notice how hot you get or how faded the furniture is when it sits in a window with full sun? This is the caused by solar radiation and can be reduced by adding a low-e coating. Here in Atlanta, look for a SHGC (Solar Heat Gain Coefficient) of .30 or lower.
Knowing what these components are gives you an advantage, but can still be confusing. This is all the more reason to get an energy audit in Atlanta or where ever you live. Having a relationship with someone that understands the components and what your home needs, can be a huge advantage when it comes to selecting the correct windows for your home.
In Part 3 of this series, I will discuss some other issues related to windows, including cost vs quality, proper installation, and what to expect from your new windows. If you have any questions related to this article, please place them in the comment section below and I will answer them asap. And remember……Don’t throw money at your problems, throw knowledge, it’s a lot cheaper!