The marketplace is inundated these days with window choices. A component that was once an afterthought when a new home was being built, windows now command multiple advertising pages in builders and home improvement magazines. Windows, both for new construction and for replacement, are big business. What constitutes a good window?
Virtually any new window you purchase will have at least two panes of glass making up the glazing. Only those designed for use in unheated areas like garages are likely to have a single pane of glass.
Two-pane, or insulated, glass has proven its worth over the decades. Sandwiching air between two separated, sealed panes increases the insulative value of the glazing many times. In recent years manufacturers have even upped the ante by sealing gases like argon and krypton, which have more density and better insulative qualities than plain air, inside that space.
The glass in the assembly can also be coated with nearly invisible films, like Low-e metallic oxides, that can be manipulated to impart various properties to the window, like better heat retention or solar heat reduction.
The sash that holds the glazing is also important to the overall thermal performance of the window. Materials that offer low heat conductance, like wood, hollow or insulation-filled vinyl, or fiberglass help reduce the transference of cold inside and heat outside.
All these improvements make both replacement and original windows more energy-efficient than they've ever been. And the technology has also increased the comfort factor. Sitting next to a single-pane window in the winter can make you feel cold, even when the house itself is sufficiently warm. Heat from your body is radiated out the window. But energy-efficient glazing keeps the inside pane of glass warmer. That reflects your body heat back inside, making you feel more comfortable and saving energy.
From an energy-efficiency standpoint, one of the most important improvements to modern windows is the in-crease in the performance of weather stripping that stops air from infiltrating. Anyone who has lived (or is presently living) in a house that has leaky windows knows how the wind outside can rustle draperies inside. That leakiness adds up to wasted energy. New windows, if properly installed, won't leak air and will save energy as a result.
The nonprofit National Fenestration Rating Council rates some manufacturers' windows based on air leakage, U-factor (a gauge that represents the window's rate of heat loss), visual transmittance (a measure of the amount of light the window lets into a room), and the solar-heat-gain coefficient (a measure of the solar heat gain possible through that window).
Labels on windows rated by the Council tell you what to expect from the manufacturers' products, and this information allows you to select different windows to satisfy different criteria for each area of your house. For instance, good properties to have in a southerly facing window in a house located in the northern part of the country would be a good solar-heat-gain coefficient rating, low air leakage, and an excellent U-factor. For a window in the same house facing in a northerly direction, the solar-heat-gain coefficient wouldn't be worth paying for, while the U-factor and air leakage rating would be even more important.
Installing Windows Right
Even good windows will not live up to their billing if they are installed improperly. That's why selecting an experienced, conscientious installer is important to maximize both the energy efficiency and your satisfaction with the windows you purchase.
Window installation is complex. Any part of the job that is left to chance can come back to haunt the homeowner with water leaks, dysfunctional opening and closing, poor energy performance, and air leakage -- everything you paid good money to avoid. This is particularly true when it comes to replacement windows, where old materials have to be incorporated into the new installation.
Improving Old Windows
Virtually any new window installed in an older home will improve energy efficiency. This is especially true if the old windows are in poor condition. How much could you save in utility bills? That's hard to predict. It depends on how leaky the old windows are, the quality of the windows with which you're replacing them, and the quality of the installation. But beyond the energy savings, one of the most important improvements you will likely notice right away is the way upgraded windows make a house feel cozier, quieter, warmer, and more secure.
Installing new windows in an existing home makes the house "live larger." In other words, if your old windows were so leaky that the cold made you stay away from them in the winter, you confined yourself to a smaller area of the house. If reading at night by a window made you feel cold, you retreated farther toward the middle of the house in order to stay warm. The same might be true if you upgrade your windows to block out sun or heat in southern climates. It's uncomfortable sitting in the sunlight inside if the house already feels too warm. New windows might allow you to sit near the exterior walls of the house in greater comfort, in effect increasing its square footage.
New windows can also affect your attitude about your house and neighborhood. Along with stopping air leakage, modern windows are much more effective at blocking noise. Traffic, air conditioners running in the summer, and other normal neighborhood noise might not be as distracting with new windows.
Homeowners who are either tired of or not capable of climbing ladders to clean windows outside the house will appreciate the tilt-in sash feature on most new windows. With just a flick of two buttons you have access to the exterior glass for cleaning. This saves time and is much safer than climbing a ladder to do the job.
Evaluating Old Windows
Despite all the advantages of new windows, economic or historical concerns may be a factor in considering window upgrading. While it is true that no original single-pane glass window can match the thermal performance of a new window, it's surprising how close it can come -- albeit with a lot of work.
If you own a house with historical features, it is worth considering restoring rather than replacing your original windows. There are situations when even the best new windows look out of place, and one of those is in a house that was designed and built with architecturally significant windows. While not impossible to duplicate today, such windows can be prohibitively expensive to reproduce. The solution is to make the existing windows as energy-efficient as possible.
Old windows usually require at least scraping and painting, and perhaps glazing compound replacement. You'll also need to repair broken sash cords or chains just to get them working properly and safely again. If they are in poor condition, some might require the re-gluing of joints, epoxy or wood repairs to the sash, total glass removal and re-glazing, and maybe even some replacement of cracked or broken panes.
From there, you can upgrade thermal performance by adding weather stripping around the perimeter of the window sash and along the meeting rail between double-hung windows. You can also install draft-blocking devices that plug the cord or chain holes and reduce the amount of air infiltration from those portals. To achieve the best efficiency possible, adding storm windows to either the outside of the house or to the interior will help thermal performance considerably.
If every advantage is taken, if all weather stripping is installed properly, and if storm windows are added to the outside, it is possible to achieve near-new window performance with old windows. However, while the outlay for materials to restore older windows is relatively low, the labor factor is high. This is a good job for those handy enough to do the repairs or for those with the means to hire professionals.
Older windows can last for 100 years or more if maintained attentively. Modern windows are unlikely to hold up that long.
When you are having windows or other new fixtures installed in your home, it's important to hire a reliable contractor. On the last page, we'll find out what you need to know about choosing a contractor.