A Guide to Energy-Efficient Windows and Doors

In calling on windows to perform these many functions, we still expect our windows to be inexpensive, easy to operate and maintain, durable and attractive - and energy-efficient. Because they are called upon to perform so many functions, it may be difficult for windows to do all of them equally well.

For example, a large north-facing picture window may give you a breathtaking view of the countryside. But if the window is not very energy-efficient, the heat loss from it may be quite high; indeed, it may be very uncomfortable to sit beside this window on a cold winter day.

If you have a large window wall facing south or west, the heat gain can make the rooms on that side of the house unbearable. There is the problem of fabric-fading ultraviolet light to consider as well.

Fortunately, technical breakthroughs have improved window technology immensely, ushering in the era of high-performance windows. If windows are over 15 years old, it may be time to think about replacing them. If you’re designing a new home, you must decide on whether your client is going to buy windows or invest in windows.

In recent years, we have spent nearly as much on renovations as on new construction, with windows representing one of the largest single investments in a typical renovation. And, when it comes time for major renovations around the home, an increasing number of people are paying as much attention to energy efficiency and economics as they are to architecture and aesthetics.

Remember that a typical window will last up to twenty years or more. Therefore, the decisions consumers make in the selection of windows and doors - either for a renovation or a new home - can help define energy efficiency and comfort levels in the home for years to come.

Section 2 shows you how to assess your current situation and what to look for in windows and doors. Section 3 walks you through a primer of window and door types and terms. Section 4 discusses how windows perform as part of the house, while Section 5 explains the causes of condensation on windows and how to reduce or prevent it.

Section 6 introduces you to the various window-rating systems currently in place, with special emphasis on the NFRC (National Fenestration Rating Council) numbers and the Solar Heat Gain Coefficient. Section 7 describes the advances and innovations in window components currently coming on the market in the form of high-performance windows.

Section 8 translates all the technical terms and performance characteristics into the bottom line for you, the consumer. It helps you appreciate the benefits of high-performance windows, in addition to understanding the technology.

Section 9 describes what to look for in doors, patio doors and skylights. Section 10 shows you how to develop a checklist before you shop and how to choose a supplier. It also shows you how to make informed decisions about what to buy, based on the NFRC number, Solar Heat Gain Coefficient, cost and appearance.

Section 11 makes sure that you understand the importance of warranties, choosing a contractor and proper installation. And, finally, Section 12 provides you with directions on where you can obtain further information.