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Q. I’ve lived in my home for thirty years and never had any termite repairs done. There is a lot of exterior wood that needs to be replaced and most of the windows are so damaged that there’s little hope of keeping them. Now I have to make a decision as to what kind of window I should purchase. What would you recommend?

A. You’re fortunate that the windows are currently being replaced rather than five or ten years ago because you have so many more environmentally friendly choices. First, you might consider energy efficiency options which will minimize your home’s heating, cooling and lighting costs.

You didn’t mention what kind of windows you have, but based on the time you’ve been in your home, they are probably a combination of fixed pane and single- or double-hung. When properly installed, fixed pane windows are airtight, inexpensive and can be custom designed for a variety of applications. The big draw back is that they can’t be opened for ventilation. Although double-hung are a popular type of window, they can be inefficient because they are often leaky. The single-hung fare a little better because there is only one sash that moves.

Horizontal sliding windows that are good for long narrow spaces provide minimal ventilation and, like double-hung windows, can be quite leaky. Casement, awning and hopper windows with compression seals are moderately airtight and provide good ventilation.

Now that you have an idea of the window types, let’s see what you can do if you want to keep your single- or double-hung windows. There are two ways of controlling the air leaks – caulking and weather-stripping. Caulks are airtight compounds (usually latex or silicone) that fill cracks and holes. Weather-stripping is a narrow piece of metal, vinyl, rubber, felt or foam that seals the contact area between the fixed and moveable sections of a window joint.

Next, let’s look at frames. You have wood and already know the inherent problems. On the positive side, they usually have a fairly high insulating value and are not affected by temperature extremes. Though ideal for strength, aluminum frames conduct heat and, therefore, lose heat faster and are prone to condensation. This can be rectified by insulating strips. Vinyl windows offer many advantages. Available in a wide range of styles and shapes, they have a good insulating value, are competitively priced and require low maintenance. While they don’t possess the strength of metal or wood, larger windows are often strengthened with aluminum or steel reinforcing bars. Other frames may be a combination of different materials keeping the best qualities of each or recycled wood and plastic. Fiberglass is excellent for insulating and will not warp, shrink, swell, rot or corrode. It is strong and durable and requires virtually no maintenance. Because it’s a fairly new framing material, it has not had time to be tested for long term performance and is more expensive than other framing materials.

Last, but not least, what are your choices in glass? There are certain factors to be considered such as their U-value (conductance of heat) and R-value (resistance to heat flow). Do you want your windows to have special glazing that can help control heat loss and condensation? Do you want multiple panes to increase the window’s energy efficiency?

So, as you can see, choosing a window can be quite confusing. Different combinations of style, material and glazing can yield different results when weighing energy efficiency and cost. No one window is suitable for every occasion. To make a wise purchase, first examine your heating and cooling needs and prioritize desired features such as daylight, shade, ventilation and aesthetic value.