Energy Efficient Home Heating and Cooling

Energy efficient replacement windows can save the average homeowner hundreds of dollars per year in reduced energy costs for heating and cooling.

In some cases, the increased insulation and heat reflective coatings can allow a smaller air conditioning unit to be installed after the window replacement is completed. This saves money on both the new HVAC equipment and reduced energy consumption. If you are replacing both windows and HVAC - make sure to factor the efficiency of the windows when doing your heat load calculations.

The reason for these increased savings is the reality that a significant portion of the exterior walls in the average home consist of windows. Single pane and low quality double pane windows provide very little insulation protection against heat and cold loss. The typical home loses over 25% of its heat through windows.

Critical Factors in Choosing Replacement Windows

There are three primary factors to consider when selecting the replacement windows for your home. They are the space between the individual panes of glass (referred to as the 'intercept space'), the coatings applied to the glass, and the materials used to construct the frame of the window.

Intercept Space - The main way an energy efficient window prevents heat and cold from transferring through the glass is by creating each window sash out of two panes of glass that are separated from each other. The space between the glass is filled with a dense gas, like argon, that does not move as easily as air (this movement is what transfers the heat and cold through the window glass unit.) The wider the separation between the glass, the higher the insulating effect. 7/8" intercept spacing results in an efficient window that is still practical and attractive. Spacing of less than 1/2" should be avoided due to the dramatically reduced efficiency.

One critical thing to look for is a high quality spacer separating the glass panes in the window. This intercept spacer, and the sealing material used to hold it together, are the only things holding the gas between the glass panes. If that seal fails, the efficiency of the window drops dramatically and condensation can build up on the inside of the glass unit.

Glass Coatings - The two important coating options available on energy efficient replacement windows are UV (ultraviolet) and Low-e coatings. The UV coatings filter out the ultraviolet light that contributes to the fading of curtains, carpets, furniture, and photographs. Some UV light is needed by houseplants, so avoid total blockage in rooms where you keep plants.

Low-e stands for low emissivity. It is the trade name for a soft coating of silver oxide (the same material used on the back side of a mirror.) Low-e allows visible light to pass through a window, but blocks radiant heat. This coating is critical in climates where cooling is the primary concern for home air conditioning. In far northern climates, radiant heat from the sun is just free solar heating on a cold day.

Frame Materials - Common materials used to create the frames of a replacement window are steel, aluminum, vinyl, and wood. Wood and vinyl both have excellent insulating qualities. But each has pros and cons.

Steel and aluminum frames should be avoided at all cost. Both metals easily allow heat and cold energy to transfer through the frame material. If you created two identical windows in every way except that one had a vinyl frame and the other uses aluminum, the aluminum window would be 35% less efficient.

Vinyl Replacement Windows

Vinyl is one of the most popular window materials. It has nearly the same insulating quality of wood, but is far more durable and low maintenance - if you get a quality window from a reputable manufacturer.

There is a huge range of quality in the vinyl windows available. Vinyl is somewhat soft, so it is important that the window frame be substantial enough to provide the strength required to prevent the frame from warping. Low-end discounters use less vinyl (resulting in a weaker frame) and often mix in chalks and fillers which reduce the strength and durability of the material itself.

Another way cut-rate window companies save money is by building frames to lower tolerances and using screws and brackets to hold the windows together. Fusion welds are the most durable method for assembling vinyl frames.

Wood Replacement Windows

Wood is another popular option for frame construction. It is easy to work with, has excellent insulating properties, and can be painted to any color you want.

The main drawbacks are that wood frames are extremely prone to warping and rotting and they they require routine maintenance. You need to factor into the price the costs of painting to keep the exterior of the wood looking good and sealed from moisture.

Low cost wood replacement windows tend to be manufactured from softer woods which increase the chances of warping and rotting.

Other Considerations

Beyond the basic performance of the windows and the materials in the frame, pay attention to the overall design of the window. Most manufacturers offer tilt-in options on double hung windows for easy cleaning and lots of other bells and whistles.

Night locks, continuous tension coil counterweight springs, integrated screen frames, and even the warranties backing the windows are important in your decision of which windows to install in your home.

Make sure you are working with a company that has a long track record (warranties are only as good as the company that backs them) and insist on seeing a sample of the window so you can try it out - hands-on!