Proper Window Selection Makes A Big Difference - Another Helpful Article for Homebuyers in Wimberley, Austin, Fredericksburg, Dripping Springs, San Marcos, Kerrville, New Braunfels, Canyon Lake, Spring Branch in the Texas Hill Country.

Find it in the guides at
HillCountryHome.com

HOME Hill Country Home

Roofing

Floors

Supplies and Materials

UTILITIES

AC, Heating

Communications & AV

Electrical, Gas, Solar

Plumbing

Rainwater Collection

Water, Wells & Septic

GET ON THE GUIDE!


- - Featured Articles - - : General Articles

Proper Window Selection Makes A Big Difference

How to choose windows to minimize a home's heating, cooling and lighting costs. Factors that effect efficiency and comfort in custom, vinyl, fiberglass and wooden window choices.

Windows bring light, warmth, and beauty into our homes and provide openness and space to living areas. Unfortunately, they can also be a major source of heat loss in the winter and heat gain in the summer. However, properly selected and installed windows can help to minimize a home's heating, cooling and lighting costs.

When choosing a window, it's wise to consider what purpose your window will serve, the direction it faces, and local climate issues. No one window is suitable for every application. Many types of windows and window films that serve different purposes are available. To make wise purchases, first examine your heating and cooling needs and prioritize desired features such as daylighting, solar heating, shading, ventilation and aesthetic value.

FOR ENERGY EFFICIENCY

Control air leakage. Air leakage through the centers, edges and frames of windows contributes to wasted energy. Eliminating or reducing paths allowing air flow can greatly improve the energy efficiency of windows and, ultimately, of homes. Several options are available to reduce air leaks around windows.

Caulk all gaps. Proper application of caulking is an inexpensive solution to air leakage. By caulking the unwanted gaps around window frames and joints, air leakage can be significantly reduced, thus reducing the amount of energy wasted.

Before applying new caulk, old caulk or paint residue around a window should be removed using a putty knife, stiff brush or special solvent. After old caulk is removed, new caulk can then be applied to all joints in the window frame and the joint between the frame and the wall.

Caulk in warm temperatures so the caulk will set properly and adhere to the surface.

Apply weather stripping. Weather stripping is a very cost-effective solution to wasted energy through air leakage. Weather stripping may consist of a narrow piece of metal, vinyl, rubber, felt or foam that seals the contact area between the fixed and movable section of a window joint. It should be applied between the sash and the frame, but should not interfere with the operation of the window.

Reduce heat loss and condensation. Manufacturers usually represent the energy efficiency of windows in terms of their U-values (conductance of heat) or their R-values (resistance to heat flow). If a windows R-value is high, it will lose less heat than one with a lower R-value. Conversely, if a windows U-value is low, it will lose less heat than one with a high U-value.

Most window manufacturers use R-values in rating their windows performance. When comparing windows you should make sure
(1) that all U- or R-values are based on current standards set by the U.S. Department of Energys (DOE) ENERGYSTAR� program or the National Fenestration Rating Council (NFRC)
(2) that values are calculated for the entire window, including the frame, and not just for the center of the glass
(3) that the values represent the same size and style of window

The following five factors affect the R-value of a window:
1. The type of glazing material (e.g., glass, plastic, treated glass)
2. The number of layers of glass
3. The size of the air space between the layers of glass
4. The thermal resistance or conductance of the frame and spacer materials
5. The "tightness" of the installation (i.e., air leaks)

Choose the proper type of glazing. Traditionally, clear glass has been the primary material available for windowpanes in homes. However, in recent years, the market for glazing�or cutting and fitting windowpanes into frames�has changed significantly. Now several types of special glazings that can help control heat loss are available.

Low-emissivity (low-E) glass has a special surface coating to reduce heat transfer back through the window. These coatings reflect from 40% to 70% of the heat that is normally transmitted through clear glass, while still allowing the full amount of light to pass through.

Heat-absorbing glass contains special tints that allow it to absorb as much as 45% of the incoming solar energy, thus reducing heat gain. Some of the absorbed heat, however, passes through the window by conduction and reradiation.

Reflective glass has been coated with a reflective film and is useful in controlling solar heat gain during the summer. It also reduces the passage of light all year long, and, like heat-absorbing glass, it reduces solar transmittance.

Plastic glazing materials...acrylic, polycarbonate, polyester, polyvinyl chloride and polyethylene...are also widely available. Plastics can be stronger, lighter and easier to cut than glass. Some plastics also have higher solar transmittance than glass. However, plastics tend to be less durable and more susceptible to the effects of weather than is glass.

Layers of glass and air spaces matter. Standard single-pane glass has very little insulating value. It provides only a thin barrier to the outside and can account for considerable heat loss and heat gain. Traditionally, the approach to improving a window's energy efficiency has been to increase the number of glass panes in the unit, because multiple layers of glass increase the windows ability to resist heat flow.

Storm windows can increase the efficiency of single-pane windows. For people with tight budgets, a less expensive option to replacement windows is to use storm windows. Even though storm windows add to the insulating performance of single-glazed windows that are in good condition, they can help to reduce air movement into and out of existing windows, and thus reduce heating and cooling bills. They are made for installation on the interior or exterior of the primary window. They range from the inexpensive plastic sheets or films designed for one heating season, to triple-track glass units with low-e coatings that offer many years of use.

Double- and triple-pane windows have insulating air- or gas-filled spaces between each pane. Each layer of glass and the air spaces resist heat flow. The width of the air spaces between the panes is important, because air spaces that are too wide (more that 5/8 inch) or too narrow (less than 1/2 inch) allow too much heat transfer. Advanced, multi-pane windows are now manufactured with a less conductive, more viscous, or slow-moving gas like argon or krypton. By minimizing the convection currents within the space, conduction through the gas is reduced, and the overall transfer of heat between the inside and outside is reduced. The introduction of argon and krypton gas fills has lead to a considerable measure of improvement in thermal performance over traditional air-fills.

Window frames are available in a variety of materials including aluminum, wood, vinyl and fiberglass. Frames may be primarily composed of one material, or they may be a combination of different materials. Understanding the advantages and disadvantages of the different materials used for window frames is important when choosing an energy-efficient window.

Though ideal for strength and customized window design, aluminum frames conduct heat and therefore lose heat faster and are prone to condensation. Through anodizing or coating, the deterioration of aluminum frames can be avoided. Additionally, the thermal resistance of aluminum frames can be significantly improved by placing continuous insulating plastic strips between the interior and exterior of the frame. These insulating strips will virtually halt temperature transfer.

Wood frames have higher R-values, are not as greatly affected by temperature extremes and do not generally promote condensation. Wood frames, however, do require considerable maintenance in the form of periodic scraping, painting and/or staining. If not properly protected, wood frames can swell, develop wood rot, warp and eventually become inoperable.

Vinyl window frames, which are made primarily from polyvinyl chloride (PVC), offer many advantages. Available in a wide range of styles and shapes, vinyl frames have moderate to high R-values, are easily customized, are competitively priced, and require very low maintenance. While vinyl frames do not possess the inherent strength of metal or wood, larger-sized windows are often strengthened with aluminum or steel reinforcing bars.

Fiberglass frames are relatively new and are not yet widely available. With some of the highest R-values, fiberglass frames are excellent for insulating and will not warp, shrink, swell, rot, or corrode. Some fiberglass frames are hollow while others are filled with insulation for greater heat gain protection.

Spacers are used to separate multiple panes of glass within the windows. Although metal spacers are commonly installed to separate the glass in multipane windows, they conduct heat. During cold weather, the thermal resistance around the edge of a window is lower than that in the center; thus, heat can escape, and condensation can occur along the edges. To alleviate these problems, many manufacturers have developed multipane windows using a butyl spacer along the perimeter and between both panes of glass. These spacers help to alleviate thermal transfer through the glass.

Considering all these issues, it's easy to see how properly selected and installed windows can help to minimize a homes heating, cooling and lighting costs.

Click here to get on The Home Guide today!

in Central Texas

Visit Wimberley!
Click here...