Benefits of Improving Windows
The solar spectrum is made up of ultraviolet (UV) light, visible light, and infrared (IR) light. In the past, many commercial buildings used reflective or tinted glass products to reduce solar heat gain through the windows. Unfortunately, these products also reduce the amount of visible light. This reduction in Visible Transmittance (VT) can lead to an increase in the amount of artificial lighting needed in buildings.
To take advantage of potential savings from daylighting, the industry has seen growth in the use of spectrally selective glass. This type of glass has special properties that actually block or re-radiate the IR energy from the sun, reducing solar gain through the windows, while maintaining higher levels of visible light transmittance. This type of product is also available for use in residential windows, typically with a higher spectrally selective low-E coating on the interior surface of insulating glass units.
Improve Energy Efficiency
Windows may appear passive, but in reality they are always performing. They affect the flow of heat in and out of your home, as well as the amount of natural light, and this influences how much electricity you need to use to keep your home comfortable.
The U.S. Department of Energy (DOE) estimates that the amount of energy lost annually through windows is $35 billon.
Furthermore, the DOE estimates that the average American household spends $1500 - $2500 every year on energy bills and estimates that 45 percent of this amount is for heating and cooling. By using the NFRC label to ensure they are meeting building energy codes, consumers can reduce their energy costs while improving their comfort.
The NFRC label is highly regarded and commands respect throughout the building industry. In fact, to qualify for an ENERGY STAR® label, residential windows must be NFRC certified. NFRC’s rigorous certification program has even served as a model for some of the U.S. Environmental Protection Agency’s (EPA) efforts to develop its new certification body requirements.
To encourage energy efficient homes, some utility companies offer rebates for home improvements such as new windows. Check with your local utility to find out about rebates and to ensure that you purchase qualifying products.
- In winter, poor quality windows, and those that aren’t well insulated, can create drafts in the home.
Poor quality, inefficient windows create the feeling of draft due to the physics of changing air temperatures – warm air near a cold pane of glass will quickly cool, fall, and create a cycle of moving air. Windows and doors with lower U-factor ratings will lessen this effect, reduce the feeling of draft, and lower heating bills.
Improving the insulation around doors and windows with weather-stripping may also reduce drafts by reducing air flow.
- In summer, it can be difficult to adequately and efficiently cool a room with poor window quality because the sun is able to directly influence and heat the air temperature of the room. Windows with lower Solar Heat Gain Coefficient (SHGC) will lessen this effect and improve the ability to efficiently keep a room cool — lowering cooling bills and reducing frequent temperature fluctuations.
Solar radiation is the main cause of fading. The sun's energy is made up of three distinct parts – UV, visible, and infrared (IR) radiation. While visible light, artificial light, heat, humidity, age of fabrics, and fabric dyes all play a part in fading, UV radiation is responsible for about 40-60 percent of the damage. Protecting against UV radiation is important in all types of climates, whether sunny and warm, or cloudy and cold. Although invisible to the human eye, UV radiation enters a home through its windows. Clear, single-pane glass reflects about 25 percent of the sun's UV radiation while insulating glass reflects up to 40 percent. Using low-E coated glass provides additional protection, reflecting up to 74 percent.
Some window film products and laminated glass products can block up to 99 percent of UV radiation. Window film is the combination of a form of transparent plastic and an adhesive, which creates a light, reflective covering for windows. These films provide a nearly invisible barrier.
Laminated glass has an inner layer of film sandwiched between two window panes, similar to the glass used on a car's windshield. This gives windows the strength needed to stand up to impacts caused by storms. It also filters the sun's light, admitting the desirable, visible radiation while blocking the harmful, invisible UV radiation.
When it comes to insulating your home against heat and cold, a window is like a "hole-in-the-wall". In summer, ordinary glass lets the sun's heat penetrate your home, making you and your family very uncomfortable and forcing your air conditioner to work harder. In winter, glass panes lose a substantial amount of your home's heat.
Solar control window film applied to the interior of your windows is a transparent "solar shield" that can reject up to 80 percent of the sun's heat. In summer your home is cooler and more comfortable, so you can save on energy bills. In winter, some window films trap room heat for year -round comfort.
Solar control window films are available with a scratch resistant coating and in a variety of elegant tints like bronze and gray, and in neutral tones that appear virtually invisible on your windows.
You can download the International Window Film Association's Consumer Booklet to find answers to questions on:
- Glare Control
- Environmental Impact
- Types of Window Film
- Window Film Certifications
Improve Safety and Conform to Codes
In some instances, replacing old windows can improve the safety of the home.
- Egress windows (sometimes called escape windows), for example, are required by many building codes, for any room to be used as a bedroom. This means that if there is no door directly to the outside, at least one window must provide an opening wide enough to allow an adult to exit the house to the outdoors. Local codes specify the size of the opening and, if the standard window does not provide that sized opening, special windows must be used that can produce that area. This is often a consideration for basement renovations.
It is also possible (but not guaranteed) that upgrading to meet egress window code requirements can improve home value. For example, adding an egress window to a room may add a bedroom to the total bedroom count of your home. (Local codes may have additional requirements for a room to qualify as a “bedroom.”)
- Impact-resistant windows are required in some building codes, such as in South Florida, to provide greater protection during hurricanes and storms. These windows are built to withstand strong winds and wind-borne debris but that added strength can also reduce breakage from other causes too (such as wayward golf balls or burglars).
- For added security, window options that incorporate wire mesh to reduce penetration can also be purchased. These windows can be used to prevent burglary and may reduce damage to windows in areas that are prone to flying debris.