An energy efficient window is one that helps to minimize the use of artificial heating and cooling in a building. Technological progress in the last 25 years has made it possible to design windows which insulate against heat and cold up to four times better than conventional windows.
In many parts of Australia, the priority is to keep solar heat out of the home, except during colder months, when ‘free’ solar heat gain and retention of warmth in the house become important. Ideally, this calls for strong solar protection on east and west windows, but deliberate use of free sunlight from northerly windows which receive the most sun. This means different window solutions will benefit different orientations.
Alternatively, it is possible to use the same uniform high-performance window type on all sides of a home – provided it is correctly chosen. From an energy point of view, this is not the best solution but it does simplify the specification process and still results in substantial energy savings and improved comfort compared to inefficient, clear, single-glazed windows.
What makes a window energy efficient?
Windows are made up of various components such as the glass, frame and hardware all acting together to provide a certain level of performance. Those components that provide substantial protection from heat gain and heat loss and reduce the energy consumed by the whole building are considered energy efficient.
Low-e (low emissivity) glass uses a transparent coating to minimize the amount of heat passing through the glass while still allowing light through. This near invisible coating reduces the U-value of the glass which measures how well a window prevents non solar heat loss or gain. The lower the U-value, the greater a window’s resistance to heat flow and the better its insulating value. While a low-e coating on standard single glazing reduces the heat transfer caused by the sun’s rays (solar radiation), it does nothing to reduce conductive and convective heat flow.
Double glazed windows
An ideal energy efficient solution is to reduce all forms of heat transfer. Double glazing is considered the vehicle for all high-performance windows, in climates hot, cold and mixed. When combined with low-e glass on at least one pane and argon gas in between, double glazing provides the best thermal performance. U-values as low as 1.8 are possible, compared with about 5 in the case of a single-glazed clear window.
The narrowest air gap used in double glazing is 6 mm but this should be avoided unless there is no alternative. The use of wider gaps (10-20 mm) will improve the U-value and can increase its star rating by at least half a star (see Windows Energy Rating Scheme below).
To complement the glazing system, a frame with a low U-value assists in reducing the whole window U-value. Frames that use timber, uPVC, or a composite Aluminium/timber design, outperform standard Aluminium windows by providing advanced thermal performance.
Good Weather Seals
Hot and cool air can escape or enter a home through gaps and cracks around sashes and frames. Good window seals are essential to improving energy efficient performance. Traditionally, windows with compression seals, as fitted to awning and casement windows, tended to have superior air infiltration performance. However, recent advances for the seals in sliding windows have improved.
Windows Energy Rating Scheme
The Windows Energy Rating Scheme (WERS) rates the energy impact of various window types and allows you to easily compare their performance. The window’s cooling and heating performance are rated on a separate scale of 0 to 10 stars – the more stars the better. These ratings indicate the effect the window will have on the energy performance of the whole house. In most climates, windows with at least four heating or four cooling stars, on all sides of the house, will ensure that conductive heat losses and heat gains are minimized.
6 Types of Windows That Increase Energy Efficiency
1. Fixed Windows
Fixed picture windows don’t offer any functionality. But when it comes to energy efficiency, that’s actually a good thing! Since you can’t open a picture window, you never break its airtight seal. No other window style can make that claim.
Fixed windows are a great solution for parts of your home where you don’t need ventilation. Or in window combinations and a wall of windows where the airtight design can help keep large expanses of glass from feeling drafty.
2. Hinged Windows
Hinged windows are designed for ventilation. With the twist of a crank or push of your hand, they pivot outward on a hinge. This design offers a major benefit over windows that slide open and closed: lower air leakage rates. When closed, the single sash of a hinged window presses firmly against the frame. Whereas sliding, double-hung and single-hung windows have two sashes with a slight overlap.
Awning windows, casement windows and hopper windows are all types of hinged windows. The only difference between them is where the hinge is located — top, side and bottom, respectively. They can be used for strategic ventilation or paired with picture windows to add some functionality to your window combinations.
3. ENERGY STAR® Windows
While every window is clearly labeled with energy performance ratings based on National Fenestration Rating Council (NFRC) testing, only the most energy-efficient windows earn the coveted blue sticker from ENERGY STAR.
ENERGY STAR windows are certified by the government and are based on performance ratings similar to NFRC. So if you see an ENERGY STAR logo, you know it’s a higher efficiency window than one without the star. But note: ENERGY STAR certification is based on climate and geography, so a window that rates highly in the Southwest sun may not perform as well in the cold of the Northeast.
4. Insulated Windows
A single pane of glass was the standard in windows for centuries. Then, in the 20th century, something innovative happened. Manufacturers found that adding another pane of glass provides extra insulation. In NFRC energy efficiency terms, it lowers both the U-Factor and Solar Heat Gain Coefficient (SGHC).
Today, insulated windows don’t just have extra panes of glass. Each window pane is separated by insulating gas, too. So triple-pane windows actually offer a total of five layers of insulation — two more than dual-pane windows and four more than single-pane windows — helping you eke even more energy efficiency out of your windows.
5. Low-E Windows
What’s on the outside of the window pane matters, too. Low emissivity coating on the panes, often described as Low-E glass, helps boost thermal performance. Low-E glass helps block both ultraviolet and infrared light, but lets in the visible light.
Infrared light is associated with heat energy. By blocking it out, Low-E windows help keep the heat from the sun from entering your home. There’s an obvious benefit to keeping the sun and heat out in the summer, but Low-E glass works the opposite way as well. In colder temps, it can actually reflect heat back into your home to help reduce heat loss and maintain efficiency.
Depending on where you live, you can choose from different types of Low-E window glass to fit your climate. Pella offers four different window glass options:
6. Lifestyle Series Windows
It’s no coincidence that Pella® Lifestyle Series windows harness many of the features above to earn the designation as some of the Most Efficient ENERGY STAR certified products of 2020.1 They were designed to deliver solutions for real life, with one of the most important considerations being energy efficiency.
Lifestyle Series windows are built with wood frames, which provides natural insulation from the elements. They offer triple-pane glass and a number of energy-saving features to make them 83% more energy efficient.2 These design features help Lifestyle Series windows meet or exceed ENERGY STAR guidelines in all 50 states.
Wherever you live and whatever styles you love, there are multiple ways to make your windows more energy efficient. With the help of ENERGY STAR labels and your local Pella representative, you can choose the best types of windows for your home and customize them to maximize your home’s energy efficiency.
Energy efficient windows are not a recent technological breakthrough. These windows have a history that stretches back several decades. It has taken less than a century to jump from uber-thin window panes that let in heavy drafts to glazed and coated windows that are nearly impenetrable.
How It all Began
The origins of energy efficient windows stem back to the 1920s when architects launched efforts to improve the comfort of those who lived/worked in buildings. This push led to the creation of insulated glass units (IGUs) and windows with double-glazing. Iron-rich glass with green tint was also implemented to minimize the level of heat transferred from the sun to building interiors.
The federal government soon became heavily involved in the push to decrease energy use. After conducting extensive research, it was clear that windows were one of the primary sources of heat loss. Studies showed that about one-quarter of home heating costs were attributable to heat loss through windows. Research and investments made by the federal government are partially responsible for the breakthroughs outlined below.
Before the 1970s the majority of windows were single pane with a wooden frame perimeter. Those who lived in cold parts of the nation attempted to minimize heat loss with the use of storm windows. Multi-pane windows were implemented toward the latter portion of the 70s in an attempt to boost energy efficiency. Similar to storm windows, multi-pane windows created an insulating layer with additional glass. This style of window evolved to the point that this space was filled with inert gasses like argon to boost insulation.
The Move Away From Aluminum
As the 80s rolled around, window manufacturers began to learn that aluminum frames were insufficient for insulation purposes. Manufacturers transitioned to wood-vinyl and vinyl composite frames to boost efficiency and lower heat transfer. Manufacturers also switched out metal spacers that kept multi-pane windows separate with new plastic/foam spacers. Such non-metallic spacers served as superior insulators.
The Low-E Era
By the late 80s, window manufacturers began to use low-emissivity (low-e) glass containing a metal oxide layer that permitted visible light to pass through and also prevent heat from seeping outward. This glass was actually made with several thin layers of gold that created a green tinge. By 1981, low-e glass coatings were completely colorless thanks to the use of silver in place of gold. Low-e glass did more than merely keep the warm indoor air inside the home/office. It also functioned as an excellent means of preventing heat from entering the home during hot summer days.
Energy Efficient Windows of Today and Tomorrow
Modern day efficiency windows are absolutely spectacular in every regard. They are visually attractive, easy to use, offer an excellent return on investment and most importantly, they keep warm/cool air inside the home. As time progresses, we are figuring out more ways to reduce home utility bills and keep homeowners as comfortable as possible.
Researchers are currently working on special window coatings that use electric current that is sensitive to outdoor conditions. Absorbing Electrochromic (AE) windows utilize a thin material to alter shade levels with electric currents. This style of window is built with a light sensor that automatically alters the level of electrical current. These futuristic windows turn darker when subjected to sunlight and transition to a translucent state when there is minimal outdoor light. Contact us for more information.
ENERGY STAR has several globally, partnered manufacturers who are working together to help you save money while protecting the environment through energy efficient practices and products. The following are eight ENERGY STAR window manufacturers.
1.EASTERN ARCHITECTURAL SYSTEMS
EAS manufactures a complete line of custom-made windows & doors in both aluminum and vinyl at our 172,000 square foot facility in Ft. Myers, Florida. We offer the highest quality of impact resistance and energy efficiency!
Whether impact glass or insulated impact glass, we have a style that will meet the needs of your customer. EAS is the only company in Florida that offers a vinyl impact window with the Good Housekeeping Seal of Approval. EAS Windows & Doors are tested to the most stringent standards in the industry including:
2.CGI WINDOWS AND DOORS
Founded in 1992, CGI® is a premier manufacturer of hurricane resistant windows and doors for residential and commercial structures. Produced to the most exacting industry standards, its high performance and highly aesthetic product collections offer advanced hurricane protection of home and commercial structures, in both new and existing construction. Our CGI® manufacturing and delivery facilities are based in Hialeah, FL.
3.CUSTOM WINDOW SYSTEMS, INC.
Custom Window Systems, Inc. (CWS), has been in business for over 30 years and prides itself in producing high quality, American Made window and door products for both residential and commercial use. We specialize in impact-resistant windows and doors designed for the Florida and coastal markets. We have two locations with a combined manufacturing space of nearly 1 million sq. ft. Our headquarters are in Ocala, FL and our other location is in Hendersonville, TN where we produce MGM branded products. CWS produces both energy-efficient vinyl, and aluminum window and door products which are distributed throughout the Midwest and Southeastern parts of the country. Recognizing the demand for an energy efficient window, CWS was the first window manufacturer in Florida to obtain an Energy Star® rating from the National Fenestration Rating Council (NFRC.) Having a window that is energy efficient and engineered to meet high design pressures, has separated our product from the traditional windows being offered for the past 30 years. We manufacturer a full platform of both Impact-Resistant and non-Impact-Resistant vinyl and aluminum windows and doors for both replacement or new construction.
4.DOERS WINDOW MFG
Doers Window Manufacturing is a manufacturer of energy-efficient uPVC windows and doors for commercial projects and retrofit applications.
Kennedy Skylights is a leading manufacturer of traditional glass skylights. We provide all the sizes and types needed to meet or exceed your expectations. Kennedy Skylights’ mission is to provide eco-friendly products using the finest quality materials.
6.NEWSOUTH WINDOW SOLUTIONS
NewSouth Window Solutions is the manufacturer and installer of high performance, energy-efficient replacement windows and doors made specifically for the Southern climate. NewSouth has 10 factory showroom locations across the Southeast region.
PGT Industries is a U.S. manufacturer and supplier of impact-resistant windows and doors with its WinGuard-branded product line. The company’s impact-resistant products combine aluminum or vinyl heavy-duty frames with laminated glass to provide protection from hurricane-force winds and windborne debris.
Sun-Tek Skylights is one of the leading skylight manufacturers in the United States. For over 30 years we have provided an affordable, easy way to let the sun shine into your home.
Sun-Tek has been providing the home building industry with quality natural lighting products and accessories for over thirty years. A privately owned American corporation, Sun-Tek offers its customers – service before, during and after the sale. We provide all needed support to achieve the customers stated goals for total satisfaction.
Our headquarters and factory are located in the heart of Central Florida, where we are famous for both our year round sunshine and our annual hurricane season.
So it should come as no surprise that Sun-Tek Skylights are designed and manufactured to withstand whatever punishment the sun, wind and rain can deliver. Call us today and Let the Sunshine In!
• Glass Skylights – 8 Models / 21 standard sizes
• Polycarbonate Skylights – 10 Models / 17 standard sizes
• Tubular Skylights – 2 Models / 3 standard sizes
• Multi-Tube System – 5 Configuration Models
• Extreme Weather Units – 6 Models for all Applications
• Commercial Models – CM & SF, thermally broken and non-thermally
• We fabricate custom skylights in both Glass & Polycarbonate on a daily basis
Energy efficient windows are an important consideration for both new and existing homes. Heat gain and heat loss through windows are responsible for 25%–30% of residential heating and cooling energy use.
If you are selecting windows for new construction or to replace existing windows, it’s important to choose the most efficient windows you can afford that work best in your climate.
If your existing windows are in good condition, taking steps to reduce the energy loss through windows can make your home more comfortable and save you money on energy bills.
You have two broad options if you hope to reduce the amount of energy lost through your windows and improve the comfort of your home:
source: build.com.au– windowsguide.co.uk– danddglassworks.com– pellabranch.com– michaelhomesinc.ca– easternarchitectural.com– easternarchitectural.com–cgiwindows.com– cws.cc– doerswindow.com– kennedyskylights.com– newsouthwindow.com– pgtwindows.com– sun-tek.com
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