PART ONE: FRAMING THINGS RIGHT If there’s one thing that unites people, it’s the universal desire to save money. Bills are soaring, but it comes as no surprise that people are willing to spend more so long as they know that each dollar stretches farther. Because if the recession taught us anything, it’s that spending smart trumps spending less. Nowhere is this truer than in the average American home.
We’re insulating our attics, swapping out standard bulbs for CFLs and LEDs, washing fuller laundry loads, taking shorter showers, and painting our roofs white because it has finally (finally!) sunk in that energy equals money. Windows are getting a fair share of the action, too. While results vary depending on factors like climate zone and the extent of the upgrade, switching to energy-efficient windows can save a household up to $465 a year. That’s quite a hefty chunk of the $2000 the average American household spends on energy each year! Windows are able to save that much energy through a combination of energy-efficient components. While it’s true that a window is greater than the sum of its parts, the individual energy efficiency of each component still contributes significantly to the whole. First up to bat is the window frame.
PART ONE: FRAMING THINGS RIGHT WHAT DOES A WINDOW FRAME DO? The primary function of a frame is to provide structural support for the window, but it can also contribute to energy efficiency in two ways:
BY PREVENTING HEAT TRANSFER
BY PREVENTING AIR LEAKAGE
Both mechanisms are a function of the frame material. Frames can be made of wood, vinyl, aluminum, steel, fiberglass, or a combination of these materials. And then there’s Fibrex®, a wood-fiber-and-polymer composite perfected and patented by Renewal by Andersen. WHY THE SPECIAL MENTION? Fibrex® deserves some extra attention because of how well it has been proven to perform on the energy efficiency front: • Fibrex® is 700 times better than aluminum when it comes to insulation. Its thermal insulating properties are on par with that of pine and vinyl. Outside heat stays out, indoor heat stays in. • Fibrex® is 2.5 times less likely to leak air and moisture than vinyl. Its thermal expansion rate is on par with that of aluminum. This preserves the integrity of the glass seal.
PART ONE: FRAMING THINGS RIGHT WHAT ELSE CAN FIBREX速 DO? Fibrex速 is good for the environment because 40% of it is reclaimed wood fiber. And although Fibrex速 gives recyclable materials a second life, it does not look second-class. Its finish can be made to mimic other premium materials. It can also be injection-molded or extruded into frames and other functional components for custom window projects. The result: a window that is not only energy-efficient but truly beautiful as well.
PART TWO: THROUGH THE WINDOW GLASS As the biggest component of your window, glass contributes the most to its energy efficiency. And when it comes to energy efficiency, the industry standard for glazing is low-E glass. WHAT IS LOW-E GLASS? The “E” in low-E stands for emissivity, which is the ability of a material to reradiate or reflect energy. The lower the emissivity of window glazing, the better it is at keeping outside heat out during summer and inside heat in during winter.
Low-E glass may vary in performance depending on the manufacturer. Renewal by Andersen’s Low-E4® glass, for instance, offers energy efficiency boosts of 45% in winter and at least 56% in summer. It’s also capable of blocking out at least 84% of incident UV light. HOW DOES LOW-E GLASS WORK? Sunlight entering your window can be split into three different categories depending on wavelength: • ultraviolet (UV) – 10 nm to 380 nm • visible – 380 nm to 780 nm • infrared – 780 nm to 1 mm
PART TWO: THROUGH THE WINDOW GLASS Visible light is exactly what it says on the tin: it’s the “natural” light that you see and the portion of the spectrum that you do want. Infrared and UV light, on the other hand, you’d much rather do without because they heat up your home unnecessarily and cause premature damage on your furniture, carpets, and drapes. Low-E glass works by reducing the levels of infrared and UV light that enters your home without blocking visible light.
MOST UV REJECTED
MOST WARMTH RETAINED
INSIDE
OUTSIDE
MOST VISIBLE LIGHT ADMITTED
MOST SOLAR HEAT REJECTED
HOW DOES LOW-E GLASS IMPROVE ENERGY EFFICIENCY? The average American household spends a small fortune on energy every year thanks (or rather, no thanks) to overworked HVAC. This happens when there’s an imbalance in indoor temperature, which is the result of too much heat coming in from the outside during summer and too much heat escaping during winter. Low-E glazing increases your home’s energy efficiency by helping to stabilize indoor temperature. A QUICK “WINDOW SHOPPING” TIP: Look for window glass with the ENERGY STAR seal and National Fenestration Rating Council (NFRC) certification. This will let you see at a glance whether or not a window can offer you the energy efficiency benefits you’re looking for. The ENERGY STAR seal also offers the additional benefit of letting you know which products are the most suitable for your climate zone, taking the guesswork completely out of window shopping.
PART THREE: WHAT’S IN A WINDOW RATING There are two kinds of labels you can expect to see on an energyefficient window: one is from ENERGY STAR and the other from the National Fenestration Rating Council (NFRC). THE ENERGY STAR SEAL ENERGY STAR is a standard formed as a collaborative effort by the Environmental Protection Agency (EPA) and the Department of Energy (DOE) to identify and promote products that meet certain requirements for energy performance. In the case of windows, the ENERGY STAR seal shows the climate zone/s in which the product qualifies. The four U.S. climate zones are: Northern, North/Central, South/Central, and Southern.
NORTHERN NORTH/CENTRAL SOUTH/CENTRAL SOUTHERN
THE NFRC LABEL NFRC is a non-profit organization created by representatives of the door, window, and skylight industries. Like the ENERGY STAR seal, the NFRC label offers information on products certified for their energy performance, which is based on the following metrics: U-factor, Solar Heat Gain Coefficient, Visible Transmittance, Air Leakage (optional) and Condensation Resistance (optional).
PART THREE: WHAT’S IN A WINDOW RATING WHAT DO THESE NUMBERS MEAN? U-FACTOR The rate at which heat is lost through a window. The lower the number, the better. Solar Heat Gain Coefficient (SHGC) The fraction of solar heat that will pass through a window. The lower the number, the better. Visible Transmittance(VT) The amount of visible light that will pass through a window. The higher the number, the more light is transmitted (which can be good or bad depending on daylighting needs and glare). Air Leakage (AL) The amount of air that will pass through cracks in a window system. The lower the number, the better. Condensation Resistance (CR) How well a window resists condensation on the inner surfaces. The higher the number, the better.
PART THREE: WHAT’S IN A WINDOW RATING HOW DO WINDOW COMPONENTS AFFECT THESE NUMBERS? We’ve already established how window glass and frames affect energy efficiency and, by extension, the values shown on window labels. But these ratings factor in the entirety of the window system, meaning even the smaller components—like gas fills and spacers— also matter.
GAS FILL SPACER
Viscous, low-conductivity gas fills affect how much heat is transmitted by convection through double- or triple-glazed windows, thereby affecting U-factor. Argon and krypton, which are 34% and 63% less conductive than air, respectively, are often used. Spacers, on the other hand, influence U-factor by affecting how much heat is transmitted by conduction, so insulating materials like silicone foam are preferred over aluminum. Spacers also influence AL and CR values. MAXIMIZING WINDOW ENERGY EFFICIENCY Choosing window products based on their ratings is a good first step, but if you want to really make the most out of them, you need to make sure they’re installed properly. For best results, work only with a factory-certified contractor with a good local reputation.
Renewal by Andersen of Greater Philadelphia 761 5th Ave #3 King of Prussia, PA 19406
610-563-2190 ChooseBetterWindows.com