Did you know that a quarter of your home’s energy usage goes towards heating and cooling? That’s a hefty amount, especially if you have large energy bills. However, do you also know that you can reduce this amount drastically just by choosing the right windows? Aside from poor wall and roofing insulation, windows are one of the main culprits to be blamed for increased energy consumption. Heat passing through the window pane or frame results in increased energy costs during summer to cool the home. In winter, heat passing through the window’s glass panels forces the home’s heating system to work harder, thus also resulting in increased energy costs. Fortunately, the technology used in modern windows can reduce your home’s energy consumption significantly simply by preventing heat from passing through the window’s glass panels and frame. However, with so many window styles, types and manufacturers, how would you know which products to choose? Here are some simple tips on how to choose the right energy-saving windows for your home.
PART 1: LEARNING ABOUT NFRC RATINGS
The National Fenestration Rating Council (NFRC) is an organization that compares different window, door and skylight products, and rates these products’ energy efficiency characteristics. Their ratings are then placed on the product so consumers are aware of how the product performs in terms of energy conservation. The problem is, some of the terms on the labels are somewhat technical in nature, so you might find it difficult to understand what the ratings mean. In this post, we give you a brief overview to help you understand them. An NFRC Energy Rating label consists of four main quadrants:
• U-Factor • Solar Heat Gain Coefficient • Visible Transmittance • Air Leakage
Here’s a brief explanation of each quadrant and what figures you should be looking for.
• U-Factor – U-Factor is a unit of measurement that indicates the amount of heat loss. It measures the amount of heat inside the home that can escape through the window’s glass panels and frame. The lower the U-Factor rating, the better the window’s insulation properties, which would mean that your home will need less energy to keep it warm inside. Most windows with double glass panes have a U-Factor rating of 0.30, which is far better than ordinary, non-energy efficient windows.
PART 1: LEARNING ABOUT NFRC RATINGS
• Solar Heat Gain Coefficient (SHGC) – This unit of measurement indicates how much solar heat passes through the window’s glass panels and frame. Windows with a low SHGC rating prevents more solar heat from entering the home through the window, which translates into lower energy costs to cool the home. The SHGC rating is a figure between 0 and 1. Look for windows that have an SHGC rating closer to 0.
• Visible Transmittance (VT) – Although you’ll need to prevent heat from passing through the window to conserve energy, you also want as much light as possible to pass through as well. If more natural light enters the home, you’ll consume less energy in lighting costs. The amount of natural light that passes through a window is measured in visible transmittance. This rating is between 0 and 1. You’ll need to look for a rating closer to 1, which would mean that more natural light is getting through the window. • Air Leakage (AL) – Heat can also be lost through air passing through small gaps in the window’s structure. The fewer gaps there are in the structure, the less air leaks, which would mean lower energy consumption to keep the room warm. Look for the lowest air leakage rating. ooooo
In the next post, we’ll take a look at the importance of selecting good window frame material. Stay tuned!
PART 2: CHOOSING AN EXCELLENT WINDOW FRAMING MATERIAL
Heat not only escapes through the glass panels of a window, but also the frame. On a hot summer’s day, try feeling the outer and inner portions of the window frame. The outer portion will definitely be hot, especially if the window is exposed to direct sunlight. In some windows, the inner portion can also be warm because heat is conducted through the frame. As you already know, heat passing through the window, whether through the glass or frame, means more energy is being used to keep the home cool or warm. Therefore, you’ll need to look for window frames that conduct less heat. The question is, which type of window frame material is more energy efficient? The most common window frame materials in the market today are:
• Wood frames • Aluminum frames • PVC frames • Metal frames • Fibrex®
Of the above materials, aluminum and metal frames conduct heat the most, so if you’re looking to conserve energy, you definitely want to avoid buying window frames made from those materials.
PART 2: CHOOSING AN EXCELLENT WINDOW FRAMING MATERIAL
Frames made of wood don’t absorb and transmit heat as much as metal frames. However, wood is prone to warping, peeling, decay, rotting and all sorts of damage. Wood may be energy-efficient, but you’ll need to spend more money on maintenance and repair costs. PVC frames are somewhere in between wood and metal frames in terms of energy conservation. Unfortunately, PVC is a somewhat weak material and is prone to damage. The material may also disfigure in extreme climates.
Perhaps one of the best framing materials available today is Fibrex, which is a composite of wood fiber and PVC. Fibrex is tough and highly durable. Moreover, Fibrex does not decay, warp, peel or blister. In addition, Fibrex is highly energy-efficient as the material prevents heat from passing through the window frame. ooooo
In the next post, we’ll talk more about a very important aspect of a window: its glass. Stay tuned!
PART 3: CHOOSING ENERGY-EFFICIENT WINDOW GLASS
In every type of window, glass makes up the largest portion, which is why it can significantly impact energy loss. Windows made of ordinary glass do poorly in terms of energy efficiency. Try feeling the inner portion of the glass on a hot summer’s day, and you’ll notice how hot it can get. Fortunately, modern window glass can prevent heat from passing through. This means you can improve your windows’ efficiency by:
• Adding more glass panels • Adding low-emissivity (low-e) coating • Adding gas between the glass panels
Today’s energy efficient windows have at least two glass panels with a small space between them. The additional glass panel provides some space in between that can be filled with inert gas, such as argon, which is capable of blocking more heat and thereby making the window more energy-efficient. Aside from adding more glass panels and filling the gap between them with gas, manufacturers also coat the inner and outer portions of the window glass with a low-e coating, which is a virtually invisible layer of metallic oxide. This coating prevents heat from passing through the glass, allowing only visible light through and thus increasing the window’s overall energy-efficiency rating.
PART 3: CHOOSING ENERGY-EFFICIENT WINDOW GLASS
So, how do you choose the best energy-efficient glass for your window? The best way is to check the NFRC rating of the window. This rating will show precisely how good the window is at conserving energy. Another way is to check the manufacturer’s specifications of the window. You’ll need to look for window glass that not only has a low-e coating, but is also gas filled and has at least two glass panels.
Now that you know what to look for in windows, you are better equipped to pick out the most energy-efficient replacement windows out there. For best results, consult a trusted window company in your area that can provide you with professional recommendations and services.
Seamless Exterior 6227 Nordic Drive Cedar Falls, IA 50613 (319) 277-3441 www.seamlessexterior.com