We are often asked by homeowners in the Atlanta Windows market, questions about energy-efficiency, and window replacement. Here are a few words written by Tom Herron – National Fenestration Rating Council’s.
Many people in the market for energy efficient windows wonder if they can get products that will help reduce air conditioning bills in the summer and cut heating bills during the winter. Controlling solar heat gain is a year-round issue in southern Nevada’s hot, dry climate, and while it’s more the exception than the rule there are a few months each year when temperatures can drop into the 30s during the night, possibly making heat retention an issue for some. Because window technology is always improving, you don’t need to make tradeoffs. You can indeed find products that make your home more comfortable while saving energy. It’s simply a matter of understanding how combining parts affects the whole. Windows are comprised of panes of glass, spacers, and frames, and it’s the arrangement of these components that determines the product’s overall energy performance.
What’s in Your Atlanta Window?
Glass refers to the individual panes while glazing refers to their arrangement. Much of the glass used to create energy efficient windows has a Low-E coating, which enhances their ability to reflect heat back into a room on a cold day and to keep heat outside when it’s hot. This metallic coating is transparent, yet it reduces energy loss by 30 to 50 percent while guarding against the infiltration of ultraviolet light, which can cause furnishings and art work to fade over time. The space between the between the two panes of glass can be filled with a harmless gas or combination of gasses to help insulate the unit. Commonly used gasses include Argon, Krypton, and Xenon, but certain window manufacturers use proprietary blends.
The graphic below shows the anatomy of a dual pane window. Let’s take a closer look:
Assembling Components for Improved Comfort and Energy Efficiency
Spacers separate the panes of glass, maintaining the correct distance between the two while contributing to energy efficiency. Commonly-used warm edge spacers are made of steel, foam, fiberglass, or vinyl and help reduce heat flow while preventing condensation. Because they are located inside the unit, spacers affect the overall window performance rating based on their conductance — the measure of how a material takes on and transfers temperature.Finally, the glass, spacers, and harmless gas fills are assembled into the frame, which fits into the wall. Choosing a frame depends on several factors, including style preference, cost, and upkeep. Another factor to consider is the amount of stress the weight of the frame puts on your wall.
Different frame materials affect the window’s overall rating performance differently. For example vinyl frames are exceptionally energy efficient, fiberglass frames have low conductance, and wood frames provide great insulation while providing a traditional look that fits many home styles.
The bottom line is how the window performs and whether it meets your goals and expectations. When you’re out shopping, keep in mind that the U-factor is a measure of heat loss. It tells you how much heat inside your home is literally going out the window. A lower number means less heat is escaping. The Solar Heat Gain Coefficient (SHGC) tells you how much heat from the sun is entering your home. A lower number means less heat is entering, and this is especially important in southern Nevada where 85 percent of the days are sunny.
Written by: Tom Herron is the National Fenestration Rating Council’s senior manager, communications and marketing and a LEED Green Associate.