R-Factor: A measure of the resistance to heat flow. A window with a high R-Factor indicates a high resistance to heat flow and thus, a higher insulating value than windows with lower R-Factors.
The concept seems simple, but there are many things to consider when designing the right glass package for your windows.
You've already decided to go with vinyl windows, which provide better insulating values than aluminum, and comparable performance to wood without the inevitability of decay and maintenance. Now it is time to decide on the proper glass configuration.
Before I do, let me clear up the term U-Factor. U-Factor is essentially the same as R-Factor with an important difference…they're opposite! Hey, wait a minute, the same but opposite? U-Factor is defined by the inverse of R. That means that a R-10 window has a U value of 0.1. (Here's the math: R of 10 equals U of 1/10, or 0.10). A bit confusing…yes…but that's the scientists for you. Just make sure you always use the same scale. For windows, typically the R-Factors are weighed. In that case, bigger is better. If you were using U-Factors, then the lower number would be better…like golf, or age, or number of times you've been chased by an angry dog. OK - we're getting off track.
Glass in a window is comprised of what we call an "Insulated Glass Unit" or "IG". Pieces of glass are sealed together into this IG using various technologies. With different IG configurations, come different insulating abilities.
The components of the IG are: Glass, Spacer system, Coatings, and Gas Fill.
Glass: We are all familiar with glass…a truly amazing material with properties that make our lives rich through sensory experience. Man-O-Man...I love glass! Did you know glass was a liquid? Yep…a super cooled liquid that exists in a solid phase at our normal temperatures and pressures. That's what gives glass such amazing properties.
Spacer System: Sometimes people refer to dual pane glass as "thermal pane". When windows started using more than one pane of glass, the Insulated Glass Unit was born. The concept is to increase the insulating properties of a window by incorporating more than one piece of our miracle substance…glass. In order to put these pieces of glass together, there has to be a 'skeleton' if you will. That framework is the spacer system…and there are many options. Energy Plus Windows and Doors uses two types of spacer systems. The Intercept system is our standard, and Duralite Spacer is our upgrade option. Each has great insulating properties that contribute to the overall R-Factor of a window. More details are here.
Coatings: High Performance Low-E
The E is for Emissivity - Webster's Dictionary defines emissivity as "the relative power of a surface to emit heat by radiation." Emit means to "throw or give off." Okay, so Low-E glass obviously is a special glass that has a low rate of emission. In other words, if there is a heat source inside your house (or outside!), the glass bounces the heat from that object back away from the glass. So, in the winter months, if you have Low-E glass in your home, much of the warmth (heat) given off by the furnace and all the objects which the furnace has heated, is bounced back into the room.
In the summer, the same thing happens but in reverse. The sun heats things up (the air, sidewalks, driveway, next door neighbors bricks, etc.) outside of your house. This heat radiates from those objects and tries to get into your house. Of course, it tries to take the path of least resistance, that being the glass. With Low-E glass much of this heat bounces off the glass and stays outside. We use Low E Stacked for higher performance and energy savings.
Gas Fill: There are essentially three gases used in insulated glass units today. Air, Argon, and Krypton. Each is inert, and will not react adversely to the glass unit that it is contained within. Argon is a more dense gas, although still transparent, which makes it a good insulating alternative to air. Krypton is even more dense, and is even better yet. The density matters because the gas inside an IG acts as a blanket to stop heat from escaping your home during the winter and penetrating your home during the summer.
Using these four factors, Energy Plus Windows and Doors has come up with 3 different IG configurations to give you the widest choice when designing a window solution.
Energy Plus Windows and Patio Door Performance Glass and Window Systems
Window Type
U-Value
Energy Elite T3 Plus Series Composite Window
.17
Energy Elite T3 Series Composite Window
.19
Energy Elite T2 Series Composite Window
.25
Ultra- Series Vinyl Window
.22
Performa Series Vinyl Window
.28
Premium Series Vinyl Window
.30
* All Window Qualify for Tax Credit - Values as determined by NFRC *
Energy Plus Vinyl Window Systems
Comfort Extreme Glass = High Performance Low E, Argon gas filled within a 3/4" Double Glazed Intercept spacer system for maximum energy savings and efficiency. Comfort Plus Glass = Special Double Low E, Argon gas filled within a 3/4" Double Glazed intercept spacer system for excellent energy savings and efficiency.
Comfort Glass = 3/4" Double Glazed intercept spacer system, Low E insulated glass with a dead air space for energy savings and efficiency.
Energy Plus Energy Elite Series Composite Window Systems
Energy Elite T2- Double Glazed duralite spacer system Low E, argon gas for greater energy savings and efficiency.
Energy Elite T3 Triple Glazed duralite spacer system, double Low E, argon gas filled for Excellent energy savings and effiency.
Energy Elite T3 Plus - Triple Glazed, duralite spacer system, double Low E, argon/krypton gas for ULTIMATE energy savings and efficiency.
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