There are a ton of terms to know when it comes to window and door installation. Impact windows vs non-impact, low-e glass, shims, bucking, flanges, casement, awning, weatherstripping… the list goes on and on. One term a lot of people ask us about (probably because they don’t see it on an NFRC label) is R Factor… The thing is, R factor isn’t an actual industry term.
Yet, a lot of people try to search for an answer about this term that doesn’t exist for window and door installation. To help our customers in their search for impact window installation knowledge
What Is R Factor?
R factor is an accidental mixture of two actual terms used by general contractors and window installation experts: R value and U factor.
- U Factor. This is an assessment of a window’s insulative qualities that accounts for thermal transfer from one side of the window to the other. The better the window is at preventing thermal transfer, the lower the number. Usually measured on a scale going from 0.2 to 1.2 by the National Fenestration Rating Council (NFRC), the organization that serves as the independent certification body for windows and doors.
- R Value. An assessment of how well a specific material insulates typically used by general contractors, often in reference to insulation like fiberglass in walls. Unlike with U factor, with R value, the higher the number, the better the insulation.
While not exact, you can get a conversion from U-factor to R-value by dividing one by the U-factor of your window. So, if you have a window with a U factor of .22, then the R-value of that window would be around 4.5 (rounded down to the nearest tenth).
Why Is There Such Confusion about R Factor?
Honestly? We’re not sure. It just seems to be a product of there being two terms that are so similar: two words, one a letter, the other two syllables long, then both referencing the insulative quality of something. When a general contractor says R value, then a window specialist starts talking about U factor, it’s easy to see how the two terms could get mashed together by accident.
What Other Terms Should I Know for Windows?
Here are a few quick terms to know with some simple definitions that every homeowner should know before they start shopping for windows:
- Glazing. This is just another name for the glass in a window or door.
- Fenestration. Basically a fancy industry way of saying ‘window or door.’ The root of the term refers to the arrangement of windows and doors in a structure, but most use the term to refer to the windows and doors themselves.
- Double Glazing. This refers to a window that has two glass panes in it. The gap between the glass panes is often filled with heavy inert gases like argon to improve energy efficiency.
- Energy Efficiency. A term used to describe the overall energy performance of a window or door based on performance metrics like u-factor, SHGC, and air leakage. Energy efficient windows prevent the transfer of heat into the home (or out of it during the colder months), meaning your air conditioning isn’t working as hard, saving electricity.
- Cladding. A material covering the exterior of a window frame to provide added protection.
- Tempered Glass. A type of safety glass that shatters into small, mostly harmless fragments when broken that is also stronger than normal glass.
- Solar Heat Gain Coefficient (SHGC). One of the key metrics influencing a window’s energy efficiency. It measures how much of the heat of the sun is able to pass through the window.
- Low-E Glass. Specially coated glass that is designed to reflect away the sun’s harmful ultraviolet (UV) and infrared (IR) rays. As these rays carry heat, reflecting them away helps keep your home cooler year-round, enhancing SHGC and energy efficiency.
These are just a few of the key terms that every homeowner should know before they do some serious window shopping. If you have any questions about these or other fenestration industry terms, contact Karoly Windows & Doors for answers!
What To Look for in an Energy Efficient Window
If you’re researching R factor and come across this article, a natural follow-up question would be: “Okay, then what should I be looking for in an energy-efficient window?”
In the great state of Florida, if you want energy efficiency, the first thing you should do is look at the NFRC label for the windows you’re considering.
If energy efficiency is your top concern, then the three things you should check above the rest of the label are the window’s U-factor, SHGC, and air leakage values.
For each of these metrics, you want a number that is as small as possible. In fact, the minimum requirements to meet ENERGY STAR certification in Hillsborough County, Florida are:
- U-factor of 0.32 or less
- SHGC of 0.23 or less.
But, to meet the Most Efficient criteria that qualifies for tax credits, a window needs to have:
- U-factor of .021 or less
- SHGC of 0.21 or less
While air leakage isn’t listed in the requirements for ENERGY STAR certification, it has a large impact on the energy efficiency of a window, so the smaller the number, the better.
If you want ENERGY STAR certified windows installed the right way to maximize your home’s energy efficiency, be sure to choose Karoly Windows & Doors for your window replacement service!
Karoly Windows has decades of experience installing top-quality windows and doors with extensive energy efficiency features. For every install, we use our own in-house team of installers with top-quality tools to make sure that your windows are as energy efficient as possible.
That’s how we help homeowners throughout Tampa Bay stay cool and comfortable throughout the year. And, we back every installation with a 25-year labor warranty and a 50-year material warranty–-so you can rest assured that your windows are built and installed to last!
