Quality Windows, Siding and Doors Since 1976 1-866-4FELDCO® | Customer Support
  • NARI Member - National Association of the Remodeling Industry
  • energy star certified logo
  • all Feldco products are EPA certified to be lead safe
  • osi certified installer
  • window and door magazine dealer of the year
mobile call button

What Makes Up Insulated Windows, and Are They Worth It?

If you’re searching for cool points with the kids or grandkids, you might assume that IG stands for “international gangster.” but you would eliminate all street credibility with that guess, because IG actually stands for insulating glass, a type of glass that’s in insulated windows, designed to prevent heat from entering or exiting a building through the windows.

insulated windows

Insulating glass is also referred to as double or triple glazing which, sounds like the name of something you would find in a doughnut shop, topped with sprinkles that change colors with the seasons.

But again, these nicknames refer to a type of glass that can help keep your home warm in the winter, and cool in the summer—and that is pretty internationally “gangsta,” we suppose.

The Structure of Your Insulated Windows

Basically, insulating glass is made from multiple panes of glass (two or three) separated by metal or structural foam spacers. Between the spacers, gases like Krypton and Argon are present. These gases have a low reactivity, therefore being more energy efficient.

The entire insulating glass unit is comprised of multiple pieces of glass, materials that set distance between the panes, and potentially any gas inserted into the space between the panes, effectively creating an incredible piece of clear insulating material.

All of these pieces—the glass, the spacers, and the insulating noble gasses—are assembled into a single, well-constructed prefabricated unit that holds itself together, and these complete units are referred to by the nickname of IGUs, or insulating glass units if they’re required to sign their full name.

Low-E Glass

Low-E glass doesn’t mean low energy, but rather low emissivity glass, which is typically utilized for the panes of an insulating glass unit, and it has a special film meant to combat the entry of ultraviolet and infrared light that would typically pass through regular old un-insulated or unglazed windows.

Since these light types occur naturally from the presence of, you know…the sun (that big ball of light in the sky you should not look at directly). Low-E glass helps regulate temperature in the home by sending that heat back from where it came.

In case you’re curious about the exact battle strategy of Low-E glass, the coating is made of microscopically thin material that isn’t so adept at absorbing or emitting heat, but a natural pro par excellence at reflecting it.

What’s more, because low-E glass reflects heat away and prevents it from traveling through the window panes, it can keep out heat in the summer, and keep heat in during the window, greatly improving the energy efficiency of your home, lowering consumption, and reducing your power bill.

Location, Location, Location

The location of your home is a big part of your search for insulating glass windows. As you can imagine, developments in technology and the fluctuating but ever-present need for new construction has resulted in insulating glass units that are regionally specific.

You can learn more about what’s available in your area by consulting with qualified (and certified) contractors, or sales associates at the hardware store, but suffice it to say, that as an example, glass in cold regions like Wisconsin will be geared toward keeping the winter out, while windows in New Mexico will be designed to exclude heat.

Important Variables to Consider: U-Factor, SHGC, VT, and AL

Regardless of location, the U-factor, solar heat gain coefficient (SHGC), visible transmittance (VT), and air leakage (AL) are important pieces of information to be aware of.

U-factor indicates the rate of heat loss; essentially it is a numeric qualifier of how well the window serves in its insulating role. U-factors usually range from .25 to 1.25, but the Department of Energy suggests using windows with the Energy Star designation that have a U-factor of less than .25. In fact, a triple-pane window can get the U-factor down below .15, making it a clear winner in the U-factor limbo contest.

SHGC (solar heat gain coefficient) measures how much solar radiation is carried through a windowpane. It can be measured from the middle of the window (which only takes the pane into account) or it can assess the entire window (including the frame and mullions). The SHGC ranges between 0 and 1, but a lower number indicates less heat transmitted through the window.

Another factor to consider is visible transmittance (VT) which indicates how much visible sunlight gets through the window. The more sunlight you desire in your home, the higher the VT should be for your windows, but the great thing about technological advancements in window coatings is that the VT can be high (if so desired) while the SHGC and U-factors can be low—essentially meaning that your windows can let in desired sunlight, but still effectively insulate the home.

A final factor, air leakage (AL) is important for determining how much air gets through the cracks in the assembly (namely, the space between the glass panes and the frame). An insulating glass unit with a good AL (.30 or lower) is important for contributing to the overall effectiveness of your home’s insulation.

The Window Frame

Just like a great painting looks best when it’s in a good frame, energy-efficient windows need excellent window frames, and they need to be joined to that window frame with quality workmanship.

window insulation

And yet, while the look of glass windowpanes is mostly standardized, there are a lot of options when it comes to windowpanes for homeowners who want their façade to look a particular way.

Aluminum frames tend to conduct heat rapidly, so they are probably the least energy efficient. Vinyl frames have air cavities that can be filled with insulating material, so the insulation they offer is extremely quite good.

Wood frames do insulate well, but the material itself can expand or contract based on the extremity in the temperature, resulting in a potentially unwanted transfer of energy.

Cost vs. Savings

Like any home-improvement project, it’s difficult to determine how much you’ll actually save with insulating glass windows. Higher priced windows aren’t necessarily a better insulator, so bring some research on the variables we mentioned above (U-factor, SHGC, VT, and AL) to the discussion you have with salespeople.

Insulating glass windows will reduce the burden on your heating and cooling systems, so do factor this into the equation as best as you can. Check with your local utility company to see if they offer rebates for purchases of new, energy-efficient windows.

Even if they don’t, single-pane windows often account for up to 30% of heat loss in your home, as an example, so upgrading your windows is sure to lower your energy bill.

The Department of Energy (DOE) suggests installing products that specifically carry the Energy Star designation, and estimates savings of 12% percent off your utility bill—and that’s a great reason alone to replace those single-pane windows in your home with some double or triple pane insulating glass units.

Looking for great quality insulated windows? Feldco is a leader in great quality insulated windows. Get a free quote Today.

Did you enjoy this article? Please share it!

Just click one of the links below to share this article with your friends and family.

Get a Free Quote

It's easy, fast and completely free. Get started below:

Yes, Quote Me! No, I'm Not Ready Yet