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What Are Thermal Windows (Double Paned)

Thermal Windows

What Are Thermal Windows?

Thermal windows or thermal insulated windows are double paned windows with special gas inbetween that helps reduce heat transfer/loss.

They are often used up north to keep the warm air inside, however, in southern climates, they can be used to keep cool air inside.

Here is an example of an argon filled thermal insulated window from Home Depot.

How Efficient Are Thermal Insulated Windows?

Typically, the gas inside the thermal window is Argon gas which is used as the insulator. To tell the efficiency of a thermal insulated window, just check the label for the efficiency rating.

The rating is usually comprised of a “u-rating” which is on a scale from 0.2 to 1.2. The lower the number, the better the insulating window.

The U-Rating is basically the reverse of an R-rating which is known as the insulating rating for any type of material. So, a low U-rating means a high insulating rating or R-value.

Thermal insulated windows can have an R-rating from 3-5. This means heat loss can be from 30%-40% – which is really good savings since windows are responsible for 25%-30% of the total home’s energy loss (for HVAC systems). has further information for shopping for energy efficiency windows.

Failures to Thermal Windows

Thermal windows can sometimes fail. This is actually more common than you may think and is caused by tiny cracks in the seal from manufacturer defects or dropping the window.

To tell if a thermal insulated window is failing, check for condensation or haziness between the two panes. Condensation will typically appear in the early mornings.

Also, you can check for thermal seal slippage, which is the black seal that coats around the two panes (in the middle so you can’t touch it). If the black seal appears to be “slipping” in between the two panes, your thermal seal might be compromised.

Good News On Window Seal Failures

Most of the time, this is on brand new windows. So, your windows should be covered under warranty where the manufacturer will replace them for free.

Bad News on Window Seal Failures

In almost all cases, you will need to replace the entire window as there is no simple fix.

Looking For The Best Thermal Windows

With windows, obviously design is important for you. As mentioned above, you should also take into consideration the energy efficiency ratings of the windows.

However, another side which many home owners do not consider is how well windows are designed to wick away moisture. A good contractor can general recommend reliable windows. Moreover, a good contractor can properly flash around your newly installed windows to remove the chances for water intrusion.

Be sure to check online ratings, as well as, ask for contractor opinions.

How Much Do Thermal Windows Cost?

Thermal insulated windows can be quite costly. But ultimately, it depends on the quality of window you are looking to purchase.

On the low end, you can have basic, small windows that are about $130 per window. On the high end, you can purchase windows that are near a thousand dollars per window (bay windows or double hung).

This is compared to regular single pane windows that can start at $100 per window.

Thermal Windows & Home Inspections

Home inspectors should always report on defects, such as, a failed thermal window. This is most often found by the above mentioned criteria: a loose thermal insulating strip that is slipping, or, a window with condensation in the middle.

Concluding on Thermal Windows

If you have more questions on thermal windows comment down below!

Want to learn more about energy efficiency for your home? Check this post on radiant barriers.