Which is better?
- Tinting the glass in old windows, or…
- Replacing the entire window (frame and all) with a modern double pane window?
First, let’s go over a few of the ratings that determine whether a window is Energy Star Certified (An energy efficient window).
Solar Heat Gain
Solar Heat Gain is the type of heat you feel on your face when the sun is shining through your car window directly on your face. Some people refer to SHG as radiant heat.Window tints (or films) and dual pane replacement windows both help reduce solar heat gain by reflecting or absorbing the sun’s ultraviolet and infrared radiation. (As long as the replacement window glass is at least 3 coat Low E glass)
The U-Rating determines how quickly heat or cold flows from one side of the window’s glass and frame to the other side. (In either direction, whether winter or summer). Some people refer to this as ambient or conductive heat. There usually isn’t a single window in a home that gets direct sunlight for more than few hours per day. However, every window in a home, whether it’s in the sun or the shade, is directly exposed to the air temperature outside 24 hours per day. If it is 110 degrees outside in the shade, the glass heats up rapidly and transfers that heat to the inside constantly. If it is 25 degrees outside, the 70 degree air inside the home transfers through the glass to the outside, non-stop.
Think about it this way. Let’s say you have tinted windows in your car. The SHG properties keep your face shaded from the direct sun but the hot glass surfaces make the entire inside of the car warm very quickly (try turning off the AC and see how quickly the car heats up). Tints (or films) are great for shading body parts and reducing glare.
Modern Energy efficient double pane replacement windows carry excellent U-ratings. Of course some are better than others.(Replacement windows that are 15 years old or older don’t have the modern technology that newer dual pane windows have for the U rating)
Window tints (or films) don’t enhance the U-rating for windows. They will help add shade, but hot and cold air will change the temperature of the glass considerably. In fact, when a tint reflects or absorbs radiation from the sun, the glass surface actually gets much hotter, thus contributing to the increase of heat flow inside the house.
“Can applying a tint to a window help increase a window efficiency enough to satisfy energy star requirements”?
The answer is no. After-market tint applied to a non-energy star rated window will not bring it up to compliance because the U-rating will always worse after applying the tint (or film).
Here’s a quote from the website of a popular residential tint company, this statement is in reference to applying a 3M window tint to dual pane glass. – www.arizonatints.com/home-tints.
“3M has continuously tested insulated glass units. The results our most popular residential film only increases the summertime airspace temperature by no more than 22 degrees, a pressure increase of only .55psi (pounds per square inch).”
The increase in glass temperature for a single pane does transmit heat inside the home, but can’t breach an air seal. Single-pane glass has no air seal.
However, quality dual pane windows have sealed glass packs. Heating up the air between the 2 panes of glass is not only decreases the energy efficiency of the unit, but also weakens the integrity of the moisture seal. That is why any after-market tint or film applied to a dual pane replacement window will void the manufacturers’ warranty for the glass. For this reason, it is not recommended to apply an after-market film to double pane windows.
PLEASE CONSULT THE CHARTS BELOW FOR A DIRECT COMPARISON:
If you are having trouble with the sun shining right on your desk in your home office, then maybe a tint is all you need for comfort. Especially if this is not a home you are planning on keeping for any length of time.
If you are planning on keeping the home for a while, replacing the entire window is worth the extra cost for the amount of benefit received.