The Setup:
Both bedrooms are similar in size, west facing, with the same window arrangements. On the window in bedroom #1 we installed an exterior sun screen and on the window in bedroom #2 we installed interior window film.
We turned off fans and lights in both bedrooms and placed an empty drinking glass in the light shining on the floor to measure both the temperature of the windows themselves and objects in the room. We measured the same drinking glass (glass temperature) in each experiment and we measured identical window panels (window temperature) in each room.
Date & Temp: August 18, 2003 – afternoon high 107 degrees
The Results:
| TIME | PLACE | ITEM | TEMPERATURE |
| 2:40pm | Bedroom #1 | Window Temperature Glass Temperature | 93 83 |
| Bedroom #2 | Window Temperature Glass Temperature | 102 83 | |
| 4:00pm | Bedroom #1 | Window Temperature Glass Temperature | 98 85 |
| Bedroom #2 | Window Temperature Glass Temperature | 113 85 | |
| 4:50pm | Bedroom #1 | Window Temperature Glass Temperature | 99 85 |
| Bedroom #2 | Window Temperature Glass Temperature | 108 84 |
The Conclusion:
The window in bedroom #2 where we installed interior window film was substantially hotter to the touch whereas bedroom #1 with an exterior sun screen was much cooler. Overall, both treatments work well and offer relief from the sun. The way the light looks and feels with the window film is a softer, more diffused light; however, sun screens offer more privacy in addition to the fact that they reduce the amount of heat entering the home in the first place. If your goal is to keep the heat out, sun screens may be a more attractive option for your investment with the added bonus of a little extra privacy.
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