Calculate U-factor for Window Film
Calculating the U-factor for window film is crucial for improving energy efficiency and reducing heating and cooling costs. The U-factor, or U-value, measures the rate of heat transfer through a window, with lower values indicating better insulation.
- Select the glazing type (single, double, or triple).
- Enter the film thickness in mils.
- Enter the ambient temperature in degrees Fahrenheit.
- Click “Calculate” to see the U-factor and a visual representation.
The U-factor is calculated using the following formula:
U = (k * t) / (t + (2 * L * k) / h) + (L / h)
Where:
- U = U-factor (Btu/hr-ft²-°F)
- k = thermal conductivity of the film (Btu/hr-ft-°F)
- t = film thickness (ft)
- L = film edge loss coefficient (Btu/hr-ft-°F)
- h = convective heat transfer coefficient (Btu/hr-ft²-°F)
| Glazing Type | U-factor (Btu/hr-ft²-°F) |
|---|---|
| Single | 1.13 |
| Double | 0.72 |
| Triple | 0.40 |
| Film Thickness (mil) | U-factor (Btu/hr-ft²-°F) |
|---|---|
| 5 | 0.65 |
| 10 | 0.55 |
| 15 | 0.48 |
- Consider the climate and insulation needs when choosing a film thickness.
- Install window film in combination with other insulation methods for maximum efficiency.
- Regularly inspect and maintain window film to ensure its effectiveness.
What is the optimal film thickness for my window?
The optimal film thickness depends on your climate and insulation needs. In general, thicker films provide better insulation but may also affect visibility.
Can window film be installed over existing window treatments?
Yes, window film can be installed over existing window treatments, but it may affect their appearance and functionality. Remove any treatments before installation for best results.
Learn more about window film from the U.S. Department of Energy
Read a detailed study on window film U-factors from the National Renewable Energy Laboratory