Window film is no substitute for window replacement.

Partly true and partly false. Window film may or may not be a substitute for window replacement. Replacing an inefficient window with a new efficient unit is probably the best solution in terms of performance. However, replacement may not be practical, cost-effective, or structurally feasible, and that’s where window film presents itself as a wonderful solution.

Improved performance is measured by reducing a window’s Solar Heat Gain Coefficient (SHGC) for solar heat gain reduction (in order to reduce air conditioning bills) and U-Value for winter heat loss reduction (in order to reduce heating bills). The most effective way of reducing either of those two performance characteristics is by window replacement. Replacing a single pane window with a double pane window will provide a higher U-Value reduction than will installing an insulated window film like 3M Thinsulate Climate Control Series. Replacing non-Low-E windows with Low-E windows will also provide a higher U-Value reduction than will installing a window film such as Thinsulate. And replacing a standard window unit with a high-efficiency unit will provide a higher SHGC reduction than will installing window film.

However, window replacement is costly. It’s an undertaking. The process may disrupt nearby occupants, and touch-up work and painting may be required after the fact. Window film is a retrofit product that can approximate the decrease in SHGC and/or U-Value at a fraction of the price (25%-33%) of window replacement. The installation process is fast, easy, and non-disruptive to those nearby.

Finally, replacing a single pane unit with a double pane — or a double pane unit with a triple pane — may not be feasible if the building’s curtainwall structure has not been engineered to withstand the additional weight of an extra pane of glass per window opening.

In conclusion, there are many building-specific factors that determine whether window film is a substitute for window replacement. When cost, ease of implementation, and structural implications are considered, window film is certainly a value-engineered alternative to window replacement.