Most Energy Efficient Windows: Triple-Pane Or Suspended Film?

While many people believe triple (or even quadruple) pane windows offer the best energy performance, high-performance windows with two panes of glass and a layer of suspended film actually deliver equal or better R-values with less weight, longer expected life, increased design freedom and lower total installed costs.

Suspended film technology uses spectrally selective film mounted inside an insulating glass unit to create between two and four insulating air chambers. These air chambers, filled with inert gases like argon or krypton, provide exceptional insulation performance that reduces conductive and radiated heat, but without the weight and size restrictions imposed by triple-pane insulating glass. The layer, or layers, or suspended film also present additional surfaces that can be treated with low-E coatings to achieve finely-tuned solar control.

1. Less Weight with Equal or Better R-Value: The single most important performance characteristic of an energy efficient window is R-value, or the thermal insulation value. High performance windows range in R-value from approximately an R 4 to R 11. While triple pane windows can achieve good R-values, the third pane of glass makes them heavier and thicker than windows with only two panes of glass and a thin, light-weight film. Additionally, triple-pane windows imply extra weight, which places stress on the overall structure and can lead to gaps that allow air, water or dust to penetrate around the window. Air infiltration significantly lowers the thermal performance of the whole window unit, and water and dust infiltration can cause serious damage to the structure as well as interior furnishings.

2. Longevity: By eliminating the additional structural concerns that can be involved in a triple-pane design approach, dual-pane glass units with suspended film also increase the life of the glass unit and hardware by removing extra weight, which results in unnecessary wear and tear on both the window and the surrounding structure.

3. More design flexibility: Because of the excess weight and thickness of triple-pane windows, architects and designers may face size constraints when specifying the size and number of windows. These design limitations can affect aesthetics by limiting the number and size of windows in a home, which also affects the amount of natural daylight enjoyed inside the home.

4. Lower Total Installed Cost: Due to their increased weight, triple-pane glass units require stronger framing units, which can increase the total cost of the building. In fact, the entire structure in which the windows unit is installed must be sturdier in order to support the extra weight. Triple-pane windows also may require unusually wide frames or openings to accommodate the thickness of three panes of glass. These structural modifications increase the overall cost of working with triple-pane windows. Dual-pane windows with suspended film on the other hand, are comparable in weight and thickness to average, dual-pane windows and can fit into standard width window openings.

Across the board, dual-pane windows using suspended film technology deliver the best overall results compared to triple-pane windows. If you’re considering replacing your existing windows or choosing energy-efficient windows for your new home, high-performance, dual-pane windows with suspended film technology can help you achieve optimal thermal performance with no tradeoffs.