Window Frame Materials and Energy Efficiency
While the material that comprises a window frame effects the the frame durability, thickness and weight, it also has a major impact on the window’s thermal characteristics. The window U-factor incorporates the thermal properties of the glass and the frame. The properties of the frame definitely contribute to the energy efficiency of the window as the sash and frame account for 10-30% of the window unit’s total area.
This video presents the different types of windows and doors:
The following is a comparison of the energy efficiency of different frame materials:
Aluminum: The high thermal conductance of aluminum is its greatest disadvantage. It greatly increases the overall U-factor of a window unit as it readily conducts heat. In cold weather, moisture of frost condensation can occur on the inside surface of the frame.
Aluminum with Thermal Break: The heat conduction problem of aluminum frames can be resolved by providing a thermal break, which is created by splitting the frame components into exterior and interior sections and joining them with a less conductive material. This method has reduced aluminum frame U-factors as much as 50%.
Wood: While not the most durable material, wood window frames perform well in terms of thermal conductance. Wood clad frames are manufactured by cladding the exterior frame face with aluminum or vinyl. They require less maintenance than wood frames but retain the attractive wood finish on the interior.
Vinyl: Because they are virtually maintenance free, vinyl frames are a popular choice for homeowners. Vinyl frames have good moisture resistance and are comparable with wood in terms of thermal performance. They can be insulated by filling the hollow frame cavities with insulation. Insulated vinyl frames are thermally superior to both vinyl and wood.
Fiberglass: Glass-fiber-reinforced polyester, or fiberglass, frames are dimensionally stable and have air cavities similar to vinyl. When the cavities are filled with insulation, fiberglass frames, like insulated vinyl frames, have a better thermal performance than wood or vinyl.
