Window Technologies: Frames
Window frames hold glass panes in place, but in efficient windows they do more. Frames help to reduce energy use, resist temperature changes that impact the rest of a window’s performance, and keep interiors comfortable. Consumers often pick frames based on style, cost, and maintenance requirements, and all these needs can be met using efficient materials. Frames are also an important element of the National Fenestration Ratings Council’s energy-efficiency ratings, which evaluate all parts of a window. NFRC labels affixed to windows are easy to understand and help you find the right windows for your home.
Until the introduction of new technologies featuring composite materials, window frames were mostly made of metal and wood, both of which are still popular choices. Wood is an efficient material because of its density. Wood is also widely available, inexpensive, and easy to form into the complex shapes required. Consumers often find wood frames attractive, and like that they can be painted any color. However, wood frames require extra maintenance to avoid rotting and warping.
Metal frames are light, strong, durable, and easy to maintain, but are not always efficient. They are typically made of aluminum or steel, which is formed into the many complex shapes required in windows. However, heat passes quickly through metal frames, which makes them inefficient. In cold climates, heat escaping a home through the windows creates drafts, condensation, water stains, mold, and mildew. In hot climates, heat entering a house forces air conditioners to run more often to keep temperatures stables. This problem can be solved using non-metal layer sandwiched between the metal edges. This is called a thermal break and is usually made of plastic.
PVC Vinyl Frames
Frames made of vinyl, also known as polyvinyl chloride (PVC), offer a level of energy efficiency similar to wood, but resist moisture and require no maintenance. Newer versions also offer protection from sunlight and extreme temperatures. Some vinyl frames have hollow areas, and filling these spaces with insulation can boost efficiency. They can be painted or coated with another type of finish.
Hybrid frames combine multiple materials to offer efficient options for different tastes:
- Wood-clad frames are made of wood but with vinyl or aluminum covering their exterior side, to provide the look of wood inside and protect against the elements outside. Vinyl frames with wood veneers offer a similar combination.
- Split-sash frames use fiberglass for exterior surfaces and wood for interior ones.
- Composite frames mimic wood’s appearance but resist moisture and are more efficient and durable. They are made of plastics and processed wood products such as particle board. They can be stained or painted like wood, and sometimes are made from recycled materials such as sawdust and scrap wood, which can make them more environmentally friendly.