A wood-clad window has a wood internal structure but is wrapped with a vinyl or aluminum exterior. This is intended to combine low maintenance with the superior insulative properties of wood, though s [..]

The visible transmittance (VT) rating indicates how much light passes through the glass, with higher numbers indicating greater light transmission.

A window's U-factor measures a windows thermal conductivity. A lower U-factor indicates less conductivity and better efficiency.

the same as double-glazed windows except that they use three panes of glass rather than two. Triple-glazed windows are extremely efficient but can be more expensive choices. They may also inhibit visi [..]

glass that has been processed and treated to increase its break resistance

a measure of how well a window blocks heat gain from solar radiation. The rating ranges from 0 to 1, with lower numbers indicating better heat resistance.

Spectrally selective coatings on energy-efficient windows block infrared light wavelengths that transmit heat while allowing visible light to pass through the window.

A single-hung window looks much like a double-hung window, but only the bottom sash is operable, while the top sash is fixed in place.

R-value measures a substance's resistance to the flow of heat. It's most commonly used when discussing insulation products but is useful to understand when looking at windows because it' [..]

NFRC labels offer information on a model's U-value, solar heat gain coefficient (SHGC) and visible transmittance. Information on air leakage and condensation resistance may also appear but is not [..]