Homeowners who want to reduce their heating and cooling costs often look to replacing their single-pane windows with more energy-efficient windows to help them achieve that goal.
But, knowing which energy-efficient windows are the right ones for your home, its location, and your budget, can start with learning the main factors that affect the performance of energy-efficient windows: the frame, the glass, the design and the installation.
The Window's Frame
Wood-frame windows are less prone to heat and cold transfers than aluminum ones, but wood windows won't necessarily go as far as lowering your utility bills. They need more upkeep than other types of frames, and since wood has the potential to rot, a different choice may be in order for a home in a humid or rainy climate. However, well-made wood-frame windows often remain in good shape through several decades.
Aluminum-frame windows, while not the best performer for preventing heat loss, aluminum windows are practical in damp, rainy climates, and will meet building codes in costal, hurricane-prone areas.
Vinyl-frame windows, when well-made and properly installed, vinyl can be a more economical choice while providing good energy efficiency with insulated glass and tight construction that reduces air leakage.
Wood-clad windows offer a combination of benefits: a low-maintenance exterior (usually vinyl or aluminum) and a temperature-transfer-resistant wood interior. But, wood-clad windows can be prone to water leakage in sills and jambs. Installation with waterproof rubber membranes and a stand-alone flashing assembly can minimize problems.
The Window's Glass
Double-pane windows with Low-E glass and vacuum-sealed argon gas can provide significantly more insulation than single-pane windows. They protect the inside of the house from the sun's heat and UV rays during the summer months, and can prevent heat from escaping your home in winter months. For homes that must endure harsh climates, though, triple-pane windows should provide more efficiency.
The Window's Design
The most efficient window designs are double-hung windows and casement windows.
Double-hung windows are traditional in a large number of American homes, and open by sliding the bottom section of the window up. In extreme weather, however, outside air can enter between the sliders.
Casement windows use a crank to swing the window out and back to open and close. When closed they seal off tightly in stormy weather. They will require occasional maintenance on their hinges and seals to ensure their on-going efficiency.
A proper installation does not rely on expanding foam or a sealant to get windows to fit well; they aren't waterproof and can lead to leakage problems. A professional contractor or window installer will install your energy-efficient windows correctly, including pre-installation waterproofing.