The Frame

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Most people know a wood frame is less prone to heat and cold transfer than an aluminum one, since metals conduct temperature much more easily than wood. But that doesn't mean wood is always the best choice for a utility-bill-friendly window. A variety of materials are available for window frames, and each has positive and negative aspects. Here's a look:

• Vinyl: Just because vinyl is a less expensive material doesn't mean it has to be "cheap." A well-constructed, properly installed vinyl window can be a practical choice budgetwise while still offering excellent energy efficiency measures through insulated glass and tight construction that reduces air leakage. Vinyl windows can be limited in color choices, however, and the fact remains that some people simply don't like the look of vinyl on their home.
• Wood: Wood windows offer the best insulative value, though they also require more upkeep than vinyl, wood-clad or aluminum frames. Because of the potential for rot, they may not be the best choice for extremely humid or rainy climates. A well-built wood window will stand the test of time, however; many original wood windows in older homes are still in good shape thanks to the high-quality cut and species of wood used.
• Aluminum: While not the top-performing material in terms of heat transfer and loss, aluminum windows are practical in rainy, humid climates, and they meet stringent coastal building codes in hurricane-prone areas thanks to their strength.
• Wood-clad: Wood-clad windows seemingly offer the best of both worlds: a low-maintenance exterior (usually vinyl or aluminum) and a temperature-transfer-resistant wood interior. But clad windows can be prone to water intrusion, which can cause rotting, especially in the sills and jambs, where water tends to pool. Proper installation of wood-clad windows should include use of waterproof rubber membranes around the cladding as well as a stand-alone flashing assembly called a sill pan. The sill pan drains any water that gathers around the sills and jambs, minimizing moisture intrusion (and resulting wood deterioration).
• Composite: These windows, made from scrap wood shavings and plastic resins, can effectively mimic the look of wood but are virtually maintenance-free. And because the resins used in the window-manufacturing process are often from recycled plastics, they're an eco-friendly choice.
• Fiberglass: These are technically composite windows, since they're made of a mixture of glass fibers and polyester resins, but they're often discussed independently of other composite windows because that term is increasingly being used solely to describe the wood-pulp-and-plastic composite material. Fiberglass windows are more expensive than other similarly equipped window units, but their selling points are many: They’re extremely energy efficient thanks to their low thermal conductivity; they’re the strongest and most durable windows on the market; unlike vinyl windows, they can be repainted several times; and they don't twist or warp like vinyl or wood frames can.