Tips for preserving and replacing old windows

Old windows aren't just charming. They can be surprisingly efficient, too. Here's how to preserve yours. When the time comes to replace them, know how and what to buy.

• You wouldn't use harsh detergent and water on your fine furniture, would you?
• If your home is graced with wooden windows that have a natural varnished finish, not a painted one, treat them with the same care.
• To make sure the windows are around for the next generation to enjoy, vacuum the wood rather than washing it with detergents that will eventually dull the finish and dry out the wood.
• If a really grimy wooden sash (the frame around the glass) needs washing, use a mild oil-based wood cleaner labeled for use on natural wood finishes.

• If you have to replace a windowpane, brush a generous coat of boiled linseed oil onto the raw wood the putty will go on.
• Let the oil soak in for about half an hour. This will prevent the wood from sucking the linseed oil out of the putty, prolonging the life of the putty and the window sash.

• You'll never see professional painters wasting their time lining window glass with masking tape.
• They know it is much quicker to zip dried paint off the glass with a razor-blade scraper. You get a better job, too, because you can focus on getting plenty of paint on the window putty.
• When you do use the scraper, leave about 1.5 millimetres (1/16 inch) of paint overlapping the glass to seal out moisture. That thin margin of paint will make your window last much longer.

• During the 1970s energy crunch, misguided remodelers sometimes removed the counterweights and filled the weight chambers with insulation.
• If you discover insulation instead of weights in the jamb pockets, your best bet is to install vinyl or aluminum friction sash channels sold in kits.

When buying replacement windows, you have a number of choices that will last you a lifetime or more. Here are some factors to consider:

Wooden windows: The traditional choice, wood windows are still the sturdiest and most handsome you can buy, and when maintained, they can last for centuries — as the ones in historic houses attest. However, their exteriors must be painted regularly.

Vinyl windows: These windows need no paint and require little maintenance. Good-quality, well-installed vinyl windows are sturdy and energy efficient. But if they are cheaply made and poorly installed, they can leak air like a sieve. Look for good strong welds at the corners. You won't have much colour choice — some come only in white.

Clad windows: Wood windows covered on the outside with vinyl or, less often, aluminum are a popular compromise. A vinyl-clad or aluminum-clad window gives you a relatively maintenance-free exterior with the elegance of wood on the interior.

Aluminum windows: These are a sturdy, economical alternative, but aluminum readily conducts heat and cold, so these have become less common. If you do buy aluminum windows, look for ones with thermal breaks — a core of insulation that stops much of the heat loss and keeps your energy bills lower.