Since the frame can account for as much as 25% of the total window area; it should be at least as well insulated as the glass. Several different frame types are available.
Solid Wood and Clad Wood
Solid wood frames are a good choice from an energy standpoint. The colour choices are unlimited but wood does require regular re-painting inside and outside.
Clad wood frames are protected on the exterior with a covered of pre-painted aluminum or vinyl. Clad frames are more expensive than plain wood but eliminate exterior painting. Claddings must be well designed to prevent water from becoming trapped behind them.
Aluminum frames are durable, and good designs are available for residential windows, aluminum conducts heat rapidly. To prevent condensation and frost from forming on the frame, the frame and sash must be equipped with well-designed thermal breaks.
It is difficult to judge whether an aluminum frame is equipped with a good thermal break. One thing you can do is ask people who have lived with the brand you are considering whether they have experienced any condensation problems.
If a metal window frame has a CCMC number, it has passed the CSA A-440 standard test for condensation resistance. Be particularly wary of inexpensive aluminum replacement windows.
Vinyl frames provide good insulation and do not require painting. However, some manufacturers reinforce the vinyl with metal, which can decrease the frames insulation value. Wood reinforcing is preferable.
Fiberglass window frames are a recent innovation available from a limited number of custom manufacturers. Fibreglass frames will hold their shape permanently and will not warp, shrink, rot, bow, dent or twist.
If you are going to the expense and trouble of replacing windows, make energy efficiency one of your most important considerations. I talked about draftproofing in an earlier article, so I will focus on air leakage here.
There are some major air leakage areas in the basement. After construction the sill plate can shrink away from the concrete foundation and leave you with a wind chill factor. Leakage in the header area wastes money and can make the floors upstairs chilly.
Let’s not forget the attic. Care should be taken to seal around all the openings in the attic floor, such as ceiling light fixtures, plumbing stacks, exhaust fans and chimney chases. Otherwise warm moist air can escape into the attic, where it can condense and cause moisture damage. Before leaving the attic remember to weather-strip the hatch and latch it snugly.
Extreme air sealing will make power ventilating a necessity. Care should be taken to enable all power exhaust systems to have adequate replacement air inlets.
It’s Just That Easy!