A thorough home inspection will evaluate a home’s windows, checking them not only for structural soundness and use, but also to some degree, energy efficiency.
Today, many different types of windows are available and you’ll find an even greater variety in older homes that have not had windows replaced. Here are the different types of windows, their features and benefits, common problems, and your options for fixing the problems and make them operate more smoothly.
First, we will look at window frames, and then glazing:
- Metal or aluminum frames: Strong, lightweight and virtually maintenance-free, metal or aluminum frames also conduct heat very quickly, making them terrible at insulation. Homeowners with metal windows typically complain of being very cold when sitting near the windows in winter. A thermal break (an insulating strip of plastic) is commonly found in newer metal windows but older windows may not have these.
- Fiberglass frames: great insulating performance due to air cavities that can be filled with insulation; they are also dimensionally stable, making them less prone to warping.
- Composite frames: made of laminated composite wood products (strand lumber or particleboard), they are very stable, similar thermal properties as wood, and better moisture and rot resistance than wood.
- Wood frames: decent insulating properties; however, wood expands and contracts in response to temperature and moisture fluctuations. They require regular maintenance unless clad in aluminum or vinyl.
- Vinyl frames: excellent at avoiding UV-induced fading or breakdown; highly moisture-resistant; and their hollow cavities can be filled with insulation for superior thermal performance.
Types of glazing (window glass) – the type(s) you choose depends on the window’s orientation, the climate, use (operable or fixed) and building design. You may even choose various types of glazing for different windows, depending on these factors:
- Gas-filled: improved thermal performance due to inert gas (argon or krypton) between the panes that resists heat flow.
- Tinted: heat-absorbing tints change the color of the glass according to sunlight levels, to reduce solar heat gain and glare. There are various levels of tints available and if you have houseplants, keep in mind that plants will not do well if a window transmits less than 70% of visible light.
- Low-emissive coatings: “Low-e” windows control heat transfer through the application of a virtually invisible metallic layer applied to the glass panes; while they are more expensive (up to 15%) than regular windows, they can reduce energy loss up to 50%. They also reduce glare and fabric fading, and the coatings last 10-15 years.
- Insulated: if a window has two or more panes of glass that are spaced apart and hermetically sealed to create an insulating air space, it’s considered an insulating window. Virtually all new homes have double- or triple-paned windows.
- Spectrally selective coatings: a special type of low-e coatings, spectrally selective coatings filter out 40-70% of neat that would normally be transmitted through insulated glazing, while still allowing for full natural light transmission. They can reduce space cooling by more than 40%.
- Reflective coatings: metallic coatings reduce solar radiation and are intended to block more light than heat, making them perfect for hot climates to control solar heat gain. However since they block natural light, they necessitate the use of daytime lighting which offsets some of the energy cost benefits.