How window glass contributes to window value

SEEING THE LIGHT: HOW WINDOW GLASS CONTRIBUTES TO WINDOW VALUE

EYES GLAZING OVER? WINDOW TERMS EXPLAINED!



P A R T O N EEYES GLAZING OVER? WINDOW TERMS EXPLAINED!

Energy-efficient windows are a big thing these days; both homeowners and potential home buyers want to make sure that they benefit from the latest energy-efficient technologies. Despite the fact that windows are mostly glass, however, discussions on windows and energy efficiency often seem to concentrate on the frame, the window style, etc. – just

about everything but the glass.



A D E F I N I T I O N O F T E R M SNo discussion is possible without a thorough understanding of the terms that measure a window’s energy efficiency. It is important to understand these terms to properly compare different home situations and window features.

A window’s U-factor is a measure of how much heat is transferred through the window from outside the home to the inside, and vice-versa. A window setup will often have multiple U-factor ratings listed, as U-factor is measured for just the window frame, just the glass, and for the window as a whole.

A lower U-factor is always better for energy efficiency. The lower the U-factor is, the less heat escapes through the window in winter, and the less heat enters your home during the summer.

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The Solar Heat Gain Coefficient, or SHGC, measures how much heat from sunlight, and other forms of solar radiation, enters your home through the window. The climate you live in will determine what SHGC rating you’ll want for your windows. A window with a low SHGC, for example, is good at providing cooling and shading to reduce cooling costs during hot summers. A higher SHGC, however, is better at letting solar heat through during the winter, to offset heating requirements during the cold months

U - F A C T O R



Finally, Visible Transmittance, abbreviated VT, is a measure of how much visible light the window allows into your home. The higher the VT, the more light the window lets in, helping offset artificial light-ing requirements. A lower VT, on the other hand, serves to reduce glare and brightness in a room; if the VT is low enough, the window will either appear opaque or reflective from the outside, depending on the glass.

S H G C

V T

With an understanding of your window glass’ features, Part II goes on to list how your window

glass contributes to your home’s value.



P A R T T W OACHES AND PANES: HOW, EXACTLY, DO YOUR

WINDOWS AFFECT YOUR HOME?

So you’re looking at the different ratings and features of an energy-efficient window and, having slogged through our previous installment, you now understand exactly just how efficient window glass can be at keeping out excess heat and light, etc. What’s the big picture, though? How exactly does this translate into concrete benefits for you? How do the energy-efficient features of a window actually

affect your home?


ACHES AND PANES: HOW, EXACTLY, DO YOUR WINDOWS AFFECT YOUR HOME?

E N E R G Y S AV I N G SFor starters, you can expect to save on your energy costs. By reducing the amount of heat entering your home during the warm months, and the amount of heat escaping during the cold months, you can ex-pect to see a reduction in your energy bills. This sav-ings can be dramatic – gearing your windows towards keeping you cool in the summer can save you up to 24% on your cooling bills. Gearing them towards reducing your heating in the winter can result in as much as a 31% drop in your winter heating costs.

M O R E C O M F O R TInstalling energy-efficient windows goes a long way towards eliminating drafts. By eliminating cold glass as a cause of draftiness in your home, energy-efficient windows keep your home cozy while simultaneously reducing heat loss.


ACHES AND PANES: HOW, EXACTLY, DO YOUR WINDOWS AFFECT YOUR HOME?

L E S S C O N D E N S AT I O NLow-emissivity glass comes with a micro-thin layer of metal that repels condensation and prevents the buildup of frost on the window panes. This, in turn, reduces the need for extra heating to keep your windows frost-free.

L O W E R H V A C C O S T SAs a result of preventing leaks, drafts, and condensation, energy-efficient windows reduce your home’s peak heating and cooling requirements. This allows you to install smaller heating and cooling systems which, incidentally, require less of a cash outlay.

B E T T E R V I E W S A N D L I G H T I N G

Because energy-efficient windows do not require dark or reflective tinting to keep your home cozy, you can install windows that do not restrict your view of the outside. This, in turn, can help reduce your dependence on artificial lighting, as light streaming through the windows can be sufficient to illuminate your home during the day.

With a firm idea of how exactly your window affects your home, Part III goes on to discuss your different

options for energy-efficient window glazing.



P A R T T H R E ECLEAR CHOICES: WINDOW GLASS OPTIONS DETAILED

If you’ve been following our series on energy-efficient window glass, you should now have a good idea of what goes into an energy-efficient window, and how it can benefit you. How does all this translate into window features, then? What window

glass options do what for you?


CLEAR CHOICES: WINDOW GLASS OPTIONS DETAILED

D I F F E R E N T W I N D O W C O AT I N G SHow the surface of your window glass has been treated has a tremendous effect on how the glass itself performs. Depending on what, exactly, you’re looking for in a window, you will likely find the features and windows that are just right for you.

H E AT - A B S O R B I N G T I N T SBy changing the color of the glass, heat-absorbing tinting absorbs a large amount of solar radiation passing through a window. This significantly reduces the glare, as well as the window’s SHGC and VT ratings. The tinting, however, does not reduce the window’s U-factor at all.

The most common gray and bronze tinting for windows serves to reduce the penetration of both light and heat. Blue and green window tinting lets more light through, with a lower amount of solar heat transfer blocked. The closer a tint gets to black, the more light it absorbs; if a window lets less that 70% of visible light through, indoor plants will grow slowly or even die.


CLEAR CHOICES: WINDOW GLASS OPTIONS DETAILED

L O W - E M I S S I V I T Y G L A S SLow-emissivity, or “Low-E” glass, is an option for controlling heat transfer through the glass in your window. A low-e coating consists of a microscopically thin, virtually invisible layer of metal or metal oxide applied to the glass. This lowers the U-factor of the glass, reducing energy loss by 30-50%.

Depending on the specific low-e coating used on your window glass, it can also allow for high, moderate, or low SHGC through the glass. Low-e coatings can also reduce the visual transmittance of the window glass.

S P E C T R A L LY - S E L E C T I V E C O AT I N G SSpectrally-selective coatings are a special type of low-e coating designed to filter out more heat (anywhere from 40-70%) without affecting light transmission at all. This results in glass with low SHGC and U-factor, but with a high VT. It is possible to combine both spectrally-selective coatings with tinting to produce customized window glazing systems that can increase or decrease solar heat gains as desired, and can reduce electric cooling requirements for homes by up to 40%.



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How window glass contributes to window value

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