Glass Insulation Value
Buy the wrong glass and you’ll be literally tossing money out your window
Standard insulating glass can be made super effective with a Low-E (emissivity) coating and Argon gas. For the following reasons this is often called smart glass:
Cooling your home: During the hot months the steeper angle of the summer sun allows the low-E coating to more readily reflect incoming heat, saving you air conditioning costs.
Warming your home: During the cold months the lower angle of the winter sun allows the Low-E coating to accept more incoming heat, while reflecting existing heat back into the room, saving you fuel.
Fade protection: Low-E coating blocks approximately 85%to 95% of the sun's ultraviolet rays this protects furniture, drapery, flooring, and your other furnishings from fade damage.
Be careful, smart glass should be designed specifically for your climate.
The wrong glass can squelch your energy savings. You will want the best U-factor that supports the appropriate solar heat gain coefficient for your climate zone (see below).
Too much of LOW-E coating can actually choke your energy savings.
Not all glass energy star values are derived the same way. Some window companies have to add an excessive amount of this coating in order for their windows to meet R-Values. This can destroy your winter time solar gain, which can actually cost you more money than you save in the summer. (Not good for home owners in heating climates).
MR Planners solves this problem by leading you to the best energy factor that supports the appropriate solar heat gain for your climate zone.
This technology is designed to give you maximum benefit year round.
NFRC-certified products. All reputable window manufacturers rate and certify their products according to National Fenestration Rating Council requirements.
U-Factor. This number tells you how well the window insulates. The lower the U-Factor, the better. To qualify for the Federal Energy Tax Credit available through December 31, 2010, this number must be 0.30 or lower.
Solar Heat Gain Coefficient (SHGC). This number tells how effective the window is at blocking the sun’s radiant heat. The lower the SHGC, the less solar heat the window allows into your home.
U-Factor is a measurement of insulation value and how well an entire window controls non solar heat flow. It measures how well a product prevents heat from escaping a home or building. National Fenestration Rating Council U-Value ratings represent the entire window performance, including frame and spacer material. U-Value ratings generally fall between 0.20 and 1.20 Btu/hr-ft2-ºF. The lower the U-Value, the better a product can keep heat in. U-Value is particularly important during the winter heating season.
Solar Heat Gain Coefficient (SHGC) is the standard indicator of a window's shading ability.
The lower the SHGC, the less solar heat it transmits past the window.
A product with a high SHGC rating is more effective at collecting solar heat during the winter.
So just like with Low-E, the SHGC measurement you need is determined by such factors as your climate, orientation, and external shading.
The Solar Heat Gain Coefficient measures how well a product blocks heat from the sun. SHGC is expressed as a number between 0 and 1.
The NFRC label can be found on all ENERGY STAR® qualified window, door, and skylight products, but ENERGY STAR bases its qualification only on U-Value and SHGC ratings.
Insulation value is worthless unless you stop air leakage which is our next point.