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Energy Efficiency

Energy Efficiency Ratings

There are 3 common criteria used to measure a windows energy efficiency: Solar Heat Gain Coefficient (SHGC), Visible Transmittance (VT), and U-value. These terms are defined below and will help you evaluate windows for your home.

The National Fenestration Rating Council (NFRC) administers a certification process that some manufacturer's use to certify their test results. The ratings in the chart below have all been certified by the NFRC.

BTU - An abbreviation for British Thermal Unit - the heat required to increase the temperature of one pound of water one degree Fahrenheit.

Solar Heat Gain Coefficient (SHGC) - A measure of the solar radiation admitted through a window or skylight. It is expressed as a number between 0 and 1. the SHGC can be expressed in terms of the glass alone or the entire window assembly (our numbers are entire window values). The lower the number, the less solar heat that it transmits, and the greater it's shading ability. This is the standard indicator of a window's shading ability.

Visible Transmittance (VT) - A measure of the amount of light admitted through a window or door. It is expressed as a number between 0 and 1 (1 being full transmission). This has little direct impact on heating or cooling loads within a building, but is an important factor in determining visibility as well as controlling glare and fading of interior furnishings.

U-value - A measure of the rate of non-solar heat loss or gain through a door or window. The U-value may be expressed for the glass alone or for the entire window (all of our published numbers are entire window values). The lower the U-value, the greater the unit's resistance to heat flow and the better its insulating value. The U-value is measured in BTU's per hour per square foot per degree fahrenheit..

Energy Smart and Solar Smart Glass options below are ENERGY STAR qualified in most zones.

Product	Glass	Gap Fill	U-Value w/o Grids	U-Value w/ grids	SHGC w/o grids	SHGC w/ Grids
270 / 570 SH	Clear	Air - Intercept	0.49	0.49	0.61	0.55
	Low-e	Air - Intercept	0.36	0.36	0.29	0.26
	Energy Smart I	Argon - Intercept	0.32	0.32	0.29	0.26
	Energy Smart II	Argon - Superspacer	0.31	0.31	0.29	0.26
	Solar Smart I	Argon - Intercept	0.32	0.32	0.25	0.22
	Solar Smart II	Argon - Superspacer	0.30	0.30	0.25	0.22

270 / 570 Slider	Clear	Air - Intercept	0.49	0.49	0.61	0.54
	Low-e	Air - Intercept	0.36	0.36	0.32	0.29
	Energy Smart I	Argon - Intercept	0.32	0.32	0.28	0.26
	Energy Smart II	Argon - Superspacer	0.30	0.30	0.28	0.26
	Solar Smart I	Argon - Intercept	0.31	0.31	0.24	0.22
	Solar Smart II	Argon - Superspacer	0.30	0.30	0.24	0.22

270 / 570 PW	Clear	Air - Intercept	0.48	0.48	0.64	0.57
	Low-e	Air - Intercept	0.34	0.34	0.34	0.31
	5mm glass	Air - Intercept	0.38	0.36	0.33	0.30
	Energy Smart I	Argon - Intercept	0.30	0.30	0.30	0.27
	5mm glass	Argon - Intercept	0.34	0.33	0.29	0.26
	Energy Smart II	Argon - Superspacer	0.30	0.30	0.30	0.27
	5mm glass	Argon - Superspacer	0.33	0.32	0.29	0.26
	Solar Smart I	Argon - Intercept	0.30	0.30	0.26	0.23
	5mm glass	Argon - Intercept	0.34	0.33	0.25	0.22
	Solar Smart II	Argon - Superspacer	0.29	0.29	0.26	0.23
	5mm glass	Argon - Superspacer	0.33	0.32	0.25	0.22

TrustGard DH DuraTrust DH 730 DH	Clear	Air - Intercept	0.48	0.48	0.60	0.54
	Low-e	Air - Intercept	0.35	0.35	0.32	0.29
	Energy Smart I	Argon - Intercept	0.31	0.31	0.28	0.25
	Energy Smart II	Argon - Superspacer	0.30	0.30	0.28	0.25
	Solar Smart I	Argon - Intercept	0.31	0.31	0.24	0.22
	Solar Smart II	Argon - Superspacer	0.30	0.30	0.24	0.22

TrustGard Slider DuraTrust Slider 730 Slider	Clear	Air - Intercept	0.47	0.47	0.59	0.53
	Low-e	Air - Intercept	0.34	0.34	0.31	0.28
	Energy Smart I	Argon - Intercept	0.30	0.30	0.27	0.25
	Energy Smart II	Argon - Superspacer	0.29	0.29	0.27	0.25
	Solar Smart I	Argon - Intercept	0.30	0.30	0.24	0.21
	Solar Smart II	Argon - Superspacer	0.29	0.29	0.24	0.21

TrustGard PW DuraTrust PW	Clear	Air - Intercept	0.45	0.45	0.64	0.57
	Low-e	Air - Intercept	0.31	0.31	0.34	0.30
	5mm glass	Air - Intercept	0.35	0.33	0.33	0.30
	Energy Smart I	Argon - Intercept	0.28	0.28	0.30	0.27
	5mm glass	Argon - Intercept	0.30	0.28	0.30	0.27
	Energy Smart II	Argon - Superspacer	0.27	0.27	0.30	0.27
	5mm glass	Argon - Superspacer	0.29	0.28	0.30	0.27
	Solar Smart I	Argon - Intercept	0.27	0.27	0.26	0.23
	5mm glass	Argon - Intercept	0.30	0.28	0.26	0.23
	Solar Smart II	Argon - Superspacer	0.27	0.27	0.26	0.23
	5mm glass	Argon - Superspacer	0.29	0.28	0.26	0.23

730 PW	Clear	Air - Intercept	0.47	0.47	0.69	0.63
	Low-e	Air - Intercept	0.32	0.32	0.37	0.33
	5mm glass	Air - Intercept	0.36	0.34	0.36	0.33
	Energy Smart I	Argon - Intercept	0.27	0.27	0.32	0.29
	5mm glass	Argon - Intercept	0.30	0.28	0.32	0.29
	Energy Smart II	Argon - Superspacer	0.27	0.27	0.32	0.29
	5mm glass	Argon - Superspacer	0.29	0.28	0.32	0.29
	Solar Smart I	Argon - Intercept	0.27	0.27	0.28	0.25
	5mm glass	Argon - Intercept	0.30	0.28	0.28	0.25
	Solar Smart II	Argon - Superspacer	0.26	0.26	0.28	0.25
	5mm glass	Argon - Superspacer	0.29	0.27	0.28	0.25

4000 / 5000 CASEMENT	Clear	Air - Intercept	0.43	0.43	0.51	0.47
	Low-e	Air - Intercept	0.32	0.32	0.27	0.25
	Energy Smart I	Argon - Intercept	0.29	0.29	0.24	0.22
	Energy Smart II	Argon - Superspacer	0.28	0.28	0.24	0.22
	Solar Smart I	Argon - Intercept	0.29	0.29	0.21	0.19
	Solar Smart II	Argon - Superspacer	0.28	0.28	0.21	0.19

4000 / 5000 AWNING	Clear	Air - Intercept	0.43	0.43	0.51	0.47
	Low-e	Air - Intercept	0.32	0.32	0.27	0.25
	Energy Smart I	Argon - Intercept	0.29	0.29	0.24	0.22
	Energy Smart II	Argon - Superspacer	0.28	0.28	0.24	0.22
	Solar Smart I	Argon - Intercept	0.28	0.28	0.21	0.19
	Solar Smart II	Argon - Superspacer	0.27	0.27	0.21	0.19

4000 PW	Clear	Air - Intercept	0.44	0.44	0.61	0.54
	Low-e	Air - Intercept	0.31	0.31	0.32	0.29
	5mm glass	Air - Intercept	0.35	0.33	0.32	0.29
	Energy Smart I	Argon - Intercept	0.27	0.27	0.28	0.26
	5mm glass	Argon - Intercept	0.30	0.28	0.28	0.25
	Energy Smart II	Argon - Superspacer	0.27	0.27	0.28	0.26
	5mm glass	Argon - Superspacer	0.29	0.28	0.28	0.25
	Solar Smart I	Argon - Intercept	0.27	0.27	0.24	0.22
	5mm glass	Argon - Intercept	0.29	0.28	0.25	0.22
	Solar Smart II	Argon - Superspacer	0.26	0.26	0.24	0.22
	5mm glass	Argon - Superspacer	0.29	0.27	0.25	0.22

5000 PW	Clear	Air - Intercept	0.45	0.45	0.61	0.55
	Low-e	Air - Intercept	0.32	0.32	0.32	0.29
	5mm glass	Air - Intercept	0.36	0.34	0.32	0.29
	Energy Smart I	Argon - Intercept	0.29	0.29	0.28	0.26
	5mm glass	Argon - Intercept	0.31	0.29	0.28	0.26
	Energy Smart II	Argon - Superspacer	0.28	0.28	0.28	0.26
	5mm glass	Argon - Superspacer	0.30	0.29	0.28	0.26
	Solar Smart I	Argon - Intercept	0.28	0.28	0.25	0.22
	5mm glass	Argon - Intercept	0.31	0.29	0.25	0.22
	Solar Smart II	Argon - Superspacer	0.28	0.28	0.25	0.22
	5mm glass	Argon - Superspacer	0.30	0.29	0.25	0.22

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