IG window unit including double silver coating having increased SHGC to U-value ratio, and corresponding coated article for use in IG window unit or other window

An insulating glass (IG) window unit comprising:

• first and second glass substrates that are spaced apart from each other with a gap therebetween and substantially parallel to each other, wherein the first glass substrate is adapted to be at a building exterior and the second glass substrate is adapted to be closer to a building interior than is the first glass substrate;
• a low-E coating on a major surface of the second glass substrate facing said gap;
• the low-E coating comprising, moving away from the second glass substrate:
• a dielectric layer;
• a first lower contact layer comprising zinc oxide;
• a first IR reflecting layer comprising silver located over and directly contacting the first lower contact layer;
• a first upper contact layer located over and directly contacting the first IR reflecting layer comprising silver;
• a layer comprising tin oxide and/or zinc stannate;
• a second lower contact layer comprising zinc oxide;
• a second IR reflecting layer comprising silver located over and directly contacting the second lower contact layer;
• a second upper contact layer located over and directly contacting the second IR reflecting layer comprising silver;
• and
• another dielectric layer;
• wherein the low-E coating has only two IR reflecting layers comprising silver, and wherein the low-E coating has a normal emissivity of no greater than 0.04;
• wherein a ratio of a thickness of the first IR reflecting layer comprising silver to a thickness of the second IR reflecting layer comprising silver, calculated as the thickness of the first IR reflecting layer comprising silver divided by the thickness of the second IR reflecting layer comprising silver, is from 0.30 to 0.50;
• and
• wherein the IG window unit has each of:
• (i) a visible transmission of at least about 69.5%, (ii) an SHGC value of at least 0.50, (iii) an outside visible reflectance of no greater than 15%, and (iv) a U-value of no greater than 0.253 BTU/hr-ft2-° F.

An insulating glass (IG) window unit comprising:

• first and second glass substrates that are spaced apart from each other with a gap therebetween and substantially parallel to each other, wherein the first glass substrate is adapted to be at a building exterior and the second glass substrate is adapted to be closer to a building interior than is the first glass substrate;
• a low-E coating on a major surface of the second glass substrate facing said gap;
• the low-h coating comprising, moving away from the second glass substrate:
• a dielectric layer;
• a first lower contact layer comprising zinc oxide;
• a first IR reflecting layer comprising silver located over and directly contacting the first lower contact layer;
• a first upper contact layer located over and directly contacting the first IR reflecting layer comprising silver;
• a layer comprising tin oxide and/or zinc stannate;
• a second lower contact layer comprising zinc oxide;
• a second IR reflecting layer comprising silver located over and directly contacting the second lower contact layer;
• a second upper contact layer located over and directly contacting the second IR reflecting layer comprising silver;
• and
• another dielectric layer;
• wherein the low-E coating has only two IR reflecting layers comprising silver, and wherein the low-E coating has a normal emissivity of no greater than 0.04;
• wherein a ratio of a thickness of the first IR reflecting layer comprising silver to a thickness of the second IR reflecting layer comprising silver, calculated as the thickness of the first IR reflecting layer comprising silver divided by the thickness of the second IR reflecting layer comprising silver, is from 0.30 to 0.50;
• and
• wherein the IG window unit has each of:
• (i) a visible transmission of at least about 69.5%, (ii) an SHGC value of at least 0.50, (iii) an outside visible reflectance of no greater than 15%, and (iv) a ratio calculated as SHGC/U-Value of at least 2.20, where U-value is in units of BTU/hr-ft2-° F.

An insulating glass (IG) window unit comprising:

• first and second glass substrates that are spaced apart from each other with a gap therebetween and substantially parallel to each other, wherein the first glass substrate is adapted to be at a building exterior and the second glass substrate is adapted to be closer to a building interior than is the first glass substrate;
• a low-E coating on a major surface of the second glass substrate facing said gap;
• the low-E coating comprising, moving away from the second glass substrate:
• a dielectric layer comprising silicon nitride;
• a dielectric layer comprising titanium oxide;
• a first lower contact layer comprising zinc oxide;
• a first IR reflecting layer comprising silver located over and directly contacting the first lower contact layer;
• a first upper contact layer located over and directly contacting the first IR reflecting layer comprising silver;
• a dielectric layer comprising metal oxide;
• a second lower contact layer comprising zinc oxide;
• a second IR reflecting layer comprising silver located over and directly contacting the second lower contact layer;
• a second upper contact layer located over and directly contacting the second IR reflecting layer comprising silver;
• and
• another dielectric layer;
• wherein the low-E coating has only two IR reflecting layers comprising silver, and wherein the low-E coating has a normal emissivity of no greater than 0.04, and wherein the IG window unit has only two glass substrates;
• wherein a ratio of a thickness of the first IR reflecting layer comprising silver to a thickness of the second IR reflecting layer comprising silver, calculated as the thickness of the first IR reflecting layer comprising silver divided by the thickness of the second IR reflecting layer comprising silver, is from 0.30 to 0.50;
• and
• wherein the IG window unit has each of:
• (i) a visible transmission of at least about 69.5%, (ii) an SHGC value of at least 0.50, (iii) an outside visible reflectance of no greater than 15%, (iv) a U-value of no greater than 0.253 BTU/hr-ft2-° F., and (v) a ratio calculated as SHGC/U-Value of at least 2.0.