Not all of the products that I sell qualify for the federal tax credit. While the vast majority do qualify, the Bryn Mawr II double hung and Double slider do not. That's unfortunate , since the Double Hung window is one of the more popular styles. They meet the SHGC requirements, but have a U-Factor of .34. With LowE3 Glass, it can be brought down to .32, but it still doesn't reach the .30 necessary to qualify for the rebate.