A little leak here, a major draft there. Windows let natural light and openness into homes, but they’re also just big holes in the wall, and can become the most common points of air. The bigger the holes, the more conditioned indoor air is wasted to the exterior, forcing homeowners to crank up furnaces in the winter, air conditioners in the summer, and utility bills all year long. By installing new windows, like those in the slideshow at left, homeowners can seal off those drafts and can also benefit from increased U-factor and solar heat gain coefficients for boosted energy efficiency. All the windows in this section qualify for federal tax credits, available through Dec. 31, 2010.