When homeowners consider ratings on replacement windows, air infiltration is often overlooked. That's not surprising. Currently this information isn't placed on windows - yet it is an important detail in assessing how well they'll perform.
Manufacturers do provide U values to help buyers gauge window performance. That's a helpful measurement, and it should be considered whenever you think about a window purchase. But it doesn't tell the whole story. If a window isn't doing a good job of preventing air infiltration, rooms can feel cold and drafty. Windows made without today's high-tech airlocks, weatherstripping, and air-trapping baffles won't deliver the comfort you want.
Infiltration is measured in cubic feet per minute, or CFM. The industry average for new windows is .30 CFM where the wind load is 25 miles per hour. A traditional wood window protected only by weatherstripping comes in at .23 CFM. Standard vinyl windows carry a somewhat better air infiltration rating of .15 CFM.
If you want really exceptional resistance to infiltration, we recommend our flagship windows from SoftLite. The popular, mid-line Bainbridge window is rated at .07 CFM - and the premium Elements window allows only .01 CFM of air leakage per minute.
To put that in perspective, you could install 23 Elements windows and have only as much air infiltration as a single wood-framed window would allow. Think about that seriously before you purchase a window that's not really built to limit air infiltration. You won't experience the same comfort with a window that leaks a lot of air. That's another reason we encourage you to call us first at 610-398-2430 anytime you're considering replacing your windows.