Windows on Washington wrote:
Patio doors will inherently have slightly higher numbers based on their designs. Even the best units are only in the mid 0.05 range most of the time.
I know, and that makes sense, given that a sliding seal is inherently less airtight than a compressible gasket. That said, there's a local company that makes sliding windows with an air infiltration value of 0.03, which is pretty phenomenal. They say they specifically engineered it to be as airtight as possible with quadruple weatherstripping, because we get extremely strong winds around here. If only they made patio doors! I am strongly considering their windows though.