I have noticed that infiltration makes up most of the winter heating
load for several high-bay single-story commercial buildings I'm
modeling. (big-box retailer, light manufacturing facility)

I've used a variety of methods - ACH estimates, CFM / so of facade (per
ASHRAE F27.10), and Area(crack) x Velocity(winter wind) - to estimate
infiltration.

Have other people stuck with these methods? Or does anyone know of
better ways to estimate infiltration?

Aaron Dahlstrom