m Ransley wrote:
Why use sliders, they are poor by design as you see, tracks get ditry in
a week. Casements are a proven design, with a positive air seal, they
have less air infiltration due to the pulled tight design. Air
infiltration is usualy overlooked in ratings but accounts for half of
heat loss on old windows. Check ratings, learn the ratings, everything
is rated independantly on good windows.

I can't comment on sliding windows in general, but I can tell you that
no window I've ever installed pulls and seals tighter than the Andersen
gliders. It's more energy efficient due to it's tightness and lower
air infiltration - check the ratings.

R