0.48 is not outside the normal range. That VT number is for the total unit (i.e. frame edge to frame edge). In that case, you are not getting light through the frame, grids, or sash components.

Ask them what Low-e range they are specifying in this case, but to answer you question, that isn't abnormal.

That makes sense - if that number was for the whole unit. So to find out VT of the glass (E-272), I would to go Cardinal? I think i read that Marvin uses Cardinal glass? Thank you! https://american-windows.com/wp-content/uploads/2015/03/cardinal.pdf

Is there a reason that you are looking for the VT of the glass alone? I only ask because its easy to get twisted around and end up comparing apples to oranges when you start getting into ratings of individual components as opposed to the overall window. Getting that rating for the entire product tells you exactly what you are getting.

As WoW mentioned, 48 is not bad all things considered, particulalry with the SDL grids. The other populer glass option from Marvin would be 366, that would cause that VT to go down.

When i was doing my research, I came across VT numbers in the 70s as being ok (which makes sense now, as those were for glass alone), so of course when I saw Marvin numbers at .48, my first reaction was the windows will be too dark. But if you are saying that’s in line and should be ok, that’s the answer I was looking for. We are not doing 366, we are ordering 272. Thank you!

Low-e 272 = VT of 0.72.

By the time you factor in all the edges and grids, you get the 0.48.