Some companies place the laminated lite inboard and some place it outboard and some do it both ways depending on their specific line, i.e. double hung vs casement.

I would suggest that the number one reason for installing the impact glass inside vs outside has to do with window structure. Basically the window company installs the glass in the location that best benefits their test performance. They want the heavier impact resistant laminated lite attached to the fixed stop and not the glazing bead when installed in the window sash or frame.

If the window is externally glazed then the fixed stop is to the inside of the home and the laminated glass more often than not will be installed in that location. If the window is internally glazed then the fixed stop is exterior so structurally it makes sense to have the laminated glass outboard.

Leaving out what I just said about structural considerations, it's easier and usually less costly for a few different reasons, to apply LowE coatings to the monolithic lite rather than to the laminated lite. LowE coatings intended for any cooling dominated climate should always be installed on the inside surface of the outer lite in an IGU. This results in the monolithic glass, with LowE coating, on the exterior lite and the laminated lite once again interior.

Throwing out everything I said about structural and LowE coatings, we have my personal preferred reason...it's ultimately safer to the occupants to have the monolithic glass exterior and laminated interior. Something that many window companies definitely take into consideration as a reason to build their windows this way.

Think about being in your home when something unpleasant strikes your window hard enough to break the glass. If the laminated lite is outside then whatever hit your glass hard enough to break it may not penetrate the laminated glass but it will produce a pressure wave that almost certainly will break the monolithic interior lite. When that lite goes it's going to shatter and potentially propel very pointy and very sharp shards of glass into your home and into whatever or WHOMEVER is standing in the way. That result isn't one that anyone wants to contemplate.

Building a window with the monolithic lite outside and the laminated lite inside results in those potentially lethal shards remaining outside your home and falling harmlessly to the ground in the event of an impact strong enough to break the glass.

And doesn't much matter what category hurricane you are dealing with, if the glass is seriously impacted it's probably going to break. If it's not impacted then it's much less likely to break.

@oberon476, thank you so much for this explanation. I just started looking for replacement windows for my home and want impact windows, and was wondering about this. I’m currently looking at impact windows from PGT, CGI, Anderson A Series, and Marvin. Do you know if they are all built in the manner you’ve described?

Tony,

Unless something has changed recently, both Andersen and Marvin manufacture all of their impact windows with the laminated lite inboard.

I believe that PGT and CGI do the same, but I would suggest that you should ask them directly to make sure.