Just reading your post. We do narrowline all the time. IF (a big if) the replacement window is measured correctly a replacement window will be fine. If the installer removes the entire window sashes and frame, you MUST install a new prime window. With that being said, if the window is mis-measured or installed incorrectly, which happens a lot, the window will not perform correctly.
As far as the RBA guy, the previous post is correct. Saleman in general are not educated for the facts, they are just schooled in the art of selling. However the fibrex window is not a bad window either. What most people do not realize is that while all RBA saleman bad mouth vinyl windows, the Anderson window company purchased Silverline which is a huge vinyl window manufacture. Thier windows are available in all the big orange stores.
With that being, if you are interested in vinyl window DO NOT TAKE THE LOWEST PRICE! Do you homework on both the window and the company installing them. His statement may be over reaching but is correct. Many contractors do not even know the difference between either the replacement or the prime window. Also, ask them who pays for a mis - measure? Depending on the opening, the gap around the window from the inside should not be more than 1/2" height or 1/2" width. That may need to be adjusted depending on the condition of the rough window frame.
Thanks for your post. We are pretty confused right now and want to do the right thing. We will probably end up with vinyl replacements but are most concerned about the install. We are not looking at the lowest price but are not sure about finding contractors or companies who install them. Some of the companies recommended by Harvey were not great and we've already eliminated them for various reasons....some couldn't really be bothered, some don't really have recent or great references. We don't know anyone who has had windows replaced so can't use a contractor by word of mouth. We seem to have two independent contractors that seem to be good, but don't really know all that much about them. We are working on it.
Actually, I have to say that we have not had a lot of follow up after these companies have come out and measured. Maybe the job is too small (11 double hung windows) or maybe there is more work than we know of out there. Most of them seem dismayed to see that they are Narrowline construction windows and think the job will be a little tricky until they look closer and then they seem to come around. That concerns us a little.
When you replace Narrowline construction windows with vinyl, do you use quarter round on the inside to finish off? What do you use on the outside? Everyone we've spoken to seems to have different opinions.