Doors and Windows - question about replacement windows

i recently had 19 windows replaced using thermal industries replacement windows.i have a concern with the way they were installed.my house was built in 1999 using builder grade windows with the nailing flange and were flashed with the tape flashing , no problem.the new windows after they were put in left a gap about 1/2" around the perimeter of the window,so all they did was use building paper to cover this gap and put j channel up to edge of the replacement window ,then caulked where the window meets the j channel is this enough?

The opening should have been closed up to allow for a fairly snug fit, using minimal shims. How were they attached to the old casings? Did they use any minimally expanding foam to fill in the gap from the inside?

If the frame is solid, there is no reason not to do replacement windows. One of the drawbacks is, smaller glass size, since the new windows fits inside the old frame. Not an issue with many of my customers. Another option is Marvin or Weathershield replacement sashes, more expensive than replacement vinyl, but no loss in glass area.

Proper installation is a must or you give up the energy benefits you pay for with new windows.

As suggested above, if the frames show signs of rot, forget what I said.

the windows were the type that are nailed to the exterior with a flange taped on the flange. the interior was all drywall no wood or trim except for the stud that framed the rough opening,so the drywall went right to window on the inside.when they measured the new windows they measured sheetrock to sheetrock ,so the new windows rest on the sheetrock and not the wood framing thus leaving a 1/2" gap around the exterior.they did use 1/4 round the inside to fill any gaps but only jchannel on the outside.

The problem isn't with the install, but with the person who did the initial measurements. Bad job. But, let's make lemonade! The installers did what they could, and, although not ideal, it appears by adding trim to the inside they are holding things at bay. the nailing flange, of course, will keep the window tight to the exterior, and the tape is the most important part. The j-channel is just a place for siding to go, so it won't give any water proofness. If it looks good on the inside, then I think you will be ok. Post back with other concerns, or if we can help further.