Thanks toddinmn. We foamed most of them so it was tolerable to be in the house (the bedroom was the worst one and almost unable to sleep it was so cold). We live in the Midwest, so likely will be more of a spring project, however I wanted to take the winter to research and decide. We kicked around the idea of just replacing the front two windows (one of which is the cold master bedroom) to see if we felt the rest of the house was worth it. But I thought I'd see if the pros here had any definite opinions, I know window world isn't looked upon highly and wasn't sure if Marvin Essentials line was a definite step up.

I'd be careful about putting too much emphasis on the windows being perfectly plumb and level, the walls and openings in which they sit often are not. They do need to be square though to operate, lock, and seal as designed. Its not uncommon for the windows that you have in there to have warpage issues, so prior to embarking on a project of re-installing all of you windows, make sure that is not the case. What specifically are you seeing that indicates that they are out of square?

As far as replacing, the Essentials is a solid window if it fits your needs. Its not particularly air-tight or efficient, but its not a poor window. The windows that are already installed may actually be better in those areas IF they are properly installed and not warping/defective.

My advice would be to really assess the condition of the current units and installation quality, and then determine if replacement is needed.

I should have been More clear. Plumb is kind of irrelevant in most cases . Level And square are most important . Often you can’t do much about plumb and it won’t really effect performance.

Homesealed and toddinmn, I've taken a level and many are slightly off. They have different measurements corner to corner in some places. Additionally, we can't get the screens to stay square (perhaps the screens are warped?) so bugs find their way in. Oddly, most of the warped screens are on the northern portion of the home. We get a lot of stink bugs making their way in and it always seems to be around the windows, but perhaps there are other openings we don't know about. Our front window had signs of rot (unclear if the reason the previous owners changed the windows or if it happened after the replacement), so that will have to be dealt with regardless of whether we purchase new windows or not. For reference, the windows are the window world 4000 series with something called SolarZone with argon. The previous owners left the receipt and apparently $981 gets a whole house window replacement install with custom exterior trim and they paid for foam on the jambs and head--however, that was clearly never done. Perhaps we will have to uninstall one and just see what exactly what can be done and if salvaging the windows is possible. However, if they are a poor unit and we take the time to correct things, perhaps it is worth the money to have a better unit installed? Appreciate your advice and help, any thoughts for determining whether the units are warped versus poor installation? And if after being installed poorly for 4 years, will this have had an adverse effect on the unit itself?

Here are a few photos when we first took off the trim. Sorry they aren't better, but perhaps they might be helpful.

The simplest method to determine fit with a double hung window is to look at the reveal between the bottom sash and The frame with the sash slightly open and the same with top sash slightly lowered.,The reveal or sight line should be the same all the way across. The other sight line to look at is the vertical one between the sash and frame . It should be the same from top to bottom . The pictures make it hard to determine if the install is correct. Typically on an insert install the casing is not removed, therefore the gap between the the old frame of the window and the rough framing. Do not not get addressed. The gap between the frame of the vinyl window and the frame of the old window would be accessible and should be sealed Preferably with spray foam and at a minimum with fiberglass insulation .

Window World products are made by Associated Materials of Ohio. The NFRC Directory shows info for only casement windows for them. 0.3 air leakage. It's the max allowed for Energy Star.

It leakage rate is actually less than or equal to 0.30. I doubt it is 0.30 But it could be. Almost all the windows are listed with that number and all it means is it passed there standard. If you want the real number , good luck as most manufacturers don’t list them.

I believe they are a private label Alside window which are not known to be a quality product.

Thanks everyone. I did see previous houzz discussions stating they were Aside. I googled their specs (not easy to find) and saw they were slightly worse than the basic Marvin Essentials, however I'm also interested in longevity and design of the window. Our main concern was the rot and I've read the discussions regarding sill design between various brands. I think the only way to truly answer the questions are to rip out the offending windows and see what was done and if it can't be remedied easily with the current windows, we will likely try the Marvin Essential line after finding a qualified installer who knows how to properly waterproof the window.

Published performance data is not always the best indicator of a quality window unfortunately. The durability factor goes downhill much faster in the lower quality windows due to the design, quality control, fit & finish, etc, etc.

Thermal data greatly depends upon the glass package or if a vinyl window is specced with foam filled frames. most are pretty close when specced the same. DP/PG ratings can be a better indicator of quality. Low air infiltration ratings can be a good one to but they can be difficult to to find the actual test number vs just showing the it was under 0.30. You typically only Find comments in air infiltration ratings on vinyl products since no one really seams to know what they are on wood and other composites besides vinyl.

@mcguirks, follow Todd's direction regarding the reveals. Raise the lower sash a little and drop the upper. If that gap is pretty consistent, then the windows should be pretty square. There also shouldn't be gaps where the sash weatherstripping hits the frame on the sides, and the windows should all slide and lock smoothly. If all of that checks out and there are no signs of water leakage, you can probably foam around the perimeter and be good. If these are only 4 years old they are probably the Mezzo, which is an improvement over the old Excalibur. I'm not going to say that this is a premier window or anything, but again, you could do worse, and the Essentials is worse in terms of air leakage and U value.

If OTOH, these things are all out of whack, not operating well, and have various product issues to go with what seems like a poor install, then a full window replacement product may be in order. The one thing that I'd avoid is ripping these out to reinstall, that generally doesn't end well.

Looks about par for a Window World install.

The master bedroom where those were taken was the worst by far. The original windows look like wood frame with a plastic like track that was removed and the replacement windows put inside the old wood frames. At some point someone removed the casing because there were original "penny" finish nails and then some newer machine placed nails, however I don't know why or when that occurred. I haven't gotten out the measuring tape, but I do know it takes a lot of muscle to even get the windows half way up. If the Essential line is no better than window world in terms of air inflitration/specs, I suppose I'll have to do further research if I end up needing replacements. Perhaps I'll look into the Elevate.

Good luck finding their air infiltration numbers. I would try messing around with one window at least.