@megansnowboarder5105 Good question. If the same window product is used, the efficiency ratings (U-factor, SHGC, etc.) are the same for that window whether it's insert or full frame. The main difference might be in the installation sealing. With full frame, you have the opportunity to insulate around the new window frame (between the window and the rough opening in the wall) really well when you put it in, since everything is open. With an insert, you're putting it into an existing frame, so you have to make sure the gap between the new insert and old frame is sealed (usually with spray foam or backer rod and caulk). A good installer will do that, and then effectively it's similar.
If the old frame was aluminum without a thermal break, technically leaving it in (with an insert) means a bit of that old material is still conducting heat/cold at the edges. But they usually cover or line the frame, and the impact is minimal. I think for most people you'd never notice a difference in energy performance between a properly installed insert vs a full frame replacement of the same window model. It's more about the condition of the old frame (like if it had air leaks). Seal those leaks, and an insert performs great in terms of efficiency.
@megansnowboarder5105 I'll add to what @breezetraveler said from personal experience: we did inserts and the crew did foam insulation around every new window between the insert and the old frame. Then they capped the exterior and caulked inside and out. I have zero drafts now. They basically "sealed in" the old frame. So effectively it's as airtight as a full replacement would have been.
I also worried about the old frame conducting heat, but they put a vinyl wrap over the old metal frame before installing the insert, which I guess acts like a thermal break. Maybe an energy auditor could detect a slight difference at the edges, but in everyday use it's not noticeable. Our house is comfortable and the windows are EnergyStar rated. So yeah, as long as it's installed properly, inserts won’t significantly underperform. Just make sure whoever you hire is meticulous about insulating and sealing all around.
I admit I was a bit paranoid about leaks after install, being in Florida with our heavy rains. But after two big thunderstorms, I'm happy to report no leaks at all with our insert windows. We kept the old frames but you'd never know they’re under there. We had one especially bad storm where rain was blasting the windows for hours – and not a drop inside. That was a relief because one of my old windows used to leak water at the bottom if rain blew directly on it.
So even in terms of water, a properly done insert can be just as good as a new construction window. The keys are good caulking outside, sealing any screw holes, and making sure the sills are pitched or drained correctly. The windows we got had installation instructions the contractor followed to a T. So now I don't worry when I see sideways rain pounding the glass. If you do notice any issues, get them addressed while it's under warranty.
I'll throw in a DIY perspective: I tried replacing one window myself as a test (a small bathroom window). I bought a retrofit vinyl window from Home Depot that fit the opening. Removing the old window was actually not too bad, and putting the new one in was okay, but getting it perfectly shimmed and sealed was a bit of a learning curve. I spent probably 4 hours fussing with it, and I'm still not entirely sure it's as well-sealed as when the pros do it 😅. It looks decent enough and doesn't leak, but the caulking job I did is not as pretty as the others I had professionally installed later.
After that experiment, I decided it's worth paying installers for the rest. If you are super handy and patient, you can save on labor by doing it yourself, but be prepared for a lot of measuring, leveling, shimming, and caulking. And you'll need at least another set of hands for the larger windows. I did feel proud doing one, but for me it wasn't worth the time/stress to DIY all of them.
@cocon47 Kudos to you for giving it a shot. I considered DIY as well (watched a ton of YouTube videos on window installs) but ultimately hired pros for my sanity. 😅 For anyone else thinking about it: one nice thing about using licensed installers is they usually provide a warranty on their work. So if anything leaks or isn't right, they come fix it. If you DIY and something goes wrong later, it's all on you to fix.
Plus, some manufacturers have a clause that the warranty on the window (especially for glass breakage or seal failure) might only fully apply if installed by a professional. Not always, but some do ask for proof of professional install for warranty claims. So that's something to check. For me, not having to worry about those details and knowing the job was done by folks who do this every day was worth the cost.
@cocon47 also keep in mind, permits again – if you DIY, you are still supposed to pull a permit for window replacements (technically as an owner-builder). Some folks skip that when DIYing, but they risk issues. A professional will handle all that. And as mentioned, insurance or resale time, you want paperwork. So while DIY can save money, there are considerations like that.
I ended up doing just my garage window myself (where it wasn't as critical), and hired out all the main house windows. It gave me a feel for how it's done, which was cool, but I didn't trust myself to do the big ones perfectly. And yeah, my caulking lines are not as straight as the pros either. Functionally fine, just not as pretty. 😆
For those interested in warranties: the windows we got came with a lifetime warranty on the frames and glass (lifetime for original owner) which covers any manufacturing defects or seal failures. Our installer (Karoly) also gave us a separate labor warranty (I think 10 years) for any installation-related issues. That kind of combo seems common. ProTech offered something similar when we got their quote. So either way, good coverage if something goes wrong.
Also, many window warranties are transferable to the next homeowner (often for a certain number of years or one transfer). We confirmed that ours can transfer if we sell the house within 20 years, which is nice for resale value. Just make sure to keep all documentation and receipts in case you ever need to make a claim. And register your windows with the manufacturer if they require it for the warranty to be active. It's boring paperwork but worth it.
@jjones18 That's true. I had to use my warranty actually – one of my window panes developed a small crack (manufacturer defect, it appeared a few months after install for no apparent reason). The window company arranged a replacement sash under warranty and swapped it out for me. Didn't cost a dime because it was within that coverage. The process took a couple of weeks but was smooth.
The warranty transfer was also a selling point: we sold our previous house 5 years after installing new windows and were able to transfer the remaining warranty to the buyer. I think it made the buyer feel better knowing they had, say, 15 years of coverage left on the windows. So definitely fill out those warranty cards or online registrations. It can save you headache later.
One aspect that hasn't been touched on much: the immediate boost to curb appeal. Our home in Largo looked kind of tired with the old windows – they had foggy glass (failed seals) and the frames were an ugly aluminum that had oxidized. After we put in new windows, the house looked almost like it had a facelift. Even without doing anything else, new windows made the exterior look fresher and more upscale. Several neighbors complimented the change.
Inside, same deal: the view out is clearer (no foggy glass) and the new clean frames just made the rooms look nicer. It's like upgrading an old pair of glasses to a new one – everything is clearer and the frames are stylish. That aesthetic benefit was a big plus, especially since we were considering selling. I believe the new windows contributed to us getting strong offers (and we highlighted them in the real estate listing as "new energy-efficient windows throughout").
@golfplayer86 Absolutely. We had a similar experience. Our neighbors noticed immediately when we changed out the windows. We went from old bronze aluminum frames (that were faded and some had corrosion near the coast) to new white frames. It gave the house a more modern contrast and clean lines. It's one of those things you don't realize how much it dates a house until you replace them.
On the inside, I also love that our new windows have nice clear glass with Low-E – it has a slight tint which cuts the glare. Visitors have asked if we got new curtains or something because the lighting inside is more pleasant (not so harsh). It was actually the windows reducing the glare and UV. And now we can actually open and close all our windows easily, which is great for the cool days in winter when we want fresh air. The old ones were painted shut or just plain stuck. So it's both aesthetic and functional improvements.