Let me start by saying this is the worst window installation service company you can imagine. AVOID AT ALL COSTS! I replaced the existing windows of entire house(22+ in total), brick-to-brick, wooden trim, and others. What a horrible job installers did. Some say a picture is worth a thousand words. I'll attach more than one picture so you get the idea of 'installation quality' they provide. This is only 3 of 50+ pictures I took of the worst installation service they provided. I even shared them with the sales agent.
A bit of background story: I've researched and contacted more than 10 companies, and I picked Windowtech as Eric (salesperson) seems to be honest and the total cost of replacement was about the same as other 5-6 competitors. After I deposited a fund, Eric conveniently disappeared or rarely available, and I was asked to deal with the office directly. The office rarely responds. Note of that! 1st Warning Sign!. When the installer (a team of three) finally came to install, the main installer claimed he has 30+ yrs of experience. The other two were helping the main guy with cutting wooden Window trims, caulking, sanding, moving stuff, etc. In the beginning, Window installation itself went okay, but I started noticing the window trim was cut with almost 1/4inch of a gap, which is not easy to caulk. 2nd Warning Sign! The other guy then came to caulk or applied wooden fillers. As you can see from the images, that's the mess they left with.. I asked the main guy to come and fix. He spent 2mins (no joke) sanding it and left. Then, he sent his helper to request the remaining payment. I thought I would make a payment and deal with the office separately. A big mistake. The office didn't respond, and if they did, nothing was done. 3rd Warning Sign! After 3weeks, the main installer guy came only after I threatened to leave a negative feedback. He came and spent 2mins to lecture me that the bad Window trim installation, the worst caulking job (even a 10yr old kid would have done a better caulking), and all other issues would be fixed by Painter. He can't do any work as he has a underlying medical condition. Conveniently, he now has a medical condition as the office got all my money.
The window installation itself is easy. you can do it with any good carpenter. DO NOT fall for a sales pitch!
In the end, for the AWEFUL window trim installation, I had to spend $3500 with 3 contractors to fix the mess (all caulking removal) by filling gaps, sometimes even redoing the trims.