I had a few windows and sidings installed by Delfa not long ago. The windows are ok, but my advice, DO NOT USE THIS COMPANY. Alex the owner and salesman will be very nice until taking your money, but if you have a problem with the work performed, he will never try to fix or even call you back as it is normal. Called over 30 times in the few weeks, left voice mails, even spoke with Alex 2 times and every time he said he is busy, cannot talk and will call back in few minutes ... guess what? he never called and I have now to fix myself the issues I have with the sidings Delfa didn't install properly.
I hope I'll never have problems with the windows which are under the warranty, I will check what are the right authorities to be involved in this situation and will contact Windowcity as well which is the windows manufacturer. I assume there should be some kind of business standards for their dealers. This is not acceptable business practice.