When it comes to chose a contractor to do your window installation. In the old days it use to be an easy task.If the opening was plumb, level and square, it was very easy to install a window. Today you get allot more older homes and you run into more situations where it becomes not a very easy task not to mention that window manufacturers shift more and more responsibility for failures on the contractor.
When working with a window replacement project, the HO should be aware and prepped so to speak NOT to settle on a accurate/final estimate, because if there is a need for additional repairs, the original proposal could easily increase after the window is out and there is a problem i.e. decay, termites, and rot inside the rough opening that the contractor and the homeowner didn't know at the time until existing window was removed. The possibility that the additional needed repairs will increase the overall price of the job.
If during the visit you can spot existing visible rot or there is a sign that the window's wood frame is showing signs of early deterioration,further investigation will tell how far the damage is and repair cost can be added to the overall price.
The usual scenario is, the HO is trying to get the best lowest price they can find, the companies who bid the jobs try to work for the absolute minimum cost and make it up on the volume of jobs, at the same time it means cutting corners and cutting quality of product they use.
Unfortunately some companies will bid the job low, knowing the problem exist, they will say there is no problem, and after the window is out they will show HO the problem and stick him with a much higher cost for repairs to make it up for the low-bid cost, which by that time will exceed previous proposals from other companies... and what choice the HO has at that time when the window is gone and rain in the forecast, not to mention when someone cuts the corners, the Argon Enhanced window will not be any good if space between the window is uninsulated, it will create a draft and before you know the moisture will penetrate the cavity and before you know you have a new window with remaining problems which will only get worst with time, and usually you will find out about the problem after your window warranty is up and your contractor is operating under a new name.
Take your time when selecting a contractor and don't let the price blind you.
When it comes to window installation and to make any remodeling job successfully especially when it comes to the exterior wall, and doors and windows not to mention roof and siding, the main goal is to protect the dwelling from intrusion of water, moisture, air infiltration, thermal, and vapor... This is the most crucial areas where you cannot cut corners and unfortunate some installers cut corners on or they just don't know any better, or they had it out with the boss or the wife before they came to do the job and these are the most important factors cannot be neglected.
Window opening should always be prepped right and a new window should never be installed in a bad opening, because right after the warranty is up, HO will have problems. Because rule of Thumb is, you can put the best window in a bad opening and you will have a problem.
The most common problems which occurs after window installation is improperly installed flashing or the flashing is not installed at all if it need to be there.
Each installer must to make sure the water has means of escape and not to get trapped inside the window or the window frame which over time will cause the wood to rot.
Don't spare any sealants because most window manufacturers specify that the window must be caulked on the side and top flanges—but not on the bottom. Some installers like to caulk the bottom to prevent water from entering, but what they doing is keeping the water from escaping, not to mention that un-caulked sill will not let the water in because it cannot flow upward and if a wind driven rain push some water in, it will drain right out.
A few more tips for the DIY HO and even contractors, not to take any windows out until you know you have all correct size window for that opening, or a piece of plywood to close the window up if you remove the window and the new window don't fit.
Most of the windows especially when job calls for removal of existing and installation of new construction window, you will measure window without seeing the rough opening, which means you have to get the window size as close as possible, so measure twice before ordering. Measure the top, middle, and bottom of every window, don't guess and measure in inches, rather than switching between feet and inches,because its easy for you to make a mistake if you write down 2.4 as 24" when you placing an order or when you get back to your notes after a few hours.
Always read the instructions and installation guidelines because manufacturer's make changes when they improve installation methods or to increase the time of window's performance for many years to come and some manufacturers update their instructions as often as every year because they try to be better and different from competition so instead of throwing away, break out the manual and start reading.
That is about it to know about window replacement and installation.