Remodeler, Mike Sloggatt: The first step when ordering a replacement window is to get really good measurements to make sure that the window we order is going to fit just right into the opening.
First, we want to measure from where the stop contacts the jamb, from one side to the other, at the top and in the center of the window. Then we'll open the window to get the same measurement across the bottom. Compare those three measurement and you will likely go with the smallest one, in case there's a bow in the existing window frame.
Next, we want to measure the height from just above the stop at the top of the window to just inside the bottom edge of the stool. We'll take that measurement on both sides of the window, and again use the smallest measurement when ordering our window.
For some manufacturers, sill angle is is an important factor, so we'll measure that as well. With a level sitting on the stool, measure down to the sill right at the back of the stool and then again four inches away from the stool. Then you can use a sill-angle chart to determine the rise height that you will need for your replacement window.
Another thing I like to check is whether or not the window is square. A quick comparison of the corner-to-corner diagonal measurements will work to figure that out. You can also get an idea of how square a window is by seeing if the top and bottom sash line up nicely where they meet. If it looks like the window frame has shifted significantly, you're going to need to do some extra measuring to make sure you order a window that is going to fit properly.
After removing the exterior storm glass, the next thing I'm going to do is take the stops off so I can remove the sashes. You might want to try to save the stops so you can use them again, so I'm going to be real gentle with it. Sometimes you can reuse them; sometimes you can't.
Narrator: This window had spring balances, making sash removal easy. Other windows might have window weights with sash cords. If your window has weights, it's a good idea to remove them and fill the window pockets with insulation.
Mike Sloggatt: Next, clean up the jamb and get any nails out. I need to get the storm frame out of the way before I can dry fit the new window. I'll carefully pry this out so I don't damage any of the exterior trim. Before we set the window, I will need to put some sealant on top of the sill, so I'm going to scrape any loose paint off to make sure I get really good adhesion. Then I'll vacuum up the dust and paint chips and it will be time to go get the window.