Replacing your old drafty windows with vinyl windows may seem like an easy process–after all how hard can it be to knock out old windows and put in new ones? You’re right, learning how to install vinyl replacement windows is not difficult–that is, if you follow these three important steps:

1. Measure (Twice!)

The most important first step is to measure the size of your window openings (not the entire window) before you place your order for vinyl windows. The old adage, measure twice (or even three times) applies here. Make sure that your measurements are accurate, and you are measuring the right space since vinyl windows are custom made. You won’t be able to return them if they don’t fit into your old window space. To get an accurate measurement, raise the old window and measure the opening from one jamb to the other (a jamb is the wood that frames the window). If you are replacing more than one window in your house measure all of them–while they may look the same size they may not be.

2. Prepare

Remove the old window completely–including the sash and window panel that holds in the glass–from the window opening. Save the window jambs and stops that hold the windows in place–you will need reuse them later when you install your vinyl replacement windows. Make sure that the entire area is cleared of any debris from the removal process.

3. Install

Maneuver the replacement window into the opening–you will need help with this step to avoid dropping the window. Use a carpenter’s square to center the new window and slide the sides of the window behind the pre-drilled holes in the jamb. Use the saved side jambs and drill the window in place. Replace the inside stops.

Once your window is installed, check to see if it works properly. If it does, use a caulking gun to seal any gaps on the inside and outside