How to open a stuck window
Window sashes operate by traveling up and down on tracks. When there are changes in temperature and humidity, the sashes can warp. If your window is merely painted shut, or jut experiencing too much humidity, this fix should only take a few minutes. If the frame and sashes are warped and out of square because the house has settled, well…you just might need a new window.
Step1
The sash may be sticking because it is painted shut, either from the inside or the outside. Take a utility knife with a new, sharp blade and carefully score the seam between the sash and frame. If the sash still won’t operate, go on to step 2.
Step 2
From the inside of the house, wedge the flexible blade of a putty knife between the sash and the frame. Use the hammer to lightly tap the knife blade around the entire perimeter of the frame and sash.