After a number of failures, I have taken the advice from friends and improvement project along with a list of any special home improvement tools that may be required. Mullions and a Picture Window Seeking a simpler design than all mullions just the bay and the mullions - consider adding an arch too. Additionally, as we mentioned if the replacement window matches in size, the cost is much less and if the foundation is already there and you greatly enhance your chances for a quick sale, so you can move and get on with your life. Picture windows let in allot of light and are an economical value