Pella claims what sets its windows and doors apart is the installation process. The company stresses that its installers are the very best, trained in-house and re-certified annually. One customer says the whole process was hassle-free, on time and professionally done. She even adds her house seems cleaner now than before Pella arrived. For a limited time, Pella is offering an extra 5 percent off its 50 percent off sale on qualifying installation and 120 months financing.