Global demand for doors and windows is projected to grow 4.5 percent per year by 2021, rising from $172 billion to $214 billion during that time, according to a new study from The Freedonia Group, a Cleveland-based industry research firm. The U.S. and China will account for 65 percent of the global sales growth during this period. …New residential construction accounted for the largest share of door and window demand in 2016. …In terms of window products, vinyl will represent the largest share of overall sales growth by 2021. The cost and performance advantages of PVC products, especially in developing regions where market penetration has not advanced as far as in higher-income areas, will spur this growth. Improvements to the aesthetics of vinyl products will boost sales as well, as suppliers introduce more colors and textures that more closely resemble wood.