Question: what is the difference between pvc-u and upvc?
Answer: What is the difference between uPVC and PVCu? It is the same thing. uPVC changed it's name to PVCu (you may also see it as PVC-U) in the late 1980s to fall in line with Europe. It is called PVCu there because most European languages place the noun (the word PVC in this case) before the adjective (U).