Advantages: comprehensive performance — designed for sealing, wind resistance, insulation and soundproofing together; good thermal insulation from multi-chamber structures and quality materials; good soundproofing from multi-layer seals and thick glass; strong waterproofing and wind resistance with reinforced mullions; durable, usually quality aluminium or thermal-break with long life; stylish, clean lines that suit various architectures. Disadvantages: higher price from quality materials, advanced process and precise hardware; require professional installation — complex and skill-dependent, and poor installation hurts performance and life; higher spare-part replacement cost due to specialised hardware; greater repair difficulty than ordinary windows because of complex structure.