While in theory it is not a requirement to have a Manual J calculation performed for your house before purchasing an Arctic system, it is very much recommended. All homes are different, and as such their heating and cooling demands are very difficult to perfectly estimate without certified Manual J calculation being performed. The result of cutting corners and not getting load calc performed could be a heat pump system that is oversized, or undersized for the demand load which can be difficult to fix without major replacements of key components. We would much prefer to be 100% sure that our system is perfectly sized for your actual heating load.