"Travis Jordan" wrote in message
.. .
yaofeng wrote:
Why should I?

Because you'd want to be sure that the system was sized correctly.
Maybe your neighbors with identical homes are all oversized, too. That
would be quite common. The ONLY way to know is to do a heat gain
calculation.

Or live with the question. Your choice.

He has been living with the same sized unit for years now. So have he
neighbors. What is a calculation tell him that experience is not?