mad hatter® wrote:
Guess you didn't read my post either. I wrote "rule of thumb". I
guess you don't know what that means?? Further I wrote other
solutions too but I guess you chose to ignor or address them too.

Your suggestion that the OP "qualified hvac person to do a load calc" is
the right one - didn't mean to de-emphasize that, sorry.

Having said that, none of the 'adjustment' suggestions you made will
result in an accurate heat gain / heat loss calculation. And in my area
of the country the local permitting agencies won't let you get away with
anything less than an ASHRAE-approved load calculation.