heat loss and heat load calculations air flow change variable

[old duffer]

How do you factor in the air volume changes in each room when you undertake heat load and heat loss calculations for central heating emitter size at a given delta T?

 

[Exedon]

I go back far enough to have done heat loss calculations long hand then used a calculator to get results!
Currently use Stelrad Stars the version you have to register for .
Allows you to alter all criteria you like including air change deltaT outside air temperature U value ect.