Heat-Load USA

Design HVAC - Design Air Conditioning - Design of Air conditioning systems

- load calculation - Manual N - Commercial load calculation = HVAC ENGINEERS - HVAC CONSULTANTS

- ACCA Manual N Commercial load calculation - Manual D - Manual D calculation - Manual J & D Calculations

Heating and Cooling systems are designed around internal and external temperatures, the closest weather station and of couse the loads of the home. 

Here is a link for nationally accepted design temperatures from Energy Star: