HVAC System Design - Don’t just ask for a load calculation, but ask that it be done at the correct design temperature values for your area. See below. Also, the load calculation is only the starting point. Make sure the system equipment is selected correctly, and the duct work is sized and installed correctly. A system that is designed correctly, installed correctly, and balanced correctly WILL result in a comfortable and efficient house. HVAC systems (equipment and ductwork) need to be designed in accordance with the Air Conditioning Contractors of America (ACCA) Manuals. The specific Manuals are listed below: Manual J—Calculation of Loads Manual S—Equipment Selection Manual D—Design of Ductwork Very few homes are designed using these guidance documents but rather are chosen based upon “rules of thumb” (such as one ton of AC per 500 square feet of floor space). When this is done, the system is almost always oversized, resulting in a system that can provide plenty of sensible heat removal (able to control the temperature) but a loss of latent heat (humidity) removal.