Why Square Footage Won't Size Your New HVAC System
Dennis, N.J. – November 01, 2026 -- Before you replace your heating and cooling equipment, ask your contractor for a Manual J load calculation, a home-specific measurement that guides how big the new system should be. HVAC expert Bob Schmid of Ocean View, New Jersey, explains the method in a new HelloNation article.
Two same-size homes can need very different systems
Insulation, window quality, and air leakage all change how much heat enters or leaves a house. A Manual J calculation, developed by the Air Conditioning Contractors of America, estimates a specific home's heating and cooling requirements instead of relying on a square-footage formula.
Inputs include room dimensions, ceiling heights, window direction, and local climate. Occupants, appliances, lighting, and duct location also affect the results.