MCPCalc

HVAC Load Calculator

Simplified Manual J heating and cooling load calculation.

Scratchpad (not saved)

sq ft
%

Window area as % of floor area

What This Calculator Does

Simplified Manual J heating and cooling load calculation.

It combines Total Square Footage, Number of Stories, Climate Zone, Insulation Level to estimate Heating Load, Cooling Load, Heating Tonnage.

Formula & Method

Heating load is BTU_h=Area\cdot b_{climate}\cdot f_{stories}\cdot f_{insulation}\cdot f_{airtight}\cdot f_{window} where f_{window}=1+0.005(Window\%-15) when window area exceeds 15%. Cooling load is BTU_c=BTU_h\cdot r_{climate} and tons use T=\frac{BTU}{12000}.

Notation used in the formulas: R = Heating Load; x_{1} = Total Square Footage; x_{2} = Number of Stories; x_{3} = Climate Zone; x_{4} = Insulation Level; x_{5} = Window Area; x_{6} = Air Tightness.

Method summary: inputs are normalized to consistent units, core equations are evaluated, then secondary values are derived and rounded for display.

Use this calculator for quick scenario analysis. Start with baseline values, change one driver at a time, and compare how sensitive the results are to each input shown above.

Inputs Used

  • Total Square Footage: Used directly in the calculation.
  • Number of Stories: Used directly in the calculation.
  • Climate Zone: Used directly in the calculation.
  • Insulation Level: Used directly in the calculation.
  • Window Area: Window area as % of floor area
  • Air Tightness: Used directly in the calculation.

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