Building Data

Building Length (ft)

Building Width (ft)

Ceiling Height (ft)

Number of Floors

Climate Zone

Building Type

Year Built

Total Window Area (sq ft)

Window Orientation

HVAC Load Results

Total Cooling Load
—
BTU/h

Total Heating Load
—
BTU/h

Recommended AC Size

—

tons

Recommended Heat Pump

—

BTU/h

Sensible Cooling

—

BTU/h

Latent Cooling

—

BTU/h

About Manual J Calculations

ACCA Manual J is the industry-standard method for calculating residential heating and cooling loads. It determines the exact BTU/h (British Thermal Units per hour) needed to heat and cool a building based on:

Building dimensions and construction type
Climate zone and local weather conditions
Window area and orientation
Insulation levels and building age
Internal heat gains from occupants and appliances

Calculation Method

Cooling Load

Calculated from sensible heat gain through walls, windows, roof, plus internal loads from people, lights, and equipment.

Heating Load

Calculated from heat loss through building envelope (walls, windows, doors, roof) and infiltration losses.

System Sizing

Results rounded to standard equipment sizes. Recommended AC size based on 400 sq ft per ton of cooling capacity.

Note: This calculator provides estimates for budgeting and preliminary sizing. For actual equipment selection, consult ACCA Manual J (8th edition) procedures or use Manual S for equipment selection. Professional HVAC designers should verify all calculations.