HVAC & Enclosure Thermal Load Calculator

Calculate total heat transfer, internal equipment dissipation, and required cooling tonnage for workshops, server rooms, enclosures, and commercial spaces.

Internal Heat Gains & Fenestration

Cooling & Thermal Load Summary
Total Cooling Load
0 BTU/hr
Required AC Capacity
0.0 Tons
Thermal Load (Metric)
0.00 kW
Building Volume
0 cu ft
Conduction Envelope Load
0 BTU/hr
Internal Heat Gain Load
0 BTU/hr

HVAC Thermal Engineering Formulas & Heat Gain Mechanics

Calculating the thermal envelope load determines the cooling and heating capacity needed to maintain design temperature and humidity conditions.

1. Envelope Conduction Heat Transfer Formula

Q_conduction = U * A * ΔT = (1 / R) * A * (T_out - T_in)

  • Q = Heat transfer rate (BTU/hr)
  • U = Overall heat transfer coefficient ($BTU/(hr \cdot ft^2 \cdot ^\circ F)$)
  • R = Thermal resistance rating (R = 1 / U)
  • A = Surface area of walls, ceiling, and windows (sq ft)
  • ΔT = Temperature differential between exterior ambient and indoor target ($^\circ F$)

2. Internal Heat Gain Equations

  • Electrical Equipment / Lighting: Q_electrical = Total Watts * 3.41214 BTU/(hr·W)
  • People Heat Load: Q_people = Occupants * ~400 BTU/hr (sensible + latent heat at moderate activity)
  • Solar Radiation Through Glass: Q_solar = Glass Area * Solar Heat Gain Factor (approx. 40 BTU/(hr·sq ft))

3. Air Conditioning Sizing Equivalents

1 Ton of Refrigeration = 12,000 BTU/hr = 3.517 kW

4. Typical Space Cooling Rules of Thumb

Space Application Typical Sq Ft per Ton Primary Thermal Factor
Residential Living Space 500 to 700 sq ft / Ton Building envelope & solar gain
Commercial Office 300 to 450 sq ft / Ton Lighting, computers, occupant density
Server Room / Crypto Mining 50 to 150 sq ft / Ton Extreme internal continuous wattage
Commercial Kitchen / Brewery 150 to 250 sq ft / Ton Steam, burner heat, process refrigeration