Room Heat Loss & Gain

Room Dimensions

Room length along primary axis
Perpendicular to length
Floor-to-ceiling clear height

Temperatures & Infiltration

Infiltration/ventilation rate

Enclosure U-Values

Solar Heat Gain Coefficient

Windows Exposure

North 0°
East 90°
South 180°
West 270°
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Room Heat Load Analysis

This calculator determines the peak heating and cooling loads for a room using the ASHRAE heat balance method. It analyzes heat transfer through the building envelope (walls, windows, roof, floor, door), infiltration air exchange, solar radiation through glazing, and internal heat sources (occupants, lighting, equipment). The governing design load is the maximum of winter heating or summer cooling requirements, ensuring the HVAC system is sized for the worst-case scenario.

Key Points:
  • Winter load includes transmission losses, infiltration, and solar gain offsets with 15% safety margin
  • Summer load includes envelope gains, solar radiation, internal gains, and infiltration with 10% safety margin
  • U-Value (Thermal Transmittance): Lower values indicate better insulation performance
  • SHGC (Solar Heat Gain Coefficient): Fraction of solar radiation admitted through glazing (0-1 scale)
  • ACH (Air Changes per Hour): Measures building airtightness. Lower ACH = better energy efficiency
  • Design load determines HVAC equipment capacity - oversizing wastes energy, undersizing causes discomfort
Calculation Steps:
  1. Enter all required parameters
  2. Click "Update Calculation"
  3. Review results and analysis
Formula Variables:
Q Heat Flow Rate (W)
U Thermal Transmittance (W/m²K)
A Surface Area (m²)
ΔT Temperature Difference (K)
SHGC Solar Heat Gain Coefficient (-)
ACH Air Changes per Hour (1/h)
Q_solar Solar Heat Gain (W)
Q_internal Internal Heat Gain (W)