Plan efficient HVAC systems for construction projects. Compare zones, adjust insulation, glazing, and airflow easily. See peak loads, airflow needs, and recommended capacity today.
A cooling load is the rate of heat removal needed to hold an indoor setpoint. It combines sensible gains (temperature rise) and latent gains (moisture). This calculator reports both in watts and converts the total to kW, BTU/hr, and tons of refrigeration for quick equipment checks.
Loads depend on the design day. A typical summer design might use 40°C outdoor dry-bulb with 50% relative humidity, while indoor targets often range from 23–26°C at 45–55% RH. The larger the temperature difference, the higher the sensible load. Higher outdoor humidity increases latent load through ventilation and infiltration.
Walls, roofs, doors, and glazing transmit heat based on U-value and area. As a starting point, insulated masonry walls may be near 0.6–1.2 W/m²·K, while well-insulated roofs can be 0.3–0.6 W/m²·K. Enter project-specific values when available, and use consistent units across rooms for reliable comparisons.
Solar heat through glass can dominate peak loads, especially on west and south facades. SHGC indicates how much solar energy enters; common ranges are 0.25–0.70 depending on glazing. Shading reduces this gain significantly. Use the orientation and shading fields to reflect awnings, blinds, tint, or nearby obstructions.
Internal gains are often the most predictable. Office occupants can add about 100 W sensible and 70 W latent each, while lighting is commonly modeled as 8–15 W/m² depending on fixture density. Plug and process loads vary widely; apply diversity factors to avoid assuming every device runs at full power at the same time.
Air leakage and outdoor air requirements add both sensible and latent loads. Infiltration is entered as ACH and converted using room volume. Ventilation is entered in L/s. If outdoor air is untreated, latent load can rise quickly in humid climates. Tight envelopes and controlled ventilation improve comfort and reduce peak tonnage.
Ducts routed through hot plenum spaces or attics add heat pickup, so a modest duct-loss allowance helps early estimates. Fan heat adds directly to sensible load. Keep these allowances realistic; oversizing to “be safe” can reduce dehumidification and increase cycling, especially for comfort-focused zones.
Use the room table to identify high-load zones and verify inputs like glazing area, orientation, and ventilation rates. The calculator provides a rule-of-thumb airflow estimate of roughly 400 CFM per ton for quick duct planning. For final selection, validate with detailed load calculations and local design standards.
Sensible load changes air temperature. Latent load removes moisture. Total cooling capacity must cover both to reach the temperature setpoint and maintain comfortable indoor humidity.
Glazing area, SHGC, orientation, ventilation rate, and infiltration often drive peaks. Roof exposure and internal equipment loads can also dominate, especially in top-floor or high-plug-load spaces.
Start with 5–10% for early budgeting when inputs are uncertain. Avoid large margins because oversized units may short-cycle and remove less moisture, reducing comfort in humid conditions.
Use 0.2–0.6 ACH for tighter rooms, and 0.6–1.5 ACH for leakier spaces. Construction stage, door usage, and envelope quality matter. If unsure, pick a mid value and test sensitivity.
Outdoor air carries moisture. When outdoor humidity is higher than indoors, the system must condense and drain that moisture. Higher L/s values raise both sensible and latent loads.
SHGC is the fraction of solar heat admitted through the glazing. Lower SHGC reduces solar gain and peak cooling, especially on west-facing windows. Pair it with shading for best results.
Use the total tons, kW, and airflow as a starting point. Then compare manufacturer performance data at your design conditions and select equipment with suitable sensible and latent capacity.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.