Commercial Load Input Form
Formula Used
Cooling temperature difference: Outdoor cooling temperature - indoor cooling temperature.
Heating temperature difference: Indoor heating temperature - outdoor heating temperature.
Envelope load: Area × U-factor × temperature difference.
Solar glass load: Glass area × SHGC × solar heat factor.
Lighting and equipment load: Watts × 3.412 × diversity factor.
Ventilation sensible load: 1.08 × CFM × cooling temperature difference.
Ventilation latent load: 0.68 × CFM × moisture grain difference.
Cooling tons: Total cooling BTU/hr ÷ 12,000.
Recommended airflow: Cooling tons × 400 CFM.
How to Use This Calculator
Enter the building floor area and ceiling height first. Add design temperatures for cooling and heating. Enter exposed wall, roof, glass, and door areas. Use realistic U-factors from plans or product data.
Add people, lights, equipment, motors, and process heat. Then enter outdoor air, infiltration, moisture difference, diversity, duct loss, and safety allowance. Press the calculate button. Review the result above the form. Download the CSV or PDF report when needed.
Example Data Table
| Input |
Example Value |
Purpose |
| Floor Area |
10,000 sq ft |
Sets building scale |
| Wall U-Factor |
0.08 |
Measures wall heat transfer |
| Glass Area |
1,000 sq ft |
Estimates window conduction and solar gain |
| Occupants |
80 people |
Adds sensible and latent people load |
| Outdoor Air |
1,600 CFM |
Adds ventilation cooling and heating load |
| Safety Allowance |
10% |
Adds planning margin |
Commercial Load Calculation Guide
Why Load Calculation Matters
A Manual N commercial load calculation estimates the heating and cooling demand of a light commercial space. It looks at heat entering through walls, roofs, glass, doors, people, lights, equipment, outdoor air, and leakage. The goal is not to guess equipment size. The goal is to build a clear load picture before selection.
Commercial Loads Change Often
Commercial rooms change during the day. Offices fill in the morning. Retail stores gain heat from lights and shoppers. Kitchens add process heat. Server rooms may run heavy equipment after hours. That is why this calculator includes diversity. Diversity lets you reduce internal gains when every source is not active at the same time.
Envelope and Solar Gain
Envelope load depends on area, U-factor, and temperature difference. A larger temperature gap gives a larger load. Glass also adds solar gain. The solar factor field lets you represent sun exposure, shading, tinting, and orientation in one simple value.
Outdoor Air and Moisture
Ventilation and infiltration are also important. Outdoor air improves indoor air quality, but it adds sensible and latent load. Sensible load changes air temperature. Latent load removes moisture. The grain difference field estimates the moisture difference between outdoor and indoor air.
Reading the Result
The result separates sensible load, latent load, total cooling load, tons, heating load, and suggested airflow. It also adds duct loss and safety allowance. These factors help users create a practical preliminary allowance.
Planning Use
Use the result for early planning, comparison, budgeting, and design checks. Do not treat it as a final engineered report. Real projects need local code review, exact occupancy schedules, weather design data, construction details, and equipment performance checks.
Better Inputs
Good inputs matter. Measure building areas carefully. Use realistic U-factors. Enter ventilation from the mechanical plan when available. Adjust people and equipment for the actual schedule. Review the output before selecting units. Oversized systems can short cycle. Undersized systems can miss comfort targets. A balanced load estimate supports better decisions.
Scenario Testing
For best results, run more than one scenario. Test peak summer, peak winter, and a normal occupied day. Compare glass-heavy rooms with interior rooms. Record assumptions beside each result. This makes reviews easier for contractors, owners, and facility teams. It also helps find weak inputs before money is spent on equipment, ducts, or controls during early design and bid review meetings later.
FAQs
What is a Manual N commercial load calculation?
It is a method used to estimate heating and cooling loads for light commercial buildings. It considers envelope, people, lights, equipment, ventilation, and moisture loads.
Can this replace an engineered design?
No. This calculator supports early planning and checking. Final equipment sizing should be reviewed by a qualified professional using project drawings, local codes, and design weather data.
What is sensible cooling load?
Sensible cooling load is the heat that changes air temperature. It comes from walls, roofs, windows, people, lights, equipment, and outdoor air.
What is latent cooling load?
Latent cooling load is moisture removal demand. It usually comes from occupants, ventilation air, infiltration, and humid outdoor conditions.
Why is diversity factor included?
Diversity accounts for loads that do not all peak together. For example, every light, device, and occupant may not be active at the same time.
What does ACH mean?
ACH means air changes per hour. It estimates leakage or infiltration by comparing entering outdoor air with the total room volume.
Why divide BTU/hr by 12,000?
One cooling ton equals 12,000 BTU/hr. Dividing total cooling load by 12,000 converts the result into tons of cooling capacity.
Why add duct loss and safety allowance?
Duct loss and safety allowance add practical margin. They help cover leakage, heat gain in ducts, uncertain inputs, and early planning assumptions.