Quantify leakage airflow and predict cooling impact. Check sensible and latent loads against indoor targets. Support HVAC sizing, budgeting, and commissioning decisions on site.
| Scenario | Method | Volume | ACH / Flow | Outdoor | Indoor | RH Out/In | Safety |
|---|---|---|---|---|---|---|---|
| Office shell | ACH | 45,000 ft³ | 0.50 ACH | 95 °F | 75 °F | 55% / 50% | 10% |
| Mechanical room | Flow | — | 800 CFM | 90 °F | 74 °F | 60% / 45% | 15% |
| Lobby (metric) | ACH | 1,200 m³ | 0.70 ACH | 35 °C | 24 °C | 55% / 50% | 10% |
| Metric | Value |
|---|---|
| Infiltration airflow | 375.00 CFM |
| Sensible load (with safety) | 2,611 W | 8,910 Btu/hr |
| Latent load (with safety) | 6,046 W | 20,630 Btu/hr |
| Total load (with safety) | 8,657 W | 29,540 Btu/hr |
| Estimated electrical demand | 2.81 kW |
| Estimated monthly energy | 619 kWh |
| Estimated monthly cost | $111.41 |
Uncontrolled outdoor air entering through gaps, temporary openings, and door traffic adds cooling load that is often missed in early estimates. Even moderate leakage can raise peak sensible load and drive moisture-related latent load, increasing run time and discomfort. Tracking infiltration helps align temporary conditioning plans with realistic site conditions and reduces change orders.
Use ACH when a building is still in progress, especially before envelope commissioning. Typical estimating ranges may be 0.2 to 1.0 ACH depending on construction quality, wind exposure, and how often doors cycle. Once testing or trend data is available, switch to measured airflow so the result reflects actual leakage paths, vestibules, and pressure control.
Sensible gain is driven by dry-bulb temperature difference and airflow rate. A larger ΔT or higher flow increases the sensible component directly. If outdoor temperature is lower than indoor, sensible can become negative, indicating cooling relief. That does not eliminate latent gain when outside air is humid. Apply a safety factor to cover wind spikes and operational variability.
Latent gain depends on the difference in humidity ratio between outdoor and indoor air. High outdoor RH and warm conditions can add substantial moisture. Moisture removal loads dehumidification equipment, increases condensate, and can threaten finishes, adhesives, and sensitive materials. The calculator uses psychrometric relationships with barometric pressure to improve accuracy at different elevations.
Convert total load to electrical demand using EER or COP to estimate operating impact. This supports budgeting for temporary cooling, generator sizing, and utility planning. Compare results under multiple scenarios: door-propped periods, weekend shutdowns, and partial occupancy. Use the exported CSV/PDF in submittals to document assumptions, margins, and the basis of design for stakeholders.
It estimates sensible, latent, and total heat gain caused by unintentional outdoor air entering a space, using airflow, temperatures, humidity, and an optional safety factor.
Use ACH when you only know volume and a leakage assumption. Use direct airflow when you have testing, commissioning data, or measured fan/door usage estimates.
If outdoor air is cooler than indoor air, infiltration can reduce sensible cooling demand. The tool still reports latent gain only when outdoor moisture content is higher.
Humidity ratio is calculated from dry-bulb temperature, relative humidity, and barometric pressure using standard psychrometric relationships, suitable for HVAC estimating and comparison scenarios.
For early planning, 5–15% is common. Use higher values for windy sites, frequent door cycling, poor envelope control, or when occupancy and schedules are uncertain.
EER and COP convert thermal load to estimated electrical demand. Lower efficiency increases kW and monthly cost. Use equipment submittal values or conservative assumptions.
Yes. A negative sensible result indicates heating demand may increase instead of cooling. Review sign and magnitude, and adjust operating assumptions to match the season.
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.