HVAC Load Calculator
Estimate heating and cooling loads by room using your building dimensions and component properties.
System of units
Changing units converts entered values without intentionally changing their physical meaning. Loads remain displayed in BTU/h.
Project design conditions
Enter design temperatures appropriate for your location. These values are not looked up automatically.
Rooms
Results update automatically.
Your estimate
Total heating load—BTU/h
Total cooling sensible load—BTU/h
Total cooling latent load—BTU/h
| Room | Heating | Cooling sensible | Cooling latent |
|---|---|---|---|
| Add a room to see estimates. | |||
These are component-based estimates, not an ACCA Manual J calculation or a final equipment-sizing recommendation. Accuracy depends on the quality of user-supplied inputs and assumptions.
How to Use the Calculator
- Enter indoor and outdoor design temperatures.
- Add each room and enter the net areas and U-factors for its exterior surfaces.
- Enter window solar gain only when you have a defensible solar input for the design condition.
- Enter infiltration airflow and moisture difference if known.
- Results update automatically as inputs change.
Assumptions and Limitations
- Surface conduction uses Q = U × A × temperature difference.
- Cooling solar gain is a user-supplied input: window area × SHGC × incident solar irradiance × shading factor.
- Sensible air load uses 1.08 × CFM × ΔT; latent air load uses 4,840 × CFM × ΔW under standard imperial assumptions.
- Airflow must be entered for each room as a room allocation; do not enter the same whole-house airflow in every room.
- Ground-contact floors, thermal storage, detailed orientation/time effects, and duct distribution are not modeled comprehensively.
- This tool is an educational estimator, not a substitute for a qualified HVAC design or Manual J.
