HVAC Sizing Guide
Oversizing an HVAC unit is the most common mistake in residential construction. It leads to short cycling, poor humidity control, and premature failure.
The Rule of Thumb vs. Manual J
Contractors often use a rule of thumb: 1 ton of cooling capacity per 400-600 square feet. This is dangerously inaccurate. A proper ACCA Manual J calculation considers:
- Climate zone and orientation
- Insulation R-values
- Window types (U-factor and SHGC)
- Air leakage rates (Blower door test)
Common Mistakes
Bigger is not better. An oversized AC cools the house too quickly before it can extract moisture, leaving the home feeling cold and clammy.
| House Size | Climate (Hot/Humid) | Climate (Moderate) |
|---|---|---|
| 1,000 sq ft | 2.0 Tons | 1.5 Tons |
| 1,500 sq ft | 3.0 Tons | 2.5 Tons |
| 2,000 sq ft | 4.0 Tons | 3.0 Tons |
| 2,500 sq ft | 5.0 Tons | 3.5 Tons |
*Estimates only. Always perform a Manual J load calculation.