Estimate heating and cooling loads and equipment size for a dwelling.
Fabric and ventilation losses are calculated separately because insulation and airtightness are independent properties. Cooling load includes internal gains from people and equipment, which heating load does not credit. Oversized equipment short-cycles, which worsens humidity control and efficiency, so a load calculation matters more than adding a safety margin.
HVAC Load Calculator (Manual J Simplified)
Load = fabric loss + ventilation loss, where ventilation loss = 0.33 × ACH × volume × ΔT
Load = fabric loss + ventilation loss, where ventilation loss = 0.33 × ACH × volume × ΔT Fabric and ventilation losses are calculated separately because insulation and airtightness are independent properties. Cooling load includes internal gains from people and equipment, which heating load does not credit.
Oversized equipment short-cycles, which worsens humidity control and efficiency, so a load calculation matters more than adding a safety margin.
This calculator takes 5 inputs: Conditioned floor area, Ceiling height, Envelope quality, Design temperature difference, Occupants. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.