📏 Thermodynamic Loads
Residential HVAC sizing is a complex calculation of heat gain, but can be estimated using reliable industry baselines for square footage.
Required BTU = SqFt x 20 (base) + (Ceiling Additives)
- The 'Ton' Constant: In North America, cooling capacity is often measured in tons. One "ton" of cooling is equal to 12,000 BTU per hour.
- Ceiling Height Impacts: Standard 8ft ceilings allow for the 20 BTU/sqft rule. Every additional foot of ceiling height increases the volume of air that must be conditioned, requiring a higher static pressure and load.
- Occupancy & Appliances: Kitchens and high-occupancy living rooms usually require an additional 2,000–4,000 BTUs to account for human body heat and cooktop heat gain.
💡 Expert Tip
Do not "Oversize" your system. A system that is too large for the space will cool the air so fast that it doesn't have time to actually dehumidify the room, leading to a "cold and clammy" feeling and potential mold issues in the ductwork.