Accessory Dwelling Units (ADUs) are booming in the Bay Area. Here's what you need to know about heating and cooling your ADU.
ADU HVAC Requirements
California Building Code - ADUs must have heating - May require cooling in some climate zones - Ventilation requirements must be met - Title 24 compliance required
Common Requirements - Adequate heating for all habitable spaces - Bath and kitchen ventilation - Smoke and CO detectors - Proper permits and inspections
Popular ADU HVAC Options
Mini-Split Systems **Most popular choice for ADUs:** - Heating and cooling in one - No ductwork required - Very efficient - Individual control - Compact footprint - Cost: $3,500-$7,000 installed
Wall Heaters **Budget heating option:** - Gas or electric - No cooling included - Lower installation cost - Good for mild climates - Cost: $1,500-$3,000 installed
Central Extension **If ADU is attached:** - Connect to main house system - Requires ductwork - May need HVAC upgrade - Most complex option - Cost: Varies widely
Sizing Your ADU HVAC
Typical ADU Sizes | ADU Size | Heating/Cooling Capacity | |----------|-------------------------| | 400 sq ft | 9,000-12,000 BTU | | 600 sq ft | 12,000-18,000 BTU | | 800 sq ft | 18,000-24,000 BTU | | 1,000 sq ft | 24,000-30,000 BTU |
Factors Affecting Size - Insulation quality - Window area - Climate zone - Occupancy
Climate Considerations
Coastal ADUs - Heating primary need - Cooling often unnecessary - Mini-split ideal
Inland ADUs - Both heating and cooling needed - Mini-split recommended - Higher capacity needed
Cost Considerations
Budget: $2,500-$4,000 - Electric wall heater - Portable/window AC - Basic ventilation
Mid-Range: $5,000-$8,000 - Single-zone mini-split - Bathroom exhaust - Kitchen ventilation
Premium: $8,000-$15,000 - Multi-zone mini-split - Whole-unit ventilation - Smart controls
Permitting Tips
Include in ADU Plans - HVAC equipment location - Electrical requirements - Ventilation details - Title 24 compliance
Work with Your Contractor - Get proper permits - Schedule inspections - Ensure code compliance
Mini-splits have become the go-to solution for Bay Area ADUs—efficient, compact, and providing both heating and cooling.