HVAC for ADUs & Garage Conversions

Converting a garage into livable space, or building a standalone accessory dwelling unit (ADU), means starting from zero on comfort. These spaces were never designed to be conditioned space, so insulation, permitting, and equipment choice all need real attention before the space is actually comfortable year-round.

Common Systems in ADU/Garage Conversion Homes

• Ductless mini split systems are the most common and often most practical choice, since running new ductwork into a converted garage or standalone ADU is frequently impractical or prohibitively disruptive
• A dedicated small split system is sometimes used for larger ADUs, particularly ones intended for long-term living rather than occasional use
• Whatever the equipment, the space is typically zoned independently from the main house's system, which is also generally what local building code expects for a converted or detached space

Key Considerations

• Insulation should be addressed before or alongside HVAC installation, garages in particular are rarely insulated to a standard that makes conditioning them efficient without it
• A permit is typically required for converting a garage or building an ADU, and that usually extends to the HVAC work itself, not just the structural conversion
• A window unit might seem like a cheaper shortcut, but it's generally less efficient, less durable, and less comfortable long-term than a properly sized mini split, worth weighing against the real cost difference