Dedicated HVAC mini-split
A dedicated HVAC mini-split for an ADU or in-law suite provides independent heating and cooling without extending the main house's HVAC system into the addition.
How dedicated hvac mini-split actually works.
A dedicated HVAC mini-split for an ADU or in-law suite provides independent heating and cooling without extending the main house's HVAC system into the addition. Mini-splits (Mitsubishi, Daikin, Fujitsu) install with an outdoor condenser and one or more indoor head units; the result is precise zoning, lower operating cost than running the main system into a peripheral zone, and the ability to keep the suite at a different temperature than the rest of the house.
Sizing is critical — a 12,000 BTU unit is appropriate for ~500 sq ft, 18,000 BTU for ~800 sq ft, 24,000 BTU for larger. Oversizing causes short-cycling and humidity problems in NE Florida; undersizing causes the unit to run continuously without keeping up.
The execution details that decide outcome.
Right-sizing. Manual J calculation for the conditioned space; not a default value.
Outdoor unit placement. Noise to neighbors, salt-air corrosion on coastal homes.
Refrigerant line set length and rise. Affects efficiency and capacity.
Other adus & in-law suites outcomes I've built.
Read the Clay County adu & in-law suite guide.
Tier-by-tier costs, the full permit walkthrough, and the FAQs Mark hears most often.
Read the guideSee your range in 90 seconds.
Tell me about your project — you'll see a real budget range mid-flow, and I'll call within 24 hours with a fixed quote.