Learn · Mini splits for every space
The right HVAC for a casita or ADU is ductless
A detached casita can't share the main home's ductwork, and it needs its own independent control. Ductless — single-zone for a studio, multi-zone for a larger unit — is purpose-built for the job.
The problem with a detached casita
A casita or accessory dwelling unit — a guest suite, in-law quarters, rental, or pool house — is a structural mismatch for central HVAC. It doesn't share the main home's ductwork, and running ducts out to a separate building is impractical, expensive, and leaky over that distance. Tying it to the main system also forces everyone onto the same thermostat, which defeats the point of a space meant to function on its own.
A casita usually needs independent control: a guest or tenant sets their own temperature without touching the main house, and the space stays comfortable on its own schedule. Many casitas are also small full dwellings — a living area, a bedroom, maybe a kitchenette and bath — each wanting its own comfort.
Why ductless is the fix
Ductless is purpose-built for the casita. A single-zone system handles a studio-style unit; a multi-zone system — one outdoor unit feeding a head in the living area and another in the bedroom — handles a larger one, with independent thermostats in each space. There's no existing system to integrate with, so the install is clean: the small outdoor unit sits beside the casita, and a three-inch line-set hole connects it to the heads. Every unit is a heat pump, so it covers both San Antonio seasons.
The cost & effort reality
A studio casita is a single-zone job — typically $3,000–$5,500 installed. A one- or two-bedroom casita moves into multi-zone territory, generally $6,000–$14,000 for 2–4 rooms depending on head count and capacity. Because there's no old system to remove or rebalance, the install tends to be one of the more straightforward ones we do.
What we'd recommend
Match the number of zones to how the casita is actually used. An open studio is fine on a single zone; a separate bedroom and living area each deserve their own head for independent comfort — especially in a rental, where tenants notice the quiet operation and low bills. We run a Manual J on each space, since casitas often combine glass doors and exposed exterior walls that change the load. As a true second dwelling, ductless gives it its own comfortable setpoint, fully independent of the main house, by default.
Frequently asked questions
Should a casita have its own system or tie into the main house?
Its own. Running ductwork out to a detached building is costly and inefficient, and sharing the main thermostat removes the independent control a casita needs. A dedicated ductless system gives better efficiency and lets a guest or tenant manage their own comfort.
Single-zone or multi-zone for a casita?
It depends on the layout. One open studio space works on a single zone. A separate bedroom and living area call for a multi-zone system so each room has independent comfort. We size it to the floor plan on the free in-home estimate.
Is ductless a good fit for a rental unit?
It's excellent — low operating cost, quiet operation, individual thermostat control, and simple filter maintenance the tenant can do. They get comfort and control; you get an efficient, durable system that's easy to maintain between occupants.
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Written & reviewed by
Manny Pozos
Owner, The Mini Split Company
Manny Pozos founded The Mini Split Company after years of watching San Antonio homeowners get stuck with HVAC that doesn't fit their homes — older houses without ductwork, additions, garages, and rooms that never stay comfortable. He built a company that does one thing exceptionally well: ductless mini splits. A specialist in the systems he installs, he leads every job to factory spec.
The Mini Split Company
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