Mini-split installation is one of the most common upgrades in Mill Valley, and the reasons are built into the houses. Many homes near Mount Tamalpais date from the early 1900s to the 1960s, with an aging forced-air system whose ducts run through a cramped crawlspace, or rooms the heat never reached properly. Adding new ductwork through tight crawlspaces and finished walls is disruptive. A mini-split is a heat pump that needs only a small refrigerant line between an outdoor unit and each indoor unit, so it can heat damp, shaded rooms for most of the year and cool the sunny ones on warm afternoons without opening up the house.
Choosing the indoor units
- Wall-mounted units are the most common and the least expensive. They need a stretch of wall high in the room, ideally on or near an outside wall.
- Ceiling cassettes sit flush in the ceiling and spread air in several directions. They need space above the ceiling.
- Floor consoles sit low on the wall, a good fit under windows or in rooms with sloped ceilings.
- Ducted (concealed) units hide in a closet, attic or crawlspace and feed two or three nearby rooms through short ducts, so all you see are grilles.
Older houses often end up with a mix: a ducted unit for the bedrooms, a wall unit in the living room, a console in a converted attic.
Planning the layout
Capacity and zones. We size each zone from a room-by-room load calculation, not a guess. A shaded downstairs bedroom and a sunny upstairs office need very different units, and one outdoor unit can serve several indoor units if their combined load fits.
Line set routes. Each indoor unit connects to the outdoor unit through refrigerant lines, a drain and a control cable. We route them through closets and crawlspaces where we can and use a paintable line-set cover where they run outside, so the result looks finished on shingle or board siding.
Drainage. Indoor units make condensate when cooling and need a drain path. Where gravity will not work, we add a small condensate pump.
The outdoor unit. On steep lots we use a level pad or wall brackets that keep the unit above leaf litter and off damp ground, with clearance for airflow and for defrost water to drain away.
Living with it in a damp climate
Mini-splits have a dry mode that removes moisture with little cooling, which helps in shaded rooms that feel clammy. Their filters sit behind the front panel and need rinsing every few weeks in heavy use. The indoor coil and blower wheel should be cleaned during yearly maintenance, so they stay clear of the growth damp rooms encourage.
How the installation runs
- Space assessment: which rooms need heat, cooling or both, and where equipment can go.
- System design: capacity and zones, indoor unit types, one outdoor unit or more.
- Location planning: exact positions for indoor and outdoor units, line routes and drains.
- Clean installation: minimal wall penetrations, sealed openings and a tidy finish.
- Training: we show you the remote or wall controls, the modes and filter care.
Upfront pricing comes with the design, and financing is available with approved credit. The general mini-split installation page covers equipment in more depth. If you want whole-house cooling through existing ducts instead, compare AC installation in Mill Valley; for the rest of our work in town, see the Mill Valley page.