In an older San Jose home, the right system depends on what the house already has. Victorians usually have no ducts and tall ceilings, so ductless mini-splits or a high-velocity small-duct system add heating and cooling without tearing into plaster. Eichlers have radiant heat in the slab and no attic: keep the radiant heat if it still works and add mini-splits for cooling. Mid-century ranch homes usually have ducts in the attic, which makes a ducted heat pump, or a new furnace and AC on sealed, insulated ducts, the natural fit.
The options at a glance
| Option | What it needs | What you see indoors | Good fit for |
|---|---|---|---|
| Ductless mini-split | A hole about 3 inches across per indoor unit, wall space, an outdoor unit | A wall or floor unit in each zone | Victorians, Eichlers, additions |
| Concealed slim-duct mini-split | A closet, attic or soffit near the rooms it serves | Small grilles | A few rooms on one floor |
| High-velocity small-duct system | Room for an air handler; tubes about 2 inches across | Small round outlets | Central air without wall units |
| Ducted heat pump | Existing or new ducts, enough electrical capacity | Ordinary registers | Ranch homes with attic ducts |
| Radiant slab plus mini-splits | Slab loops in working order | Mini-split units | Eichlers |
Mini-splits and heat pumps both heat and cool. A high-velocity system cools with an outdoor AC or heat pump and heats with the heat pump or a hot-water coil.
Victorians
What makes them hard:
- No ductwork. They were built to be heated room by room; any central heat came later.
- High ceilings. At 10 to 14 feet there is more air to heat, and the warm air collects up high.
- Ornate details. Plaster, moldings and trim do not survive full-size duct runs.
- Several floors. Heat rises, so upstairs rooms bake on summer afternoons while the ground floor stays cool.
- Single-pane windows that leak conditioned air.
What works. Ductless mini-splits are the most common answer: an indoor unit per room or per floor, each with its own setting, with the refrigerant lines run along a rear or side wall or through closets. If you would rather not see wall units, a concealed slim-duct unit in an attic or closet can serve several rooms through short ducts. A high-velocity system is the other route: its flexible tubes thread through walls and floors much like wiring, ending in small round outlets. Either way, each floor becomes its own zone, which fixes the hot upstairs.
What to avoid: forcing standard ductwork through finished rooms, relying on window units, and sizing a system before attic insulation, weatherstripping and interior storm panels have cut the leaks.
Pre-war bungalows
Older bungalows often have crawlspace ducts that are worn out or barely insulated, deep eaves that limit where an outdoor unit can go, small closets that once held a floor furnace, and older wiring. New sealed and insulated ducts let a modern furnace and AC, or a heat pump, use the same runs. A converted porch or garage that the main system never reached well is a classic job for a single mini-split. In Willow Glen, vintage ductwork and thin insulation are common; in Rose Garden, larger older homes with original woodwork and big rooms often need zoning and cooling added without harming the house.
Eichlers
What makes them different:
- Radiant floor heat. Hot water from a boiler circulates through pipes in the concrete slab. It is quiet and even but slow to respond, and it cannot cool.
- Post-and-beam construction. The exposed ceiling is the roof deck, so there is no attic for ducts and no cavity for a ceiling cassette.
- Walls of glass. Floor-to-ceiling windows bring heavy heat gain on hot San Jose afternoons, most of all on west-facing walls.
- Flat or low-slope roofs. Every penetration is a potential leak, so line runs are planned to avoid them.
- Open plans. Sound carries, so quiet indoor units matter.
What works. If the radiant system still holds pressure, keep it. Add mini-splits for cooling: wall-mounted or floor-console units suit these homes, and since they are heat pumps they can back up the radiant heat on cold mornings. An open plan often needs fewer indoor units than the room count suggests. If the slab loops have failed, a heat pump mini-split system can take over the heating too. Signs of a slab leak include a boiler that keeps losing pressure or taking on water, and a warm or damp spot on the floor. A high-velocity system is possible where a closet or a built-down soffit can hide the air handler and tubes, but it takes more planning than in a house with an attic.
Deal with the glass before sizing: low-e film or exterior shade on the sunniest walls cuts the cooling load.
1950s–60s ranch homes
What you usually find: a furnace in a hall closet, garage or attic; attic ducts that are original or close to it, with thin insulation and leaky joints; lower ceilings that limit where wall units and registers fit; and an electrical panel sized for an earlier era. An AC or heat pump installed before about 2010 may use R-22, which is now costly to service.
Why the attic matters here. On a hot San Jose afternoon the attic gets far hotter than the rooms below, and leaky, thinly insulated ducts up there lose much of their cooling before it reaches a register. Sealing and insulating them can matter as much as the new equipment.
What works. A ducted heat pump replaces the furnace and AC with one outdoor unit and suits San Jose’s mild winters; a new furnace with central AC is the other route. Either way, replacement is the time to fix the ducts. In Cambrian, where many homes are around 60 years old, original systems and leaky ducts are common.
Before you choose any system
- Insulation and air sealing first. No system makes up for a leaky shell, and a tighter house needs a smaller one.
- A duct test if the house has ducts, to see how much air leaks and where.
- A room-by-room load calculation. Rules of thumb miss tall ceilings, glass walls and thin insulation, and an oversized system short-cycles.
- Electrical capacity. Heat pumps and mini-splits run on electricity, and an older panel may need an upgrade first.
- Permits. Replacing heating or cooling equipment needs a permit, and in California a duct leakage test is usually part of it when ducts are involved.
- Incentives. Systems installed after 2025 no longer qualify for the federal tax credit on efficient equipment.
Questions to ask before you sign
- Have you worked on houses built like mine?
- Which option do you recommend, and why that one?
- Where will the lines, units and outlets go, and what will you cut or patch?
- What does the quote include: permits, patching, electrical work?
Estimates for new and replacement systems are free, so you can compare a mini-split layout with a ducted option before deciding.