LDD-05 · HVAC System (Overview)
One-line intent
Each zone uses the simplest correct system — no single system serves the entire building.System breakdown by zone
| Zone | System | Notes |
|---|---|---|
| Living wing | Ducted heat pump | Trunk + 5 branches; details in LDD-06 |
| Gym | 2 mini-splits + destrat fans | Athletic / large-volume strategy |
| Bedrooms | Ducted heat pump (separate zone) | Upper level |
| UCR | Radiant + passive cooling, fan-assisted | Lowest-velocity comfort |
| ILS | Mini-splits | Independent operation |
| Workshop | Mini-split | Independent |
| LOW | Rough-in Phase 1 | Active equipment deferred |
Constraints
- No soffits
- No overlapping systems
- No duct chaos
- No diagonal duct runs
Open items / engineer review
- Equipment selection per subsystem (Manual J per zone)
- Heat pump heat source — air-to-air vs ground-source ($25–50K delta)
- Make-up air for kitchen island system (LDD-07) — must coordinate
- Ventilation strategy (ERV/HRV) — currently missing, essential for tight envelope
- Humidity control — neither dehum nor humidification specified
Cost drivers
Living wing ducted $30–55K · Bedroom ducted $22–35K · Gym mini-splits $15–25K · ILS mini-split $7–12K · Workshop mini-split $5–8K · Destrat fans $20–35K · ERV (currently missing) $8–18K · LOW rough-in $3–6K. Total: $115–195K, mid ≈ $155K, budgeted at $175K.Air-gap concerns
- Missing ventilation system. Tight envelopes need balanced ventilation (ERV in cold climate). Add now; can't add cleanly after walls close.
- Gym cooling load not accounted for — west-facing clerestory + 20'+ ceiling = big summer load.
- Make-up air strategy missing — without it, island vent backdrafts something.
- No zoning controls / thermostats — multi-system house needs ≥5 stats and zone coordination strategy.
- Bedroom system trunk path? Named but never sited.
Cross-references
Diagram
HVAC trunk + branches occupy layers 2–3 of the exposed ceiling hierarchy.