# LDD-15 · Mechanical Room

> **Status:** 🟢 LOCKED — but tight.

## One-line intent

Organized systems, partially revealed — the room is the project's mechanical infrastructure read as architectural feature.

## Why this matters

A mechanical room that doubles as the "manifold visual wall" through a smoked-glass door is a design choice with operational consequences. Wall organization isn't free — every tank, pump, valve, and pipe in the room needs to be sited and labeled to support that vibe.

## Locked decisions

**Size**

- 10' × 7' (70 sqft)

**Zones**

| Zone | Function |
|---|---|
| North | Radiant manifold (visual wall) |
| South | Tanks + sink |
| East | Electrical + battery |
| Center | Working space (service access) |

**Door**

- Smoked glass — controlled visibility into the room

## Open items / requires engineer review

- **Is 70 sqft enough?** For the full system this room must contain: central radiant manifold + boiler/heat pump for hydronic + buffer tank + expansion tank + circulation pumps + water heater + water softener + filtration + electrical subpanel(s) for HVAC + low-voltage drivers + the "battery" mentioned (whole-house battery? UPS?) + working space. **70 sqft is tight.** Verify with mech designer once equipment sized.
- **Water heater location** — if heat-pump water heater, it needs ~700 cfm of ambient air to operate efficiently. In a small enclosed mech room, it'll just cool the room.
- **Hot water recirc pump** location and routing.
- **Buffer tank** for radiant — if used, takes 8–12 sqft of floor area.
- **Battery / UPS** — what's the intent? Solar battery? Whole-house backup? Define.
- **Mech room ventilation** — needs air movement; can't be a sealed cube.
- **Floor drain in mech room** — critical for the inevitable water heater leak, manifold drip, etc.
- **Sink purpose** — utility sink for mech work? Drain location matters.

## Cross-references

- ← [LDD-02 radiant](02-radiant-slab.md) — central manifold cluster lives here.
- ← [LDD-05 HVAC](05-hvac-system.md) — heat pumps/condensers (if any) located here.
- ← [LDD-09 electrical](09-electrical.md) — main panel sited in laundry/ops core; mech room hosts equipment subpanel.
- ← [LDD-10 plumbing](10-plumbing.md) — middle plumbing cluster pulls service from here.

## Cost drivers

The room itself is cheap shell; the equipment inside is budgeted elsewhere. Specific to this LDD:

- **Smoked glass door** (commercial-rated, frameless or thin-frame, fire-rated if required): $2–6K installed.
- **Mech room finishes** (sealed concrete floor, durable interior walls, ceiling acoustic if equipment is loud): $2–5K.
- **Floor drain + sink + supply**: $1.5–3K (part of plumbing rollup).
- **Mech-room ventilation** (small inline fan or makeup air): $0.5–1.5K.

**Likely-case rollup: $5–15K for the room finish + door (equipment costs in respective LDDs).**

## Air-gap concerns

1. **70 sqft is genuinely tight.** For comparison, a typical residential mech room with heat-pump water heater + hydronic radiant manifold + buffer tank + air handler + softener is 80–120 sqft. At 70 sqft, this room will be **service-access-tight** — every piece of equipment touches another. Strongly recommend bumping to at least 90 sqft (10' × 9' or 12' × 7.5') before structure is set.
2. **Heat-pump water heater in a small mech room loses efficiency.** The HPWH pulls heat from the room air; in 70 sqft the room cools quickly and the unit reverts to less-efficient resistance mode. Either: vent ducts to a larger space, oversize the mech room, or use a different water heater type.
3. **"Smoked glass door" + "organized infrastructure aesthetic"** = a real commitment. The room will be visible. Every label, every cable tie, every pipe stub matters. Budget for visible-grade finish quality on all manifold work (labeled valves, neat conduit, organized cable management).
4. **Battery system: code + safety implications.** A whole-house lithium-ion battery (Tesla Powerwall, Enphase IQ, etc.) has specific fire-separation, ventilation, and AHJ requirements. They typically can't be in a confined space without compliant detailing. Determine before locking the room size.
5. **Floor drain location** — must coordinate with under-slab plumbing and slab pour.
6. **Single mech room may be insufficient.** A separate small "north mech alcove" (for north plumbing manifold and ILS systems) and a "south mech alcove" (for workshop systems) may be needed in addition to the central mech room. The LDDs imply this via the three-cluster strategy but don't explicitly create the alcoves.

## Diagram

(no dedicated SVG — see [manifold clusters](../../diagrams/08-manifold-clusters.svg) for cluster locations; mech room is at the south end of the living wing, central cluster.)

## Status

🟢 **Green at strategy, 🟡 yellow on size.** Confirm 70 sqft is buildable with the full equipment list; recommend bumping to ≥90 sqft.