# LDD-08 · Lighting Framework

> **Status:** 🟢 LOCKED v1.0.

## One-line intent

Light the space, not the fixture.

## Why this matters

The lighting framework rejects the residential default (can lights everywhere, switch banks on every wall) and instead treats lighting as architectural infrastructure. This is the right move for a building with this much glass, exposed structure, and material discipline — but it's also more expensive per square foot than mainstream residential lighting.

## Locked decisions

**Core rules**

- No visible light sources
- No cans (recessed downlights)
- No track lighting

**Layered system**

| Layer | Purpose |
|---|---|
| Ambient (indirect) | Background fill, ceiling and wall wash |
| Wall apertures (type A/B/C) | Architectural perforations admitting light from concealed source |
| Task lighting | Counter, work surface, reading |
| Human-scale (lamps) | Comfortable, low-mounted personal light |
| Low-level navigation | Stair, hallway, floor-grazing at night |

**Electrical system**

- 24V low-voltage throughout
- Drivers accessible (never buried)
- Organized by zone

**Control**

- Scene-based only (no switch clutter)
- All dimmable
- Scenes: Day, Evening, Social, Night, Cleaning, Gym

## Open items / requires engineer review

- **Specific fixture selection** for each layer — not in the LDD; this is appropriate at LDD stage but needs an electrical/lighting designer to spec before bidding.
- **Driver count and locations** — driver pockets must be designed into walls/ceilings during framing. Forgetting this is the single most common lighting mistake.
- **Control system manufacturer** (Lutron RA3 / Crestron / Loxone / KNX / DALI) — major budget swing and vendor lock-in decision.
- **2700K vs 3000K** as default warm white standard — pick one and apply uniformly. Mixed temperatures look bad.
- **CRI target** — 90+ for living areas, 95+ for kitchen/island cooking, 80+ for utility zones. Spell out.
- **Color tunability** (warm-dim, tunable white) — if desired, add 20–40% cost.
- **Exterior lighting integration** — controlled by same scene system? See LDD-16.

## Cross-references

- → [LDD-12 ceilings](12-exposed-ceilings.md) — lighting is the lowest layer in the ceiling hierarchy; cannot interrupt higher layers.
- → [LDD-17 soffit serviceability](17-soffit-system.md) — soffit lighting + driver access strategy.
- → [LDD-07 cooking ventilation](07-cooking-ventilation.md) — central diffused light panel above island integrated with capture field.
- → [LDD-16 exterior lighting](16-exterior-lighting.md) — same scene control system.
- ← [LDD-06 living wing HVAC](06-living-wing-hvac.md) — diffusers must not interrupt lighting composition.

## Cost drivers

A truly custom layered low-voltage scene-based lighting system runs **$8–14 per sqft of conditioned area** for a high-design project. At ~7,200 sqft: **$58K–$100K** for fixtures + drivers + control + commissioning.

Breakdown estimate:

- **Linear LED runs** (soffit, indirect, wall washing) — ~600–900 lf at $40–70/lf installed = $25–60K.
- **Low-voltage drivers** with accessible service panels — $5–10K.
- **Control system (Lutron RA3 or similar)** — $8–16K hardware + $4–8K programming/commissioning.
- **Task + accent + lamp fixtures** — $6–14K.
- **Exterior lighting** — covered in LDD-16.

**Likely-case rollup: $70K total reflected in budget waterfall.**

## Air-gap concerns

1. **"No cans" is a strong, correct constraint and a strong cost driver.** The doc holds it well; just be ready for sticker shock at fixture and labor cost relative to mainstream residential.
2. **24V low-voltage everywhere requires careful run lengths.** Voltage drop in 24V over long runs is real; the driver placement strategy (drivers accessible, never buried) helps but requires designing the driver locations into wall framing.
3. **Scene control commissioning is a multi-visit process.** Budget two to three commissioning visits over the first 30 days post-move-in. The first scene set is never right.
4. **No mention of emergency/egress lighting.** Building code typically requires stair and exit lighting on battery backup. Add to the spec.
5. **No mention of circadian / tunable-white strategy.** If desired (especially in ILS aging-in-place context), bake in now — retrofitting later is expensive.
6. **Mockup at least the central island light panel + capture field combo.** This is the most visually critical fixture in the house. Build a mockup wall.
7. **Driver heat and cooling.** Indoor drivers (per LDD-17) generate heat. In a sealed driver pocket, that heat needs venting or the drivers fail early.

## Diagram

(no dedicated SVG — embedded in [LDD-12 ceiling hierarchy](12-exposed-ceilings.md))

## Status

🟢 **Green — framework is correct.** Choice of control system and commissioning budget are the gating decisions before fixture selection begins.