# LDD-17 · Soffit Lighting + Serviceability

> **Status:** 🟢 LOCKED.

## One-line intent

The building glows, not shines — and zero-demolition maintenance forever.

## Why this matters

Soffit lighting that wraps a perimeter with concealed linear LED is a defining aesthetic of disciplined modern architecture. The serviceability rule — bottom-access diffusers + indoor drivers — turns a hidden system into a maintainable one. Without that rule, soffits become dust-and-bug graveyards that nobody ever opens.

## Locked decisions

**Primary system**

- Concealed linear LEDs
- Full perimeter coverage

**Secondary**

- Minimal downlights as needed

**Light quality**

- Soft wash
- No hotspots

**Color**

- Default warm white (2700K or 3000K, per LDD-08 standard)
- RGB only for events (not as default)

**Serviceability**

- Protected but accessible
- Aluminum channel system
- Bottom-access diffusers (snap-on/snap-off lenses)
- Segmentation: 16'–24' channel runs (so a failed segment doesn't strand a 50' run)

**Drivers**

- **Always indoors** — never in the soffit, never exterior-exposed

**Outcome**

- Zero demolition required for maintenance ever

## Open items / requires engineer review

- **Driver pocket location strategy** — indoor pockets need to be accessible without demolition. Where do they live? Behind hinged access panels in interior walls.
- **LED tape spec** — 24V (compatible with LDD-08 framework), CRI ≥ 90, dim-to-warm vs static white, density (60/m, 120/m, 240/m).
- **Diffuser depth + lensing** — affects spread angle and hotspot risk.
- **Heat dissipation** — high-density LED tape in an aluminum channel needs heat sink contact. Aluminum channel does this passively; verify thermal margin.
- **Wet rating** for exterior soffits — IP rating of LED tape and channel.
- **Cleaning regimen** — soft brush, no solvent on diffuser? Document.
- **Failure / replacement** — every channel segment should be field-replaceable in <30 minutes without tools.

## Cross-references

- ← [LDD-08 lighting framework](08-lighting-framework.md) — soffit is one expression of the ambient indirect layer.
- → [LDD-23 build rules](23-build-rules.md) — execution discipline.

## Cost drivers

- **Aluminum channel + diffuser + LED tape** at 24V: $35–70/lf installed for a true premium system.
- **Perimeter linear footage** of the building: ~360' exterior + ~200' selected interior soffit runs ≈ 560 lf.
- **Driver pockets + commissioning**: $4–8K.

**Likely-case rollup: $25–50K for soffit lighting** (this is part of the $70K LDD-08 lighting budget).

## Air-gap concerns

1. **Indoor driver pockets vs hidden wall locations.** "Drivers indoors, accessible, never buried" is the right rule. But "accessible" needs an actual access strategy — hinged panel, removable wood panel, dedicated closet shelf. Specify per pocket.
2. **Aluminum channel thermal contact.** If the LED tape isn't pressed firmly against the channel back wall, heat dissipation suffers and tape lifespan halves. Use thermal tape or thermal adhesive at install.
3. **Hot dim-to-warm bands.** If 2700K is the default but social/evening scenes want warmer (~2200K), specify dim-to-warm tape now. Switching later means re-running 560 lf of tape.
4. **Exterior soffit wet-rating.** IP65 minimum for exterior. Don't use indoor-rated tape in exterior soffits to save cost; the difference is $2–5/lf and the failure mode is gnarly.
5. **Replacement parts stockpile.** When you commission, buy 10% spare tape + 4–6 spare drivers + diffusers. Common tape models go EOL in 3–5 years; matched color binning matters.

## Diagram

(no dedicated SVG — soffit is integrated with ceiling hierarchy. See [ceiling hierarchy](../../diagrams/10-ceiling-hierarchy.svg).)

## Status

🟢 **Green — execution discipline is excellent.** Lock LED spec + driver pocket strategy with the lighting designer before procurement.