The material of a downlight housing determines three things: how well it dissipates heat, how long it lasts, and what it costs. This comparison covers the three materials used in LED downlight housings — die-cast aluminum, steel (stainless or cold-rolled), and plastic (PC or PP) — with specific data on thermal performance, durability, and cost trade-offs.
Published: September 4, 2026 | Last Updated: September 4, 2026 | Reading Time: 9 min
Author: ECOLEDKIT Technical Team
Related: What Is a LED Downlight Housing Kit? | COB Downlight Housings | LED Downlight Housing FAQ
Quick Comparison
| Property | Die-Cast Aluminum (ADC12) | Steel (SS304/CRS) | Plastic (PC/PP) |
|---|---|---|---|
| Thermal conductivity | ~96 W/m·K [1] | ~16 W/m·K (SS304) / ~50 W/m·K (CRS) | ~0.2 W/m·K |
| Density | 2.74 g/cm³ | 7.93 g/cm³ (SS304) | 1.20 g/cm³ (PC) |
| Max service temperature | ~350°C | ~750°C (SS304) | ~115°C (PC) / ~100°C (PP) |
| Corrosion resistance | Good (oxide layer) | Good (SS304) / Poor (CRS rusts) | Excellent (inherent) |
| Recyclability | >95% recovery rate, 5% of primary energy [2] | ~85% recovery (steel scrap) | Low — mixed polymer, limited recycling |
| Tooling cost | High (steel die mold $10K–50K) | Low (stamping die $2K–8K) | Moderate (injection mold $5K–20K) |
| Unit cost (housing) | $$ | $ (CRS) / $$$ (SS304) | $ |
| Typical application | Professional/commercial downlights | Budget commercial, industrial | Residential, ultra-low-cost |
Die-Cast Aluminum — The Professional Standard
Why it dominates
Die-cast aluminum is the material of choice for 80%+ of professional LED downlight housings. The reasons are thermal, structural, and economic:
Thermal performance: ADC12 aluminum alloy has a thermal conductivity of approximately 96 W/m·K [1]. This means heat from the LED transfers rapidly from the COB mounting surface through the housing body to the heat sink fins. A well-designed die-cast housing can maintain LED junction temperature 15–25°C below what a comparable steel or plastic housing would allow, directly extending LED lifespan.
Structural integrity: Die-casting produces a single-piece housing with integrated heat sink fins, driver compartment, and mounting features. No assembly, no joints, no thermal interfaces that degrade over time. The dimensional accuracy of die-casting (±0.1mm for critical dimensions) ensures consistent fit with lenses, reflectors, and spring clips.
Surface finish options: Die-cast aluminum accepts powder coating (60–120μm), electroplating, anodizing, and wet spray. Standard colors are white and black; custom options include sand-textured white, sand-textured black, gunmetal gray, and bright silver.
Recyclability: Aluminum can be recycled indefinitely with no loss of quality. The recycling process uses approximately 5% of the energy required for primary aluminum production [2]. This matters for projects with sustainability requirements.
Die-cast aluminum limitations
- Tooling cost. A new die-cast mold costs $10,000–50,000 depending on complexity. This is why housing suppliers have high MOQs for custom designs — the tooling must be amortized.
- Weight. Heavier than plastic (2.74 g/cm³ vs 1.20 g/cm³), though lighter than steel.
- Not suitable for corrosive environments. Without surface treatment, aluminum corrodes in salt-air or chemical-exposure environments. Powder coating or anodizing is required.
Steel — The Budget Industrial Option
Cold-Rolled Steel (CRS)
CRS housings are stamped from sheet steel and spot-welded or riveted into a housing shape. They are the cheapest metal housing option but have significant drawbacks for LED applications:
| Issue | Impact |
|---|---|
| Low thermal conductivity (~50 W/m·K) | LED runs hotter, shorter lifespan |
| Rust | Must be painted/coated; any scratch exposes bare steel |
| Stamped construction | Joints create thermal resistance; heat sink fins cannot be integrated |
| No dimensional precision | Stamping tolerances are ±0.5mm, causing lens/reflector fit issues |
CRS housings appear in ultra-budget residential downlights sold in some emerging markets. They are not suitable for professional or commercial projects.
Stainless Steel (SS304)
SS304 housings are used in specific industrial and marine environments where corrosion resistance is critical:
| Advantage | Limitation |
|---|---|
| Excellent corrosion resistance | Very low thermal conductivity (16 W/m·K) — LED overheating risk |
| High temperature tolerance | Heavy (7.93 g/cm³) — 3x aluminum weight |
| No surface treatment needed | Expensive — 3–5x aluminum cost |
| Cannot die-cast — must be fabricated from sheet |
SS304 housings are a niche product. For the vast majority of indoor LED downlight applications, aluminum provides better thermal performance at lower cost.
Plastic — The Residential Compromise
Polycarbonate (PC)
PC housings are injection-molded and used primarily in residential downlights where cost is the primary driver.
| Advantage | Limitation |
|---|---|
| Very low cost | Thermal conductivity ~0.2 W/m·K — effectively an insulator |
| Lightweight | Max service temperature 115°C — close to LED junction limits |
| Electrical insulation (no grounding needed) | UV degradation over time (yellowing) |
| Complex shapes possible | Cannot integrate metal heat sink effectively |
| No recyclability in practice (mixed polymer) |
The thermal problem is fundamental. LED junction temperatures in professional downlights reach 80–120°C. A plastic housing with 0.2 W/m·K thermal conductivity cannot transfer this heat away from the LED. The LED module must rely entirely on its own small heat sink, which is insufficient for power levels above 7–10W.
Polypropylene (PP)
PP is even cheaper than PC but has lower temperature tolerance (~100°C) and is more brittle over time. It is used only in the lowest-cost consumer downlights and is not suitable for any professional application.
Thermal Performance — The Deciding Factor
For LED downlights, thermal management is the primary material selection criterion. LED lifespan is inversely related to junction temperature — every 10°C increase roughly halves the LED’s rated life [3].
Comparative thermal simulation (typical 15W COB downlight)
| Material | Heat Sink Design | Estimated Junction Temp | Projected L70 Life |
|---|---|---|---|
| Die-cast aluminum (ADC12) | Integrated fins, 96 W/m·K | ~75°C | ~50,000 hours |
| Cold-rolled steel | Separate stamped fins, 50 W/m·K | ~90°C | ~25,000 hours |
| Stainless steel (SS304) | Fabricated, 16 W/m·K | ~110°C | ~10,000 hours |
| Plastic (PC) | No metal heat sink, 0.2 W/m·K | ~120°C+ | ~5,000–8,000 hours |
These are approximate estimates based on material thermal conductivity and typical housing geometry. Actual performance depends on housing design, ambient temperature, and LED/driver selection.
The conclusion is clear: for any professional or commercial LED downlight application above 7W, aluminum is the only material that provides adequate thermal management.
When Each Material Makes Sense
| Scenario | Recommended Material | Reason |
|---|---|---|
| Professional/commercial downlight (7W+) | Die-cast aluminum | Thermal performance + durability + recyclability |
| Residential budget downlight (5–7W) | Die-cast aluminum or PC | Aluminum preferred for longevity; PC acceptable if cost is critical |
| Marine/coastal environment | SS304 (with external heat sink) | Corrosion resistance outweighs thermal penalty |
| Ultra-low-cost consumer market | PC or PP | Cost is the only priority |
| High-power downlight (30W+) | Cold-forged aluminum or extruded aluminum | Higher thermal conductivity (200–230 W/m·K) needed |
ECOLEDKIT’s Material Position
ECOLEDKIT uses four aluminum variants across the housing range, selected by power range and thermal requirement:
| Material | Used In | Thermal Conductivity | Power Range |
|---|---|---|---|
| Die-cast aluminum (ADC12) | 6101/6102/6103/6105/6205/6206/6206A/6213A | ~96 W/m·K | 5–40W |
| Cold-forged aluminum | 6201/6203/6216 | ~200–230 W/m·K | 10–35W |
| Extruded aluminum | 6208/6209/6210 | ~200 W/m·K | 7–60W |
| Aluminum profile | 6211/6212/6213/6215 | ~160–200 W/m·K | 7–65W |
No steel. No plastic. Every housing is aluminum because aluminum is the only material that provides professional-grade thermal management for COB LED downlights.
Key Takeaways
- Die-cast aluminum (ADC12) is the professional standard — 96 W/m·K thermal conductivity, single-piece construction, recyclable.
- Steel housings have poor thermal conductivity (16–50 W/m·K) and are unsuitable for most LED downlight applications.
- Plastic housings are thermal insulators (0.2 W/m·K) — acceptable only for low-power (≤7W) residential downlights.
- LED lifespan halves for every ~10°C increase in junction temperature. Material choice directly determines product life.
- Aluminum recycling uses 5% of primary production energy — a sustainability advantage steel and plastic cannot match.
Standards and official sources
Die-cast aluminum alloy grades used in downlight housings (including ADC12-type alloys) correspond to standardized die-casting specifications published by international standards bodies.
- ASTM International — standards for aluminum die castings (ASTM B85 series)
References
Related reading: SKD component supply.