Why thermal management matters in LED lighting: A guide for designers, contractors, and sustainability experts

LEDs have become the go-to solution for architectural, retail, and commercial lighting, and for good reason. They’re compact, efficient, and long-lasting. But behind the scenes, there’s a critical factor that determines whether those promises hold true: thermal management.

This article explains how and why LEDs generate heat, what happens when it’s not managed properly, and how materials like aluminium can quietly improve performance, design freedom, and sustainability, all without compromising your aesthetic vision.

Do LEDs emit heat?

Yes, LEDs do get hot. Although they’re far more efficient than halogens or fluorescents, LEDs still generate heat, primarily at the P-N junction, where electrical energy is converted into light (see diagram below).

Unlike incandescent bulbs that radiate heat outward, LEDs retain heat internally. This makes heat management in LEDs essential: if that thermal energy isn’t properly dispersed, it accumulates, leading to performance degradation and premature failure.

What causes LEDs to heat up (and why it matters)

During the process of electroluminescence, when electrical energy is converted into visible light, not all input energy becomes light. As with all lighting technologies, a portion of that electrical energy is also converted into heat energy. This heat is primarily generated at the P-N junction, the core site where light is emitted.

If this heat isn’t effectively managed, the temperature within the P-N junction can rise above its maximum rated threshold. When this happens, the LED can overheat and, in extreme cases, can suffer catastrophic failure.

Catastrophic failure is exactly what designers and users want to avoid. It occurs when thermal energy builds up inside the LED to a point where it can no longer maintain its performance, and often results in:

• A drop in lumen output
• Shifts in colour temperature (Kelvin)
• Flickering or inconsistent performance

These effects reduce the LED’s ability to illuminate a space or object properly, and in many cases, they necessitate the full replacement of an LED system prematurely.

What happens if heat isn’t managed properly in LEDs?

Without effective heat management, LED systems begin to degrade in performance, efficiency, and reliability. In some cases, they may fail entirely. This is not just a theoretical risk; it’s a well-documented consequence of sustained thermal stress at the P-N junction, where light is generated and heat is concentrated.

Here’s what can happen when heat isn’t controlled in an LED system:

1. Shorter system lifespans

As the junction temperature rises, the LED’s light output diminishes over time. This is a cumulative process, not immediate failure, but a steady drop in brightness that can lead to an LED reaching its L70 threshold far earlier than intended (more on this later).

• At 25°C junction temperature, an LED might last 60,000+ hours
• At 85°C, that same LED could reach L70 in under 25,000 hours
• At >100°C, you may see lumen degradation in just a few thousand hours

In performance-focused environments like retail, galleries, or workplace fit-outs, this means lighting consistency degrades noticeably, compromising the user experience or display integrity.

2. Colour shift and chromatic instability

Excessive heat affects not only brightness but also colour accuracy. When thermal energy builds up:

• Phosphor-based materials used to produce white light can degrade
• The LED’s correlated colour temperature (CCT) may drift, shifting from warm to cool or vice versa
• CRI (Colour Rendering Index) may fall, impacting how true-to-life colours appear under the light

This is especially problematic in applications where visual consistency matters, such as hospitality, brand-led retail spaces, or interior design projects, where lighting tone is a key aesthetic element.

3. System-wide impact

Thermal stress doesn’t only affect the LED chip. Over time, it can also:

• Degrade the PCB material (especially in FR4 boards vs. MCPCBs)
• Dry out or crack TIM layers, reducing heat transfer
• Cause lens warping or yellowing
• Lead to solder joint fatigue, increasing the likelihood of flicker or intermittent operation

This compounds maintenance issues. Instead of replacing a single diode, entire modules or luminaires may need to be swapped out, particularly in sealed units or integrated installations.

4. Increased maintenance and operating costs

Overheating shortens system lifespan, increases failure rates, and often means there’s a need for early replacements. In commercial settings, this can lead to:

• Higher labour costs for maintenance
• Disruption to business operations
• Damaged brand perception from visibly inconsistent lighting

Understanding L70: Why temperature dictates LED lifespan

There is a well-established, direct correlation between the temperature of the P-N junction and the rate at which an LED degrades. In testing environments, engineers have found that higher junction temperatures accelerate lumen depreciation, meaning the hotter the LED runs, the faster it dims over time.

This is typically measured using the L70 standard. When an LED’s output drops to 70% of its original lumen level, it is considered to have reached the end of its useful life. Beyond this point, it may no longer deliver the quantity or quality of light required by users.

For lighting specifiers, this means that thermal management directly impacts LED lifespan. Controlling junction temperature through thoughtful design (such as with integrated aluminium heat sinks) helps extend operation.

Where lifespan is critical, such as in retail fit-outs, commercial interior lighting installations, or LED display lighting, ensuring a system operates below its thermal ceiling is essential.

What are heat sinks in LEDs?

A heat sink is a thermal management component designed to absorb and dissipate unwanted heat away from sensitive electronics, particularly the P-N junction of an LED.

Heat sinks work through passive cooling: they conduct thermal energy from the PCB to a larger surface area exposed to ambient air. The greater the surface area and the higher the thermal conductivity of the material, the more effective the cooling process becomes.

There are several factors that define heat sink performance:

• Material – Aluminium is widely used due to its excellent thermal conductivity (~205 W/mK), light weight, and formability. Copper is thermally superior but heavier, costlier, and less practical in architectural applications.
• Design geometry – Finned, extruded, or folded surfaces increase surface area, enhancing convection.
• Orientation and environment – Heat sinks need airflow to perform optimally. In recessed or enclosed installations, the role of material choice and thermal design becomes even more critical.

In many of Unibox’s luminaires, the aluminium housing is structurally and thermally integrated, meaning the body of the light fitting doubles as its heat sink. This approach enables slimmer designs, simplifies component architecture, and delivers built-in thermal performance without visual compromise.

What Is the best way to dissipate heat in LEDs?

The best way to dissipate heat in LEDs is to design for passive cooling from the ground up — using thermally conductive materials, efficient mechanical interfaces, and geometry that maximises surface area and airflow.

Here’s what effective thermal dissipation looks like:

1. Use high-conductivity materials

Materials like aluminium are essential. They quickly draw heat away from the LED’s P-N junction and allow it to spread across a larger area. Plastic or composite housings trap heat and should be avoided in performance-critical applications.

2. Maximise surface area

Heat sinks should be designed with fins, grooves, or extruded shapes to increase surface area. The larger the surface area, the more efficiently heat can transfer to ambient air via convection.

3. Use premium thermal interfaces

Using a high-quality thermal interface material (TIM), like a thermally conductive adhesive or pad, between the PCB and the heat sink ensures a low-resistance thermal path. Without this, heat can bottleneck and stress the diode.

4. Promote natural airflow

Fixtures should allow for unobstructed airflow, particularly in enclosed environments. Where airflow is limited (e.g. recessed displays or architectural niches), the heat sink must compensate with better conductivity and greater surface exposure.

5. Integrate thermal function into the fixture design

Rather than bolt-on heat sinks, integrated thermal solutions – like Unibox’s aluminium-bodied luminaires – offer seamless dissipation, reduced component count, and better long-term reliability. This approach simplifies installation and ensures thermal performance is embedded in the product, not added afterward.

In essence, the best way to dissipate heat in LEDs is not just to manage it reactively, but to build thermal intelligence into the design from the very start.

Why aluminium is ideal for LED heat management

Aluminium is the material of choice for most LED heat sinks, and not just because it’s lightweight and corrosion-resistant. It offers a unique combination of thermal, mechanical, and fabrication advantages that make it ideal for integrated lighting design.

Key properties include:

• High thermal conductivity: Aluminium’s thermal conductivity (typically around 205 W/mK) allows heat to be rapidly transferred away from the LED.
• Extrudability: Aluminium can be extruded into precise, complex profiles – perfect for architectural lighting applications where space is tight and form matters.
• Dual functionality: In Unibox lighting systems, the aluminium profiles serve both structural and thermal roles, reducing the need for additional components or attachments.
• Sustainability: Aluminium is infinitely recyclable and retains its properties through multiple life cycles, making it a strong choice for circular design strategies.

Compared to materials like plastics or composites, which offer limited thermal performance, aluminium enables passive cooling at scale, ensuring reliable LED function in a wide range of environments, from retail to exhibitions and workplaces.

Where thermal design matters most: Application examples

Not all lighting environments are created equal, and when airflow is limited, runtimes are long, or design takes priority, thermal performance can make or break a system.

1. Retail displays

LED lighting in retail often runs 10–16 hours per day in enclosed fixtures or cabinetry, where heat build-up is more likely. A well-designed aluminium heat sink ensures these systems don’t overheat, even in tight spaces, helping preserve both lighting quality and brand presentation.

Explore our lighting and display solutions for retail spaces.

2. Museums & galleries

Many artefacts and artworks are sensitive to temperature and light degradation. LEDs must operate with minimal heat spill and maintain colour stability over long periods. Efficient heat sinks prevent thermal drift that can distort colour temperature or reduce light fidelity (important for CRI and TM-30 standards).

3. Offices & commercial interiors

In spaces designed for wellbeing and productivity, WELL and BREEAM certifications often require energy efficiency, longevity, and human comfort. Lighting that degrades due to thermal stress can underperform or flicker, leading to user dissatisfaction. Aluminium heat management supports consistent, stable performance across a long lifecycle.

Read our blog about the psychological impacts of lighting to learn more about specifying human-centric interior lighting solutions that support user well-being. 

4. Exhibitions & brand pop-ups

Modular installations demand lightweight, easily deployable lighting systems. Traditional active cooling isn’t practical, but passive heat sinks built into aluminium framing structures (like Unibox’s systems) ensure reliability even under variable conditions.

5. Hospitality & wellness

Design is everything in wellness spaces, and bulky, visually uncomfortable lighting systems break the ambience. Integrated thermal design allows for cleaner lines, quieter performance, and fewer maintenance issues in design-led environments like spas, gyms, or boutique hotels.

Explore our lighting and display solutions for hospitality venues

Common mistakes in LED heat management

Even experienced professionals can overlook thermal design, especially when lighting is specified late in the project timeline or selected primarily for aesthetics. Here are some of the most frequent (and costly) oversights:

1. Assuming that LEDs don’t get hot

Because LEDs don’t emit heat in the same way incandescent bulbs do (via infrared radiation), it’s easy to assume they don’t get hot at all. In reality, the internal junction temperature can reach critical levels, especially in confined installations. The surface may feel cool, but the component can still be overheating.

2. Using plastic-based fixtures in high-load environments

Plastics are poor thermal conductors. When used as the primary body of a luminaire in demanding settings, they can trap heat rather than dissipate it. This limits the LED’s lifespan and increases the risk of catastrophic failure. Aluminium, by contrast, actively removes heat from the diode’s core.

3. Overlooking heat sink orientation

Heat sinks rely on convection to transfer thermal energy into the surrounding air. If the sink’s orientation restricts airflow (for example, mounting fins vertically when there is a horizontal airflow) its performance can be compromised.

4. Failing to consider ambient conditions

Spec sheets often state performance based on 25°C lab conditions. In real-world use – like in ceiling coves, enclosed signage, or direct-sunlit atriums – ambient temperatures may be much higher. Without a buffer built into the thermal design, the system can degrade rapidly.

5. Treating thermal management as an afterthought

Retrofitting heat sinks, especially in architectural lighting, can be difficult, unsightly, and space-intensive. The best results come from integrated thermal design at the outset, such as using aluminium housing that doubles as a heat sink. 

This is one of the reasons why we advise all specifiers to involve their design or development partner from the beginning of a project. Get in touch with our team to learn more about how Unibox adds value from start to finish.

Design integration: Managing heat without compromising aesthetics

In architectural and commercial lighting, performance must often work behind the scenes. Lighting systems need to blend seamlessly into ceiling lines, wall details, or custom displays – all while delivering consistent output and longevity.

This is where integrated thermal management becomes a design enabler, not a constraint.

At Unibox, many of our luminaires use precision-extruded aluminium profiles that act as both the structural housing and the heat sink. This approach enables:

• Slimline designs without bulky external components
• Clean visual finishes that align with contemporary interior schemes
• Reduced component count, simplifying installation and maintenance
• Reliable passive cooling even in sealed or recessed installations

By embedding thermal management into the luminaire body, lighting designers are free to prioritise form, line, and light distribution without sacrificing reliability. No fans, vents, or creative compromises, meaning the lighting system works with the space, not against it.

Thermal management, sustainability, and circular design

Thermal design is often framed as an engineering concern, but it’s just as relevant for sustainability consultants and ESG-focused stakeholders.

Product longevity = Lower environmental impact

An LED system with robust heat management maintains output and stability for decades, avoiding early failure and unnecessary replacement.

Maintaining efficiency over time

LEDs that overheat consume more energy to produce the same lumen output. Thermal stability helps systems maintain their efficiency metrics, supporting operational carbon reduction strategies.

Reduced maintenance and waste

Every lighting replacement involves labour, parts, and disruption. Proper thermal design stretches the maintenance cycle, especially important in large-scale or difficult-access installations.

Material circularity

Aluminium is infinitely recyclable. By using aluminium for both structure and thermal performance, Unibox supports circular design thinking, helping projects align with BREEAM, WELL, or LEED targets.

Regulatory compliance

Specifications for many building certification frameworks require demonstrable performance over time. Thermal degradation can disqualify a product from meeting lumen maintenance or energy usage criteria.

Get in touch with our team to learn more about how Unibox works with you to engineer solutions that are sustainable by design.

Final thoughts

At Unibox, we integrate thermal performance into the core of every lighting solution we develop. Our aluminium-based luminaires are engineered to dissipate heat passively, maintain colour stability, and extend product lifespan, all while offering the clean, minimal aesthetic that modern environments demand.

If you’re looking to specify lighting systems that combine form, function, and built-in reliability, explore our full range of interior lighting, LED lightboxes, LED signage, and more, or get in touch with our team for technical guidance and tailored recommendations.