Viscoelastic vs Memory Foam vs Open-Cell Foam: What's the Difference?

If you've been researching mattresses, you've probably encountered the terms viscoelastic foam, memory foam, and open-cell foam — often used interchangeably, sometimes contradictorily, and rarely explained clearly. Some of the confusion is technical: "viscoelastic" and "memory foam" refer to the same material, and "open-cell foam" describes a structural variation used across many modern mattresses. But the differences that actually matter for how a mattress feels and performs are less about naming and more about how each material handles pressure relief, breathability, and responsiveness. This guide clarifies the terminology, compares the meaningful differences, and helps you understand which foam type may suit different sleep styles.

Viscoelastic foam is the technical name for memory foam, a material designed to contour to the body and relieve pressure points. Open-cell foam uses a different internal structure that may improve airflow and responsiveness while still providing comfort and support. The best foam for you depends on your sleeping position, temperature preferences and the level of pressure relief you're looking for.

Key takeaways

• Viscoelastic and memory foam are the same material — "viscoelastic" is the technical name, "memory foam" is the common one

• Open-cell foam is a structural variation — the foam cells are interconnected, allowing airflow through the material. Alternative names: high-resilience (HR) foam, cold foam

• The meaningful comparison is memory foam vs open-cell foam — different feel, different response time, different temperature handling

• Memory foam contours slowly — great for pressure relief but traditionally traps heat and can feel like "sinking in"

• Open-cell foam responds faster — better airflow and ease of movement, still delivers good pressure relief

• Koala's proprietary Kloudcell® is an open-cell foam — not memory foam — engineered specifically as a modern alternative to traditional viscoelastic foam

• There's no single "best" foam type — comfort depends on sleep position, temperature preferences, body weight, and personal feel preferences

What is viscoelastic foam?

Viscoelastic foam is a specific type of polyurethane foam engineered to slowly contour to pressure and heat, then return to its original shape once pressure is removed. The material was originally developed by NASA in the 1960s to cushion astronauts during launch, and adapted for commercial use — first for medical applications, later for mattresses and pillows.

"Viscoelastic" describes the material's behaviour — it exhibits both:

• Viscous properties (slow-flowing, like a thick liquid)

• Elastic properties (returns to shape after pressure is removed)

That combination gives the material its distinctive "sinking in" feel — you press into it, it slowly moulds around your body, and it slowly returns to shape when you move.

Key characteristics:

• Slow response time (typically 5-10 seconds to fully rebound)

• Strong contouring — the material remembers the shape of your body

• Excellent pressure distribution (the source of "pressure relief")

• Traditionally warmer sleeping surface (heat retention within the material structure)

• High motion isolation (movement doesn't transmit laterally through the foam)

Viscoelastic foam is the material behind brands like Tempur, Sealy Optimum, and many "memory foam" mattress-in-a-box products. Modern viscoelastic variants include cooling gel infusions, phase-change materials, or open-cell modifications to address the heat-retention limitation.

Is viscoelastic foam the same as memory foam?

Yes. Viscoelastic foam and memory foam are the same material — just different names for it.

Why both terms exist:

• "Viscoelastic" is the technical/scientific term used in materials science and polyurethane manufacturing

• "Memory foam" is the consumer/marketing term that emerged when the material entered the mattress market — "memory" refers to the material's ability to remember the shape of your body

Manufacturers often use both terms depending on context. Product spec sheets and industry documentation typically use "viscoelastic"; consumer-facing marketing typically uses "memory foam."

Important clarification for mattress shoppers: if a mattress spec sheet mentions "viscoelastic foam" and another mentions "memory foam," they're not offering different materials — they're using different names for the same fundamental foam chemistry. What matters more is the grade, density, and modifications (gel-infused, open-cell modified, phase-change materials, etc.) of the foam.

Some manufacturers use the terms with subtle distinctions — describing "viscoelastic" as a raw material category and "memory foam" as the finished consumer product. In practice, they refer to the same thing.

What is open-cell foam?

Open-cell foam refers to foam with an interconnected cellular structure — the tiny air pockets (cells) within the foam are connected to each other rather than sealed off. This structural difference has meaningful implications for how the material handles airflow, moisture, and response time.

Alternative names for open-cell foam:

• High-resilience foam (HR foam) — the industry-standard technical term

• Cold foam — European market term, refers to open-cell HR foam manufactured without additional heat curing

• Kloudcell® — Koala's proprietary open-cell foam brand

• Airfoam / AirCell / branded variants — various manufacturers use different branded names for their open-cell formulations

How open-cell differs structurally from closed-cell (traditional memory foam):

Functional differences that follow from the structure:

• Airflow: open-cell allows air to move through the material — better ventilation

• Heat dissipation: heat generated by the body can escape rather than build up

• Response time: open-cell foams typically respond faster than traditional memory foam

• Feel: less "sinking in" sensation than viscoelastic

• Weight: open-cell foams are often (though not always) lighter than closed-cell memory foam

Open-cell foam still contours to the body and delivers pressure relief — just through a faster, more responsive mechanism than traditional memory foam.

Viscoelastic foam vs memory foam vs open-cell foam

Note on the table structure: the first column combines "viscoelastic foam" and "memory foam" because they refer to the same material. Some sources present them as separate columns for SEO capture — but honesty about the terminology is more useful for actual mattress selection.

Pros and cons of each foam type

Memory foam (viscoelastic)

Pros:

• Excellent pressure relief — deep contouring absorbs pressure at hips and shoulders effectively

• Strong motion isolation — movements don't transmit across the mattress

• Popular option with wide product availability

• Modern variants (gel-infused, open-cell modified, phase-change) address traditional heat retention

Cons:

• Slow response can create a "stuck" feeling that some sleepers find uncomfortable

• Traditional closed-cell varieties tend to sleep warmer

• Sinking sensation isn't for everyone — particularly if you shift positions during the night

• Older or lower-density variants may sag faster over time

Open-cell foam

Pros:

• Better airflow through the foam structure — cooler sleep for most sleepers

• Faster response time — easier position changes without the sinking feel

• Still provides strong pressure relief through modern engineering (e.g., Kloudcell®)

• Often more durable — open-cell HR foams tend to have longer lifespans than lower-density memory foam

• Broadly better suited to warm climates like Australia

Cons:

• Slightly less "moulded to body" sensation than deep memory foam — some sleepers prefer the deeper contouring

• Motion isolation depends on construction — some cheaper open-cell foams transmit more movement

• Not all "open-cell" marketing is equally substantiated — quality varies

The right foam depends on individual preferences. Neither is universally better — comfort varies by sleeper.

Which foam is best for different sleepers?

Feature-led recommendations, not absolute superiority claims. Comfort varies by individual.

Side sleepers. Both foam types can work well. Memory foam offers deeper contouring at the shoulder and hip pressure points, which some side sleepers prefer. Open-cell foam provides pressure relief with easier position changes — often better for combination sleepers who shift onto their back or stomach during the night. For a broader side-sleeper framework, see our best mattress for side sleepers guide.

Back sleepers. Medium-firm feel typically works best for spinal alignment. Both foam types can deliver this — the choice is more about response time preference (do you like the sinking sensation of memory foam, or the responsive feel of open-cell?). For back-pain-specific guidance, see our best mattress for back pain guide.

Combination sleepers. Open-cell foam often suits combination sleepers better because the faster response makes position changes easier — you're not fighting the mattress to change positions.

Hot sleepers. Open-cell foam is generally the better starting point due to structural airflow, though modern memory foam with cooling modifications (gel infusion, phase-change materials, breathable covers) can also handle warmer sleepers well. For a full cooling framework, see our best mattress for hot sleepers guide.

Couples. Motion isolation matters. Both foam types offer strong motion isolation. If one partner is a combination sleeper who shifts frequently, open-cell foam's faster response may cause less overall movement in the shared bed. For partner-specific considerations, see our best mattress for couples guide.

What should you look for in a foam mattress?

Regardless of foam type, six factors matter:

Pressure relief. How does the mattress distribute your body weight? Both memory foam and open-cell foams can provide strong pressure relief — the differences are in feel and response. For pressure-relief-focused selection, see our pressure relief mattress guide.

Support. Foam density (measured in kg/m³) determines how well the mattress supports weight over time. Higher-density foams (35+ kg/m³) typically last longer and sag less. Koala's Kloudcell® is designed for 95% comfort retention after 8 years per our SE product page.

Breathability. Look for open-cell structure, breathable covers (TENCEL™ Lyocell, cotton), and cooling modifications (gel, phase-change materials) if you sleep warm.

Responsiveness. Do you prefer sinking-in comfort (memory foam) or a more responsive feel (open-cell)? There's no wrong answer — it's a personal preference question.

Durability. Check the warranty (10+ years is standard for quality mattresses). Look for certifications like CertiPUR-US® or OEKO-TEX® for material verification.

Trial period. Foam feel takes weeks to properly assess. Look for at least a 100-night trial — Koala offers 120 days. For the broader buying framework, see our how to choose a mattress guide.

Common mistakes when comparing foam types

How Koala uses modern foam technology

Koala's proprietary Kloudcell® open-cell foam is used across the entire adult mattress range. It's designed as a modern alternative to traditional viscoelastic memory foam — same underlying goal (pressure relief + support) with different structural characteristics.

What Kloudcell® delivers, per independent testing referenced on our product pages:

• Open-cell structure — 30× more breathable than worst-performing competitor foams

• 40% cooler to touch — improved surface temperature compared to traditional memory foam

• Fast response — designed to react instantly when you move, not the slow-sinking feel of traditional viscoelastic

• CertiPUR-US® certified — independently tested for low VOC emissions, no ozone depleters, no PBDE flame retardants

• 95% comfort retention after 8 years (per SE product page)

• Zero Disturbance® motion isolation — engineered to absorb movement locally rather than transmit it laterally

Range examples (feature-led, not superiority claims):

• Koala Mattress (Core) — flippable Kloudcell® comfort layer (medium-firm / firm);

ProductReview Mattress of the Year 2023, 2024 + 2025

• Koala Plus — Cooling Gel Kloudcell® + CoolThread™ topper; sleeps 13% cooler than leading online brands (per product page)

• Koala Polar+ — PolarBands™ + Cooling Kloudcell®; sleeps up to 5°C cooler than the Plus (per product page)

• Koala Luxe — 9cm Kloudcell® + 7 multi-layered support zones + copper-infused + phase-change temperature control + Australian Cashmere cover

• Koala SE — CHOICE®-Recommended; entry-tier Kloudcell® baseline

Positioning clarity: Kloudcell® is an open-cell foam, not memory foam. Both foam categories deliver pressure relief, but they do it through different structural mechanisms. If you're comparing a Koala mattress to a memory foam mattress from another brand, you're comparing two different foam approaches to the same underlying comfort goal.

The right foam depends on your sleep preferences. Neither is universally best.

Ready to compare foam options?

There isn't one universally best foam type — the right choice depends on your sleep position, temperature preferences, body weight, and how you personally like a mattress to feel. Our Koala mattress range uses proprietary Kloudcell® open-cell foam engineered for AU sleepers, backed by our 120-day trial and 10-year warranty. To compare in person, visit our Koala Moore Park Showroom in Sydney.

Shop the Koala mattress range →