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What Is Memory Foam?

Let's begin with a simple question: what is a memory foam mattress? By definition, these mattresses have at least one comfort layer made of memory foam, and some also have memory foam transitional layers for added support. Other components, such as the cover and support core, may be made from materials other than memory foam.

In recent years, memory foam mattresses have become very popular with sleepers. Also known as viscoelastic polyurethane foam, memory foam becomes softer when exposed to body heat. This allows the foam to adapt and contour to your body, creating a pressure-relieving cradle as you sink beneath the surface. These qualities set memory foam apart from other mattress materials that feel springier and more responsive.

We'll take an in-depth look at the history of this material up to the present day, list different types of memory foam, and discuss some notable advantages – and disadvantages – of sleeping on a memory foam mattress.

History of Memory Foam

NASA researchers first developed memory foam in the mid-1960s for use as a cushioning material in aircraft. Memory foam was notable at the time for its temperature sensitivity. The material became softer when exposed to body heat, then returned to its original shape after cooling down. This led to early names such as "spring back foam" and "temper foam."

Memory foam was widely used in medical facilities for bedridden patients. The foam was engineered to contour closely and reduce pressure, and this helped prevent health problems for immobile people (such as bedsores and gangrene). Veterinarians began using memory foam, as well, which proved particularly useful for horses with leg injuries.

Memory foam mattresses began appearing in the late 1980s. One of the pioneering brands was Fagerdala World Foams, a Swedish company that introduced a memory foam mattress dubbed the "Tempur-Pedic Swedish Mattress." The foam was brought to the U.S., and the Tempur-Pedic mattress brand launched shortly thereafter. Tempur-Pedic remains one of the most popular memory foam mattress brands to this day.

Memory foam mattresses earned an extra boost from "bed-in-a-box" brands, which began popping up in the late 2000s. These companies primarily sell mattresses online and offer free ground shipping to customers. In order to fit inside a standard shipping box, the mattress must be compressed, wrapped in plastic, and vacuum-sealed. Memory foam handles compression very well due to its excellent shape recovery, and many beds in a box are memory foam models.

Types of Memory Foam

Standard memory foam is produced by mixing polyurethane, water, and hydrocarbons. This yields a foamy, porous substance with open cells that promote airflow through the material – hence the name, "open-cell" memory foam. Manufacturers may also use additional chemical fillers and agents to soften the foam and make it more breathable. Memory foam is also known as viscoelastic polyurethane foam; viscoelastic refers to the material’s temperature sensitivity and ability to recover its full shape when cool.

Memory foam differs from standard polyfoam, which is also commonly used in mattresses. Memory foam responds slowly to your body, resulting in noticeable contouring as you sink into the material. Polyfoam is less temperature-sensitive and more responsive. It will conform to your body a bit, but you won't experience the same pressure-relieving cradle that you receive from memory foam.

That said, memory foam tends to sag more and does not provide as much support as polyfoam. For this reason, mattresses with memory foam comfort layers are almost always reinforced with denser polyfoam layers.

Memory foam qualities and characteristics vary from mattress to mattress. Differences between memory foam models often come down to these factors:

Density: Density refers to how much memory foam weighs, and is expressed in pounds per cubic foot (PCF). Low-density memory foam does not conform as closely to the body and is less durable, but it also absorbs minimal body heat, which allows the surface to resist heat build-up. High-density memory foam offers targeted conforming and consistent pressure relief, as well as exceptional durability – but for many sleepers, the material feels excessively warm. Medium density is essentially a compromise between low and high density. The table below breaks down key differences between the three density types.

Density Level Low Medium High
PCF Less than 4 PCF 4 to 5 PCF More than 5 PCF
Durability Poor to fair Fair to good Good to very good
Body-Conforming Moderate to close Close to very close Very close
Heat Retention Good to very good Fair to good Poor to fair
Motion Isolation Good to very good Very good Very good
Odor Potential Fair to good Fair Poor
Average Price $$ $$$ $$$$

Firmness: When discussing mattresses, we use a 1-10 scale to evaluate firmness with 1 being the softest and 10 the firmest. Most mattresses sold today fall between 3 and 8. How soft or firm a memory foam mattress feels will impact how comfortable and supportive the mattress feels. However, your body weight and sleep position are also important for determining a bed's ideal firmness level.

For example, a back or stomach sleeper who weighs more than 230 pounds will probably feel most comfortable on a firmer bed that sinks less and feels more supportive. A side sleeper who weighs less than 130 pounds, on the other hand, will probably prefer a softer memory foam mattress that conforms closely to improve spinal alignment and reduce pressure points.

Keep in mind these recommendations are based on feedback, making them subjective. You should test out memory foam mattresses with different firmness levels to determine which feel is right for you.

Cooling Components: Standard memory foam has many advantages for sleepers. Despite its open-cell structure, the material may absorb and trap a fair amount of body heat. This can lead to excessive warmth on the bed's surface.

To counteract this heat retention, some manufacturers infuse cooling agents into their memory foam layers. These substances can prevent heat build-up on the surface. Common cooling components for memory foam beds include gel beads, copper, bamboo, and graphite. Some memory foam models also feature phase-change material (PCM) infused into the cover.

PCM is designed to absorb heat from your body until the surface reaches a certain temperature, at which point it will maintain a constant temperature throughout the night – regardless of how hot you feel.

Pros and Cons of Memory Foam

Advantages of memory foam in a mattress include:

  • Close Conforming: Memory foam contours to the body much closer than polyfoam, latex, and other materials used in mattress comfort layers. This creates a distinct feeling many liken to sleeping "in" – as opposed to sleeping "on" – the mattress. This may be a benefit or a drawback, depending on your personal preferences, but many memory foam mattress owners report high satisfaction ratings.
  • Pressure Relief: As memory foam cradles and supports your body, you'll likely feel less pressure in the shoulders, hips, and other sensitive areas. Close conforming can also improve spinal alignment for side sleepers.
  • Motion Isolation: Memory foam absorbs movement from sleepers and isolates it to certain areas of the bed. This can be particularly beneficial for couples, since many people awaken easily when their sleep partner shifts positions and their movement transfers across the surface. High-density memory foam provides the best motion isolation, but any memory foam mattress should minimize movement-related sleep disruptions fairly well.
  • Noise Potential: Memory foam mattresses are constructed with polyfoam support components to reinforce the comfort layers. All of these materials are completely silent when bearing weight. Other mattresses may be louder due to their internal components, such as innersprings, hybrids, and airbeds.

Disadvantages of memory foam include:

  • Questionable Durability: Memory foam becomes softer with age. After a few years of sleeping on a memory foam mattress, you may begin to notice body impressions forming in the surface. These impressions can deepen over time, leading to loss of shape and uneven support – particularly around the edges where you sit when getting on and off the bed.
  • Heat Absorption: Memory foam tends to trap a fair amount of body heat. Cooling agents can offset discomfort from heat absorption to a degree – but if you tend to sleep hot, you'll probably feel more comfortable on a mattress with more breathable components, such as an all-latex bed, innerspring, or hybrid.
  • Odor Potential: Memory foam is notorious for off-gassing, or emitting tiny particles known as volatile organic compounds (VOCs) that carry a distinct chemical smell. You'll probably notice strong odors immediately after unboxing the mattress. These smells may dissipate rather quickly, but some memory foam mattresses are associated with bothersome long-term odor.

Memory Foam vs. Other Mattresses

Mattresses sold today fall into five general categories based on the materials used to construct them: all-foam (including memory foam beds), latex, innerspring, hybrid, and airbed. In the next table, we'll see how memory foam mattresses stack up to other mattress types.

Mattress Type Memory Foam All-Polyfoam Latex Innerspring Hybrid Airbed
Conforming Ability Very good to excellent Good to very good Good to very good Poor to fair Good Good to very good
Pressure Relief Very good to excellent Very good to excellent Good to very good Poor to fair Good to very good Very good to excellent
Heat Retention Poor to fair Fair to good Good to very good Very good Very good Very good
Motion Isolation Very good to excellent Very good Very good Poor to fair Fair to good Good
Edge Support Poor to fair Poor to fair Fair to good Very good to excellent Very good to excellent Fair to good
Average Lifespan 6 to 7 years 6 to 7 years 5 to 7 years 6 to 7 years 8 years or longer 8 years or longer
Average Price Range (Queen) $900 to $1,200 $900 to $1,200 $1,600 to $2,200 $900 to $1,100 $1,600 to $2,200 $2,000 to $2,400

As you can see, memory foam mattresses are relatively affordable and offer mid-level durability compared to other mattress types. They may lack strong edge support and trap body heat, but these beds also excel at pressure relief and motion isolation.

Memory Foam FAQ

Next, we'll answer some common questions about memory foam mattresses.

How do I clean a memory foam mattress?

Memory foam is susceptible to staining and can be very difficult to clean. Thankfully, mattresses made today include a cover to protect the foam from extensive liquid damage. Some covers can be unzipped, removed, and washed in any household machine. For non-removable covers, spot-cleaning with mild detergent is usually the best cleaning method.

Most covers are not stain-proof, and spills may cause liquids to bleed onto the foam. If you're concerned about this, you may want to invest in a mattress protector for your memory foam mattress. Many protectors are waterproof and can also reduce stains from food, pets, and other sources.

How long does a memory foam mattress last?

The average memory foam mattress will perform for about five to seven years before you'll need to replace it. Memory foam becomes softer as it deteriorates. Over time, this can lead to loss of shape and cause body impressions to form in the surface. Eventually, the surface will feel uneven and you may develop aches and pains from lack of support.

Keep in mind that body impressions may be covered under your mattress warranty. If the impressions are deep enough, the manufacturer will repair or replace the mattress at little (if any) cost to you. You can also minimize body impressions by rotating your mattress head-to-foot every three to six months – though you may need assistance, as most mattresses are somewhat heavy.

What should I do if my memory foam mattress starts to sag?

Let's say you regularly rotate your mattress but still notice body impressions forming along the surface. This leaves you with a couple of options. One, you can simply purchase a new bed – deep impressions are often a sign your mattress is nearing the end of its lifespan.

You can also use a mattress topper, which is a layer of cushioning that rests on the surface of your bed. Toppers are primarily designed to make mattresses feel softer or firmer, but they can also help protect the surface from sagging associated with wear-and-tear.

Do you need a boxspring with a memory foam mattress?

Technically, you don't need a boxspring for your memory foam mattress but you should use a support system that will keep the bed on a flush, even surface. A boxspring will include a flat surface by design.

You may also opt for a slatted foundation, but pay close attention to the foundation's dimensions. If the slats are spaced too far apart, the mattress will sag through the gaps and you'll feel less support. Many mattress warranties include prescribed slat widths for this very reason.

Is memory foam toxic?

The memory foam used in today's mattresses is engineered to be safe for exposure to humans. Mattress brands can obtain certifications that indicate their foam has been tested for harmful substances. The CertiPUR-US certification is most common, but other credentials denote the same qualifications.

Some consumers have expressed concerns about off-gassing. All-foam mattresses emit volatile organic compounds (VOCs), tiny particles that come from certain chemicals. VOCs carry a distinct chemical odor some people find unpleasant (see next question for more details), and heavy exposure to the particles can carry side effects such as dizziness, nausea, and irritation to the eyes, nose, and throat. However, most mattresses release a relatively small amount of VOCs, so you're unlikely to become sick.

If you're worried about VOC exposure, let your mattress air out in a well-ventilated room for at least one day after removing it from its shipping container. If your mattress is delivered via White Glove shipping and not compressed into a box, it won't release as many VOCs into your home.

Does memory foam smell?

As we hinted with the previous questions, VOCs can be somewhat stinky – at least at first. In the 24 to 48 hours after unboxing your memory foam mattress, you'll probably notice a strong off-gassing odor. These smells will most likely dissipate in a matter of days. However, mattresses with high-density memory foam may emit a bothersome odor for a bit longer, and the foam itself may carry a persistent smell.

If you have an unusually strong sense of smell, then a memory foam mattress may not be right for you. That said, most memory foam owners do not report bothersome odor after a week or so.

Do memory foam mattresses sleep hot?

Despite the open-cell structure of memory foam – which is intended to promote airflow – the material has been known to absorb and trap body heat. Softer mattresses usually sleep the warmest since they also conform the closest. As you sink into the mattress, your surface airflow will be somewhat restricted and you'll be more likely to feel excessively hot. Firmer memory foam beds generally sleep cooler.

Some mattress brands infuse their memory foam with cooling components to help the material resist heat build-up. These components may include gel beads, copper, graphite, and bamboo. Beds with covers containing phase-change material (PCM) may also be useful for hot sleepers. PCM retains and disperses heat from your body until the surface reaches a certain temperature, which allows the rest of the mattress to remain cool even if you feel hot.

What is the best memory foam mattress?

The best memory foam mattress entirely depends on one important factor: you. When shopping for a new bed, think about your firmness preferences, body type, and sleep position – these three attributes will mostly determine which mattresses feel comfortable and which ones do not.

There are other factors to take into account. If you're a hot sleeper, then you may want to choose a mattress infused with PCM or cooling components. If you frequently experience pressure points, then a softer mattress that conforms closely may be the most comfortable option. If you have a strong sense of smell, then you should consider a model that emits a mild off-gassing odor.

Our recommendation: test out multiple mattresses with different feels and materials. Brick-and-mortar mattress stores are a great starting point because you can physically lie down on different beds. Additionally, most online mattress brands offer sleep trials, which allow you to use the mattress for at least three months before deciding to return, exchange, or keep the bed.

You can choose from a wide range of online mattress companies with sleep trials spanning at least 90 nights. These include bed-in-a-box brands.  You can also shop from brands that offer free White Glove delivery and will deliver the mattress uncompressed to your door.