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Sleeping well is a dream for many people, and a right mattress can help make that dream come true. If you want the ultimate sleep experience, there are two main things you need to look for in a bed: that it offers proper support so that your body and spine stay aligned during the entire night, and that it provides enough comfort for ultimate relaxation and healthy sleep.
Foam is a crucial part of most mattress models. Innerspring and hybrid ones usually have comfort layers made of foam and a coil core that provide enough support for the sleeper. All foam mattresses have multiple layers that generally vary in density. The base is usually made from high-density foam to give the bed more sturdiness and the ability to carry more weight without deteriorating quickly. We can say the same thing about the perimeter of a mattress, as edge support is essential for utilizing whole sleep surface and preventing sagging.
But what is foam density, and how do we measure it? Read on to find out, while also learning how it affects the whole mattress, and how to pick the right density based on your body weight and sleep position preference.
What Is Foam Density?
Density, in general, represents the relationship between substance mass and volume. In the world of mattresses, it refers to how much weight a cubic foot of foam is carrying, and it is expressed in pounds per cubic foot (PCF). For example, if something weighs 80 pounds, and measures 20 cubic feet, it would mean that its density is 4 PCF, meaning that every square foot measures 4 pounds if it has a uniform consistency.
Foam density falls into three main categories: low, medium, and high. High-density foams are primarily used in mattress support cores and foundation layers. They offer enough sturdiness to hold the whole construction and all the potential sleepers that might be using the bed. Sometimes, high-density foams can be found in comfort layers, and it usually means that a mattress has a firmer feel. In contrast, low and medium density foams are mainly used in the comfort system of the bed, since using them in the support core would lead to uneven support and excessive sagging, which would have a massive impact on mattress’ durability. However, they are perfect for comfort layers. They usually offer some level of conforming, which is essential to take the pressure of critical body points and ease the pain a sleeper might be experiencing due to improper body positioning during the night.
Different Types of Foam
The saying “It’s what’s inside that counts” is especially true for mattress construction. Quality materials need to be used to get increased comfort and exceptional durability, and the manufacturing process also plays a significant role in that. When we talk about foam materials, there are several different types: latex, gel-infused, and some others. But for now, we will concentrate on memory and polyurethane foam.
Polyurethane or polyfoam is a highly flexible synthetic material made from polyol and isocyanate chemicals derived from petroleum. The use of polyfoam began in the 1950s as an alternative to natural fibers like cotton and wool. It is not expensive to make, it conforms nicely, and returns to the original shape a lot quicker than natural fiber. It is also flame resistant, resilient, and it sleeps cooler than other foam types. Polyfoam is most commonly used in bases and support cores, transitional layers, and less often in top cushions.
Memory foam is probably the most famous mattress material in use. It was first developed by NASA in 1966 to decrease the levels of stress astronauts were subjected to, due to high G force. The applied pressure and body heat soften memory foam, and as a result, it conforms closely to the sleeper’s body. That is important as it takes off pressure from the shoulders, back, hips, and joints, and it prevents the development of pain in those areas. It is called memory because it “remembers” the contours of the sleeper’s body. You must have seen one of the commercials where a person would press down on this material with their hand, and it would leave the print that would stick for a few moments and then slowly disappear. Memory foam offers great comfort and is also excellent at isolating motion, which made it one of the top picks for people who share their bed with a partner. Since memory foam is too soft, it is not used in the support cores, but all the characteristics made it perfect for comfort layers.
Density is used to describe both polyurethane and memory foam, but the PCF ranges are different for them. Low-density polyfoam is considered to have less than 1.5 PCF, medium from 1.5 to 1.7 PCF, and high-density is that of 1.7 or higher PCF. When it comes to memory foam, less than 4 PCF is considered low-density, 4 to 5 PCF is medium-density, and over 5 PCF is classified as high-density memory foam.
Most mattresses are made from different materials, and products made from just one type of foam are extremely rare. Every separate layer serves a different purpose, and choosing the right mattress depends on many factors like your sleeping style, budget, as well as temperature, firmness, motion, and many other preferences.
The Difference Between Density and Firmness
Some manufacturers use the terms density and firmness interchangeably when describing their products, but that is not correct. While the first one is used as a measurement for weight/volume, the second term refers to how soft or firm the whole mattress feels, and how closely it conforms to sleeper’s body. Firmness is usually rated on a 1 to 10 scale, with ten being the firmest and one being the softest option. However, most of today’s models fall somewhere in the middle, from 3 to 8, and it appears that medium firmness is the option that most people prefer, and the one that comes with the most benefits.
Besides this 1 to 10 scale, firmness can also be measured in indentation load deflection (ILD). To determine ILD manufacturers would put a circular disc with 1 foot in diameter on an area of foam about 4 inches thick. Then they measure the weight that is needed to compress the foam by 25%. The results are represented by the applied pressure, so if the load were 10 pounds, the material would have ILD of 10. Most comfort layers fall somewhere between 10 and 20, while the support cores and transitional layers have higher ILD measurements.
Even though there is a difference between density and firmness, there is a correlation between them. High-density foams tend to be firmer and to conform less, while soft and medium density ones fall on the softer side of the firmness scale, and tend to contour closely. That is why they are used in the comfort systems of most mattresses.
How Does Foam Density Affect Different Mattress Features?
The density of materials used in the construction of the mattress significantly impacts the overall features and performance. In this section, we review how it affects different aspects of a bed based on extensive research and numerous customer reports.
- Durability is probably most impacted by the density, and people need to pay close attention if they plan on using their new mattress for a long time. Low-density foams are more prone to sagging and are usually associated with a shorter life span. Medium-density foams are more durable but are still susceptible to some wear and tear, while high-density ones are associated with long lifespans. Picking the right density is particularly important for heavier individuals, as they need stronger support and more resilient material that won’t deteriorate quickly.
- Conforming abilities depend on the density, but also the sleeper’s body type. While there is a trend of increased contouring with a more dense structure, we can say that high-density foams are better for heavyweight individuals, while the lighter people can find them too sturdy, and not suitable for pressure and pain relief. Low and medium density is a better choice for lighter and average weight individuals since they offer just enough conforming, while the heavier sleepers will find them less adequate. They sink in too much, and their bodies get out of alignment, which can lead to the development of discomfort and pain.
- Temperature neutrality is a term that refers to how sensitive the material is to retaining heat, and it mainly depends on the ability of air to circulate and get rid of any excess warmth. Foams are generally known to trap a lot of emitted body heat, and because of that, they are not a great choice for people who tend to sleep hot at night. Low-density foams offer better temperature neutrality as they retain less heat, but they still can’t compare to innerspring and hybrid mattresses that have better ventilation and stay a lot cooler throughout the night. Heat retention increases with the density, and high-density foams are not recommended for hot sleepers.
- Pressure and pain relief is closely connected to the conforming abilities of the mattress, so it also depends on the weight of the user. Heavyweight individuals will find more benefits with high-density layers, while lighter people should go for low- and medium-density for optimal pressure and pain relief.
- Motion isolation refers to the ability of a material to stay still even when there is motion happening on top of it. That is crucial for everybody who shares a bed with a partner, as you don’t want to be woken up every time they move, switch positions, or get up to go to the bathroom. Motion isolation is excellent with all foams, but low-density ones perform slightly worse in this department, while medium and high-density ones are superb at neutralizing any movement that appears.
- Noise potential is another critical item for couples, as movement isn’t the only thing that can wake people up, so is the squeaking noise that some mattresses make. Luckily, that is mostly the case with beds that have coils in their construction, and all foam mattresses are silent when bearing weight, no matter the density.
- Off-gassing refers to a specific rubbery odor that a new mattress might have at first. It is usually the case with models that come in a box, and since they haven’t been able to ventilate properly, they emit some smell. Although there are some indications that the higher the quality of materials used, there will be less odor, you can certainly expect some degree of off-gassing with all foam mattresses.
- Sex is an essential part of every relationship, and choosing the right mattress can partially impact it. Bouncier, more responsive surfaces are better for intimacy, and that is why latex, innerspring, and hybrid beds are best for sex. Foam is considered less suitable since it is not responsive, and people may feel stuck inside. Low-density ones are a better choice of all three since they offer some springiness, which should be enough for most couples. Higher density means more sinking, and people may feel like they are fighting the mattress, to stay on top. If you keep in mind that foam responds to heat, it is clear that you can expect even more sinkage during sex than while sleeping.
- Mattress weight is directly connected to the density of materials used in the construction. All-foam models are usually heavier than innerspring and hybrid ones. The weight varies with different models, and low-density ones are generally about 50 to 65 pounds, medium ones are 60 to 75 pounds, and high-density ones are typically 75 to 90 pounds.
- The average price also corresponds with density, as it affects features, performance, and general longevity. Inexpensive lower-density models cost between $500 and $700, medium-density ones go for $700 to $1000, and high-density ones are usually between $1000 and $1400. Keep in mind that this price is for Queen size mattresses and that it is different if you select another size.
How to Choose the Right Foam Density
Now that we have established how foam density affects different aspects of a mattress, it is time to figure out what is the best choice for you. You need to ask yourself what qualities you must have, and what things you can compromise on. For instance, if you are a particularly hot sleeper, you wouldn’t want to get a mattress that retains a lot of heat, since you won’t be able to enjoy it, and you will find sleeping on it extremely unpleasant.
Your weight is one of the most important factors when considering what foam density to choose. Lower-density models seem to be a preferred choice of light individuals as they offer closer conforming and pressure relief. On the other hand, heavier people should go for models that are constructed from denser material, as they offer enough support and the right amount of conforming for their body type.
Another important factor to take into consideration is your sleeping position. Some people like resting on their back, some prefer sleeping on the stomach, but it turns out that most people prefer sleeping on the side. Your mattress should provide the right support for your body, and keep your back aligned through the night. Foam is excellent because it helps keep the pressure of your hips, shoulders, and back, which leads to fewer aches and pains. Back and stomach sleeping positions allow a person’s spine to align naturally, but if the surface is too soft, it can become uneven after some time. That can lead to heavier body parts sinking in, and the spine can fall out of alignment. Some manufacturers have decided to tackle that problem by providing zoned support in their products. They use higher density materials in the lumbar area, which usually sinks the most, and that adds to the durability and proper body positioning.
When we look at the sleeper’s body weight and their sleeping style, we see some general trends in preferences. On average, most people like medium density and moderate firmness levels of a mattress. It is the top pick of most average-weight individuals, although stomach sleepers may prefer a firmer surface. Lightweight back and side sleepers usually go for softer models, while people who like resting on their stomach need a little more support, so a medium would better suit them. Heavyweight individuals enjoy sleeping on firmer, high-density surfaces, although some of those who prefer sleeping on the side might like medium ones better, as they are softer, and eliminate hip and shoulder tension better.
If you are looking for a new mattress, there are many things to consider besides foam density. We have created numerous guides to make the choosing process easier, so check our guides and reviews to find the perfect sleeping product for yourself.
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Dusan is a biologist, a science enthusiast and a huge nature lover. He loves to keep up to date with all the new research and write accurate science-based articles. When he’s not writing or reading, you can find him in the kitchen, trying out new delicious recipes; out in the wild, enjoying the nature or sleeping in his bed.