Foam is one of the most important and most misunderstood aspects of furniture construction. It tends to be specified by designers as "medium firm" or "high density".
But what do these terms really mean and how can you order furniture that doesn't surprise you or your client by being way too firm or too soft? And what can you determine about foam content just by sitting on a sofa cushion?
Let's go over a few foam basics.
What type of foam is used in furniture?
Nearly all the furniture produced for home, workplaces, and hotels contains polyurethane foam in a variety of different quality levels, shapes, and sizes. Polyurethane foam has been use almost exclusively in furniture since the 1960's.
Other modern alternatives to polyurethane foam are natural latex, synthetic latex, and soy-based foam. Unfortunately, all of these alternatives are problematic and are not yet reliable, cost-effective solutions for broad upholstery use.
How can I be sure the sofa I order has the correct level of firmness?
This is where it can get confusing. You may read that a foam is high-density or high-resiliency, but these descriptors have very little to do with comfort level. To start to determine both the quality and firmness of your couch cushions, you'll need to understand two number.
What is foam density?
Instead of thinking of foam density has a measure of firmness, this of it as a measure of weight. Foam density is actually determined by weighing a block of foam that is one foot square. If that block weighs two pounds, it's referred to as having being two-pound density foam.
The most commonly used densities found in upholstery range from 1.5 pound to 3 pound. The heavier the density, the longer the foam will last in high-use environments. For example, Emblem regularly uses upholstery foam that ranges from 2.0-2.9 pounds.
What is the difference between high-density and high-resiliency foam?
The terms high-density and high-resiliency are generally used as non-official marketing terms, so it's up to individual buyers or specifiers to find out more. In generally, high-density foams are foams that are rated 2.0 lb density or greater. This density is longer lasting and the standard in high-use environments. High-resiliency foam has an even higher density of at least 2.5 - 3 lbs; at this density, the foam will maintains its shape even longer than a 2.0 lb density foam.
What about the firmness of sofa cushions?
Remember, density is a measurement of weight and will give you an idea of the quality and longevity of the foam. So what determines the firmness of foam?
Firmness is an entirely different rating, called Indentation Load Deflection or ILD. The ILD rating of foam is determined by measuring the force required to compress 4" thick sample of foam by 25%. A low ILD expressing a very soft foam might be 15, meaning it took 15 pounds to compress the foam by 25%.
How foam companies refer to different types of foam
Furniture companies order foam using the size needed and a four digit number that includes both the density rating and ILD rating of the foam. For example, at Emblem we regularly order 2536 foam that is 5" thick for our sofa cushions. The number, 2536 refers to a foam that is 2.5 density and 36 ILD.
How thickness of the foam affects firmness
(Example above of a 3" seat cushion)
Keep in mind that the size of the foam matters! You know that ILD is measured by compressing a 4" thick piece of foam, but what happens when you need a 5" thick seat cushion? Or 3" thick seat cushion?
A 2536 piece of foam that is 4" thick will feel much different than a piece that is 5" thick, even if the density is the same. That's because the thicker foam will change the experienced load deflection.
If you order a sofa with 3" thick cushions and use the same foam that you liked from a sofa that had 5" thick cushions, you will not experience the same "sit". The thinner cushion will feel much softer and will not retain it's shape as long as the thicker cushion.
Does higher quality foam feel firmer? Or softer?
I would be difficult to determine quality of foam by sitting on it. Sitting in new furniture made with 1.5 lb density foam versus 2.0 lb density foam will feel nearly the same, as long as the foam has the same ILD rating. The difference between the foam densities will only be apparent with use, as the lower density foam will breakdown and lose its shape faster than the higher density foam.
You can determine the difference in quality between two identical seat cushions by picking them up. Since density is a measurement of weight, the heavier cushion will be higher quality than the lighter cushion.
How do I specify foam for commercial-use furniture?
When shopping for furniture for a workplace, lobby, or other high-use area, we recommend asking your manufacturer or supplier about the density of the foam used in their furniture. Requesting a foam that is 2.0 lb density or higher is a good start.
The ILD rating is more difficult to specify because it is subject to individual comfort levels, the size of the cushion being used, and even the type of textile being used in upholstery. An ILD rating on a 5" thick cushion of around 26-28 will usually be softer and more appropriate for lounging. while an ILD of 36 on the same cushion will be a good balance of comfort and firmness that will support a professional, upright sit.
Can you value-engineer a furniture design with less expensive foam to meet a lower price point?
Higher density foam is more expensive than lower density foam, which is why many online retailers sell cheap furniture (often produced overseas) that features cushions made with 1.5-1.8 lb density foam.
It's also why some American furniture factories that produce large quantities of furniture for hotels often use lower density foam in all of their furniture. Lower density foam is much cheaper than high density foam, but it doesn't affect the appearance of the furniture.
If furniture is not used often, low density foam cushions may retain their shape for a year before they start to breakdown. This timeline might be acceptable to a hotel that replaces their furniture often.
Most business owners that purchase furniture for their workplaces and lobbies use their furniture every day and need it to last longer than a year. For this reason, a 2.0-2.5lb density if crucial. We do not recommend decreasing density lower than 2.0 to achieve a lower price.
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More questions about furniture foam?
Understanding the information above is a great basis for a conversation with your upholstered furniture partner. It's important to understand that materials used in your furniture so you get the outcome you want!
If you've been disappointed by your furniture in the past or if you have a custom furniture idea for a commercial project and want to discuss foam options, send our team of furniture foam experts an email. We'd be happy to help.