Quick Answer: IFD (Indentation Force Deflection) measures foam firmness, density measures foam durability (not firmness), and Energex is a temperature-responsive foam that bridges memory foam and latex by combining pressure relief with quicker response. Understanding these three terms helps you read mattress specs critically instead of relying on marketing descriptions alone.
In This Guide
Reading Time: 8 minutes
Mattress foam specs can look like a foreign language. IFD. Density. Visco. Energex. Transition foam. The terms show up in product listings without explanation, and most buyers either ignore them or assume the salesperson will translate.
At Mattress Miracle in Brantford, we have been explaining these terms to customers since 1997. This guide covers the three concepts that matter most: IFD ratings, foam density, and Energex foam. By the end, you will be able to read a mattress spec sheet and know what you are actually buying.
What Is IFD (Indentation Force Deflection)?
IFD stands for Indentation Force Deflection. It is also sometimes written as ILD (Indentation Load Deflection). The two terms measure the same thing: how firm a foam is.
Here is how it is measured:
- A standard foam block (15" x 15" x 4") is placed on a flat surface.
- A circular disk 8 inches in diameter presses down on the foam.
- The IFD number is the amount of force (in pounds) needed to compress the foam by 25% of its thickness, which is 1 inch in this case.
- Higher IFD = more pounds required = firmer foam.
| IFD Range | Feel Description | Typical Use |
|---|---|---|
| 10-19 | Very soft | Pillow fills, ultra-plush comfort layers |
| 20-29 | Soft | Comfort and pressure relief layers |
| 30-39 | Medium | General-purpose comfort layers, transition layers |
| 40-49 | Medium-firm | Firmer comfort layers, upper support layers |
| 50+ | Firm | Base/support layers, high-density foundations |
IFD is the most direct way to compare foam firmness across different brands and products. When a mattress description says "medium feel" or "plush," those are subjective terms. When it lists IFD 28, that is a measurable specification you can compare with another mattress listing IFD 36.
Brad, Owner, 40+ years of experience: "I always tell people to ask for the IFD on the comfort layer if they want to know the actual firmness. The word 'medium' means different things to different manufacturers. The IFD number doesn't change depending on who is describing it."
8 min read
What Is Foam Density?
Foam density measures how much material is packed into a cubic foot of foam, expressed in pounds per cubic foot (lb/ft³). It is not a measure of firmness. It is a measure of how much foam is actually there, which translates directly into durability and longevity.
Density as a Durability Indicator
A higher-density foam has more polymer material per cubic foot. More material means more cell walls, more structure, and less compression set over time. Compression set is the technical term for when foam permanently deforms under repeated load and stops bouncing back to its original shape. Low-density foam has less material to resist this deformation and will sag faster.
Research on mattress longevity consistently finds that foam density is a stronger predictor of long-term performance than foam firmness or brand marketing claims.
| Density Range | Quality Category | Expected Lifespan | Typical Use |
|---|---|---|---|
| Under 1.5 lb/ft³ | Budget | 2-4 years before sagging | Low-cost mattresses, guest beds |
| 1.5-2.0 lb/ft³ | Standard | 4-7 years | Mid-range consumer mattresses |
| 2.0-3.0 lb/ft³ | Quality | 7-10 years | Quality memory foam and hybrid comfort layers |
| 3.0-5.0 lb/ft³ | High-quality | 10+ years | Premium memory foam, base layers |
| Over 5.0 lb/ft³ | Commercial/specialty | 10+ years | High-performance base layers, specialty applications |
When reading mattress specs, pay attention to both the IFD and the density of the foam layers. A mattress can have a medium IFD comfort layer (feels right in the store) and very low density (starts sagging within three years). That is the most common quality trap in the entry-level mattress market.
Density vs. IFD: Why the Difference Matters
The most common confusion in mattress shopping: people assume that a firmer mattress is more durable. This is not how it works. Firmness (IFD) and durability (density) are independent properties. You can have:
- A soft foam (low IFD) with high density = plush feel, long-lasting
- A firm foam (high IFD) with low density = firm feel, will still sag quickly
- A medium foam with medium density = average on both dimensions
- A medium foam with high density = good durability in a medium feel
This is why the cheapest "firm" mattresses often develop body impressions within a year or two. Firm-feeling foam made from cheap, low-density materials does not hold its structure under body weight over time. The firmness feeling on day one is not related to how long it maintains that feeling.
What Is Energex Foam?
Energex is a proprietary foam technology developed by Elite Comfort Solutions (ECS), a major foam supplier to the bedding industry. It is a temperature-responsive polyurethane foam designed to combine the best qualities of memory foam and latex while avoiding their main drawbacks.
How Energex Works
Energex uses a tuned glass transition temperature, meaning it softens slightly when it senses body heat. This is similar to how memory foam responds to temperature, but Energex maintains a much faster recovery rate. Where memory foam compresses and holds the shape for a moment after you move (the "hand print" effect), Energex bounces back quickly like latex while still providing contouring pressure relief.
Energex also uses strut-reinforcing technology (SRT), which transfers polymer to reinforce the cell walls within the foam structure. This results in extremely low compression set, typically less than 1.5% material loss. In practical terms, it maintains its shape and feel significantly longer than standard polyurethane comfort foams.
Energex is primarily used as a transition layer in multi-layer mattress systems. It sits between the softer surface comfort foam (often memory foam or a plush polyurethane layer) and the denser base support layer. In this position, it creates a gradient of feel from soft at the surface to firm at the base, which distributes body weight more evenly across the mattress surface.
Energex vs. Memory Foam vs. Latex
| Property | Memory Foam | Energex | Natural Latex |
|---|---|---|---|
| Pressure relief | Excellent | Good to excellent | Good |
| Responsiveness (bounce-back speed) | Slow (5-10 seconds) | Fast (near-immediate) | Very fast (immediate) |
| Temperature sensitivity | High (stiffens in cold) | Moderate (tuned range) | Low |
| Heat retention | High | Moderate to low | Low (breathable) |
| Durability | Varies by density | High (SRT technology) | High |
| Cost | Lower to moderate | Moderate | Higher |
| Allergen concerns | None (synthetic) | None (synthetic) | Natural latex allergy risk |
The key advantage of Energex over standard memory foam is the faster recovery and lower heat retention. The key advantage over latex is lower cost and absence of latex allergy risk. It is not the "best" option in all dimensions, but it occupies a genuinely useful middle position for many sleepers.
Reading Mattress Specs Practically
When you look at a mattress specification sheet, here is what to focus on:
Practical Checklist for Evaluating Foam Layers
- How many layers? Most quality mattresses have 3+ layers: comfort, transition, and base.
- What is the IFD of the comfort layer? This determines the feel you experience. IFD 20-35 = soft to medium. IFD 35-50 = medium to firm.
- What is the density of each foam layer? Comfort layers ideally 2.0+ lb/ft³. Base layers ideally 1.8+ lb/ft³. Numbers below 1.5 lb/ft³ in any layer are a concern for durability.
- Is there a transition layer? A good transition layer (Energex, high-IFD polyfoam, or microcoils) bridges the comfort layer and base to avoid a "stuck in quicksand" feel.
- Is the foam CertiPUR-US certified? This confirms testing for low VOC emissions and absence of harmful substances.
Many budget mattresses do not publish these specifications because they do not reflect well. If a mattress only gives you IFD without density, or density without IFD, or no foam specs at all, treat that as a yellow flag. A manufacturer confident in their foam construction will typically share both numbers.
Dorothy, Sleep Specialist at Mattress Miracle: "What I find is that people focus on the feel of the mattress in the store but don't think about what the foam is made of. Two mattresses can feel exactly the same on day one and feel completely different after two years. The density is what tells you which one you are getting. It's worth asking."
Frequently Asked Questions
Energex foam uses an open-cell structure with higher resilience than traditional memory foam, providing faster response time and better airflow for cooler sleeping. Mattress Miracle at 441½ West Street in Brantford can explain the differences between foam types including Energex, memory foam, latex, and standard polyurethane. Dorothy notes that foam density (measured in lb/ft³) is the most reliable indicator of foam quality and longevity. Call (519) 770-0001 for a foam technology comparison.
Shop: Foam Mattresses at Mattress Miracle
Shop This Topic at Mattress Miracle
Popular picks at Mattress Miracle:
- Restonic ComfortCare Dalton & Albany
- Whitney double-sided mattress
- Somnia 3.0 posture support pillow
Or shop the full mattress lineup in our Brantford showroom.
Find Your Perfect Mattress at Mattress Miracle
We are a family-owned mattress store in Brantford, helping our community sleep better since 1997. Come try mattresses in person and get honest, no-pressure advice.
441 1/2 West Street, Brantford, Ontario
Call 519-770-0001What IFD rating is considered medium-firm?
An IFD rating of approximately 35 to 45 in a mattress comfort layer is generally considered medium-firm. Below 25 is typically soft; above 50 is typically firm. However, how a mattress feels also depends on the thickness of the comfort layer and how it interacts with the transition and base layers beneath it. IFD is one input, not the complete answer.
Is a higher foam density always better?
Higher density means better durability, but there is a practical upper limit for mattress applications. Comfort layers in the range of 2.0 to 3.0 lb/ft³ provide excellent durability without excessive heat retention. Very high-density foams (above 5 lb/ft³) are typically used in base layers for structural support, not comfort. A comfort layer that is too dense can sleep hot and feel stiff. The goal is matching the density to the layer's function in the mattress.
What mattresses use Energex foam?
Energex is an ECS proprietary technology licensed to mattress manufacturers. It is used in mid-to-high-range mattresses as a transition layer. If a mattress specification sheet lists "Energex" or "temperature-responsive foam," this is the material. It will typically appear in the middle of the layer stack, not at the surface. Ask the retailer for the full layer breakdown to confirm where Energex sits in the construction.
Does Energex foam sleep cooler than memory foam?
Yes, generally. Energex's open-cell structure and faster recovery rate mean it retains less body heat than traditional dense memory foam. It is not as breathable as a natural latex or an open coil system, but it is meaningfully cooler than standard viscoelastic memory foam, particularly for lighter and average-weight sleepers. Very warm sleepers may still prefer a coil-based system for the best temperature management.
How do I compare foam quality when shopping for a mattress in Canada?
Ask for the density (lb/ft³) and IFD rating of each foam layer, and check whether the foam is CertiPUR-US certified. If the retailer cannot provide these specifications, that is itself useful information. At Mattress Miracle in Brantford, we can walk you through the construction of any mattress we carry, including the Restonic line, so you know exactly what you are buying and why it is priced as it is.
Visit Our Brantford Showroom
We are located at 441½ West Street in downtown Brantford. Free parking available. Our team does not work on commission, so you get honest advice based on your needs.
Mattress Miracle , 441½ West Street, Brantford, ON · (519) 770-0001
Hours: Monday–Wednesday 10am–6pm, Thursday–Friday 10am–7pm, Saturday 10am–5pm, Sunday 12pm–4pm.