Therm-a-Rest wasn’t founded on the ambition to define the cutting edge of outdoor sleep equipment—our founders simply wanted to be more comfortable on their excursions. Yet, on the cutting edge is exactly where they found themselves when they invented the self-inflating sleeping pad. That was in 1972, more recently we changed the game by bringing ultralight and super compact air pads into popularity with our NeoAir® line. Now, the two most enduring models of the NeoAir lineup have been radically improved. Presenting the NeoAir® XLite™ NXT and the NeoAir® XTherm™ NXT, the next generation of air pad technology.

What’s Different About the XLite™ NXT and XTherm™ NXT?

We’ll keep this simple. Compared to the original XLite and XTherm models:

You might be thinking that’s superior in virtually every way. Yes, we like to think so too.

Here are the stats (for Regular size pads):

Sleeping Pad Weight R-value Thickness (in)
NeoAir® XLite™ NXT Sleeping Pad
XLite NXT Sleeping Pad
12.5 oz / 0.35 kg 4.5 3 in / 7.6 cm
NeoAir® XTherm™ NXT Sleeping Pad
XTherm NXT Sleeping Pad
1 lb / 0.44 kg 7.3 3 in / 7.6 cm

How Much Thicker are the XLite NXT and XTherm NXT?

Answer: A half-inch thicker

The previous models were 2.5 inches thick, and we boosted the thickness to 3 inches. This was the key improvement to overall comfort. The additional loft provides more overall cushion, especially for side sleepers. Importantly, the additional half-inch improves customizing how firm your pad is.

The WingLock Valve is deliberately positioned on the side of the pad to allow for use while a sleeper is on the pad. If you are trying to fall asleep but can’t shake the feeling that you overinflated your pad, no worries, the valve and pad are designed to accommodate an adjustment. Just open the valve—no air will escape as it is in one-way inflation mode—then toggle the wings to let air out. Twist them back when you’re ready. With an extra inch of thickness there is more flexibility to discover just that right level of firmness.

What Other Comfort Improvements Were Made?

Answer: Improved fabrics.

We sourced a ripstop nylon for the NXT project that is softer to the touch. While we definitely recommend that you use a lightweight sleeping pad sheet if you are going to sleep directly on the pad, the feel of the XLite NXT and XTherm NXT is noticeably softer next to skin.

How are the XLite NXT and XTherm NXT so Warm and Light?

Answer: the Triangular Core Matrix and ThermaCapture Technology.

Triangular™ Core Matrix

Since the original XLite and XTherm hit the market competitors have tried to match or outdo their warmth-to-weight ratio performance with their own designs. They haven’t been able to. Why? It comes down to our proprietary construction technique the Triangular Core Matrix™. Briefly put, the TriCore Matrix is what we call the two stacked layers of hundreds of triangular chambers on the inside of some of our NeoAir pads, including the XLite NXT and XTherm NXT. How it insulates so well while not being bulky or heavy is a matter of basic physics.

The second law of thermodynamics, states that in nature heat will spontaneously flow from hot to cold until equilibrium is reached. That is to say, when a hot body (your body) is brought into contact with a cold body (the ground) heat will always leave your body until both temperatures are equal. The bottom line is you will be cold if this process is left unchecked.

Sleeping pad warmth is denoted as R-value. R-value is the measure of thermal resistance. For sleeping pads, it measures how effective the pad is at slowing down that natural heat transfer process striving for equilibrium. Because your body won’t stop trying to establish equilibrium with the ground, your pad is there as a sort of guardian yelling, “no, no, no! You want this stuff!” doing what it can to gather up your heat and keep it around—because you need it.

How it Works
An air pad—like the XLite NXT and XTherm NXT—puts air between you and the ground. Capable of being efficiently heated (by your body), air is a pretty good thermal insulator. As a gas though, it is susceptible to convective heat loss. A gas is fluid, it is always in a state of motion. Within your air pad, there are ambient air currents picking up your body heat and moving it away, per the second law of thermodynamics.

Nature figured out a truly efficient way to reduce convective heat loss that the outdoor industry has widely adopted: down feathers. Down compartmentalizes the hot air into thousands of tiny pockets, thereby disrupting the flow of the air currents and significantly reducing heat loss. This is how the Triangular Core Matrix works with its numerous triangular chambers.

ThermaCapture™ Technology

All the materials on the inside of a NeoAir XLite NXT and a NeoAir XTherm NXT were painstakingly selected for their advantageous properties. This was a years long process of elimination via prototyping and testing that began in 2005. That was the year lead NeoAir developer, Jim Marson, pitched the original NeoAir concept to the Therm-a-Rest brass and got approval.

Key properties for the materials in the Triangular Core Matrix are thermal resistance, tensile strength for structure, lightness, packability, and critically the ability to be durably bonded together. In development, we discovered the internal structure of heat-retaining cells needed to be layered for the best thermal retention. How do we stack multiple layers of triangular chambers? The answer was our proprietary ThermaCapture material.

This layer of film runs horizontally through the pad. The two layers of triangular chambers are attached to the top and bottom, resulting in a stack. ThermaCapture is also metallicized to reflect heat back toward its source, the sleeper. It is light, flexible, abrasion resistant and highly reflective. All in all, very good at what it was designed to do.

However, ThermaCapture is the source of the crinkly sound in the original XLite. A common refrain is that the XLite sounds like a bag of chips, with commenters often referring to the ThermaCapture layer as Mylar®. It is not, as Mylar is a proprietary layer itself, but it is similar. Many of the attributes that make Mylar so popular and widely used are what make ThermaCapture the right material for our purposes. Both have great barrier properties, abrasion resistance, flexibility and are lightweight. Mylar is commonly used as food packaging—yes that includes chip bags.

Is the XLite NXT Really 6x Quieter?

Answer: Yes.

For over a decade now, the noise complaint has been the top knock on the XLite (and to a lesser extent the XTherm). As early as 2011 we were developing ways to mitigate it. One thing we did was develop and offer a new model NeoAir pad that was considerably quieter. It was called the NeoAir Trekker and it was heavier than the XLite and lower in R-value at 3.0. Those were the concessions we made at the time to reduce the noise. The Trekker ran for a while but was ultimately discontinued.

Compared to the XLite, people simply weren’t buying the Trekker. Meanwhile, the XLite became a perennial best-seller in the air pad category precisely due to the warmth it delivers while being incredibly light and packable. It was clear that any solution to the noise issue had to happen without giving up the critical performance the XLite delivers.

One reason the XTherm is not as noisy is that it’s made of thicker materials. The XLite NXT uses 30D ripstop nylon on the top and bottom, while the XTherm NXT uses 30D ripstop nylon on the top and 70D nylon on the bottom. Thicker material is more resistant to energy transfer. Energy like heat and sound. But we couldn’t simply use thicker materials to build the XLite as that would make it heavier and bulkier.

Another solution we tried was positioning the ThermaCapture layer lower in the pad. By dropping it down further away from the body we found the noise generated by moving around on top of the pad to be significantly reduced. But that messed with the heat retention capabilities of the TriCore Matrix. Remember, ThermCapture is performing double duty: it reflects heat and is the foundation of the stack structure of triangular chambers. Moving it down it increased the volume of the chambers of the top layer which hurt their ability to disrupt convective heat loss and lowered the R-value.

For years, designing a quieter XLite was the project of former NXT project lead Stacie Langtry. After years of trial and error, exhaustive research and numerous prototypes, her team found a solution. Instead of one continuous layer of ThermaCapture, the XLite NXT uses three different layers of slightly thinner ThermaCapture material. The thinner material is less noisy, while the three layers combine to boost heat retention, resulting in a higher R-value.

We took an XLite NXT and an original XLite to an anechoic chamber to measure precisely how much noise they make. The results showed that XLite NXT is 6x quieter which comes out to be an 83% reduction in noise from the original.

How Did the XLite NXT and XTherm NXT Not Get Heavier?

Answer: Improving our already-proven construction techniques and better materials.

With the original models, we had already set the standard for lightweight warmth. In this regard, we already knew how to build a class-leading air pad. We didn’t need to reinvent the wheel, only refine it. Any weight tax that we incurred by scaling the Triangular Core Matrix to a 3-inch thick pad, we made up for with the new, and lighter, ripstop nylon.

The XLite NXT and XTherm NXT aren’t revolutionary. Rather, they are well within the expectation of what we do. In their predecessors, we made the best air pads in their respective classes. In keeping with our tradition of innovation, we weren’t satisfied. More than that, we wanted to deliver our customers the best possible pad to support your adventures. Because a better night’s sleep becomes the best days out there.

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