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R-Value 101: Why Sleeping Pad Insulation Value is Important15 min read

When you are sleeping outdoors, on the cold ground, the most important factor to consider is your sleeping pad’s R-Value. This is the measure of the pad’s ability to resist(r) heat flow, hence R-Value, which basically determines how well your sleeping pad will insulate you from heat transfer to cold ground.

If you don’t have a good understanding of what an R-value is, or why it’s so important, we’ll discuss what an R-value is and why it’s so vital when thru-hiking to maintaining warmth in any weather.

What is Vital in a Thru-Hiking Sleeping Pad?

When you are living out of a shelter like the Zpacks Duplex, you have amazing cover from the rain and elements but on most thru-hikes, you will encounter cold weather and inclement conditions in general.

These conditions are what you aim to be prepared for before ever hitting the trail as you never want to be surprised with snow and winter weather while carrying only your summer kit, this could lead to life-affecting problems and dangers!

So when a thru-hiker is building out their kit they need to think about the weather now along with the weather expectations and really be ready for the worst-case situation.

Durability and Quality Construction

Always a primary concern for anyone packing gear for four to six months is in the gear’s overall durability and construction quality, those seams are all aligned and the air valve is matched to the sleeping pad so leaks don’t happen.

Replacing gear due to failure on the trail is ALWAYS expensive and frequently can lead to a loss in time or even more valuable, money, which causes many thru-hikers to fail to finish.

This is why you see people pay large amounts for a sleeping pad, like the exceptional Therm-A-Rest XLITE or the much less noisy NEMO Tensor, instead of less expensive “clones” which never seem to have the quality or durability and warranty these more costly options present.

Cold Weather Ground Insulation

When you look at your sleep system many thru-hikers will place their focus on the super amazing quilt they bought (I tackle EE vs UGQ if interested here), then they look to see if they can cut corners on their sleeping pad as their quilt is rated to “0 degrees” but this is a misconception.

The big issue here is that most of your warmth is lost to the ground below you, not the air above you. While you don’t want drafts and need to hold in the heat the ground will steal heat much faster and much more efficiently than the air ever could or will.

You want to make sure you choose a pad that can insulate you against the incredibly cold ground, the pairing of these two gear items will make you either constantly be cold or be warm and relaxed, fully stretched out and sleeping like a baby.

Insulation and The Pesky R-Value Conundrum

For most new hikers and backpackers, including myself, we begin by learning more about sleep systems and the lingo and terminology. The first time you see an R-value the system makes very little sense as it has no direct correlation to the outside temperatures if you aren’t in the home insulation market.

The R-value of your sleeping mat will be what makes your nights enjoyable and relaxing for high-quality sleep, or cold and restless when those spring freezes hit.

What is an R-value Anyway?

For myself this made literally no sense when I first started looking for a sleep system, I began reading to try and understand how this correlates to gear and what it actually represents, this is what I found out.

R-value is basically an insulation rating that has no direct ties to sleeping pads but to insulation in general for anything providing resistance to heat flow (loss). Basically, in super layperson terms, R-value is any material’s insulation properties expressed as a rating with the “R” shorthand for resistance.

This leads to a basic understanding that the higher the R-value, the more effective the resistance to heat flow and hence provided insulation will be. This is exactly what you are trying to achieve with your sleeping pad meeting or exceeding your coldest expected outside temperature range.

Measuring and Testing of R-value

To know the actual resistance level of a sleeping pad you need to test them right? Well as I read more it became truly clear that has not really been a requirement as there hasn’t been a real “standard” which has led to many issues with people making a bad pad choice that won’t fit their needs.

Current Scoring Is Unregulated

The scores currently would look to be a standard based on them all for the most part showing and displaying proudly the sleeping pads R-value, the issue here is that there is no testing standard nor validation which means a company can just put what they “feel” or believe is the right value.

For many vendors and manufacturers, this led to an increase in sales by making a pad much cheaper than the more costly vendors like Therm-A-Rest by choosing worse materials, construction methods, then marking them as having more insulation value than they actually ever could have.

Fake or “Simulated” Scoring

Many pads, especially those from China or ones you see frequently spammed into Facebook groups are pads with no viewable rating or a rating where they don’t explain on any site how they actually achieve these scores.

I have seen many people on simple camping trips have to bail to the car when their pad said it could be used as an R-value of 3 but in a Texas spring not making it to 50 degrees before cold just seeps in from the ground causing constant flipping over.

This has led to the real adoption that has just started of an ASTM R-value rating, this is an important change for us all!

New Rating System Is Coming ASTM R-value

The new rating system designed with many leaders in the industry and the ASTM (American Society for Testing and Materials) is very much similar to the standard EN/ISO ratings for other sleeping gear like sleeping bags and quilts which helps to make sure the R-value can be used to actually compare pads, it is ASTM F3340-18 R-Value Standard.

This means that if the box has the ASTM markings you can be sure the rating is actually correct and can be used to establish whether the pad will work for your temperature needs.

Instead of being left to salespeople to fake you out the number now is a true, definitive measurement and rating as to the warmth of one pad versus another where you can trust the printed number.

Why Does the Sleeping Pad R-Value Matter?

The R-value is a solid reference point to your ability to stay warm over longer and colder nights where the ground is sapping your heat, for those who “sleep cold” many are losing much of this heat to the ground and this causes rampant cold feelings throughout the body from head to toes.

If you care to get wonderful sleep you need to match your R-value to the coldest temperatures you will expect, for example, if you end up on rocks or harder earth more of you are in contact and you can lose more heat overall.

The same would be if you place your shelter and pad over a bed of fine pine needles you may sleep warmer as the pine needles make a unique insulation layer themselves which could help you sleep warmer without even realizing it.

I would always suggest making sure you go high enough in rating for a thru-hike I would personally get at a minimum a 3.0+ with my preference of getting to approximately 4.0, this can be done with a 3.5 rated main pad then supplementing an additional pad like a traditional closed-cell folding pad or one of the popular rolled 1/8th inch thin pads.

Using the R-value when choosing a sleeping pad is going to result in a much higher-quality experience for those all-important sleep hours, many thru-hikers will pass out from exhaustion but not get truly restful, restorative sleep that they need for the consistent wear their bodies face.

Finding and getting the perfect sleeping mat setup is pivotal to better, more comprehensive sleep!

What R-value Should Your Sleeping Pad Be Rated?

Now we hit on what the rating should be for a thru-hike or in general really anyone who backpacks outside of summer alone, with summer hiking you can get away with nearly any pad and only worried about the padding and comfort.

Below I have a quick explanation through a sleeping pad R-value chart showing the ranges and where the best place is for the typical thru-hike season which runs for most from early spring to late fall.

Once you reach winter or the extreme temperatures like high mountains you may need to go even higher than the recommended R-value regardless of the season and make sure it has reflective material in its core.

Hopefully, this gives you a better idea of when and where an R-value can work for you, please note that if you are hiking and the chance of extreme weather exists, then you should gear for it instead of just going lightweight to ensure protected from the ground temperature changes and body heat loss.

Dangers Of Choosing the Wrong Sleeping Pad

This is what strikes many people on long-distance hikes like the Appalachian Trail where you start in February to April and the weather can swing wildly from nice highs to lows including freezing rain, sleet, or snow.

When these conditions happen you will start to lose heat incredibly fast and this is where the pad is there to help you conserve this vital heat being generated from loss.

If you have a more insulated sleeping pad with a better R-value you will be much warmer, like the NeoAir X-LITE with an ASTM 4.2 rating than going with the lightweight backpacking style low R-value pad similar to the Klymit Static V (which states 4.4) but according to their site, the real ASTM rating is a small 1.9!

This discrepancy, or what I call a “fake rating” is what causes so many issues for people!

The reason why many cold sleepers flip over non-stop all night is the body trying to warm itself as it knows it is losing heat and it then has a stress response to readjust, this readjustment can then cause a breeze with a quilt causing more havoc.

Choosing a Sleeping Pad

So with all this said what do you need to know to choose the right pad for your thru-hike? I will take some time to cover all the different types of pads along with their shapes and sizes and why pairing them with a bag or quilt will provide a better overall sleep system.

Types Of Sleeping Pads

There are a few specific types of sleeping pads available, the most common which you see in movies is the closed-cell foam sleeping pads, then the inflatable, and the last type of self-inflating pads.

Closed-Cell Foam Sleeping Pads

Closed-cell foam pads have been around for a very long time and are what many people imagine when they hear the term “sleeping pad” and aren’t avid hikers or backpackers. This is the one you see rolled up on backpacks in movies and television.

These pads are typically inexpensive, lightweight, and easy to find these make great beginner sleeping pads but they have a few issues due to being very thin by nature.

The first being they are not very comfortable overall and provide no cushioning for your back or hips, this can lead to a very restless night of sleep as you will constantly be trying to adjust to get comfortable.

The second is over time the egg-crate shape they use starts to collapse and the insulation value lowers, personally, I would not recommend these unless used to supplement a main inflatable pad or if you are just getting started and trying to gauge your interest in the hobby overall.

Inflatable Sleeping Pads

These are a thru-hikers best friend for sleep, they provide a much-improved bed on the trail allowing for better and more comfortable sleep unlike the closed-cell pads listed above.

As the name implies you will carry this in your backpack deflated so it takes up very little space and once you set up your shelter you will then take it out and use the sack they may provide to inflate, a pocket inflator, or your own breath.

This is the favorite pad overall as they have become specialized to retain heat from companies like Therm-A-Rest and others through high-tech linings and fabric use making them perfect for colder temperatures you will encounter on a thru-hike.

Self-Inflating Sleeping Pads

Not a good fit for most thru-hikers as they are frequently heavier than any other sleeping pads to provide the ability to inflate on their own once set up, but this also comes at the cost of excess space within your backpack also.

For some though the space concerns and weight aren’t a game-breaker and this pad can make for a super simple camp setup versus other pads while giving you all the luxury, you have come to expect on the trail, more padding than closed-cell and easier inflation.

I wouldn’t suggest this as a pad option for 99% of thru-hikers, please feel free to try one at a store like REI or maybe from Amazon since they have a good return policy if the gear shouldn’t be a good match for you.

Shapes & Sizes

There is a wide range of sizes and layout of pads which leads people to paralysis in choosing the right one for their needs, there is no incorrect choice but only the right fit for you.

The most common version for most will be the mummy-style which maintains a more shape-fitted appearance, square which has 4 corners and equal size all around.

I would suggest understanding your habits while sleeping, the more you move in your sleep the better a square pad becomes to help you stay on it where if you are fairly still you can use a mummy and remove some excess material and weight without penalty.

The last pads are the short pads which are about 4′ tall for those who pull their knees up or for the ultralight thru-hiker who cuts the ounces where they are unneeded.

Sleeping Pad Depth

This is more personal, for many, the standard 2-2.5 inches will be more than enough to leave air in the pad between you and the ground, you need this space to keep the insulation value in place.

For those who are a side sleeper, or the more weight you carry the thicker the pad the better, it will be for you to not hit shoulder or hip to the ground through the pad itself, a quality thicker pad I use is the Recharge XL by Paria at 4″.

Pair With a Quality Sleeping Quilt or Bag

To get the best performance from the sleeping pad you do need to make sure you pair it with a similarly matched sleeping bag or quilt to a matching air temperature also.

Many sleeping bags and quilts will display the “limit” temperature on the packaging and on their websites, the limit temperature means survivability when laying in a more knee up style and pulled in as much as possible.

So you want to make sure you choose a bag or quilt with this in mind, you are looking for a “comfort” rating at the lowest temperature you expect and if you know it is a “limit” they use then move it up 10 degrees, so a 20-degree limit back is a 30-degree comfort bag generally.

Methods to Increase the R-value of a Sleeping Pad

You can start with a lower-rated R-value pad and then use another pad to supplement it, this is frequently easier than thought as most will carry a sit pad or a thin closed-cell pad to lay on now anyway.

Add an Additional Closed-Cell Sleeping Pad

These smaller pads are perfect for relaxing during the day weighing near nothing to add to your pack but offering a range of values like replacing your sit pad, a lounge pad, etc.

These thin and light pads also can add 0.5 R-value to your existing sleep pad which can help push a 3 to a more comfortable 3.5, so this allows you more flexibility to adjust your pad as needed.

Final Thoughts on R-value and Sleeping Pad Choice on Thru-Hikes

In what is the most important purchase decision you can make when hiking, a good sleeping pad with an insulation value that works well for your needs will help keep you warm and cozy in what could be extreme conditions.

There are many different types of pads to choose from which makes it difficult to know what’s best for your purposes. We hope this article has helped to explain what R-value is and how to choose a pad with the right insulation value for your needs.

Hopefully, you have learned a lot overall on R-values and sleeping pads overall, I appreciate you coming by and reading through leave me a comment if I missed anything or you learned something new!

If you are looking for sleep system gear you can check out my best sleep system gear here!