Camping is a wonderful activity which provides the opportunity to spend time in nature and enjoy all the benefits that go along with it. But why are so many people reluctant to try it? One of the main reasons is due to discomfort, especially while sleeping.
So what does R-value mean on a sleeping pad? The R-value on a sleeping pad is a measure of how well a pad blocks the transfer of heat. The higher the R-value, the higher the resistance to heat transfer a sleeping pad will have. Another way to explain it is, the higher R-value is of you sleeping pad, the less heat your body will lose to the ground.
Not only will you be far from many of the modern amenities that make life so easy, but you also risk spending the night on the cold, hard ground. Fortunately, a sleeping pad can help you to be comfortable no matter where you set up your tent.
What is Sleeping Pad R-Value?
When shopping for a sleeping pad, you will see that many are categorized by R-value. While there is a variety of features when it comes to sleeping pads, including the styles referenced above, R value measures the ability to resist heat flow and tells how well the pad will insulate you.
Using this terminology, the R stands for “resist” and is used not only for sleeping bags but also to measure the insulative properties of other materials such as windows, fiberglass, and housing insulation.
The resistance of a sleeping bag tells you how much it resists the ground underneath it. This is important for temperature regulation and body heat. In colder conditions, you will need more resistance as heat is lost compared to warmer seasons when less resistance is needed.
The R-value tells how well a particular sleeping pad can resist the flow of body heat into the ground. The range usually goes from .5 for very little insulation up to 10.0 or more for winter and other freezing cold conditions.
The higher the R-value, the better the sleeping pad will keep you insulated from the cold. If a manufacturer does not have the R-value listed on a sleeping pad, they will usually tell you the temperature range at which it will be comfortable to use that particular pad.
How Does R-value Effect You
Since R-value is essentially how effective the pad is retaining your body heat from the ground, the R-value will have a significant role in either keeping you warm or cool while you sleep.
In essence, you will want a lower R-value for nights over 60 degrees, an R-value of about 1.3 for nights that are in the range of 40 – 60 degrees an R-value over 3 for cold nights.
Sleeping pads not only protect you from hard surfaces but with the right R-value, essential for keeping you from sweating or shivering all night.
R Values and their Meaning
There is no standardized or independent method for determining the R value of a particular sleeping pad and each manufacturer may have its own means of testing a pad. However, the range is usually pretty accurate and will help you choose one that is ideal for your camping conditions.
Each number has a decimal point, and the ratings can sometimes be quite specific, meaning a 4.5 is slightly warmer than a 4.0 pad.
The R-value is usually broken down as follows:
- .5 – .7 R-Value: Light insulation or more of a sleeping pad for comfort.
- 1.5 – 2.1 R-Value: This should be good insualtion for temperatures of 44 degrees down about 34 degrees.
- 2.5 – 4.9 R-Value: This is good insulation from 32 degrees (freezing) down to about 0 degrees.
- 5.9 – 6.4 R-Value: Now you are getting into some heavy duty resistance good for 0 degree to about -20 degrees
- 8 – 9.5 R-Value: If you are going to be in the low negatives overnight -36 down to -48, then one of these would be for you.
Customizing Sleeping Pad R Values
You can easily combine several sleeping pads to increase the total insulation and create a cushion with a higher R-value. In this case, the R-value of both pads would be added together, and the total number will indicate the R-value of the pads when used together.
This is a good option when you don’t always need a sleeping pad with a high R-value but do plan to spend some time camping in colder weather. Instead of purchasing a warmer sleeping pad that may be heavier, you can simply bring along an additional foam pad whenever additional insulation is needed.
Anytime you stack two sleeping pads to combine their R-value, make sure there is no gap between them where air can flow. It shouldn’t matter which type of sleeping pad is on the top or bottom as long as they are pressed together tightly.
Components that Makeup R-Value
There are a variety of methods used by manufacturers and designers to increase or decrease the R-value of a sleeping bag. The materials used, construction, and design can all have an impact on the R-value.
Not all sleeping bags are insulated, and the type of insulation can vary greatly. Some manufacturers also use reflective materials to help trap heat. Sewing in baffles to create small internal chambers also helps to evenly distribute the insulating material for consistent warmth throughout the entire pad.
Closed-cell foam pads usually have quite a low R-value, but the foam is used as insulation and can affect the overall warmth depending on the thickness. Certain types of insulation, such as feathers could also get compressed over time and reduce the R-value after extended use.
Manually inflated pads may also have a minimal risk of decreasing the R-value due to moisture from your breath when blowing the pad up. Letting out some of the air out of the pad may also result in a slight reduction in R-value as well.
High R-Value Sleeping Pads
A sleeping pad with a high R-value means that is has a lot of insulation. This insulation will keep the underside of your body comfortable and warm while sleeping. It does this by preventing body heat from being lost through the pad and going into the ground beneath.
High R-value sleeping pads are ideal for camping in the winter, in places at a higher altitude, or in geographic locations where the nights are colder than the daytime temperatures. In survival situations, having a sleeping pad with a high R-value could make the difference between life and death even if you have adequate shelter.
To provide insulation, a variety of materials may be used, including polyester, fleece, foam, and down feathers. The design of the pad may also include a variety of chambers filled with insulating material.
Women may also want to choose a sleeping pad with a slightly higher R-value because they tend to become colder at night due to their lower body mass. Some sleeping pads that are specifically designed for women may include additional padding in the areas where heat is lost the fastest.
Low R-Value Sleeping Pads
Sleeping pads with a lower R-value will have little to no insulation and will not prevent body heat from being lost. They can be used primarily for cushioning and comfort during warmer weather or camping during the summer months.
Low R-value sleeping pads are ideal for backpackers because they will be significantly lighter than those with a higher R-value due to the weight of the insulation. Some sleeping pads weigh as little as 14 ounces for inflatable ones and even less for some foam pads.
Additionally, pads with a very low value might not be useful in the winter months, but they can be combined with other sleeping pads to provide additional insulation. They are usually quite affordable as well so you can easily buy several to add to another pad with a medium R-value rating.
R-Value and Overheating
Because R-value measures the thermal resistance of a sleeping pad, it does not truly tell you how warm you will be when sleeping on it. However, some people may refer to the “warmth” of a pad when speaking about its R-value.
Unlike a sleeping bag, using a sleeping pad with a higher R-value will not result in overheating or becoming uncomfortable during the night. If you use a sleeping pad with a high R-value during the summer months, you won’t necessarily become too warm. However, pads with a lot of insulation may feel warmer because minimal body heat will be lost.
To increase overall warmth, choose a sleeping pad with the appropriate R-value and combine it with a sleeping bag that is rated for the temperature or additional blankets to help retain heat. A heating pad will prevent heat loss from underneath but does not combat cold from the top, which could result if the appropriate sleeping bag is not used.
How R-Value Is Tested
Each manufacturer may have a different method for testing their sleeping pads, so it is difficult to determine the exact way the R-value was measured. Some companies may perform actual tests while others may simply guess the R-value depending on the materials and other factors used in the construction of the pad.
One method of testing is to place the pad inside a cold chamber where it is put in between metal plates with a sensor where they are kept at a specific temperature. A pad with a higher R-value will keep the metal plate warm and less energy is needed to keep the temperature steady.
Similar to sleeping bags, R-value usually takes into account a “standard” male or female who is measured to be a specific height or weight. Of course, your experience of a sleeping pad may vary depending on your own body and whether or not you tend to be cold at night.
Although there is currently no standardized means of testing, a new standard was recently passed by the ASTM International, an international standards organization, that will be used from 2020 onwards.
This will solve the lack of consistent methods of measuring sleeping pads to provide a more reliable way to compare the R-value of pads made by different companies.
The new testing process will be done by placing a pad between two plates, one hot and one cold. The R value will then be measured in three locations on the pad and then repeated on two more identical pads. Results will be averaged to determine the R-value of the pad being tested.
Other Considerations for R-Value
There are several other factors which may affect how well a sleeping pad insulates even if it has a particular R-value. One of these factors is the type of material that you are sleeping on top of.
Surfaces that are heat-conductive will require additional insulation at the same temperature when compared to organic or ground surfaces. Concrete and granite, for example, need more insulation than soil, wood, moss, or snow.
The position of your body when sleeping will also contribute to how much heat is lost. Typically more body heat is lost when sleeping on one’s stomach compared to the back or side. If there is a reduction in the contact area with the sleeping pad, then a lower R-value may be sufficient to retain body heat.
How to Find the R-Value of a Sleeping Pad
The R-value can usually be found on a tag or printed directly onto the sleeping pad. If a particular company does not use R-value, they will usually provide a temperature range instead to indicate when the pad can be effectively used.
If only a temperature range is provided, the R-value can be determined as follows:
- 40 degrees – R-value of 1.8 for male, 1.9 for female
- 20 degrees – R-value of 3.3 for male, 3.4 for female
- 0 degrees – R-value of 9 for male, 10 for female
- -20 degrees – R-value of 11 for male, 13 for female
Should you find a sleeping pad that does not have an R-value listed, it is also a possibility that R-value testing has not yet been conducted on that particular product. In that case, try to determine the type of materials used to get an idea of the insulating properties.
Choosing a Sleeping Pad with the Right R-Value
When choosing a sleeping pad, there are many other factors to take into consideration other than R-value. However, if you will be camping in colder weather, then R-value may be the most important thing to keep in mind.
For three season camping, a pad with an R-value of 3 or higher should be sufficient. In the winter, a sleeping pad with an R-value of 4 or higher should be used.
If you are camping in particularly warm weather and don’t need a lot of insulation but still want to use a sleeping pad for comfort, then you can disregard the R-value. Just make sure to go and try it in person to make sure it is supportive enough for your needs.
R-value also does not indicate how durable the sleeping pad is so you might want to purchase an additional one to protect a more delicate pad.
It is also recommended to always bring a patch kit along with you if you have an inflatable sleeping pad in case of a puncture or other damage that would render it ineffective.