Sea to Summit Alpine AP2 Regular Sleeping Bag

EN13537 is a European standard for sleeping bag temperature ratings.

Everyone sleeps differently; some people are very warm sleepers while others feel the cold easily. There are many factors that affect your warmth and comfort in a sleeping bag. An important factor is that you use a good insulating mat to prevent your body heat from being drawn into the cold ground. Other factors include your tent or shelter, gender and metabolism, clothing, sleeping bag liner, use of the hood and your daily calorie intake.

Although the EN13537 standard does not identify a single precise temperature a tested sleeping bag is suitable for, it does provide an industry standardised temperature range that a typical user can refer to as a guide for the conditions their bag will be most comfortable in.

The EN13537 standard provides three temperature levels to guide a consumer in their choice:

Comfort: The temperature at which a standard woman can expect to sleep comfortably in a relaxed position. If you consider yourself a cold sleeper use this rating to decide the coldest temperature the sleeping bag is suitable for.

Lower Limit: The temperature at which a standard man can sleep for eight hours in a curled position without waking. If you consider yourself a warm sleeper you can use this rating to decide the coldest temperature the sleeping bag is suitable for.

Extreme: This is a survival only rating for a standard woman. Between the lower limit and the extreme rating a strong sensation of cold has to be expected and there is a risk of health damage due to hypothermia. This is an extreme survival rating only, we do not recommend you rely on this rating for general use.

The EN13537 temperature tests use a thermal manikin with heaters and temperature sensors to measure the insulation value of a sleeping bag. This manikin is wearing one layer of long underwear and is placed inside the sleeping bag on an insulating mat. The test is conducted in a temperature controlled chamber and a range of comfort temperatures are derived from measuring the energy required to maintain homeostasis in the manikin
to a set temperature.

All Sea to Summit sleeping bags have been tested to the EN13537 standard. We recommend you use our EN13537 quoted ratings as a guide and a comparative reference to other EN13537 tested bags.

To achieve maximum loft and insulation, down must be dry and uncompressed. Even if sleeping in a dry tent your sleeping bag can still get damp or wet from condensation; vapour leaving your body passes through the down, and condenses on the outside and inside of your sleeping bag shell. The condensation that forms on the inside of the shell is absorbed by the down reducing its loft and warmth.

Over several days of packing and unpacking a sleeping bag, wet down mixes with dry down affecting its ability to loft. By the end of a long trip it is not uncommon for a sleeping bag to have decreased in warmth significantly because the down is damp, reducing its loft and its ability to insulate properly.

At Sea to Summit we have solved this problem with our 3D NanoShell® and ULTRA-DRY Down®.

The NanoShell® Face is a 20 denier fabric that is highly breathable, water resistant and treated with a Nano DWR for unparalleled performance in wet and windy conditions .

The 3D Barrier is a non-woven silicone encapsulated 3-dimensional layer under the NanoShell® Face.

Together they form the 3D NanoShell®, a condensation management system that insulates, repels water and protects loft.

The 3D NanoShell® provides a 3-dimensional layer between the cold external environment and the warm down inside your sleeping bag. When vapour passes through the down, it enters the 3D Barrier, before exiting the breathable NanoShell® Face fabric.

Any condensation that forms under the NanoShell® Face fabric is separated from the down by the 3D Barrier. Due to its hydrophobic nature, this 3D Barrier traps the condensation preventing this moisture from mixing with the down layer .

When conditions become favourable the 3D Barrier also promotes fast evaporation expelling moisture to the outside preserving dry and fully lofted down .

Over several days of usage, the weight of absorbed moisture and the associated drop in insulation that other bags would suffer makes 3D NanoShell® the wise choice for expeditions.

Down insulates best when it is uncompressed and fully lofted. To help the down loft correctly we use a differential cut shell and lining. The top shell of all Sea to Summit sleeping bags is cut larger than the lining. This creates space in between for the down to loft fully. In the bottom of the bag we use a reverse differential cut. By increasing the size of the lining relative to the shell, down lofts up to fill the voids around your body, torso, legs and the small of your back. Trapping heat close to the skin is essential for efficient warm sleeping.

Down is the soft plumage of birds that lives under the feathers. A single piece of down is called a plume. The majority of down used in clothing and bedding comes from geese and ducks. Down is one of the best warmth to weight insulators available. It is not only warmer for weight, but compresses much smaller and is much more durable than most synthetic fill equivalents.

Loft is the volume for a given weight of down. High loft down is warmer for a given weight than low loft down. The most common measure of loft is fill power, a term which is often used interchangeably with loft. Fill power is the volume, in cubic inches, that an ounce of down will fill. Thus, one ounce of 650 loft down will fill 650in3.

Composition refers to the percentage of down versus feathers in a batch of down. In Australian and US regulation, 90/10 means that 90% of the batch is down plumes, the other 10% is small feathers. The higher this ratio, the lighter, softer and more compressible a sleeping bag will be. It also means there are fewer feather quills or spines to poke through the stitching or fabric of a bag.

Sea to Summit Sleeping bags use down that has been sourced and certified by the Responsible Down Standard (RDS). The RDS is helping to shift the entire down and feather industry towards more humane animal rearing and handling practices. Overseen by the industry leading Textile Exchange, the RDS requires independent, third party assessments of all aspects of animal rearing and handling throughout the entire supply chain. By only using down that meets the audited requirements of the RDS we can have confidence that each phase of the collection process has been completed with the welfare and ethical treatment of waterfowl in mind. To find out more information about how the RDS is improving animal welfare during down collection, please visit responsibledown.org

• Repels moisture
• Retains loft
• Dries faster
• Anti-bacterial and anti-microbial
• Prolongs the life of your sleeping bag

ULTRA-DRY Down® is a permanent* Nano-level water repellent polymer treatment applied to our high loft, high quality down. The Nano-thin treatment vastly improves our down’s reaction to water without effecting its weight or loft performance. ULTRA-DRY Down® retains over 60% more loft and absorbs 30% less moisture when compared with untreated down. Sea to Summit sleeping bags dry out 60% faster than bags with untreated down.

The Nano-level treatment also inhibits bacterial and microbial growth, which makes Sea to Summit sleeping bags more hygienic and improves their lifespan.

*No loss of treatment effect has been seen in over 14 wash cycles.