Performance Sleeping Bags 101
HF Staff Remarks
One worry a hunter stresses over when planning a hunt where they know they will be spending nights on the mountain is if their sleeping bag is going to be warm enough or right for the trip. We would like to thank KUIU for lending us their insight and expertise in selecting the right performance bag.
Your sleeping bag contributes more weight than any other item in your pack and is often an afterthought when prepping your kit for a hunt. There have been significant advancements in sleeping bag designs and technologies over the past years that have reduced weight, increased warmth, and allowed bags to cover a wider range of temperatures and conditions.
Having just launched our Super Down Sleeping Bag line, I thought it would be helpful to share the information I learned about the advancements in bag design, construction, and fabrics. I hope this gives you a better understanding of what is important in today’s performance sleeping bags.
European Standards (EN) Testing and Ratings
Have you ever slept cold in a bag rated below the outside temperature?
Founded in 1961, the Committee for European Standards developed European Norms (ENs) in various business sectors to build a stronger market for goods and services.
The EN 13537 Test was designed to create a standard to test temperature rate sleeping bags in Europe and has become a standard worldwide. In order to be a qualified testing center, each lab must test six reference bags for calibration purposes. This ensures accuracy, which is critical.
While these tests are not required by United States manufacturers, they are being adopted by performance brands to guarantee the quality and performance of bags.
I do not recommend buying a bag that is not certified. Without a testing certificate the bag’s temperature rating is an opinion and there is no guarantee that it will meet your expectations.
The test uses manikin-generated insulation values and heat loss models to determine a temperature rating. The standard defines four temperatures that designate the range of utility for a sleeping bag. The most common temperature that performance sleeping bags report is the limit temperature. The limit temperature is the lower limit at which a sleeping bag user with a rolled-up body posture is in thermal equilibrium and not feeling cold. Bags are typically labeled with their lower limits as 0 degrees, 15 degrees, and 30 degrees.
At KUIU, we use the International Down and Feather Laboratory based in Salt Lake City, Utah for all sleeping bag and feather testing and certifications. This certification of temperature rating guarantees our customer the performance and quality that we claim from our bags.
Sleeping Bag Fill
The most important factor in choosing a sleeping bag is deciding on a fill; it drives the weight and bulk of your bag. It is critical to understand the properties of each fill in relation to the conditions you will experience in the mountains.
There are three types of fill: synthetic, down, and water-repellent down.
Synthetic fibers, which are less expensive than down, were originally the only option for wet conditions. This insulation retains loft when wet and dries relatively quickly.
Synthetic insulation is polyester threading that is designed to mimic the loft of natural down. Thinner threads fill voids and trap warm air, while thicker strands sustain the loft and durability of the fiber. Due to their hydrophobic nature, polyester synthetic bags are a smart choice in wet and humid conditions.
If considering the synthetic route, I recommend premium synthetic insulation. Primaloft One™ or TORAY 3D Continuous Fiber™ each have very high warmth to weight ratios for synthetic insulation. However, Primaloft One™ compares to a 650-700 fill power down, which is a low performance in comparison to premium goose down.
Down is next to the skin plume feather of a duck or goose. Not all down is created equal. Birds that come from colder climates produce larger and warmer plumes.
Older birds also produce larger and higher quality plume feathers, which translates directly to warmth. European birds used for harvest are typically 2 years older than anywhere else in the world, making Eastern Europe, specifically Poland, home of the finest quality down in the world.
Both duck and goose down is used in down products. While duck down is sufficient in comforters, pillows, and lower quality products, performance gear uses 100% goose down. Goose down is significantly lighter and warmer than synthetic insulation, but it is expensive due to the limited supply chain and high demand. The price of Eastern European Polish Goose Down is at an all time high.
Most manufacturers will not advertise the origin of the down because they buy it on the open market. Commodity sold down comes from Asian countries, such as China, and costs less due to the larger supply chain. Asia does not produce the same quality down because it is harvested in a warmer climate and at a younger age. This down does not have the life Polish Down has.
Because Eastern European and Polish Down plumes are larger and more durable, they hold their loft longer, thus extending their performance and life. I recommend researching the origin of the down fill before buying your bag. If this information is hard to find, you are likely purchasing a bag with Asian-sourced down.
Fill power is the most frequently used measure of down quality. It involves measurements taken from a one-ounce sample of down in a Plexiglas cylinder with a weighted piston compressing the down. The test requires controlled temperature, humidity, and preparation of the sample. A higher fill power reflects higher quality down because it fills more volume of the cylinder, which translates to more loft per weight. For garments it typically ranges from 600 to 850+ fill.
I recommend the highest fill power you can afford. The demand for down has increased over the past few years and the supply has decreased, driving up the price for down by as much a 60% to 70%, depending on the origin.
Besides being significantly more expensive than synthetic fill, when wet, down loses all of its insulating properties and takes an incredibly long time to dry and regain loft. This is why synthetic insulated bags were the only logical choice for wet hunting conditions, but then water repellent was introduced.
Water-repellent down is the most recent development in insulation. This highly specialized down has all the benefits of synthetic insulation and traditional down combined. Water-repellent down coated on an individual fiber level is the best long-term fill option available. Treated down holds its loft when wet without altering compressibility and durability features. The best water-repellent downs keep their original loftiness after washing.
The quality of water-repellent down varies. After long exposures to water, most repellency starts to fail. TORAY Quixdown™ has been scientifically proven to perform better than other treated down. Because of the durability and longevity of TORAY Quixdown™ it is the only water-repellent down I feel confident using.
Sleeping bag fabrics also affect the durability and weight of your bag. Lower performing bags use polyester fabrics, whereas higher performing bags use nylon. Nylon is known for its lightweight durability that provides wind and abrasion resistance.
A new advancement in fabric technology is stretch, down proof nylon fabric. TORAY Stunner Stretch™ stretches without adding heavy and moisture absorbing Lycra. This allows sleeping bags to stretch with your body, significantly increasing the comfort of a mummy style bag. These fabrics are a unique breakthrough in down proof fabrics and remain incredibly lightweight and durable.
The outer fabrics of high-quality bags are treated with a durable water-repellent (DWR) finish to protect your bag against moisture and condensation. DWR is a critical component in a sleeping bag because it protects your fill, especially in down bags.
There are two common baffle types: sewn through and true baffles.
Sewn through baffles are created by taking the outer fabric of the bag and sewing it to the inner fabric. This compresses the down, creating cold spots around the stitch line.
The most efficient way to construct a baffle is to create a true baffle. Down constructed with true baffles have several mesh walls that enclose down and prevent it from shifting.
Baffles can run vertically or horizontally. Because they are easier to construct, most bags are designed with horizontal baffles. This allows the down to shift to the outside of the baffle, creating cold spots at the top of the bag. Vertical baffles, however, utilize flow gates to keep down from shifting. Despite being more expensive to produce, this has proven to be the warmest and most efficient design.
For mountain hunting, I only recommend a hooded, mummy sleeping bag design with robust zipper, shoulder, and halo baffles to reduce heat loss. A cinch cord around the halo baffle for extreme cold conditions is also recommended. In combination, this allows you to utilize your bag in a wider range of temperatures.
We are now in the golden era of innovative technology for mountain hunting. This has spread into creating sleep systems that are lighter, warmer, and more reliable, giving us the opportunity to further chase our dreams into harsher climates.