Materials and construction of sleeping bags
Understanding sleeping bags correctly
Individual temperature perception: everyone freezes differently
Buying a sleeping bag is a highly individual decision – depends on the intended use, personal warmth sensitivity, and your own physical constitution. Just because a certain sleeping bag "works" well for a friend doesn't necessarily mean it will work for you too...
There's a very simple reason for this: every person has a different, highly individual perception of heat. Therefore, all 'official' temperature specifications (e.g., according to the European standard EN 23537) can only serve as guidelines.
How does a sleeping bag keep you warm?
A sleeping bag doesn't release heat; thanks to its insulating properties, it merely retains existing body heat. The more air a sleeping bag retains and the less air circulating within it, the better it performs.
Heat loss in the sleeping bag
There are various reasons for the heat loss when sleeping in a sleeping bag:
- convection (Air exchange): Air circulation, for example, when the zipper is open or when the thermal collar is missing or not in use in subzero temperatures, leads to heat loss because the warm air from the sleeping bag mixes with the cold ambient air. As a result, the body constantly needs new energy to maintain a constant temperature inside the sleeping bag. This also applies if the sleeping bag is too big or too small.
- Radiation (Radiation): Our bodies radiate heat. The better a sleeping bag reflects and stores this heat, the less energy the body needs to maintain a constant temperature inside the sleeping bag.
- Evaporation (Evaporation): Every person loses approximately half a liter of moisture through their skin overnight while sleeping. If the moisture remains on the skin, evaporative cooling occurs, and the body attempts to dry the skin with heat. The drier a sleeping bag keeps the skin, the more energy the body saves.
- Conduction (Heat conduction): The less insulating properties a material has, the faster heat flows away, e.g. in direct contact with the cold ground.
A good sleeping bag should keep heat loss to a minimum. The materials used, the construction and the shape of the sleeping bag all play a role in this. direct Influence on the insulating capacity.
Comparable temperature information
The uniform Test procedure according to European standard 'EN 23537' guarantees a neutral comparability of the temperature information of sleeping bags.
Here is a detailed explanation the temperature specifications and the test procedure.
Materials for sleeping bag filling
There are many ways to achieve good insulation. Down or synthetic sleeping bags, as well as wool sleeping bags, have become established in today's outdoor environment. Which sleeping bag made of which material is suitable for what depends primarily on the intended use and is determined by the following material properties:
Synthetic fiber in sleeping bags – the easy-care ones
The raw material polyester as filling material
The raw material for synthetic fiber filling is usually polyester, which is processed into fine fibers. Such fibers are composed of several so-called filaments.
A distinction is made between staple fibers and continuous filaments.
Staple fibers are cut and "glued" together, either thermally or with real adhesives. Due to their construction, these filling materials are fluffier and softer to the touch. Depending on the fabric construction, these fibers sometimes require an additional fleece. The insulation thickness is very uniform. With appropriate water-repellent treatment, they "float" on water.
Continuous fibers are extremely tear-resistant and generally more stable. However, they are somewhat "heavier." This allows for the use of slightly less dense outer fabrics. A typical example of this group is Polarguard. Additional interfacing does not need to be sewn.
Shape variants of synthetic fiber filaments
These filaments can have different geometric designs. Some are hollow, hence the name hollow fibers. Their hollow chambers are round, star-shaped, or triangular. Some manufacturers bundle several hollow fibers together. Three-dimensional shapes of the filaments or crimped structures ensure greater stability and loft of the filling.
Type of filling
Synthetic fiber fillings can be incorporated into a sleeping bag in different ways.
Chamber filling
Similar to down filling, the synthetic fiber fill material is loosely blown into individual chambers of the sleeping bag shell. This achieves a very high loft, but the filling can shift and, depending on the chamber construction, create cold spots.
Fleece/Mat
Synthetic fiber fillings are often processed in the form of a mat or fleece. This allows for a uniform thickness of the filling material, which can no longer shift. It also allows for a construction with very few seams/cold bridges.
Special treatments
Fibers are often further treated to achieve special properties. This is referred to as "finishing." A silicone coating makes the fibers more supple and thus more resistant to shear forces that could otherwise break them. Additional finishes are available to make the polyester filling itself water-repellent.
Advantages of synthetic fiber fillings
The fineness of the fiber and the three-dimensional structure, achieved through construction and bonding of the fiber (e.g., air-textured) and/or stacking technology, traps the air, reduces air circulation, and thus increases the insulating effect. This largely remains even in "normally humid" conditions. Other advantages of synthetic fiber sleeping bags include the generally relatively low price, their robustness, and low maintenance.
Disadvantages of synthetic fiber fillings
Synthetic sleeping bags quickly become relatively heavy when lower temperatures are required. Compared to down, synthetic sleeping bags are significantly less compressible. After compression, the filling also takes longer to regain its full loft. The biggest disadvantage is the uncomfortable sleeping environment, as synthetic fibers have very limited ability to regulate temperature and humidity.
Synthetic fibers are sensitive to:
- The same rolling and packing over and over again. In the high-stress areas, you thin out and become weaker.
- Machine washing and excessively high dryer temperatures. Adhesives will dissolve!
- Incorrect storage (compressed in the transport bag).
- Tensile stress (packing or turning in the sleeping bag).
- They cannot develop as good a climate as natural fibers.
Down – Resting on feathers
Down is a natural product. It offers an excellent insulation-to-weight ratio. Compared to synthetic fibers, it provides a more comfortable sleeping environment (only in combination with breathable inner and outer fabrics!). It can also be extremely compressed over a short period of time without losing its properties. The resulting pack volume, as well as the aforementioned insulation-to-weight ratio, make it particularly attractive for alpine use.
Down and feathers - what's what?
Down – here, we mean the so-called down ball, a point-like core with three-dimensional branches – is never used alone, but always in conjunction with supporting feathers. These form a stable, "elastic" matrix in which the down expands. This is expressed in a mixing ratio, e.g.: 80% down, 20% feathers. The ratio is determined based on the intended use and the price-performance ratio. Many people forget that the quality of the feathers is almost as important as that of the down. If, for example, the feathers are brittle and the quills are splintered, the sharp remnants of the quills will cut the fabric and the seams. 1 kg of down contains between 500.000 and 1.000.000 down feathers.
Down/feather ratio:
- 50% : 50% = bedding, cheap sleeping bags. No weight-related use. Less insulation.
- 60% : 40% = Beginner camping. Affordable sleeping bags.
- 70% : 30% = Good camping sleeping bags. Robust construction, partially duck down.
- 80% : 20% = Alpine entry-level models, more expensive models. Better weight-to-insulation ratio. Almost exclusively goose down.
- 90% : 10% = Top alpine sleeping bags. Expensive. High-maintenance. Very good weight-to-insulation ratio. Goose down.
Bulking power or fill power
The bulk of the thumbs is measured in CUIN . Fill power is a characteristic measure of down and other upholstery fabrics, which indicates the volume that a certain mass of the fabric regains after some time of compression.
Standardized test procedure for determining bulk power
A common unit in trade is the Anglo-American cubic inches pro ounce (English cubic inches per ounce, short in³/oz or cuin (for cubic inches). Measurements are taken, for example, according to US Standard 2000, in a glass cylinder with a diameter of 241 mm (compression 68,3 g) by... ounce (≈ 28 g) of the down mixture is compressed in the measuring cylinder for 24 hours. The volume to which the sample expands is then measured and expressed in inches (1 inch³ ≈ 16,4 cm³).
The European and American standards differ slightly, but the results are comparable (EN 284mm DM, 94,25 g mass. Down weight 30g – IDFB testing regulations).
The higher the bulk value, the better the thermal insulation relative to pack volume. Fill power is one quality measure, but not the only one.
Cuin Values in practice
- 400-500 cuin are good and sufficient for many applications such as bed linen.
- 500-600 cuin That's already a good value; with duck down, this is the limit. The models with 600 cuin are significantly more expensive.
- 600-700 cuin It should have a high-quality down sleeping bag. However, it requires a bit more care.
- 700 - 750 cuin is a top-quality product.
- About 800 cuin or even higher levels are rarely achieved. (However, they can be achieved through intensive cleaning. This causes the down to lose its protective oils and become more sensitive to moisture.)
Further quality indicators for down
The purity (after washing and processing) of the down is indicated by the so-called oxygen number. A higher number indicates the presence of organic residues, possibly even bacteria. 1,6 to 3,2 are very good values. The highest tolerated value is 10.
Other values include the turbidity number, the oil/fat content, and the pH value. These values usually don't appear in the descriptions, as they can vary depending on the user and washing habits.
Origin and species
Furthermore, the Origin of the down a role. Goose down is generally larger than duck down, meaning its three-dimensional structure is larger. If the animals come from colder regions, this structure is also denser compared to animals from more southerly climes.
Down and moisture
Objectively speaking, down is generally very robust – even when it comes to moisture. However, it loses some of this property due to the process of cleaning and processing it into sleeping bag down. This means that down is significantly more susceptible to moisture than synthetic fibers. If it absorbs more moisture in certain situations and clumps together, it no longer creates volume. The result is reduced insulation capacity.
Therefore, it is necessary to air a down sleeping bag as often as possible and, in more extreme cases, to dry it.
In winter or in regions with permafrost, problems often arise with down sleeping bags. Body perspiration is trapped in the down and freezes there. Drying is almost impossible. After a while, the down clumps together and loses its insulating properties. This problem can be reduced by choosing suitable functional underwear.
Down and chambers
To prevent slippage, the "loose" down is packed into chambers. Cheaply stitched chamber seams create cold spots. Good sleeping bags are characterized by slanted chambers, trapezoidal chambers, or so-called H-chambers.
In addition to the shape of the chambers, their arrangement, elasticity, and fabric selection also play a role. Elastic chambers prevent excessive force from being exerted on the seams, preventing them from stretching and allowing the down to "slip through." If the chambers are arranged in a ring around the sleeping bag, you can shake the down more toward the front or back as needed, thus adapting the sleeping bag to the current temperature.
Down sleeping bags are therefore particularly suitable for tours where small pack size and weight are important, while at the same time providing optimal insulation (e.g. mountain tours).
In general, down is more resilient to packing than synthetic fibers. Nevertheless, a down sleeping bag should be stored in a slightly larger, breathable storage bag in a dry, airy place.
Down should be washed with a special moisturizing detergent to keep the down soft and supple. Down sleeping bags are very durable when stored properly, even more durable than synthetic sleeping bags. Here you will find a detailed washing instructions.
Wool – climate regulation at the highest level
The development of a climate miracle
Anyone who's ever camped, trekked, or slept in a sleeping bag anywhere else is probably familiar with the damp, cool feeling of waking up the next morning. The body releases moisture (up to 500ml per night), and the dew adds the rest.
This damp, cool combination requires a lot of energy from the body to regulate its temperature. This means you don't sleep as well and wake up feeling unwell, usually with back pain, as the humidity cools your muscles.
This is exactly what Markus Wiesböck, the founder of Grüezi bagHe wanted to sleep well on vacation, wake up refreshed, and have renewed energy for his adventures.
In his 30 years of experience with sleeping bags, the development of sleeping bags always revolved around making the sleeping bag even lighter, and Markus found himself sleeping worse and worse as a result.
So he began experimenting with different materials. After what felt like endless tests with synthetic fibers, down, kapok (nature's finest hollow plant fiber from the kapok tree), beech, alpaca, camel hair, virgin wool, and much more, he finally achieved the desired result: good sleep. And he did it with a material that has been used for thousands of years, just not in sleeping bags.
Alpine wool as a natural air conditioner
The alpine wool used in sleeping bags acts as a natural climate control system: The body constantly releases moisture. However, if there is too much humidity in the sleeping bag, the body freezes, and a good night's sleep is no longer possible. Wool absorbs moisture and releases it to the outside in a controlled manner, preventing evaporative cooling. This regulation allows for a warming or cooling effect, creating a balanced climate inside the sleeping bag. The resulting feeling of well-being ensures restful sleep. Wool remains warm even when damp. It can absorb up to 30% of its own weight in moisture while still retaining its insulating properties.
Grüezi bag uses wool from Alpine sheep as filling for its Biopod product line. It is supplied by the renowned wool supplier Lavalan. To make the Alpine wool washable and even more stable, PLA (corn starch) is added to the wool. This prevents the wool from slipping, makes it washable, and dries even easier.
Wool and sleep research
Studies like those conducted by Woolmark Australia show that people sleep longer and more restfully with wool. People sleep best at a skin temperature of 33°C. The climate created by Alpine wool under a blanket or in a sleeping bag is very close to this temperature. Other materials are less able to achieve this. Synthetic duvets, in particular, are significantly inferior to wool, especially Alpine wool. If the climate regulation isn't working properly, you'll start to sweat easily and kick yourself free from the blanket while you sleep. Without a blanket, you'll cool down too much, freeze, and sleep will be restless.
This was tested in sleep labs at a normally comfortable ambient temperature of 22°C. Incidentally, a blanket made of alpine wool is also comfortable for partners sleeping under the same blanket: each body temperature is regulated separately.
Download Wool Study German as PDF file
Download Wool Study English as PDF file
Alpine wool is a renewable raw material
Robust, natural, biodegradable, and renewable: Sheep's wool, in this case the special Alpine wool, can be sheared annually. For today's consumers, who are increasingly sensitive to the environmental impact of clothing, wool is a product of responsible consumption. Alpine wool is a natural raw material that grows back again and again and degrades without residue.
Advantages of wool filling:
- Alpine wool balances the climate
- Alpine wool isolated
- Alpine wool is a renewable resource
- Alpine wool is odorless and antibacterial
- Alpine wool in the sleep laboratory
- Alpine wool is easy to clean and robust
- Alpine wool in the sleeping bag
- Alpine wool and Moisture wicking
Once you've slept with Alpine wool, you won't want anything else. We promise!
DownWool – A special combination
DownWool* is an innovative HIGH-END filling made of 70% down and 30% specially treated wool.
Daune Down has very high insulation performance despite its low weight. This makes it an excellent filler for sleeping bags and jackets. However, down only insulates when dry. As humidity increases, its fine structure collapses, significantly reducing its insulating effect.
Wool It has excellent insulating properties and absorbs moisture without losing its insulating power. This is its major advantage over down. Furthermore, wool regulates temperature very well and also has antibacterial properties. Its disadvantage compared to down is its slightly higher weight.
In DownWool we have mixed both materials in a perfect ratio
To ensure that the down and wool bond together permanently, we have developed a sophisticated technical process. The great advantage of DownWool is that, compared to pure down, it is not as sensitive to moisture and therefore insulates better in high humidity. Compared to pure wool fillings, DownWool the advantage of being significantly lighter.
With the unique material mix of DownWool we achieve the best insulation and a perfect dry climate with low weight.
DownWool can do all this:
- DownWool is less sensitive to moisture
- DownWool naturally balances the climate
- DownWool is light and insulates excellently
Cut, shape and construction of sleeping bags
There are basically two different sleeping bag designs: the blanket and the mummy. Both have their advantages and disadvantages.
mummy sleeping bags
The mummy shape offers the best compromise between sleeping bag space, pack size, and weight. It follows the shape of the reclining person and minimizes the amount of air inside the bag that needs to be heated. The more tightly the sleeping bag fits around the body, the better it retains warmth. However, this only applies as long as the filling isn't crushed.
blanket sleeping bags
Ceiling shape For people who need more freedom of movement and primarily sleep outdoors in temperatures above 0°C, the blanket sleeping bag is ideal. This is a rectangular sleeping bag with or without a hood that can be completely unfolded into a blanket.
Egg-shaped sleeping bags
For people who place more value on sleeping comfort than on weight and warmth, or for whom mummy sleeping bags are too tight, mixed forms are also suitable, such as: egg-shaped sleeping bagsHere, the aim is to combine the shape of a mummy and a blanket. The result is a narrow head, shoulder, and foot area like a mummy, but with a very wide waist that allows freedom of movement for the arms and legs.
Other form variants
Shorter people should buy short sleeping bags to minimize airflow around the foot area. Alternatively, you can tie the foot section behind the feet (e.g., for children) or fill the foot section with sweaters or other clothing.
There are also sleeping bags that grow with children. This version has a zipper around the foot area that allows for an extension. This makes the sleeping bags ideal Grüezi bag Children's sleeping bags for body sizes from 100cm to 155cm.
The length of the zipper as well as the use of filled thermal collars or lined zipper covers contribute significantly to the insulating capacity of the sleeping bag.
Special features of the Grüezi bag models
outer material
Grüezi bag uses high-quality, uncoated, and rustle-free polyester or nylon fabrics with a high fiber density (thread count), usually in rip-stop construction. The high fiber density is important to prevent the filling from penetrating the fabric. Rip-stop fabrics feature thicker, more stable threads woven into the fabric at regular intervals. If the fabric tears, it stops at one of these thicker threads, preventing the damage from spreading.
Water-repellent impregnation Bionic Finish Eco from Germany
In addition, the outer fabrics are water-repellent.
Breathability and the resulting sleeping environment, as well as the resulting comfort, are very important to us. With cheap, coated materials, condensation condenses on the inside and drips back into the filling. That's why we use highly breathable, PFC-free impregnations.
Lining:
Here we use highly breathable, skin-friendly, partly softly brushed, lightweight materials.
DOMESTIC EQUIPMENTS:
Important features of a Grüezi bag-Sleeping bags are: