Rab Lab – Sleeping Bags
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SLEEPING BAGS
Discover what goes into the design and construction, and find out what to look for in your next sleeping bag.
Discover what goes into the design and construction, and find out what to look for in your next sleeping bag.
Sleeping Bags: Then to Now.
Sleeping bag technology has come a long way. Thousands of years ago, we were wrapping ourselves in animal pelts and skins just to stay warm. Today, we're using cutting-edge insulation technology and fabrics to craft the lightest, warmest sleeping bags built for adventure. Even since the first Rab sleeping bag was hand-cut and sewn in the early 80s, its warmth, weight and efficiency have dramatically improved.
A sleeping bag enables us to explore and experience the world in an extraordinary way. Keeping us warm and comfortable when we need to rest and packing down small when we're on the move.
Baffled by baffles?
All down bags need baffles. These fabric chambers hold the down in place and stop it from migrating to one end of the bag, like a duvet on your bed. Baffles can either be stitch-through or boxwall. Almost all of our bags use boxwall chambers as this is the best method of construction to minimise heat loss.
In down sleeping bags we talk about baffle height and baffle offset.
Baffle height is the height of the internal mesh that separates the inner and outer fabrics of the sleeping bag and baffle offset is how much the mesh deviates in a horizontal direction producing a trapezoidal chamber shape.
How do we build a sleeping bag?
There are different ways to build a sleeping bag. Its construction and insulation type tell you a lot about its potential to keep you warm and the environment it's intended for.
Down to Detail
Filling chambers with down may sound straightforward, but simple doesn't mean easy. Our designers and UK factory team meticulously work to ensure that the down is efficiently distributed and maximizes the performance of your sleeping bag.
VOLUME
We calculate the exact volume of down required within each individual chamber (or baffle) and ensure it is accurate to the gram when we fill our down bags in our own Derbyshire factory.
BODY MAPPING
More down around the torso and footbox is an efficient way to keep you warm and optimizes the warmth-to-weight ratio.
GENDER
Men and women lose heat differently, with women requiring an extra 2.5°C to maintain the same core temperature. Our women's down bags are cut shorter with narrower shoulders, but filled with the same volume of down to accommodate for this.
COMPRESSION
When you lay in your sleeping bag, the base of the bag is more compressed but the top has better lofting potential. We distribute a different ratio of down into the top and base to make the most of the top's lofting ability.
Synthetic Specifications
We use a couple of clever construction techniques to make the most of the synthetic insulation we use in our sleeping bags.
CONCERTINA CONSTRUCTION
Single, double or even triple layers of synthetic sheet insulation are arranged in an accordion-like structure to maximise air trapping and improve heat retention.
OFFSET LOCALISED QUILTING
This means the stitching that holds the insulation in place (quilting) has been minimised to reduce cold air passing through the stitch lines.
IN ACTION
In this example, you can see two layers (double layer) of insulation with offset localized quilting. The inner layer of insulation is arranged in an accordion (corrugated) shape to trap more air.
By offsetting the quilting of the insulation between the outside and inside of the bag, we can reduce the amount of cold air that can enter the bag through the stitch lines.
What shape is for you?
Our sleeping bags come in a variety of different shapes. The different bag shapes will not only influence weight and pack size but also the bag's performance in certain conditions.
MUMMY TAPER SHAPE
It is the narrowest of our bags and eliminates “dead space” making it as thermally efficient as possible. This cut will generally mean the bag will roll with you as you sleep. Although it compromises on space, this shape will maximise performance and minimise pack size and weight.
WIDE MUMMY SHAPE
A more generous cut for extra comfort as you sleep with room to move your legs. These bags will increase in bulk and weight but will allow for a more relaxed sleeping position.
EXTRA-WIDE MUMMY SHAPE
These bags are generally much larger than the rest of our bags. They allow you to sleep in extra layers, such as our Expedition bags, which are designed for extremely cold environments.
RECTANGULAR
These bags are rectangular in shape and often have an L-shaped zipper. You can open them up like a quilt or zip them together to make a double sleeping bag. These bags are all about comfort, space and versatility.
Some Extra Things to Consider…
Regardless of fill power or fill weight, if a sleeping bag is too large for you, you will lose heat. Some of our bags come in more than the standard size; we offer women's, extra wide, and extra long styles to help accommodate different body sizes. Our Expedition series is oversized to accommodate the bulky insulating clothing required in extreme environments. Like buying a jacket, the best way to ensure a sleeping bag is right for you is to try it on for size, as each model will fit slightly differently.
What does differential cut mean?
Differential cut is the difference in size between the inner and outer shell of the sleeping bag. In some bags, like our Ascent range, the inner shells are usually the same size across the range, while the outer shells increase in size to accommodate more down.
We use differential cut along with baffle height to scale the size of the bags' chambers across a range. A higher fill weight or higher fill power of down needs more space to loft.
We believe we use some of the largest differential cuts in the industry, allowing our bags to loft higher than our competitors.
Dreamworthy Designs
At Rab, all our sleeping bag designs have a range of clever features aimed at helping you get a good night's sleep.
The hood drawcord means you can seal in the warmth and prevent it from escaping through the top of your head while keeping your face open for comfortable breathing.
The elasticated internal quilting (or stitching) pulls the insulation towards the user to eliminate cold air pockets.
An angled footbox (or shark fin) offers a more comfortable position for your toes and minimizes the chance of down migration and cold spots.
The baffles at the neck and shoulders with an adjustable drawcord achieve a perfect fit and keep the warmth inside the bag.
Internal zippered pockets keep batteries or your phone warm and within reach, so you can still hear your alarm on an early mountain start.
It's also useful to know that all our bags have their stats printed on the inside of the zip baffle so you can always remember what temperature range your bag is designed for.
The hood drawcord means you can seal in the warmth and prevent it from escaping through the top of your head while keeping your face open for comfortable breathing.
The elasticated internal quilting (or stitching) pulls the insulation towards the user to eliminate cold air pockets.
An angled footbox (or shark fin) offers a more comfortable position for your toes and minimizes the chance of down migration and cold spots.
The baffles at the neck and shoulders with an adjustable drawcord achieve a perfect fit and keep the warmth inside the bag.
Internal zippered pockets keep batteries or your phone warm and within reach, so you can still hear your alarm on an early mountain start.
It's also useful to know that all our bags have their stats printed on the inside of the zip baffle so you can always remember what temperature range your bag is designed for.
What temperature is your bag rated for?
All these construction methods, insulation types, and design features will impact the weight and packability of your bag, but most importantly, they will influence the temperature range at which it will be most comfortable for your use.
EN Testing – Lab Temperature Testing
At Rab, we use the EN ISO 23537 standard to classify most of our sleeping bags. This standard was implemented to help provide benchmark temperature measurements of sleeping bags across the industry. EN ISO testing produces a series of temperature limits that are described as:
The comfort temperature indicates the minimum temperature at which a person can sleep in a relaxed position and get a good night's sleep.
The comfort limit rating is the temperature range at which a person sleeping in a curled position and fighting the cold can still sleep through the night.
The Extreme Rating is for an emergency scenario: it is the minimum temperature a person can remain in the sleeping bag for up to six hours in a curled position while truly fighting the cold. It is worth noting that frostbite at these temperatures is very possible.
How does it work?
A thermal mannequin is placed in the sleeping bag during the test on a standard foam roll mat. A series of measurements are taken to see how insulating that sleeping bag is at various temperatures.
Rab's Sleep Limit: Real-World Temperature Testing
Weight and Packability
Sleeping bag temperature ratings can often be a primary concern when purchasing a sleeping bag, but both weight and pack size should be considered in the selection process.
If you're driving to the campsite or setting up a base camp, then a larger or heavier bag might suffice and be more comfortable. However, when carrying gear in the mountains, every gram often matters.
Generally, bags with high fill power will be lighter for the same warmth as those using a lower fill rating or even synthetics.
Introducing TILT Technology
We have spent decades refining the construction of our sleeping bags. Exploring insulation and perfecting our technique, but we knew there was more to do. Our goal was to find a way to significantly improve heat retention without compromising weight, breathability, or pack size.
Taking inspiration from technology used in space exploration and emergency blankets, we created TILT (Thermo-Ionic Lining Technology). The fabric fibers are coated with vaporized metal particles that reflect heat back to the body with incredible results.
LINING
In our down bags, TILT is applied to the lining fabric, keeping it as close to the user as possible and maximizing its effect. The silver sheen of the titanium particles used is physically visible on the inside of the bag, but the fabric remains as soft and lightweight as any other down-resistant material.
INTEGRATED
In our synthetic bags, we use aluminum particles to coat an ultra-thin gauze-like layer (fabric) that is part of the bag's construction. It is placed as close to the body as possible, just behind the lining, to improve its efficiency.
From construction, insulation, and design to weight, pack size, and temperature ratings. There's a lot to unpack when it comes to sleeping bags.
The next time you're considering purchasing a new sleeping bag, be sure to look for the Rab Sleep Limit and consider the reasons why one bag may offer greater performance than another.
