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Modular Approach to a Sleep System

We received an amazing response to the blog posting ‘Modular Packing in your Backpack’ – how to keep order and keep your gear dry in your pack. If you didn’t catch it, you can read it here.

In this posting, I’d like to suggest another ‘modular’ concept – thinking of a sleeping bag as just one component in a system. The other components are a liner, a sleeping pad/sleeping mat, a pillow and a dry storage option.

Most outdoor end-users have heard about sleeping bag liners. They may know that a liner can keep your sleeping bag clean, is easy to wash, and may add a few degrees of warmth. However, it’s much less common to think of a liner as managing moisture in warm or humid conditions, and it’s very uncommon for end-users to think of a liner, a sleeping bag, and a sleeping mat forming a ‘modular system’ for use in a wide variety of temperature/humidity conditions.

The ‘sleep system’ for colder weather environments would work like this: the end-user can choose a slightly lighter and less bulky sleeping bag than otherwise would be the case, and pair it with a Reactor, Reactor Compact PlusReactor Extreme, or Thermolite® Fleece Liner to provide adequate warmth.


The sleeping mat would need to deliver the correct level of insulation, probably an R-Value of 3 or above – you can read about insulation values for sleeping mats here. Because all the components in the system are optimized for the conditions in which they are being used, they offer the best possible performance for the least possible weight and packed volume. Compare this with the end-user who carries around a heavier, bulkier sleeping bag without a thermal liner and without an adequately warm sleeping mat – who is surprised when he or she gets cold.


The sleep system for warmer weather environments comprises of a wicking liner and a sleeping bag which can be gradually opened up for ventilation, all the way to forming a full quilt.

The ideal liner for this is the Coolmax Adaptor (available in Mummy and Traveller shapes), and the perfect sleeping bag is either the Trek or the Micro (both available in different temperature ratings).


Imagine you’re traveling through Southeast Asia: at the beginning of your trip (perhaps in Bangkok), you may be at a lower elevation in warm and humid conditions, maybe even in a budget-priced hotel or hostel. For these conditions, you would sleep in just the Adaptor liner, which would help you sleep more comfortably while keeping you away from less-than-pristine bed sheets. (If there is concern about mosquitos or bugs, you could also opt for the Coolmax Adaptor liner with Insect Shield). As you travel to higher elevations (say, Chiang Mai), you would sleep in the Adaptor with the Trek (opened fully as a quilt) over you. As elevation increases further, you would progressively close the zippers (foot zipper and side zipper) on the Trek until at the coldest point of your trip you would be inside the Adaptor in a fully cinched up sleeping bag.

In the above case, you may well be traveling from hostel to hostel, and thus might not have a sleeping mat with you. A pillow, on the other hand, should definitely be part of this system.

Perhaps the most classic example of the use of a sleep system in moderately cold to warm conditions would be the Appalachian Trail. At the start of the trail in Georgia in April, a Micro Mc II would keep you snug and warm with the Adaptor inside it; you might even open the foot box drawcord for a little ventilation. Further north in the chillier conditions of the Nantahala Forest, or perhaps the Mount Rogers Wilderness, you may well have all the drawcords cinched tight. As you progress through Virginia, and the temperature and humidity increases you would progressively open the side zipper and eventually sleep under the Micro opened like a quilt. In the hot humid nights in Pennsylvania, the Adaptor by itself would suffice, before you head up to New England and once again use the system’s ability to cope with increasingly cold nights.

The soft, stretchy Adaptor liner will provide you with supreme comfort in both the above scenarios. The sleeping mat you would include in this system would not need to provide a particularly high level of insulation, except at the northern end of the trail. For this reason, an uninsulated mat such as the Ultralight Sleeping Mat (R-Value 0.7) might be your choice. On colder ground, the Insulated Ultralight Sleeping Mat (R-Value 3.3) would be the appropriate system component.

For travel and general backpacking, the Trek is a roomy, comfortable sleeping bag which is surprisingly light – the Tk I weighs only 1lb 13oz / 830g. It also has a lot more flexibility than many other sleeping bags – especially when used with the wicking Adaptor liner or Thermolite® Reactor liner.

And, on the Appalachian Trail (where weight and packed volume are paramount), the Micro / Adaptor system weighs only 1lb 12oz / 800g together. It packs down to around 3 Liters (about two and a half Nalgene bottles). The 850+ UltraDry Down and box-baffle construction of the Micro, plus its highly water resistant shell make it a very capable sleeping bag – paired with the Adaptor liner it may be the best possible AT sleep system, period.micro

Sea to Summit sleeping mats are an integral part of any sleep system – they are more comfortable, easier to inflate and deflate and are made of higher quality materials than any other air-filled sleeping pad. Reading the above-mentioned blog post on the physics of comfort and insulation may take the mystery out of the purchase of a mat (helpful given the prevalence of marketing-speak rather than facts when it comes to sleeping pads).

A Pillow is also a key element in a good night’s sleep – and the Aeros Pillows are not only incredibly comfortable, they are light and very packable.


Finally, remember that the best sleeping bag and liner will only offer very modest comfort if they are wet or even damp. Make sure you pack them away in an appropriate dry-storage option inside your pack (you don’t want to run the risk of snagging your sleep system or even your shelter on a sharp branch or rock). The eVent Compression Dry Sack, eVent UltraSil Compression Dry Sack and eVac Dry Sack are all great candidates for packing away your sleep system.

If you have questions on which liner will work best with your sleeping bag, or which sleeping bag or sleeping mat is most suitable for a particular application, all you have to do is –

Ask Baz

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