Everything you always wanted to know about sleeping bags, but were afraid to ask.

Aconcagua is a very cold place, especially at night. In the high camps, when the sun disappears behind the Pacific Ocean, the temperature drops dramatically reaching 30 or 35 degrees below zero in camp Colera, almost 6,000 meters above sea level. In weather like this, spending a good night before going to the summit or when returning from it, after a strenuous day, is a necessity. But before we start analyzing the points for or against the available options for insulating, it is convenient to start from the basis for what we are looking for. Of course, the overall idea is not going to the mountain to have a bad time, but quite the opposite, and the sleep − or the quality of it − plays a key role in this matter. One of the questions that we receive the most is about this regard. In the expedition gear checks, right after the briefing, it is common to find out that a passenger is not properly equipped with the type of sleeping bag we recommend for Aconcagua. The latter is explained by a kind of “underestimation” towards Aconcagua, which is eventually compared to another of the Seven Summits, such as Kilimanjaro. This comparison is shattered at the very moment passengers arrive at Plaza de Mulas, or Plaza Argentina, or even when they start the summit push. Aconcagua is way more than trekking, and that is why the gear must be in accordance with the challenge that we have ahead. But let’s go back to the initial premise: synthetic or down sleeping bag? 

Both, down and synthetic filling have pros and cons when it comes to performance, so choosing the right type of insulation wisely can turn a cold and uncomfortable excursion into a pleasant trip in the great outdoors, assuming that the filling we choose will have a direct impact on the weight of the bag, its size when compressing it, its ability to dry, the heat it provides us and even what we are going to pay for it.  

Let’s start with the down sleeping bag.

Down sleeping bags, compared to those made of synthetic materials, have an excellent compression capacity (not a minor detail when it comes to loading the backpack on the expedition) and, if we take good care of it and follow all the cleaning instructions of the manufacturer, it can last us for several years without losing its effectiveness in providing heat. 

Another undeniable advantage of the down filling is its ability to load the bag more effectively, which directly affects the heat-weight ratio, and that translates into a lighter result. But not everything is advantageous in feather filling. One of the most common criticisms usually made is its tendency to pack when it gets wet, with the consequent loss in its ability to generate warmth, and for that reason, it is essential to always keep it as dry as possible during the entire ascent. Another point against it is its price. Expedition-type sleeping bags tend to be substantially more expensive than synthetic fiber ones. Anyway, if we consider that a good down sleeping bag can last many years, it is worth considering the investment. 

Now let’s take a look at the synthetic-filled sleeping bag.  

In general terms, sleeping bags with this type of insulation are usually cheaper and with much more acceptable performance. The mountain gear industry − and most manufacturers − (has come a long way since these bags became popular, and their quality has been improving. Unlike down, the synthetic filling provides thermal insulation even if wet, in addition to having a higher drying speed. 

Another point to consider is the difference between continuous filament or short-staple synthetic filler. The former uses a thicker continuous filament, which is stronger and more durable, but has less compression capacity than the short-staple, although it tends to remain more reinforced, which leaves fewer places that let cold in. 

Synthetic short-staple insulation is made of fine strands that are tightly assembled to minimize heat loss, making sleeping bags feel more flexible and even soft, a feature that brings them closer to down filling. This similarity to feather brings the same disadvantage: the insulation tends to move, creating cold spots, as well as having a shorter useful life than continuous filament filling. 

Finally, we must also talk about compression. Synthetic sleeping bags are bulkier and heavier, and each time we put them in the compression bag, the cushioning slowly undergoes a degree of deterioration. 

After having seen all the pros and cons of both options, one must analyze what to look for and how much we are willing to pay to sleep more comfortably, knowing that neither option is perfect. Of course, sleeping well on an expedition is truly priceless. 

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