Learning how to choose a bivy sack is quite essential, especially for individuals who are looking for an emergency shelter that they can use. Bivy sacks can be used with sleeping bags; in fact, they are a tandem that can provide you shelter and protection during multi-day hikes. Many hikers bring these bivy sacks whenever they are trailing along and within towering walls.
In the past, these bivy sacks were just rough drafts; most of them were nylon slipcovers designed for sleeping bags. These covers are waterproof, which enables them to protect the sleeping bags from the elements. In that aspect, those old-model bivy sacks were sufficient. However, they didn't excel when it comes to dispersing water vapor generated by your body's temperature.
These days, bivy sacks have multi-functional construction already. Read on to learn more about these bivy sacks so that you can choose one that suits your needs.
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How To Choose Bivy Sacks
Fundamentally, modern bivy sacks have two layers of fabric:
The top layer of these bivy sacks is typically tailored from ripstop nylon or any lightweight material. The said layer is then applied with a laminate layer, which makes the fabric breathable and waterproof. A common example of this laminate is Gore-Tex.
Meanwhile, the bottom layer of these bivy sacks is crafted from highly rugged nylon. Most of the time, the nylon is treated with urethane so that it can provide a degree of waterproofing. Keep in mind that this material is also used on the floors of 3-season and 4-season tents.
Furthermore, there are also other types of bivy sacks that have an architecture similar to a tent. These options have distinct features that aren't available with normal bivies. The first one is the added reach or area where you are shielded from the elements. The second feature is an enclosure to which you are sheltered against insects and weather.
Because of these added features, many have grown accustomed to the service of these bivy shelters. For instance, ultralight hikers who are conscious of the weight they carry prefer these bivy shelters over burly tents.
Bivy Shelters vs. Bivy Sacks
Essentially, bivy sacks are tailored for minimalist outdoors or mountaineers who want to shed weight. They have two fundamental functions, and they should be able to provide you with these things for them to be useful in the field. These are those functions:
Bivy sacks ensure that the sleeping bags of hikers and mountaineers remain dry, especially in humid conditions.
These amenities also help increase the insulating capacity of sleeping bags. Specifically, it is said that a bivy sack can add at least ten degrees Fahrenheit of warmth.
Bivy sacks have openings on their heads. Of course, this serves as an entry point for moisture. You can prevent this occurrence from happening by pulling the drawstring of the head as tightly as possible. Once you can do this, the entry point will be reduced to the size of the hole of your nose. Some people find this setup too tight for their own liking. Meanwhile, others can deal with the restrictions to protect them from becoming cold and wet.
When choosing a bivy sack, it is essential that you consider the following features:
- Zipper sliders provide opening spaces for your arms to move. In this way, you will be able to fix your gear, access your equipment, or even cook while still inside the bivy.
- Lengthy zippers also offer ventilation capabilities.
- Seams that have been welded or stitched for additional waterproofing.
- Straps that help secure the bivy to your sleeping pad.
Meanwhile, bivy shelters are considered low-profile tents. Most of these shelters have meshed panels that are affixed to the opening hole of the head. They also have hoops or poles that elevate the fabric away from your face. These components effectively shield you from precipitation and insects. However, heavy downpours still require you to do waterproofing techniques to guarantee your dryness.
In a nutshell, I can say that these bivy shelters are designed for ultralight campers, backpackers, and mountaineers. They are also valuable for touring cyclists who spend days and weeks on the road. These amenities have a wedged headroom that creates an area where you will not feel restricted or claustrophobic while lying in your sleeping pad.
However, keep in mind that during rainy conditions, these shelters may not be as ergonomic and comfortable as many think. While they can shield you from the rain, the mere fact that you can't stand inside them makes the experience more agonizing!
Other Considerations In Choosing Bivy Sacks
- The space provided by the bivy sack - Always remember that these bivy sacks don't offer the same kind of space as tents do. Even a single-person tent is more spacious than a bivy shelter. But of course, this doesn't mean that these bivy sacks and shelters aren't a good option. They are still a great alternative to tents, especially if you are always on the move. It also allows interaction with the world around you, which makes your outdoor experience a riveting one! Moreover, they can also protect you from the rain and insects. But if you are not really comfortable with small spaces, then you have no other choice but to pick a tent.
- Ventilation of a bivy - When choosing a bivy sack or shelter, it is crucial that you pick those that have breathable laminates. As I mentioned earlier, an excellent example of this layer is Gore-Tex. With this laminate, the vapor generated by your body will be dispersed outside the bivy. It is an essential feature if you are situated in a cool and dry area. If it is raining, then the bivy you pick should have enough zippers so that you can vent some of the internal humidity without getting wet. It is manual work, but it can prevent things from being too uncomfortable.
- Waterproofing of a bivy - Of course, you should never discard the fact that these bivies have to be waterproof. After all, they are designed as an alternative to tents. Hence, it is just a given that they should provide you the same level of protection that tents give. Fortunately, it is possible for these bivy sacks and shelters to be waterproof--not just water-resistant. For instance, a Gore-Tex laminate can keep things dry on your end. It might feel wet inside when it rains, but that's just a feeling.