A portable shelter comes in very handy on multi-day hiking trips because it allows you to set up camp almost anywhere and anytime you like, rather than having to reach accommodation facilities like mountain huts. While tents are the most versatile and comfortable, you might find a tent to be too heavy and bulky to carry if you are hiking alone – especially if you are on the trails for less than three days. On such trips a bivy sack is a great alternative to a tent as it is lighter while providing similar weather protection. On average, a high-quality bivy sack is twice as light and 30 % smaller (packed size) than a high-quality two-person tent. Besides taking up less space in your backpack, it can also be set up very fast if the weather is against you. Bivy sacks are, however, not suitable for longer hiking trips because they provide very limited comfort/space and often require that the backpack is left outside.
Here we selected and reviewed the best bivy sacks for hiking, backpacking and mountaineering. We decided to only list products made of waterproof/breathable materials as these provide the best versatility in various weather conditions. We were especially looking for lightweight and well-packable products. All bivy sacks listed in this review can naturally only accommodate one person.
If you are undecided between getting a bivy sack or a tent, you should also check out our selection of the Best Backpacking Tents. If you want even more minimalistic portable shelter than a bivy sack, check out our review of the Best Lightweight Tarps. As for the comfort inside the portable shelter of your choice, we have also made reviews of the Best Sleeping Pads, and the Best Sleeping Bags.
1. Buying a Bivy Sack – What is important?
Lightweight equipment allows you to reach your goals faster and easier. As shelters are usually among the heaviest items of backpacking/hiking gear, a lightweight shelter can make a big difference in the weight that you carry. For example, a low-quality one-person tent can easily weigh as much as 6 pounds while a high-quality bivy sack weighs no more than 2 pounds. Read more about why it is important to use lightweight gear in our article Why hike lightweight.
Bivy sacks usually offer just enough space for one person. However, some allow you to suspend the material above the head which reduces the claustrophobic effect of the small shelter and thus increases your comfort. There are two different systems to suspend the material above the head area; the pole system and the flexible wire system.
The pole system is very reliable but requires additional work when you are setting up the bivy sack as the pole has to be inserted in the sleeve and secured.
The flexible wire system is common on bivy sacks that feature a relatively low head height. The wire in the head area stretches automatically when the product is unpacked and thus slightly suspends the material above the head area.
Hikers and mountaineers always strive to have equipment that packs small as such equipment allows them to pack their backpack more efficiently. In this selection we only included bivy sacks which pack very small.
All bivy sacks in this review are made of waterproof/breathable fabrics such as Gore-Tex, eVent and Pertex (these fabrics are also used for rain jacket). Waterproof/breathable fabrics differ in weather resistance, breathability and durability.
3-layer fabrics (consist of a face fabric, membrane and an inner fabric) are very durable and offer great breathability and rain resistance. Thus, bivy sacks made of 3-layer waterproof/breathable fabrics offer a superb performance but are also quite expensive.
2.5-layer fabrics (consist of face fabric, coating or membrane and a non-fabric inner layer) are extremely light and offer decent breathability and rain resistance. Bivy sacks made of 2.5-layer waterproof/breathable fabrics are therefore very light, but they might occasionally have buildup of condensation due to the mediocre breathability of the fabric. Ventilation holes/panels might be used to minimize condensation issues.
2-layer fabrics (consist of a face fabric and coating or a membrane) are heavier due to thicker individual layers and offer inferior breathability and weather resistance in comparison to 2.5- and 3-layer waterproof/breathable fabrics. Bivy sacks made of 2-layer fabrics are usually only used as emergency shelters – which is why we didn’t include any in this review. They are occasionally equipped with ventilation holes to mitigate the condensation issues which can appear due to the poor breathability of the fabric.
To learn more about waterproof/breathable fabrics check out the Hard Shell section in our Comparison of Shell Materials.
Regardless of the number of layers, any fabric used for portable shelters should be treated with DWR (durable water repellant) so that it repels the water rather than absorbing it. The floors are usually made of polyurethane-coated nylon for better durability and water resistance.
Weather and Condensation Resistance:
The weather and condensation resistance of a shelter greatly depend on the fabric. Unfortunately, the two qualities are mutually exclusive to some extent. The higher the breathability of the fabric, the better the condensation resistance as it allows moisture and warm air to escape to the outside. However, there is no such thing as highly breathable fabric that is also completely waterproof. Therefore, manufacturers have to find the right ratio between breathability (condensation resistance) and weather resistance in order to achieve the best functionality.
In general, bivy sacks offer inferior rain and condensation resistance in comparison to double-wall tents (which are equipped with a completely waterproof fly that comes over a breathable canopy) but on the other hand they are also faster to set up and much lighter. We do not recommend using a bivy sack (or indeed a single-wall tent) in areas that are known for continuous heavy rain.
We only list top-tier products. Read how our selections of best hiking products differ from others here.
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2. The Best Bivy Sacks Review
The Best Bivy Sacks – List
- Outdoor Research Alpine Bivy
- Black Diamond Spotlight Bivy
- Black Diamond Big Wall Hooped Bivy
- Rab Alpine Bivy
- Outdoor Research Interstellar Bivy
|Feature/Product||Outdoor Research Alpine Bivy||Black Diamond Spotlight Bivy||Black Diamond Big Wall Hooped Bivy||Rab Alpine Bivy||Outdoor Research Interstellar Bivy|
|Packed Weight||1 lb. 16 oz.||1 lb. 7 oz.||1 lb. 15 oz.||1 lb.||1 lb. 4 oz.|
|Packed Weight (Metric)||907 g||660 g||870 g||470 g||546 g|
|Packed Size||3.9 x 15 in.||4 x 7.5 in.||5.9 x 13 in.||4.7 x 12 in.||n/a|
|Packed Size (Metric)||10 x 39 cm||10 x 19 cm||15 x 33 cm||12 x 30 cm||n/a|
|Size (Length/Width)||84 x 26 in.||92 x 30 in.||99 x 35 in.||93 x 31 in.||82 x 26 in.|
|213 x 66 cm||234 x 76 cm||251 x 89 cm||235 x 80 cm||208 x 66 cm|
|Material||3-layer Gore-Tex Respiration||Single-layer NanoShield||3-layer ToddTex||3-layer eVent||3-layer Ascentshell|
|Head Area System||Single-Pole System||Single-Pole System||Free-Standing ( Flexible Wire)||None||Single-Pole System|
1. Outdoor Research Alpine Bivy
- Alpine Climbing
The Outdoor Research Alpine is very popular among hikers and mountaineers as it is very comfortable but at the same time super lightweight – it weighs merely 2 pounds. It is made of a 3-layer Gore-Tex Respiration Positive fabric which offers great tear- and abrasion-resistance. It also provides good weather protection and breathability. Due to high-quality fabric, condensation issues rarely appear in this bivy sack. The floor is made of resilient nylon for increased durability and water resistance. The Outdoor Research Alpine allows you to suspend the fabric above the head as it comes with a pole. The pole comes in a sleeve outside and can be secured with Velcro closures at the bottom. The bivy sack is also equipped with sleeping pad straps, five stake loops, internal mesh pocket and no-see-um mesh to keep the insects out. The Outdoor Research Alpine is perfect for hikers, mountaineers and backpackers who want a reliable shelter for their adventures.
2. Black Diamond Spotlight Bivy
- Alpine Climbing
The Black Diamond Spotlight offers slightly more space (length, width and height) than the Outdoor Research Alpine bivy sack mentioned above. The upper part of the Spotlight is made of a single-layer Nanoshield fabric (developed by Black Diamond) while the floor is made of durable abrasion-resistant nylon. The bivy sack comes with one DAC Featherlite pole which allows you to suspend the material in the head area. When the head area is suspended the Spotlight offers an internal height of 51 centimeters which is indeed good for such a light and small (packed size) shelter. The bivy sack is also equipped with four stake loops and a no-see-um mesh door to keep the insects out. The main benefit of this bivy sack is that it’s extremely light while the downside is that the Nanoshield fabric is not as breathable as 3-layer fabrics such as Gore-Tex.
3. Black Diamond Big Wall Hooped Bivy
- Alpine Climbing
- Emergency shelter
The Black Diamond Big Wall Hooped differs from products listed above in design – it is a very minimalistic bivy sack. It features a significantly lower head height than the other products here because it does not use a pole system to suspend the material. Instead it uses a sewn-in flexible wire which suspends the material automatically when the shelter is unpacked. The good thing is that the flexible wire makes the Black Diamond Big Wall Hooped easier and faster to set up. It is made of Todd-Tex waterproof/breathable material. The Todd-Tex material is very similar to Gore-Tex; it uses a PTFE membrane that is bonded to the face fabric and internal fabric (3-layer design). The material provides good weather protection and breathability. Therefore, condensation is rarely an issue. It is also equipped with a dual zipper, no-see-um mesh and taped seams. The Black Diamond Big Wall Hooped is best for those who want a minimalistic but very reliable shelter for trips in all conditions.
4. Rab Alpine Bivy
- Alpine Climbing
- Emergency shelter
The Rab Alpine is another high-quality minimalistic bivy sack. It is best for demanding trips where lightweight and highly reliable equipment is required. It is made of a 3-layer eVent material which is very breathable and provides good weather protection. The Rab Alpine bivy sack has a durable floor which is reinforced with 70-denier nylon. Unlike the other bivy sacks in this review, the Rab Alpine is not equipped with a system to suspend the fabric in the head area – it has a completely minimalistic design. However, it is mummy shaped to fit technical sleeping bags. Even though it offers very little space, condensation is rarely an issue as the eVent fabric provides great breathability. The Rab Alpine bivy sack is primarily designed for mountaineers and alpinists, and works best in tough winter conditions (snow).
5. Outdoor Research Interstellar Bivy
- Alpine Climbing
- Emergency shelter
The Outdoor Research Interstellar bivy sack is very similar to the Outdoor Research Alpine bivy sack. It has similar dimensions, comes with one Delrin pole to suspend the head area and is equipped with mesh fabric to keep the insects out. However, the Outdoor Research Interstellar bivy sack is made of Outdoor Research’s proprietary 3-layer Ascentshell fabric instead of Gore-Tex and is significantly lighter – it weighs merely 1 pound. The Ascentshell fabric is extremely lightweight, breathable and provides great protection against the elements. Hence, this top tier bivy sack is also slightly more expensive. The Outdoor Research Interstellar bivy sack is perfect for 4-season hiking and mountaineering. As it is super lightweight, it can also be efficiently used as an emergency shelter.
3. Questions and Answers
What are bivy sacks used for?
Bivy sacks, also called bivouac sacks, are one-person water-resistant shelters. Initially they were mostly used by alpine climbers on expeditions, due to the low weight and small packed size, Nowadays they are used by hikers, mountaineers, backpackers and other outdoor enthusiasts. A bivy sack is a lightweight and more compact alternative to a one-person tent.