If you’re shaping up for a multi-day race or fast-packing adventure, then you’ll be faced with an inevitable trade-off when purchasing your overnight set-up: a good night’s sleep or running with a heavy bag. This dilemma boils down to comfort versus speed – the lighter your pack, the faster you will be able to travel.
Some one-man tents are now so small and light, it’s hard to imagine that it’s even possible to take a more minimalist approach. But it is: enter the bivvy bag.
What is a bivvy bag?
A bivvy bag is essentially a lightweight sleeping bag cover that protects you from the worst of the elements but offers little in the way of shelter. It is usually composed of a waterproof bottom fabric (groundsheet) and a lighter upper fabric that is waterproof but also breathable.
What is the difference between a bivvy and a sleeping bag?
A sleeping bag is an insulated bag that is designed to keep you warm. This warmth is provided by either a down or synthetic filling that traps air around your body as you sleep. In contrast, the single-skin fabric of a bivyy bag provides negligible warmth. It is designed to keep out moisture (from rain, dew or snow) while having sufficient breathability to minimise moisture build up on the inside. A sleeping bag will often cover the head but doesn’t cover the face, where most bivvy bags allow for the whole person to be sealed inside (i.e. the bag is closed fully over both the head and face).
Do I need a sleeping bag with a bivvy?
Although you can sleep in just a bivvy bag, it’s generally a pretty unpleasant experience – both should be used in combination. In all but the warmest weather you would feel uncomfortable and cold without a sleeping bag once the sun has gone down.
However, in an emergency situation, especially one that is wet and windy, a bivvy bag (or basic survival bag) can offer enough protection to save your life. For this reason, it is advisable that all trail runners carry a survival bag when running in high or remote areas – even if you’re not expecting to be out for long.
Is a bivvy bag worth it?
The appeal of a bivvy is that it's an affordable, ultra-lightweight, stripped-back approach that enables you to, quite literally, sleep out under the stars. For many, this is the ultimate wild camping experience – but it’s not for everyone.
Types of bivvy bag
A basic bivvy bag weighs in at around 300-600g and packs down to the size of a water bottle. Such designs close or tighten around the face, creating a small opening for you to breathe. Irrespective of the breathability of fabrics used, it is common to feel a bit damp in the morning as a result of condensation build up overnight. A bivvy with a full-length zip, however, provides better ventilation options. Usually, your bivvy bag would rest on a sleeping mat for improved comfort and insulation from the ground, though with some designs it is possible to fit the sleeping mat inside.
Hooped bivvy bags have to be pitched like a tent but their structured design keeps the fabric off your face, offering better ventilation and a much less claustrophobic experience – sometimes with a little room to store some of your gear. Hooped bivvy bags come with pegs and poles, so tend to weigh more and take up more space when packed.
Low weight and a compact shape are the most important factors for runners, since a bulky or heavy bag makes running feel awkward and also more strenuous.
Is a bivvy better than a tent?
To address this quandary, you should first consider the location, terrain and weather that will be encountered on your run. Tents are always going to be the better choice in very poor weather (greater protection and ventilation), whereas in a warm, dry climate, a bivvy bag may be all you need. In the mountains, a heavy bag will really hold you back if your route involves a lot of ascent. However, mountain weather can be severe, so the decision should ultimately revolve around the forecast.
Next, consider the nature of your running excursion. For a long adventure (more than a few nights), the importance of comfort and plenty of rest can't be underestimated. This is where a slightly heavier set-up might be preferred (eg a one-man tent with some space inside and a comfy sleeping mat).
But if you’re racing, then pace tends to take precedence. In a short race (only one or two nights), it’s easier to rough it and sacrifice a good night's sleep in favour of better running performance. But for long, expedition style races or Fastest Known Time (FKT) attempts, the situation is more complex, with the aim of the game being to maximise performance over a prolonged period and changing circumstances. In this situation, you'll need to consider the following: will you be able to cope with prolonged sleep deprivation? Will you be able to dry out your kit? What is the terrain on the course? What is the climate and season?
Another consideration is insects. If you dislike the idea of waking up covered in slugs, then a tent might be for you. Most tents are twin skin, with the inner offering good protection from mosquitos and midges. They also provide a space where you can pass the time, protected from biting bugs or to wait out a storm.
What are the best bivvy bags?
We tested a range of bivvy bags and shelters with running adventures in mind and below we’ve listed our favourites. Most these models also work well for fast-hiking, trekking and thru-hiking expeditions.
Best in test: Alpkit Hunka
- Weight: 360g
- Packed size: 10 x 24cm
- Base waterproofing: HH 10,000mm
Simple but effective, the Hunka is light, breathable, packable and very affordable – everything we look for in a good bivvy bag. We recommend sizing up to the XL if you’re tall or just like a bit of room to move. 'Ideal for the occasional fair-weather bivvy, the Hunka is a great no-frills way to get into fast and light overnight adventures’ said one of our testers, Raeanne Miller, a trail running guide for Girls on Hills.
Best mountain bivvy: Outdoor Research Helium
- Weight: 484g
- Packed size: 31cm x 9cm
- Base waterproofing: HH 15,000mm
The Helium Bivvy is the lightest hooped bivvy bag on the market, offering all the comfort benefits of such a design but at no additional weight. It’s also really packable with good levels of waterproofing and has a built-in bug mesh to keep the insects out. Fastpacking and ultra endurance athlete Jenny Tough is a fan. ‘In drier climates, I don’t often use a bivvy bag and opt for just a hydrophobic sleeping bag instead. But whenever I need proper shelter, I use the OR Helium bivvy. A great lightweight option that kept me dry and mossie-free during a 25-day run across the Canadian Rockies.'
Most spacious: The North Face Assault Futurelight Bivy
- Weight: 740g
- Packed size: 25cm x 14cm
- Base waterproofing: HH 3000mm
Designed for mountaineering, the Assault Futurelight is designed to accommodate a big pack and boots inside, so there is easily room for all your lightweight running kit. As a minimalist hooped bivvy, the poles provided improve the headroom and the extra space reduces the sense of feeling constrained. However, the sheer amount of fabric does mean extra weight.
Our tester said ‘If you’re someone who feels claustrophobic in a bivvy bag then this could be the one for you – spread out a little and relax! It;s is also incredibly breathable thanks to the innovative Futurelight fabric.'
Best for long adventures: Terra Nova Jupiter Lite
- Weight: 770g
- Packed size: 40cm x 11 cm
- Base waterproofing: HH 15,000mm
The Jupiter Lite is a very lightweight hooped bivvy bag – it's only 548g without pegs. It has above average headroom and levels of waterproofing (both upper and groundsheet) and good ventilation, thanks to its breathable fabric and fully mesh door. Our tester said: 'You can rely on the Jupiter Lite; it’s a robust design that combines comfort and durability, making it perfect for travelling long distances, where having confidence in your kit is key.'
Best for: fast and light adventures: Msr Pro Bivy
- Weight: 340g
- Packed size: 20cm x 10cm
- Base waterproofing: HH 1200m
The Pro Bivy has a light and simple design – its extremely light and packable. The main advantage of this bivvy bag is its roomy design (space for a sleeping bag, mat and a few personal effects), which is remarkable given its low weight. Our tested said: ‘We like this bag for no-frills, multi-day trail running adventures. This bag can cope with anything you throw at it and is more durable than it looks’
The bag’s opening doesn’t zip closed, meaning it’s not ideal for very wet or windy conditions (and it won’t keep the Scottish midges at bay), but the fabric copes well with a range of conditions across all seasons.
Best for comfort: Sierra Designs Backcountry 3000
- Weight 400g
- Packed size: 25.4cm x 10.2cm
- Base waterproofing: HH 3,000mm
The Backcountry 3000 scores well in many areas, but’s its standout feature is its volume. It's designed to accommodate the luxurious Backcountry Bed system and an inflatable sleeping mat, but there is enough space inside for whatever sleeping bag and mat system you choose. 'This is ideal for runners who like a comfy bed,' said our tester. 'Its low weight means that you can put your weight where it matters and bring along your most comfortable sleeping bag and mat combo.' It also offers high levels of breathability and effective venting, so you can expect a good night’s sleep wherever you are.
Best for staying dry: Rab Ridge Raider
- Weight: 890g
- Packed size: 32cm x 15cm
- Base waterproofing: HH 15,000mm
The Ridge Raider has a spacious hooped design, which combines a high level of waterproofing underneath with good breathability up top – it’s moisture vapour transmission rate is higher than all other bivvy bags we tested. Despite being heavier than some ultra-lightweight tents, this bivvy bag is sturdy, reliable and keeps you dry in changeable weather. 'I felt pretty chuffed with myself when I hunkered down in the Ridge Raider and read a book in comfort when it was battering horizontal rain outside,' said our tester Sam Jones, a trail runner and amateur aurora photographer. 'You can manage good ventilation without letting water in and, with a bit of contortion and swearing, you can even get changed while zipped inside! The only downside we found was that the single curved pole was tricky to install.
Most minimalist bivvy bag: Terra Nova Moonlite bag cover
- Weight: 180g
- Packed size: 21cm x 6cm
- Base waterproofing: HH 15,000mm
When you buy the Moonlite bag cover, you’re paying for premium materials and design quality, as you don’t get a lot of bag for your money. Coming in at under 200g, this packable bag weighs marginally more than a plastic survival bag but all the key features are there – high levels of waterproofing, good breathability and a bug screen. Pair this super light option with a simple tarp for extra protection and you can create a really flexible sleeping system. ‘I love the idea that you can run with this bivvy bag instead of a survival bag on remote/backcountry epics and be prepared to sleep out if it comes to it,' said our tester, 'it's the ultimate minimalist solution.’
Best for sleeping under the stars: Lightwave Starlight 1 Tarp
- Weight: 77g
- Packed size: 6cm x 18cm
- Waterproofing: (Unknown)
Set your bivvy experience free by sleeping under a tarp. Protection from rain and wind plus complete ventilation is all possible with even the simplest of designs. But not all tarps are made equal. Different shapes, sizes, specs and attachment points make tarp camping a specialist art form. Whilst any old budget tarp might keep the rain off, the Starlight 1 is the premier choice for ultra-light camping: small in size and made of extremely tough Dyneema Composite Fabric (DCF). This tarp can be pitched and tensioned in a variety of ways according to your needs. You can buy poles, use your running poles or simply use surrounding rocks or trees to set it up. It might take a while to master, but for less than 100g, you won’t even know you have it with you.
Best for Alpine/High Mountain: Black Diamond Twilight
- Weight: 370g
- Packed size: 8cm x 13cm
- Waterproofing: (Unknown)
The Twilight Bivy is incredibly lightweight and simple but – best of all – packs down to a tiny size. This makes it ideal for ‘fast and light’ exploits where the size and weight of your pack is critical. Best suited to drier/alpine climates, this functional bivvy bag will keep you protected through the night by way of water-resistant, breathable nano-shield fabric (seams can be sealed as required). Our tester said: 'This snug-fitting bivvy won’t keep you dry in wet weather, but with good breathability, it offers a level of comfort above a survival bag and leaves you plenty of room in your pack for a day or two more of food supplies!'
Best on a budget: Rab Trailhead Bivvy
- Weight: 406g
- Packed size: 18cm x 12cm
- Waterproofing: HH 10,000mm
This basic model is an entry-level bivvy bag that goes easy on the purse strings. It has only a snap opening entry with stiffened peak that doesn’t zip up or have any bug-mesh. And because of the construction of the opening, it isn't watertight. It is, however, very durable, has an effective rain gutter and will protect your sleeping bag from dew overnight, while keeping the wind off. The experience is definitely on the claustrophobic side but it's a practical way to bivvy out in dry weather on a budget.
Best for pure survival: SOL Escape Bivvy
- Weight: 238g
- Packed size: 10cm x 19cm
The Escape Bivvy bag is the go-to choice for an unplanned or emergency bivvy – one to take with you if you don’t expect to spend the night out but are pushing your limits. The inner reflective surface minimises heat-loss but the bag isn’t waterproof. The advantages of this option are its low price, low weight and durability. You could use this bag deliberately and repeatedly in a reliably dry, warm climate as it’s reusable within reason, however, in the UK it’s really only a survival option.