A bivi bag is an essential item for anyone that is planning on going camping. A bivi bag is there to keep you dry if you are sleeping in the great outdoors! They were originally created as a safety measure for those hiking up mountains, but now they are used in many more situations than just this! There are also various different spellings for this type of bag, whether it be bivi, bivvi, bivvy or bivy, it doesn’t really matter – what matters is that you find one that is going to work for you. This means it has to be waterproof, breathable and compact. Keep reading to help you make an informed purchase.
Why Do I Need a Bivi Bag?
Bivi bags originated as safety equipment for those people climbing up mountains, particularly when conditions are less than predictable. If the weather was to go downhill then a bivy bag would be a safe place to lie (allowing warm air to accumulate) and keep you dry while you wait out the storm. Not only this but they could keep you warm through the night when in conditions below -10℃!
Nowadays there are many reasons why you might need a Bivi bag – as well as for their original safety purposes! Firstly, they provide you with that extra protection when you are sleeping. When the weather is particularly dreary only the best of tents will keep you completely dry. Having a waterproof bivvy bag on top of your sleeping bag means that you can be sure you will be staying dry overnight – which not only makes for a more comfortable nights sleep but from a health point of view is also very important.
Also, if you are hiking between different camp sites then it may not be possible to take a tent with you everywhere you go, they are large, heavy and difficult to pack. Bivi bags are so much smaller that they can be packed away and put in your backpack, then simply pulled out and you are ready to settle down for the night! Not only from a practical point of view, it can sometimes be nicer to be closer to nature and falling asleep out in the open!
There are also more expensive “hooped” Bivi bags that are basically a small tent! You can literally set up your Bivi bag and sleep wherever you end up lying down! They will be a lot lighter and smaller to carry around than a tent and are much easier to set up! Perfect for if you are in a rush or have long days walking ahead!
Bivi Bag Features
There will obviously be some main things that you need to look out for before purchasing a bivvy bag. Keep reading to make sure you make the right purchase!
The most important features of your bivi bag is that it is waterproof – if it isn’t then there really isn’t any point! “Waterproofness” is measured using a term known as hydrostatic head – the amount of water that a material can repel before it starts absorbing the water instead. Many bivi bags will actually have two hydrostatic head readings – one for the base of the bag and the other for the top. As the base will be touching the floor, it is essential that this has a rating of at least 2,000mm, although the greater the amount the better! Some models go up to a rating of 10,000mm and more, but these are for the bivvy bags for real extreme weather conditions and locations!
Make sure to also check for whether the seals are “storm proof” as this will stop any drips of water from finding their way into you bivy bag when you least expect it. Check for zips that have storm liners and seals that are robust and lined so that you are sure to be protected.
Material and Breathability
The breathability of your bivy sack is crucial, particularly if you are going to be using it to keep you dry instead of using a tent. In these situations you are going to be sealed into your bivy sack for a number of hours (usually overnight) so it is important that it is breathable if you don’t want to wake up rather hot and sweaty the next morning!
Cheaper models will be made out of membrane material (similar to cheap, waterproof coats) which means that although they are waterproof and will stop water from getting in, they will also stop moisture from getting out!
If you are planning on sleeping in your bivi bag overnight then you will need to opt for a material that is more breathable, such as Gore-tex or eVent, lined or other more breathable membranes. These will still be waterproof on the outside but will have pores on the inside that allow for condensation to be wicked away. Many manufacturers will advertise their MVTR (Moisture vapour transmission rate) which is a good way to judge the breathability of the material. For easy comparison, materials such as Gore-tex have a rating of over 25,000, but 10,000 plus should be enough for most situations!
It is also worth remembering that cheaper, thinner materials will be less durable, and therefore more likely to rip and tear when they come into contact with your shoes or if they are put down on stoney surfaces! Sometimes you won’t have a choice where you “bed down” with your bivvi bag if the weather turns suddenly, so you need one that is going to have thick enough and strong enough material (at least on the base) so that it can withstand the pressure of these surfaces.
TOP TIP: Even bivy bags with more breathable membranes still tend to become rather “damp” if you are in them for too long! If you know that you are regularly going to be sleeping in your bivy bag overnight then it is important to push your budget and go for a high end model with a few breathable layers!
Hooped or not hooped
There are two main styles of bivi bags – hooped and not hooped. A hooped bivi bag will have rods that run through the “hood” of the bag. The idea of this is that the hood will then be lifted away from your face so that you have more room while you are sleeping. These are a fantastic idea for you if you are going to be using just the bivi sack alone to sleep in as it will stop you from getting as warm and claustrophobic. Because of their designs they are often known as bivy tents instead of bivi bags.
The one main downside to hooped bivi bags is that they will be larger to carry round and won’t fold up the same way that others do because of the metal rods that are built into them. This can mean that if you are hiking from one place to another, and carrying the bivi bag with you, that it may take up more room than is really ideal! They also tend to be more expensive than non-hooped models, but in our opinion this is worth it for the extra space and comfort that they offer!
TOP TIP: If you are looking for a hooped model then we would recommend looking out for scaffolding with a “criss-cross” design. These will offer more stability in windy conditions and be more likely to stay upright, keeping the material away from your face when you are laid down in your bivi bag.
Different bivi bags will have different levels of fastenings and what you need will depend on the level of walking that you are planning on doing and where you are planning on going! If you know that you are going to be venturing into some extreme conditions then you are going to need a bivi bag that seals up completely to protect you from the elements – so this means that you will need a zippable model (often with more than one zip in place so that you are fully secure). However, in any lesser condition, or if you are going for a simple bivi bag to be used inside an additional tent, then you will only need simple fastenings such as drawstrings and hook-and-loop fastenings.
The size of your bivi bag will make a big difference, as the whole point of the bag is that it is portable and can be taken with you when you are out walking. A larger bivvi bag (such as one of the hooded models) will be more cumbersome to carry around, taking up more space in your backpack or lugging down the bottom of your backpack if you have it strapped to the bottom. But the benefits of a larger model is the additional space that it provides (ideal for if you are going to be in it for a longer period of time). Larger (single) bivi bags are around 60cm x 20cm whereas smaller (single) bivi bags are more in the region of 25cm x 10cm – as you will see there is quite a difference in size!
There are also double bivvy bags which will be large enough for two people – perfect for keeping extra warmth when out and about. Although bear in mind that these will be considerably bigger (but smaller than carrying two singles!).
Make sure to look how small your bivi bag can be folded down to. Some will shrink right down to fit almost in the palm of your hand. This makes them super easy to carry and throw in your backpack when out walking!
The weight of your bivi bag is crucial because you are likely to be carrying it for miles at a time, and if you are a serious hiker then up some inclines as well. Bivi bags that we found range in weight from around 150g to just over 1kg. This is a massive difference in weight – especially when you are carrying it on your back all day, so it is crucial that you opt for a model with the least weight possible for the features that you need!
The material used for your bivi bag will largely impact on the weight that you will find. PU materials will be very lightweight (although usually lesser in quality) whereas bivi bags that use a number of membraned layers will be heavier but also better at keeping you dry.
Frequently Asked Questions
Do you need a sleeping bag with a bivi bag?
If you are just using your bivi bag to keep you protected from a storm then you won’t need a sleeping bag as well as the bivi bag – your body heat will usually be able to keep you warm enough. However, if you are planning on sleeping in your bivi bag overnight then we would recommend carrying a sleeping bag as well – not just for extra warmth but comfort as well.
Can I wash my bivi bag?
Yes! In fact, it is a good idea to wash your bivi bag after use to stop it smelling and developing mould from the wet weather or condensation inside the bag! If you have a simple model without rods (or if the rods can be removed) then you can just put it in the washing machine as you would your other waterproof camping items. It may be worth considering reproofing your bivi bag at the same time!
What should I do if my bivi bag stops repelling water?
Over time your bivi bag can begin to absorb water instead of repel it – which is the last thing that you want if you are using it for camping! In these situations, it is very simple to reproof your bivi bag, in the same way, that you would reproof your clothes. Simply buy a reproofing liquid that can be added to your washing machine and allow your bag to dry, or buy one of the reproofing sprays (just make sure that there are no parts of the bag that you have missed!).