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How Do You Stop Condensation in a Bivvy?

If you’re a hiker or backpacker, you know the importance of staying dry and warm. And if you’ve ever used a bivvy sack, you know that condensation can be a major issue. So, how do you stop condensation in a bivvy?

Check out the tips below!

First, you should always make sure your bivvy sack is completely sealed before stepping inside. Leaving any openings for air flow will cause the warm moist air that your body creates to escape and because cold air sinks, it’ll bring in chilly air from the outside.

Next, get close to your sleeping bag – as close as possible! The closer you are to the opening of the bag (where all of its insulation value exists), the less area there is for condensation to form on the outer shell because heat travels upwards; it’s much more difficult for warmth to transfer downwards. Be careful not to stick your hands or face out of the opening as you won’t be able to regulate your warmth and they’ll get wet.

Also, make sure that any material you sleep on doesn’t touch the bivvy sack. If it does, humidity from your body will condense onto the exterior of the shell and drain down to the point of contact.

If you’d like additional protection, there are a few different materials and products available to help prevent condensation inside your bivvy sack.

For instance, Thermalite tiles (made by accident in space) can be placed between your sleeping bag and bivvy sack to absorb body heat that would otherwise escape through the shell. And a vapor barrier liner, which is typically made of a plastic film, stops any humidity from reaching the inside of your bivvy sack and keeps it completely dry.

What does a bivvy overwrap do?

A bivvy overwrap is a piece of gear that many hikers and backpackers may not be familiar with.

This lightweight, water-resistant layer goes over your sleeping bag to provide extra insulation and protection from the elements. While it’s not necessary for everyone, it can be a lifesaver in cold weather conditions or when you’re trying to cut weight from your pack.

If you’re considering investing in a bivvy overwrap, it is a great piece of kit and here’s what you need to know.

Air Flow

The airflow provided a bivvy overwrap encourages airflow and helps to keep you dry

This ensures that moisture does not build up on the inside of your bivvy and can help to keep you warm when it’s cold out. A bivvy overwrap is a good choice for winter camping or alpine expeditions where conditions can be unpredictable and unforgiving.

Using a Bivvy

A bivvy can provide you with a lightweight, low-cost shelter that is easy to transport.

If you are looking for an alternative to investing in a tent or other more expensive shelter, then a bivvy may be right for you. It’s important to understand the limitations of this type of gear though, as it will not protect you from wind, rain, or bugs.

Zippers and Seam Taping

Zippers and seam taping help to keep moisture out and ensure your bivvy will last for years without any harmful effects.

When choosing a bivvy, look for a product that has been seam taped in the places where the zipper opens. This will ensure that water does not seep into your sleeping bag when you’re sleeping. A longer zipper allows for increased airflow which can be helpful if it’s very warm outside.


Bivvy overwraps commonly include pockets to store personal items like your phone or wallet while you sleep.

This is another reason why this piece of gear makes such a great addition to your bag; its easy to access storage space. The pocket on your bivvy overwrap is also a great place to store your headlamp so it’s not rolling around in the bottom of your bag.

What if I don’t need an overwrap?

If you’re not sure whether or not you will benefit from a bivvy, you will be better off testing out this piece of gear before making the investment.

If it turns out that the lightweight, waterproof piece of gear isn’t for you, then you can probably find another use for it in your bag. It’s likely to be versatile enough to simply become an additional pocket or storage space in your pack.

Just make sure to take good care of it and store it safely when you’re not using it.

Other Considerations

When purchasing a bivvy it’s important to consider the type of weather you will be using it in most frequently.

The best choice for mild conditions is likely going to be less durable than one that is meant for cold weather use. Using a bivvy in extremely low temperatures can reduce its lifespan and may compromise its waterproofing.

Final Thoughts

A bivvy overwrap is a great piece of gear to consider investing in if it makes sense for your needs.

At the very least, you can use it as extra storage space or as a pocket that will keep your headlamp from rolling around at night. This lightweight layer is worth having on hand as an emergency measure to protect you in cold weather conditions or when you know your trip will be taking you into the woods.