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Integral Designs eVent Micro Bivy Sack

Integral Designs eVent Micro Bivy Sack
Integral Designs eVent Micro Bivy Sack

I invested in a winter bivy sack this year because I wanted to be able to use it for camping under a shaped tarp or in snow shelters, as a lighter weight alternative to my Black Diamond FirstLight winter tent. I also do more day hikes in winter than overnight backpacking trips, and I wanted a lightweight shelter to bring along for emergency use, in case I have an unexpected night out.

The difference between 3 season bivies and winter ones really comes down to size. For a winter bivy, you need extra girth and length to hold a sub-zero sleeping bag, without compressing its loft and reducing its ability to hold your body heat. Winter bivies should also be a little more resistant to puncture, particularly for use in snow shelters, and to help retain more warmth..

event Micro Bivy in a snow cave

Earlier in the year, I made a decision to buy an Alpine Bivy from Mountain Laurel Designs, since renamed the eVent Soul Bivy, for winter use. MLD also makes my 3-season bivy sack, the Superlight, which is an awesome product, and was a huge success for me last year. So, it might come as a surprise to many of you that I bought an Integral Designs Micro Bivy, instead.

Price Sensitivity

Honestly, I changed my tune because of price. While almost 50% heavier, the Micro Bivy cost half of what I would have had to pay for the MLD Alpine Bivy. Except for weight (18.5 oz vs. 12.75 oz), the two products are almost identical to one another, except that the MLD bivy has a side zipper. In the end, I just couldn’t cost justify paying over $30 per ounce, for the lighter weight but more expensive product, so I bought the ID Micro Bivy instead.

Functionally, the Micro Bivy has a 3 layer eVent top and a 70 denier nylon base, almost identical to eVent Soul Bivy from MLD, but without a zipper. While a zipper would make peeing at night a bit more convenient, there’s enough slack fabric in the hood of the Micro that I can scootch my butt up into it from my sleeping bag and hit my pee bottle without any issues.

This might sound like a private concern, but in winter it helps to hydrate all night long to make up for the fact that you can’t drink enough water during the day. You can’t stop to melt more snow when hiking without getting chilled and you can’t carry a full day’s supply because it’s too heavy.

Micro Bivy Dimensions

So far, I’ve used the Micro Bivy on two nights under a shaped tarp and I expect to use it in a snow shelter by the end of this winter. It’s large enough to contain an inflatable down pad and a -25 degree sleeping bag without compressing the loft. It’s 88 inches long, with a tapered torso (72″ in chest, 64″ in hip, 58″ in foot.)

Construction wise, the Micro Bivy Sack is built like a tank. All of the seams are factory taped and the stitching is tight. The hood has a slight peak on top and has an elastic cord running around its circumference, with cord locks over the shoulders to close the sack off from the elements. In practice, I’ve found it a little difficult to pull closed, but in a worst case scenario, such as a blizzard or driving rain, the Micro is long enough that you can scrunch down it’s length (88 inches) and fold over the door area for additional protection.


I have experienced minor condensation on the top of my sleeping bag when using the Micro, but it froze on the surface of my sleeping bag and I was able to shake it off the next morning without the liner getting wet. Truth is, I was experimenting that night with chemical warmers and I got too hot in my sleeping bag. My guess is that the sweat condensed and froze before it could breath through the bivy’s eVent top.

The next night I slept without  a chemical warmer and didn’t experience any condensation, despite the fact that more snow fell that evening. Honestly, I’m not that worried about condensation in the Micro, especially since I only plan to use it in winter when normal nighttime temperatures range from the single digits to 15 below zero (F). Crazy, huh?

This may change when I use the bivy in snow shelters that are warmer and have a potentially more humid micro-climate. It will be interesting to see what happens then and whether the eVent top is really required, or whether the condensation will continue to freeze on the top of the sleeping bag as before.


The Integral Designs Micro Bivy Sack is perfectly adequate for my needs and I expect it to perform well on winter trips for years to come. However, what was striking about this purchase was the fact that I bought a heavier product over a lighter one, based on price. I haven’t done that for a long time.

Truth is, my winter backpacking/mountaineering gear list is hovering around 28 lbs, which I consider to be pretty good, and I’m not ready to spend much more to buy its weight down until I wear out some gear and need to replace it.

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  1. Buying down your weight only when needed is a really good course of action once you have your weight to managable levels. For tents, bivy's, and other high wear items, it makes a real lot of cents.

    I am still waiting for my SVEA to give up the ghost, that said. But at a 9-11 pound base weight, I don't really care. It is managable. Maybe in another 40 years… The point is that this strategy doesn't always work. Some things, if you get good gear, refuse to quit working: ice axes, water bottles, cups, etc.

    28# in winter? Good weight!

    • 28# is an awesome pack weight. There are too many variables, like water, that won’t change much for a given amount of time on the trail. However, my pack adds more weight than I would like it to. It fits me well but it’s heavy. I am looking to save by purchasing a light weight pack that still has some support. Do they exist?

      • Take a look at the Hyperlight Mountain Gear (Porter) Expedition. I’m testing one now. It weighs under 3 pounds and has internal stays. You should also check out the packs from Cilogear and Cold Cold World. These are all 4000 ci3 and up packs.

  2. Nice review. I've been wondering whether I should buy a winter bivy for use in Southern Finland (in treeless Arctic, a tent is a must have).

    "- – the fact that I bought a heavier product over a lighter one, based on price"

    If the aim is not to see what is the lightest set up possible, there is always the point of diminishing returns.

    And pee bottles for the win! Essential piece of winter comfort. =)

  3. Korpijaakko – you hit the nail on the head . diminishing returns.

  4. Korpijakko- dont you have trees down there? What do 3m and fasson make their paper out of?

    You have trees in Levi up north too :)

    I dont understand "diminishing returns".. help me out!

    Great bivy review, did you turn down the ID south col because of its weight?

  5. Yep. It was the weight (25 oz) and it has a lot of features that are already provided by my Superlite, such as the bug netting. I really just needed a big breathable waterproof bag.

  6. "I am still waiting for my SVEA to give up the ghost,"

    hahaha you might be waiting a long time

    love my svea 123R

  7. I've come close to buying one myself this year. It is a work of art. What do your burn it in? Coleman fuel?

  8. SVEA 123R

    Yes, coleman fuel.

    It is heavy, difficult to simmer, and the base only carries about 45 min of fuel.

    But it is also extremely reliable due to few moving part and it's self-pressurizing operation.

    Once you get good at judging how priming is needed based on the ambient conditions, it is fun to use.

    My biggest issue is in the winter I need to re-fill it once or twice in the field and I am always worried about getting a frost burn.

    I agree that there is something very pleasing about its design.

    I am trying to purchase an aftermarket metal burner cap that makes the stove quieter but they are rare and valuable.

  9. Glad to hear the ID bivy is working out for you!

    What's the cutting edge nowadays for pee bottles? I'm still searching…

  10. 32 oz. wide mouth Gatorade bottles. Can't miss, even without my glasses on!

  11. SVEA? Yes, it burns white gas. Or 10% alky and WG mixed. Or, it will burn unleaded auto gas. (Not as hot, though and burn it outside of your tent.)

    40 years? Well, I've had it that long (1971, I think.) Maybe another 40 years…

    I have been thinking about a bivy, so was much interested. They promise a much lighter weight for solo use. The ones I have are all for winter use and don't have screen's. A flat tarp and bivy makes for a good UL set up.

    • I bought one for ten dollars forty years ago. I didn’t realize what it was until recently when I decided to Google SVEA 123 after reading about them here. I’m going to dust that little beast off and try it out again. I haven’t lit the thing in about thirty years.

  12. Phillip<

    Thanks for reviewing the bivvy. I am pondering getting one for winter.

    I'd like to know why the MLD Superlight that you already owned, didn't suffice for winter?


    Marty Cooperman

    Cleveland, Ohio

  13. The superlight is not big enough to hold a -25 down sleeping bag without compressing the loft and turning it into a 0 degree bag.

  14. Exactly marco – very flexible too. You just need a small flattish area in the woods, near water, and you can plunk right down and camp. Really opens up some interesting cross-country wilderness scenarios, especially when you throw some bushwhacking into the mix, but what to keep your gear weight down. Thinking about the dacks…

  15. I've kicked around getting one of the ID bivies. Any reason you didn't get the all-eVent ID bivy instead of the Microbivy?

  16. Ironically, I did buy one, only to return it. It's a long story, but there are a lot of pictures.
    Ultimately, the Microbivy was the least expensive option. It also feels a bit smaller than the all event Overbag, which is simply huge!

    Why can I ask, would you consider the Overbag instead of a lighter, custom, all-event from Ron? I got a quote of $390, I think.

  17. Looking at previous version of BA three wire bivy, the orange with full event top. Did you consider that model? I assume the pole weight would be seen as a negative but I like the idea of a small canopy and spot for head lamp and glasses. Thanks.

  18. I never really considered it seriously – it weighs 28.5 ounces. You could do I suppose, but I don't know if it will fit a winter bag. If we get any decent snow this winter, I'm hoping to try igloos, especially above treeline.

  19. Ended up returning the BA three wire bivy after one weekend winter trip. I got significant condensation at the non event (sil-nylon) foot box each night even with the bivy flap full open.

    I see that BA has gone back to the full event top for the 2012 model. The eVent material was amazing in the relatively cold weather [5 deg F] but the exit and entry was a pita.

  20. Good notes on the ID Bivy. I am looking to replace my Mountain Hardware and have been looking at the ID. However, one of the things I really like about the MH is it’s light and doesn’t compress down. I’m thinking the ID would be more appropriate for use outside a tent which is rare for me.
    PS Why did the tangerine Marmot not do well?

  21. Thanks for posting this review. I’m buying a 2nd hand ID SOUTH COL BIVY. Your post just confirmed my choice!

  22. I own an early version of this bivy –soak and wet from sweat every time.

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