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Mountain Laurel Designs Superlight Bivy Bag

Mountain Laurel Designs Superlight Bivy Bag

I'm pretty psyched about my new Superlight Bivy Bag from Mountain Laurel Designs (6.8 oz) and I'm looking forward to using it in Scotland next week in combination with my Mountain Laurel Designs Duomid pyramid tarp.

I got this bivy bag because conditions in Scotland are very wet in May and I want a little extra moisture protection for my down bag. I've also found it useful to have bivy when sleeping under a tarp to protect my bag from condensation in wet weather or rain-splatter. This isn't a life or death issue on shorter 3 season trips, but it really irritates me when I have to put a sleeping bag with a damp foot box into a waterproof sack in the morning before breaking camp. It's worth carrying the extra bivy weight to avoid the issue entirely.

The top of the Superlight bivy is made out of Momentum fabric with a DWR coating. The foot box is made out of eVent fabric to promote extra breathability and the bottom is made out of silnylon. I tried it on a section hike along the Connecticut Appalachian Trail recently and it worked fabulously during a rainy night under the Duomid, preventing condensation transfer between the inside of the tarp wall and the outside of my sleeping bag.

I ordered the Superlight Bivy with a couple of the special options offered by Mountain Laurel Designs, getting the bag in an extra long size (to enable use with my -25 winter bag) and optional bug netting around the head. The bug netting will  limit condensation from my breath, especially in the winter, and keep time bugs at bay.  Having a bivy bag with this much bug netting does limit the bivy's utility as a standalone shelter in foul weather, but I don't use a bivy as my sole shelter, so that's not an issue for me.

Mountain Laurel Designs Superlight Bivy Bag

There is a bungee cord attached to the top of the Superlight's netting which can be attached to an interior tarp hook or to a bunk bed frame in a trail shelter. Though delicate, the zipper around the netting works fine as long as you remember that this is fragile, ultralight piece of gear.

This particular bivy bag is designed to fit a Thermarest NeoAir inside it with a 3 season sleeping bag. It works fine with a full length 72" pad, but for my upcoming trip to Scotland, I've switched over to a 47" NeoAir which weighs just 9 oz, 5.4 oz less than the full length NeoAir pad. I store the pad, deflated inside the bivy, making it a lot easier to set up in the dark.

Honestly, after I ordered the Superlight bivy with all of these special features, I wondered if I had made a mistake. But after field testing, I'm confident that it's exactly what I need.

Disclosure: The author owns this product and purchased it using their own funds.


  1. Does it build up condensation inside of the bivy? That seems to be the problem I encounter most with my bags, less to none with the Tyvek one but the TiGoat Ptarmigan was rather moist, thus looking for an alternative.

  2. I changed my mind – the duomid has more space and is more robust in high winds. It becomes rather obvious when you set them up side by side. The hexamid is a nice shelter, and I plan to use it in new england's forest, but it is in a different class.

  3. Henrik – only one night of testing so far, but 0 interior condensation even in high humidity weather. I attribute that to the netting and the event foot box, but I guess we'll see. Only 1 night of testing so far. Otherss who have it however rave positive.

  4. Having used the same bivy in the damp UK and the last version as well in sub zero conditions inside a DuoMid with no condensation build up in the bivy, and outside with ice on the outside of the bivy on a -4 night I can say you have made a good choice.

  5. GoLite Shangra-Li 3 / SpeedMid


    Could do with an opinion….

    My friend and are looking for a new two person solution with some extra room. My first thoughts are above. Can you offer any pros/cons?

    TiGoat Ptarmigan / MLD Super Light


    Also I was looking at the Ti Goat bivy (mainly due to price) – is the extra money worth it?



  6. Shelter – depends what you want….Speedmid is worth a look . Colin Ibbotson has a good review – see my blog roll for his site. It provides less bombproof shelter than the Shangri-la, so depends on your target use, comfort zone, and your other gear systems.

    Personally, I would go with a MLD bivy (many models to choose from) over a Ti goat one, but again depends on your usage plan and climate. See Hendrik and Martin's comments above. For example, down vs synthetic sleeping bag/quilt system, 3 season vs winter, and length of trip may impact your decision.

    It all depends – there are no absolutes with UL gear. That's why it is worth talking about.

  7. Thanks for the feedback. Actually after reading about the MLD Trailstar on Andy Howells site, I love the idea and the weight, but frankly seam sealing frightens the life out of the me! It make the GoLite seem more attractive even if it is heavier.

    On the subject of the bivy – I sleep quite warm, so will the MLD be more breathable as only the footbox is eVent?



  8. "… with all of these special features, I wondered if I had made a mistake."

    ~ This is confusing. How could you possibly have too many special features?

    ~ Your shelter looks very secure. Looks like there is room for 2 in there. I like pyramidal tent designs because the shape is inherently strong. There is no bending moment–everything is loaded purely in tension or compression.

    ~ However, they rely on the guy lines to develop usable space under the eaves. Is it feasible to shorten the pole and pull the sides out further? That is the traditional approach to providing more foot space with knee walls.

    ~ Is is possible to use your pack to push up the tent slope into a vertical knee wall?

    ~ Once upon a time, we were climbing with a 6 foot high pyramidal tent, and one of my partners lost the pole. (Rolled it into the center of a foam pad.) We got by for a night by tying the guys up over the top of stone walls. If you have a cooperative tree trunk or fence, try that trick on the foot side of your tent and you will get a nice high knee wall. Maybe you could get this to work by threading the guy through the wrist strap on your 2nd hiking stick.

    ~ Remember, high humidity is not a condensation threat. You will see much more condensate out in the open on cold, clear, low-humidity nights.

  9. Helen – I have to warn you, that my best friend and my father-in-law have doctorates in physical chemistry, so you can't confuse me with all this chemistry mumbo jumbo. I'm already immune!

    One downside of the Duomid is that it has a very narrow preferred pitch height and is intolerant of pole heights out of it's preferred range – shorter or longer. The Grace Duo Tarp, also owned by me, is far more flexible in pitch configurations in wooded settings. Unfortunately, Scotland is a desert. Not many trees left. Mostly heather, boulders and puddles.

  10. "I'm already immune!"

    ~ Most cavemen are, so let me put it this way.

    1. The phase change of water imparts enormous amounts of heat into your tent fabric.

    2. Regardless of any ambient RH, your tent cannot condense until it gets substantially colder than the ambient temperature.

    3. Cloud cover is almost as good as tree cover to mitigate radiant cooling. ((Hotel ceilings work best for me.))

    4. High ambient RH protects the inside of your tent by promoting condensation on the outside.

    5. Don't hate me because I'm counter-intuitive. Yesterday, I mumbo jumbo'ed a 1-day building science consultation into a fee that will pay for my LT trip.

    6. Believe me, we'd all like to deforest Vermont again. Back in the 1800's, VT reminded people of Scotland for the lack of trees. Makes better pictures and tourists love it.

    7. Just figure out how to jack up your guy lines, and then you'll have a roomier, drier shelter.

    8. Disclaimer: All this is based on laboratory experience. Your results on the trail may vary. (Not really. Chemistry rules.)

  11. In other words use the 9" Easton aluminum stakes. Yea, I figured that out without science :-)

  12. Mike – there is no reason to fear seam sealing, particularly when you compare the pack weights of a shangrala to an MLD tarp.

    Regarding the bivy – it's really hard to say. You probably should ask Helen about relative humidity and phase changes of water vapor in zero atmosphere conditions under trees. :-)

    Ok, I've been drinking scrumpy all night and I'm leaving for Scotland in 20 hours.

  13. No, without dependable fog you'd need 2 footers to make it work. OTOH, if you simply brought an umbrella, this wouldn't be an issue. Just saying.

  14. With security for international flights, you'll be heading to the airport soon. In case you're foolish enough to be on the interweb at this late hour–farewell.

  15. Hi Philip, Im slightly confused with the idea of using eVent for the footbox, for breathability purposes. Wouldn't the momentum, being a non-waterproof fabric, be more breathable than the use of eVent, a waterproof fabric? Or is it meant to suggest that eVent was used for more breathability, as opposed to some other waterproof fabric. I imagine the waterproof fabric is there so if in the event you brush up against a tent wall or tarp and knock off some condensation, at least the footbox is protected from the wetness?

  16. Here's my experience – my feet sweat constantly. If (and I've done this) I slip a plastic bag over the footbox of my sleeping bag at night, there is a lot of condensation on the footbox shell the next morning. However, when using the MLD superlight with an event footbox, I believe that this perspiration is vented at night, since I always wake up with a dry footbox. I think that's what Ron at MLD intended.

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