Down Bags: GoreTex vs. Microfiber
I got an email the other day from a Sierra mountaineer who was wondering what the pros and cons were of getting a down sleeping bag with a GoreTex Shell versus microfiber. GoreTex, of course, is the famous waterproof-breathable membrane that dominates the outdoor clothing industry. Microfiber, or its relatives, refers to the standard nylon or polyester sleeping bag exterior.
Microfiber shells are usually woven as tightly as possible and DWR treated to make them water-resistant. Since down sleeping bags become useless when they get wet, it would seem to make sense to give them all GoreTex shells. So why make microfiber down bags?
As anyone who's glanced at a tag in a ski shop knows, GoreTex is expensive. Add Gore to your bag, and you can expect to pay a significant premium. Along with the extra cost comes extra weight, and (somewhat) reduced packability. So, the Gore-Tex option is not without its liabilities. But perhaps the more salient question is: does it keep your bag drier?
That answer probably depends on a variety of factors, the most important of which is the climate and conditions you'll be facing in the backcountry. I imagine a GoreTex bag would be a better choice in truly wet conditions like the mountains of the Pacific Northwest. Then again, if it's really that sloppy-wet, shouldn't you be using a synthetic bag?
Another complication concerns water vapor from a surprising source: your body! I've read estimates suggesting your body gives off a liter or more of water overnight, which means you're basically dumping a Nalgene's worth of H20 into your sleeping bag every time you use it.
While GoreTex is breathable, it's not nearly as breathable as a good Microfiber shell. A GoreTex bag is naturally going to trap more of that moisture inside your bag, rather than allow it to pass harmlessly through. So, while GoreTex may be helpfull in preventing your sleeping bag from getting wet from external sources (rain, snow, spilled soup), it seems likely it will make it more difficult to dry out your bag when it does get wet.
For these reasons, I tend to tilt toward getting a MF bag myself, rather than Gore. If I am especially worried about external moisture, I'll pair my down bag with a good bivy, like Black Diamond's Winter Bivy Sack. This seems to me to be the best solution, as it preserves the versatility of a MF bag while conferring the advantages of GoreTex, if needed. Also of note: some bags exist with Event™ or Epic™ exteriors, perhaps offering a better blend of waterproof-breathable performance.
Still, someone out there must be using a Gore bag, down or synthetic. Maybe you can add a different perspective?
Andy Lewicky is the author and creator of SierraDescents
Cailin February 10, 2009 at 12:49 pm
While I haven't used a sleeping bag with a full Gore-Tex shell (what are some examples?), several manufacturers put out down bags that utilize a Windstopper shell (MEC - Mountain Equipment Co-op, Western Mountaineering). A Windstopper shell makes the bag totally wind-proof, as well as water resistant, without sacrificing breathability. In general these bags are really functional almost all the time (you wouldn't sleep out in a rainstorm in any down bag, would you?) and are very packable. In addition the ones from MEC (the Canadian equivalent of REI) come at a great price point. As far as the eVent and Epic fabrics - Epic isn't waterproof, only water-resistant. eVent, on the other hand does make a waterproof fabric - though it is no more breathable than Gore-Tex, and does not come with the same lifetime performance quarantee. In my opinion, if you are looking for a good cool/cold weather down bag - look for one with a Windstopper shell, and for the utmost protection, bring along a Gore-Tex bivy just in case.
rod georgiu August 8, 2009 at 7:53 pm
I used both, and microfiber is the superior choice. You can wear your wet stuff inside the bag to dry it. in a gore bag, all you would acomplish is getting the down wet. However, if you also want to sleep in a bivy, wearing your gore pants and jacket inside the bag will reduce the perspiration, almost like vapor barrier. I used microfiber bags on a 12 month mountain climbing trip around the world in single wall tents. The bag fabric would get wet or iced up by the morning, but not the down, which I verified by weighing the bag. Half an hour in the sun would dry it. On days when I had to leave before sunrise, I simply packed the bag and dried it ar night. Being breathable, my body heat was enough to dry it.
Mike Stevens August 19, 2009 at 3:51 am
Just back from walking the Fairfield Horseshoe using my 25 yr old Gore-Tex shell for the first time with a down bag - although the rain chucked it down all night high on an exposed ridge in thick mist (typical Lake District) my bag was bone dry. I can't see the point of a Gore-tex sleeping bag though. A bag and a shell is much more versatile & a good shell can last a lifetime - apart from having to reseal the seams a couple of times my Gore-tex bag still looks and performs like new and is so small I take it with me even on day walks in case of emergency
Carl Geers September 20, 2009 at 2:49 pm
Ok... rumors rumors rumors. You know a friend even told me that purchasing a goretex sleeping bag would dehydrate me. Does it get wet in the bag from your moisture? ABSOLUTELY NOT. Years ago, and i'm talking about 12-15 I was living in a tipi out in Durango, Colorado. I lived in it year round for two solid years and I slept in an amazing bag I still own and use to this day. I've slept outside at 11,000 feet in mid Colorado winter. When I say outside I mean no tent, no bivy, not in a cabin but under the stars and I had to strip off clothes because the bag was almost too warm. I woke up to, wait for it....... FROST about an 1/8 thick covering my entire bag. Inside was dry and warm but the moisture from my BODY, that most would say would soak the bag, was neatly delivered to the outside of the shell and stayed there. I've just recently been sleeping in the backyard of a friend of mine and have been sleeping tentless through light rain showers. The only weakness with this bag is the stitching wasn't seam sealed and washing it is a tedious process but most down bags are difficult. The brand name.... and you are going to laugh... is SLUMBERJACK. Yah I know it doesn't seem right but I referred several hard core friends to the same bag and they still have them. Oh... yah... here's the best part. I was shopping for a -20 bag and found nothing but $600-800 bags and very few with a waterproof shell. I stumbled into this "hunters" shop and just browsed through there rack of hanging bags and couldn't believe the price of their -20, down, goretex shelled bag. $278.00. It had insane loft and was aptly named the Slumberjack Everest Elite. It is at the end of it's lifecycle and I'm so bummed they don't make the same bag because i'd surely purchase another one. I'm really going to miss my old sleeping partner when I let her go.
David Kyle December 3, 2013 at 6:24 am
Carl, I also have this same Slumberjack bag (and strangely enough also lived in Durango for 18 years '82 -> '98). My experience has been the same, 10+ years of 3/4 season camping in this fabulous bag. Can't say enough about it.