By the Numbers: Rethinking Fleece

Hi Jerry:  I think my Warm Wet Wet article demonstrated that with minimal moisture intrusion, synthetic insulation looses substantial warmth.  I would not want to rely on wet synthetic insulation for survival.  I would rather dispel that myth.  I don’t know that you can even claim warmer (rather than the industry standard-warm) when wet.  In order to do that you need to state if wet means damp, saturated, or somewhere in between.  The problem is, it’s pretty hard to find head to head studies that relate the warmth of synthetic and down with similar levels of moisture intrusion.  Until that is done, and it is something I hope to do, I think the prudent outdoors person should strive to keep any insulation as dry as possible.

By the way, here is what is Patagonia says about its DAS Light in this regard: Lightweight 100% recycled polyester PlumaFill insulation offers the warmth and packability of down but performs when damp

This is certainly more responsible than claiming “warm when wet”.  Of course, we have no idea how wet is damp, nor do we know the level at which it performs when damp.  We can just be certain that it performs.

Concerning the weight of down vs synthetic.  There are numerous kinds of synthetic insulation and various fill power downs that are available.  These will impact the weight/warmth relationship.  Of course, you don’t use insulation.  You use a finished product.  The product weight relationships will depend on the specific type of  synthetic insulation or down, construction details,  fabrics, features and much more.   Of course,  down is more efficient per unit weight than most synthetics.  However, as the fill power goes down, the scales become somewhat more balanced in terms of weight and cost.  Just as something to ponder,  below is a little information I have gathered on some jackets.

I thought I could save some weight by replacing my Micro Puff with a Montbell Superior Down Jacket.  You can see, they are similar in warmth.  The weight difference is about 61 grams or  2 ounces.  I concluded it was not worth laying out $179 to save 2 ounces.  Now, if  I were pondering which to buy today, I would pick the Montbell Superior Down and save 2 ounces and $70 and maybe a little pack space.

Just remember that the various ‘grades’ of down shown in the above table may not mean anything at all. The idea of 1000 down is mildly amusing.

Cheers

It might be packing my fears, but I would always have an extra, dry wool base layer for winter trips. One I wear, one I pack. I also bring the down pants for in-camp comfort. I have headed out on an overnight at 20F and returned at minus 20F with a strong headwind and blowing snow. We cross flowing creeks and risk wet feet (yes even at minus 20 sometimes, there can be open water). I want a dry everything in my pack ready to put on to be warm and dry. Obviously your circumstances vary.

I tend to agree with Karen.

We have waded open creeks in the snow. Well, they were too wide.
The water is not so bad – you don’t feel anything!, but standing around afterwards on the snow is ghastly! We drop gaiters to stand on, drop foam sit-upon to sit on, and put thick (Darn Tough) socks on quickly. Never mind the towel!

Cheers
PS: we also carry spare dry underwear for the tent.

Thanks all. Karen and Roger you both make convincing points for carrying the extra base layer on planned overnights. However, in terms of unplanned (emergency) overnight on day hikes I’m still torn, as the extra base layer alone would not provide the needed warmth overnight (on a planned overnight I’d have a winter bag so they’d be fine). Of course falling into water does provide great pause and I could carry both. Day pack is about 15# already. Do I go to 16#? The more weight, the more likely I get tired and something happens…

if one was unfortunate enough to fall into the water, you’d definitely want synthetic layers- it gets wet obviously BUT it dries much quicker

you can look up the videos on YouTube, but the Special Forces have adapted a rewarming drill- no stopping and trying to build a fire, they wring out their layers (synthetic layers) as best as possible and then start hiking.  The hiking dries out the damp layers, quicker than you would think with the right layers.

If it’s cool to cold, I’m hiking with an synthetic insulation active layer (Polartec Alpha) and in my pack is a Apex parka and a a Apex half bag (more like a 3/4 bag :) ) for an unexpected night out

yeah, exactly Mike, that video has been posted before on BPL

you do not want even synthetic to get wet, but it’s better than down

I have measured the temperature difference across synthetic insulation to be cut in half if it’s wet, then it gradually increases back to normal as it dries out.

That would be equivalent to the R value being halved when it’s totally wet, except it’s not actually conduction that’s happening, it’s evaporation.  Half the heat is consumed with evaporating water.  As the water gradually evaporates, less heat is needed to evaporate the rest so the temperature difference across the insulation gradually increases.

^ that makes sense

they have another video floating around where they cut a hole in the use and jump in and if they’re backpacking, they wring the clothing out as best as they can they set up their shelter, get into their sleeping bags, fire up the stove for some hot liquid calories and eventually dry out

tough guys!!!

Hi Jerry and Mike:  You two are probably some of the most experienced backpackers in the community.  I get your point.  On the way to gaining your experience you have obviously lived through and learned from the mistakes that we all make.  You know the limitations of your equipment, you know how to deal with it and you know how to survive.   On the other hand, there are great many people who purchase gear and rely on the claims they read in manufacturer’s advertisements and ill-informed product reviews and then go forth into unforgiving environments secure in the knowledge that they will, in this case, stay warm when their insulation gets wet.  Of course they won’t.  You know what to do about it.  They probably don’t.  For every pound of water someone needs to dry from their clothes, they are expending 252kcal of energy, just to vaporize the water. In addition, you need to warm the water to get it to vaporize.  Suppose you need to warm 1 pound of water from 35F to 75F.  That requires another 100 kcal of energy.   So getting wet is not just a matter of suffering through getting dry.  You need to supply the energy for drying  and still have enough left to complete your activity.    We all know the consequences this can subject a hiker to.  The least people should know is that they cannot trust their synthetic or any other insulation to keep them dry when wet and they should do all they can to avoid that possibility.  Here is one of those inspirational  videos  of someone walking their clothes dry.  At least these clothes are well designed to get rid of moisture trapped within a garment.  Others will find it harder to dry insulation that is encapsulated in fabrics that  typically have low air permeability, low MVTR and are designed to make it hard for water to get in, which means, it will have a hard time getting out.

Good points.  Synthetic (or fleece) is not a panacea, just better than down.  Don’t get wet.  Manufacturers may overstate the advantage of synthetics.

I appreciate your experiments and articles.

During a brief immersion I’ve found that a heavyweight base layer tends to trap air against the skin so that I didn’t get too cold even below zero. Paramo clothing and the old Buffalo pertex and pile excel in these situations as they allow the water out through the fabric.

the Special Forces have adapted a rewarming drill- no stopping and trying to build a fire, they wring out their layers (synthetic layers) as best as possible and then start hiking. The hiking dries out the damp layers, quicker than you would think with the right layers.
It works too.

Yeah, I fell through the snow into the creek. Italian fleece trousers, We just got going asap, once I had wrung them out.

Cheers