I lost my Houdini. What now?

Brett,

The Westcomb Crest Hoody is made from Pertex Equilibrium. Rab specs this material, via ASTM D737, air permeability as 10 cc (SI). The equivalent ASTM D737 imperial value is 19.69 CFM. Spec values and tested values are not always the same and I have not tested this material.

What shell is most comfortable to you will depend primarily on your clothing insulation, MET rate, and the environment. Most UL backpackers carry a rain garment in addition to a wind shirt. The best rain garments have an air permeability value no higher than .5 CFM.

If you are CONSISTENTLY WARM and it is not raining, no rain shell or wind shirt should be worn.

If you are CONSISTENTLY COLD, your rain gear is the more appropriate shell in lieu of having more clothing insulation.

If due to changing micro-climates and/or a varying MET rate, you are SOMETIMES COMFORTABLE, sometimes too cool, and sometimes too warm, wearing mid-point comfort insulation, then an optimal CFM wind shirt is without equal. The wind shirt adds about .6 clo of non-wind-speed-varying insulation to offset sometimes being too cool. When you are sometimes too warm, your body will automatically generate sweat to reduce your temperature through the latent heat of evaporation. The optimal CFM wind shirt allows that evaporated sweat to automatically and quickly cool you to your body’s optimal comfort level. It does this without leaving sweat on your skin. Non evaporated sweat on ~20% of your skin surface is perceived as being uncomfortable. It is primarily the sweat caused friction between your skin and your base layer that causes the discomfort.

All wind shirts are a compromise between providing warmth and facilitating your body's automatic cooling when needed for comfort. There are a large number of light weight wind shirts available with CFM values less than 10. If you want something to wear for low MET activities, they are great choices.

Backpacking is an activity that averages 7 MET; that is the highest indefinitely sustainable MET rate. The sometimes too warm case, mentioned above, creates a unique engineering problem. That is, "wearing a base layer and a shell layer, what is the cross-over point for the maximum moisture transport curve and the wind resistance curve?" The engineering solution is a unique compromise.

It is a different solution from what shell layer is optimal for watching a baseball game on a cool/cold and windy day. That engineering problem is “what is the cross-over point between the insensible moisture transport curve and the wind resistance curve?” The engineering solution is a unique compromise.

Okay, it is probably me because most of around here is flat so I really don't sweat unless it is above 90F and the hiking is not that exertive and I don't run or bike. I still don't see how it is wind protection at 45CFM when I can feel the air movement from the wind at 10CFM. I even tried an eVent jacket one time and definitely felt 'cooler' in it than a regular membrane one. So yeah, maybe someone with a rain jacket that had pit zips and mesh pockets might be better served by rain jacket if they are not doing high exertion activities.

Add-on.

Okay, thanks Richard. So roughly 20CFM is more than I will usually need. It is good to know that. As for the warm/cold thing it varies because it seems to flip sometimes in the same trip and conditions.

Brett you are over analyzing things a little bit.

Our senses don't always match up perfectly to numbers. In fact, if our vision is anything to go by, senses are more logarithmic than anything. Eg, twice as much CFM resulting in only being noticeably more breathable. In the flashlight world, it is a strongly recognized phenomenon that it takes double the lumens for something to appear "noticeably brighter," that is, you can tell it is so without a direct side by side comparison. Anything less than double and we can only discern by really squinting and doing A-B testing.

We're also creatures of circumstance, that is, things that we allow ourselves to get used to, seem perfectly fine. That's the reason we can be happy as a clam not knowing about CFM and MET and just be happy our jackets are keeping the rain out but as soon as our eyes are opened we start questioning how good everything is, really. Is my jacket breathable enough? Ironically, we're all here because we pursue better, better, best.

Your Westcomb Crest is a great jacket. So is the Squamish. And the Houdini. Even the new Houdini isn't too shabby. Enjoy!

It looks like the Squamish could get a new fabric for FW15 or perhaps the fabric is simply renamed Tiono 30 as specs. stay the same. As the workbook says nothing about an update, so it seems the latter might be more plausible.

BTW, the same counts for the Atom-models.

True. I did not know there is only a small noticeable difference in jackets that have twice the CFM.

It is indeed a new fabric but the CFM remains nearly the same.

I have a number of wind shirts, but in an effort to cut ounces I have been looking at the Zpacks wind shell.

They have one in 0.75 oz/sqyd Pertex GL ripstop nylon, and now one in 0.70 oz/sqyd Ventum ripstop nylon. These weigh 2.1 oz and 1. 96 oz respectively for the XL size.

Being so light would you expect them to be rather wind porous?

just read this: Zpacks windshirt test

"Being so light would you expect them to be rather wind porous?"

But I don't think that is the case. Pretex quantum gl is a great down proof fabric but the proportions that make it down proof (tight weave) make it less breathable and IMO a less than perfect windshirt material. It is light however and weight may trump breath ability for some users.

Thanks for the link, missed that first time around.

In the worbook, the fabric is described as a taffeta weave and no longer a ripstop weave.

>> So, Squamish owners, the PU coating inside sounds like it would be unpleasant against the skin. Is that the case? I had a Montbell wind shirt (presumably a Tachyon) and it felt clammy. Hence my lust for breathability.

I very much like the feel of the Squamish. It is interesting fabric — it feels "fuzzier" than most windshirts, if that makes any sense. I would consider it a lot more comfortable than the Montbell windshirt I own or any windshirt I've owned. But it is still a windshirt. Don't expect it to feel like fleece or wool.

But to answer a previous question, here is why I am only interested in very breathable windshirts (the top half of that diamond): they can work as a bugshirt. That is why, for example, I would buy an Argon 67 windshirt (in a hood, please). Wow, that material really stands out. It is lighter, and more breathable than almost everything else on the list! Oh, I know you can get lighter (by less than an ounce) and more breathable, barely (and only if you carry a windshirt about as heavy as my rain jacket) but you can't get anything that is more breathable and lighter. That makes it an outstanding choice as a bug jacket (again, a hood is great for that, even if it is bunched up around the neck).

To me a windshirt like that compliments a rain jacket. I always carry my Propore when backpacking. It can handle really heavy rain (as long as I don't bushwhack). So, if I'm hiking and get to the top of the mountain and it is really windy, on goes the Argon 67. Still too windy? Fine, on goes the rain jacket. Moving again? Off goes the rain jacket, but the Argon stays on.

So, if any gear makers are interested, I prefer a slim (Montbell style), size large — don't forget the hood. :)

Oh, and thanks Richard. Great stuff (as always).

I just wish Montbell would get away from shiny fabric in some of their clothing. I got accused of wearing Michael Jackson clothes on one trip.

I found myself wearing the Houdini often to keep brush, bugs, or sunburn at bay. Consequently when mine wore out I replaced it with a marmot trail wind hoody, which is like the Houdini but has large mesh panels in the armpits. If I truly need a wind proof layer, I can add a puffy jacket of raincoat. The rest of the time, the marmot wind shirt is super breathable yet still protective where it counts. I was put off by the design at first, but it works great. Mine was around $40 at STP.