Why grid fleece?

[Richard Nisley]

What the Polartec Engineers Intended:

Grid fleece – Designed as a base layer by virtue of its Lycra and bi-component construction for optimal wicking (efficient liquid water vs vapor water transport for all other insulation types)

100 / 200 / 300 – Designed as an active insulation layer

Thermal Pro – Designed as an active insulation layer with increased clo/oz after lofting

What I measured in lab tests:

Grid fleece has the lowest clo/oz

100 / 200/ 300 has a higher clo/oz

Thermal pro has the highest clo/oz (-30% variance if compressed and not shaken)

[Brett Peugh]

I have an odd duck in an OR Radiant fleece Hoody I got a few years ago.  It is like it is a knit on the outside and microfleece on the inside.  A bit heavy at 17oz for an XXL hoody that really is not as warm as my R2 from just a few years earlier.

[Jerry Adams]

Richard, how does the clo/oz of those fleeces compare to synthetic like Apex or down?

[Richard Nisley]

Jerry,

Active insulation solutions such as Alpha + ~4 oz of required fabric tests at the same system cl/oz as a Thermal Pro High Loft + wind shirt.

Static insulation pieces test higher clo/oz than active insulation pieces with down averaging about ~2x the equivalent synthetic.

Backpacking is a 7 MET activity vs camp chores which is a 1.75 MET activity; so, you need 4x the static insulation for the same temp.

[Jeff McWilliams]

Richard,

Did you mean to say, “Active insulation solutions such as Alpha+ ~4 oz of required fabric …” ?

Polartec Alpha:  active insulation

Climashield Apex, Primaloft, Down: static insulation

Yes?

[Richard Nisley]

Jeff,

You are correct; I changed my post after reading yours.

[Woubeir (from Europe)]

What with insulation like Climashield Apex that is rumoured to be the actual product behind the active insulation Coreloft Continuous ? Does it ‘breathe’ enough ?

[Richard Nisley]

Woubeir,

Apex (continuous fill) has an air permeability similar to Thermal Pro High Loft (TPHL ~240 CFM). The shell fabrics on either side need to be known to determine the active insulation garment’s composite air permeability but, it should be easy to achieve because you don’t have to worry about fine fiber migration through the shell fabrics.

But…

At a backpacking level of 7 MET, you only require an ~1.2 clo active insulation garment for temps down to -20F. The dual shell casing air gap provides .6 clo by itself; so, that only requires approximately .6 clo from the insulation encased in it. This is so minuscule that the active insulation type (Apex, Alpha, etc.) is almost irrelevant.

[Jerry Adams]

Yeah, it’s the amount of insulation that’s more important than breathability.

If you have too much insulation you’ll start sweating and that’s difficult to get rid of regardless of breathability.

A base layer and outer layer of fabric with the air layer next to them provides enough insulation even when it gets quite cold if you’re exercising.

[Edward Barton]

One good thing about grid fleece vs. trad is that it’s cooler without a shell than an equivalent weight of trad fleece, meaning you can exert yourself more without overheating, but layering a shell over top, it is warmer than a non-gridded baselayer that would otherwise be as cool without the shell.

I personally like to vary my pace and exertion quite a bit on my trips, and think I spend a good amount of time outside the 7 MET window, either fastpacking or scrambling to times where I want to go slow, view wildlife, start and stop more frequently, etc.

In below freezing temps a cap 4 weight grid fleece is a good base for this because of the breadth of METs it can accommodate together with other layers. If your MET range is narrower, I imagine a non-gridded option may make more sense?

[Eric Blumensaadt]

Paul,

Is that what is known as “smart rain”? Or just heavy rain?

[Woubeir (from Europe)]

Oh, I don’t plan on getting one of those. Even when It’s already freezing, I just need to wear one of my windshells and one or two thin baselayers. For static use, I wear a synthetic puffy above and a bit below freezing and a down puffy when it’s colder. I only wear fleece when feel I need it (which is really not that often). So, something with ‘active insulation’ will likely never be in my closet.

[Eric Osburn]

Is the EMS micro fleece 1/4 zip decent? It’s on sale at the moment.

[Brett Peugh]

I like it.  Can be a bit warm for some people but if you can get it for around $20 it will do you well both for camping and around town and last over a decade.

[Anonymous]

Edward touched on it earlier, but it seems worth restating. The good thing about grid fleece imo is that the higher void area means less conductive fabric when it’s potentially wetted out.  That can only be a good thing, and is more noticeable when directly worn against the skin. Against the skin especially, it can feel a bit warmer when wet than some other fabrics. Especially so with the high void grid fleece like Polartec’s baselayer line which I think is now called Powerdry Expedition weight? (Use to be Capilene 4).

The inexpensive, no name brands I have of regular grid fleece only have 5% spandex–not particularly high amount.

The issue with spandex holding water is not the issue of it’s innate moisture absorption of the actual material itself, but rather looking at it at a micro level, spandex is made up of many stretch bundles of fibers with more space than say a very tightly wrapped traditional fiber yarn or thread.  The space between these is what holds the water.

Some of you might remember a thread started by Richard N. awhile back that talked about how, generally speaking, the material itself was less important than the thickness (and lesser extent the weave) in how long it takes for a garment to dry. Perhaps with the slight exception of sheep’s wool because it has such a high moisture absorption. (All things being equal though, course a polypropylene garment would dry a bit faster than a polyester, the polyester a bit faster than the acrylic, the acrylic a bit faster than nylon, nylon a bit faster than linen, linen a bit faster than other cellulose based garments [while linen has a bit higher moisture absorption than cotton, ime it at least feels drier faster than cotton and I think that’s because of the fiber structure differences–linen fibers are hollow tubes and cotton, more flat, twisty ribbon like]).

Connect that to spandex and the increased spaces for water to be held seems to explain well why it does tend to hold water and take a bit longer to dry, especially when there are higher amounts in a thicker garment. However, 5% is not egregious by any means. When you start getting closer to 10% or above in a thicker garment with a lot of fiber and spaces, then it can start to become really noticeable.

[Hans Dampf]

I need a new base/insulation layer for the colder days while active, and now want the get the popular Thermal Weight Zip-Neck (former Cap4).

I’m unsure if I should get the version with hood or without. Usually in winter I take a beanie and/or buff if it’s cold anyway.

What’s your experience?

[Lorenzo M]

My cool temp choices are montane allez power dry hoody and windproof or berghaus hypertherm (40g/m synthetic insulation with windproof (I think 7d) shell and more breathable inner shell

If its likely to be consistently wet I go for the fleece as it keeps me drier longer and feels less wet when wet. Also more breathable if windproof is removed. The hypertherm is lighter though 160g v’s 180+110g

[Matt Dirksen]

I’ve had the cap4 hoody for 4-5 years and very much appreciate the hood. When fully zipped up, its more like a balaclava so it covers my mouth. It fits very well, easy to thermally adjust (with a long zipper) and I barely notice it behind my neck when I’m not wearing it.

While It’s a part of my kit all year round (I like sleeping in it) I also always bring a  beanie along, which lives in the front pocket of my windshirt – all year. There’s always a day or two where the Cap4 might be too much insulation, so my Echo-LS, the beanie, and my windshirt work just fine.

In my experience, the beanie and the Cap4 hoody are definitely more complementary than redundant, but they can also easily be layered.

[Paul S]

My understanding is that air by itself is not a good insulator due to possible convection currents in the air. To insulate you need dead air space and you need to prevent the convection currents (where sir flows due to thermal differential).

So, the part of grid fleece where the fleece has been carved (or cut) away will not insulate as well as regular fleece because the space between the grids allows convection currents. An air space alone is not as good as an air space with something present to prevent convection currents. And I am not referring to wind, I am talking about air currents inside the air spaces of the fabric due to a temperature differential across the fabric..

That is my understanding…..

[Daryl and Daryl]

Theoretical vs Actual Use

My first venture into grid fleece was via a recently purchased North Face Borod Hoody.

My perception is that the Borod is the same or cooler than regular fleece per ounce of garment.

When I add a wind shell to each the Borod still seems the same or cooler than the regular fleece.

I’m a heavy sweater and am always wet.  This may affect my experience and it may differ from yours.

 

 

[Edward Barton]

Not sure if this has been mentioned, but a benefit of grid fleece is the ability to turn it grid side in or out, where it is more or less insulative. This is true even under other layers, but especially when worn on its own. It can be worn in a wider range of conditions because of this, and spends less time in one’s pack in my experience.

[Author]

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