The Search for a Fleece Replacement – A Close Look at Active Insulation and the role of MVTR

[Shawn Bearden]

Thanks, Stephen. Indeed, I’ve read all of them, several times each…and all the comments. This factor for which traditional fleece seems to still be popular in my experience and that of those I know who still use it doesn’t seem to be addressed by these alternatives. Hoping someone else will be able to chime in with similar experience/use.

[Brett Peugh]

As I side note, I don’t find the really thin fleeces much for warmth value and barely more for abrasion.  If you go fleece, go full in.  Get a 200 or 300 wt one that can take the abrasion and keep you warm while moving. And they will shed the moisture some also.  MH Monkey Man and TNF Campshire tend to be the most fluffy and can be really warm under a shell.  They are not light but then again you are wearing it and not have it stuffed into a pack.  These types of fleeces will last decades and you won’t have to be careful with them.

[Christopher S]

This is great stuff for comparing different similar options but I am still not convinced we should be relying so much on MVTR for real world moisture transport. I have not found it accurate in predicting real world moisture transfer in any of the bivies I have made and I am not convinced it is an accurate way to compare very different garments like shelled active insulated puffies vs fleece vs merino or other.

In addition I still maintain that matching the CFM of a garment to a persons individual heat output is the best metric to start with – I can guarantee you that I would be able to produce sweat faster than any of these garments can dump it by a fair margin if airflow is too restricted or if I am wearing too much insulation. It wont matter how good a garment can technically move moisture across it if the user is producing it at a much higher rate. I know other people who can sustain a decent athletic output wearing something close to a 0 CFM hardshell and be perfectly comfortable.

As for specifically comparing fleece to these newer garments I think there is also an extremely important difference – the amount of water the garment itself can absorb. Even though Apex might be “warm when wet” I challenge anyone to take their apex puffy and get it completely soaked in cold water in the shower and then put it on. I guarantee you its not going to feel very warm and it is going to lose a lot of its insulation. If you squeeze it dry it will still remain wet for some time. 100% polyester fleece on the other hand (like classic 100) will absorb only about 2% of its total weight in water and most of that can be easily squeezed out. Try the same test in the shower, do a single squeeze, and then put the garment back on. It will feel almost dry. Below freezing if this happens you can simply shake the fleece and most of the frozen water will just fling off – again you end up with a garment that is mostly dry.

I am not saying that these synthetic puffy active insulations do not have their place but I am not convinced they are a substitute for fleece. I am really not a fan of the types of fleece with tons of spandex and ridiculously hairy structure (that sheds super bad and are very fragile) as they seem to try to be something like Apex but done poorly. I would probably switch to a synthetic puffy for active use below 10-15F daytime temperatures assuming moderate wind and some sun.

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