REI Co-op Midweight Half-Zip Review

We've been pleasantly surprised and more than impressed at just how well REI Co-op has executed its own line of clothing, including the Midweight Half-Zip base layer. The design features a half zip, out-of-the-way thumb holes, and a double-padded collar. It provides a surprising amount of warmth for non-wool layer, and it dries quickly.

Performance Comparison

Warmth

Cozy! With an advertised fabric weight of 220 grams per square meter, the REI Co-op Midweight Half-Zip will get you better prepared for chillier alpine starts than many other synthetic tops in our roundup. In our testing, I found its performance to be a little less than a wool top of comparable weight, but not by too much. The big advantage you get from this synthetic base layer is much better durability. This is one of the few synthetic base layer tops I'd seriously consider wearing when hiking a Colorado 14er in winter. Warmth coupled with durability is a winning combination in more harsh conditions.

You'll find some very welcome features to help thermoregulate, including comfy, well-designed thumb loops to protect and warm your hands. They won't replace gloves but can assist with keeping drafts from creeping up your sleeves. Unlike many other base layers, the REI Co-op Midweight Half-Zip sews additional fabric so that your whole thumb has a place to live when it's in the thumbloop. The front zipper travels halfway down the front, allowing you to dump tons of heat out after hard ascents. And when you're ready to zip things back up, the high, double-padded collar will keep your neck warm.

Breathability

The breathability of the REI Co-op Midweight Half-Zip was much better than I anticipated. The midweight synthetic fabric isn't as breathable as some of the flyweight synthetics in our lineup, but it performed more than adequately in the barrage of tests we threw at it - especially for the weight of the fabric. During our tests, this fabric absorbed approximately 52% of its weight in water when fully wetted and spun dry, which rates slightly less than the wool/wool blends we tested and on par with other synthetics. This gives support to the theory that wool fabric holds onto water internally a little more easily than synthetics.

Our simple air permeability tests using a peak flow meter also showed favorable results. Generally, in a base layer, you want a fabric that has lofted-up material to have nooks and crannies for warmed-up air to occupy while also allowing water vapor to escape to the next layer up. Air passed through the fabric of the Midweight Half-Zip easier than most other synthetics of similar weight, though not as well as the loftiest of wool tops. This continues a trend where this fully synthetic top performs almost as well as far more delicate (and usually more expensive) wool layers.

Comfort and Fit

I found the REI Co-op Midweight Half-Zip true-to-size, fitting close to my body without being too tight, which works well as a base layer that anticipates having more layers worn on top of it. Smooth, flatlock seams are used throughout the garment, further enhancing the top's comfort rating. The half zip is padded at the collar, so you won't be in contact with the zipper's perchance icy-cold metal.

The fabric has a little stretch in it, care of the 8% spandex within. Stitching is used quite minimally. Although there is a top seam on the shoulder, it's located a little forward from the center line and shouldn't be too annoying or abrasive when wearing a backpack. You'll find semi-raglan sleeves on the Midweight Half-Zip which complements the gusseted under-the-arm area to allow a little more room to stretch when raising up your arms in triumph of your latest summited peak.

Durability

Durability is certainly one of the many stronger qualities of the REI Co-op Midweight Half-Zip. Its synthetic midweight fabric has proven that it can take a beating far better than most any wool or wool blend. Strong flatlock seams are everywhere and allow the fabric to stretch. If you're planning on wearing your base layer as your only layer, this would be a good choice. It's not as durable as some other synthetics we've tested, but it is a whole lot more comfortable due to the fabric's soft hand and the addition of just a touch of the additional stretch from the embedded Spandex.

In our extended real-world tests, I experienced no seams coming undone, no pilling of the fabric, and no rips or tears. The fabric also comes back to its original shape after being stretched out. And to add another feather to its impressive cap, the Midweight Half-Zip can be machine washed and tumbled dry on low. I admit to abusing the Midweight Half-Zip more than most while traveling. Even with all we've been through together, it looks almost as good as the first day I started wearing it.

Drying Speed

Our line dry test resulted in fair to good results for the REI Co-op Midweight Half-Zip — just about what we expected for a top with heavier fabric, 220 grams per square meter. Approximately five ounces of water—52% of the total weight of the fabric—was absorbed when we washed and spun dry this garment, which then needs to evaporate off.

This time can be drastically reduced by first wringing out the shirt before putting it out to dry - something you can do without fear of damaging the fabric of this fully synthetic top. And at home, putting this in the dryer on low still follows the manufacturer's suggestions. This top sneaks into my regular wash sometimes, as it doesn't look super technical. Drying it in the dryer doesn't seem to bother it.

Layering Ability

Once again, the REI Co-op Midweight Half-Zip beautifully navigates a narrow channel when it comes to the various characteristics of the chosen fabric. The material is thicker than many other synthetics we've tested but not so thick that it should be designated as a mid-layer. The material is also soft, but not so soft that it won't slide over most any other layers I put over it. The inclusion of just enough Spandex into the fabric allows it to move and conform to your own body without feeling too clingy. All in all, I was quite impressed.

Several of the Midweight Half-Zip's features stand out when it comes to layering, especially the thumb loops. When utilized, they can help keep the sleeves in place and not lost or bunched up under several other layers of clothing. The half zip can also help dump out a little heat when you can't stop to de-layer. Branding is kept to an absolute minimum, which is nice. Wearing this as your top layer won't seem out of place even around town, as this top doesn't have an “underwear” feel to it.

Should You Buy the REI Co-op Midweight Half-Zip?

It's really hard to come up with reasons not to recommend the REI Co-op Midweight Half-Zip — especially for the price — unless you need the absolute maximum performance that only a wool or wool blend will offer. For those seeking out an alternative to wool or who need the durability that a synthetic has in spades over wool, the Midweight Half-Zip turns out to be one of our favorite base layers for colder conditions to recommend. If you need a warm base layer but don't want wool, we recommend this one.

What Other Base Layers Should You Consider?