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 not being wool, 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, we 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.

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. 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

Surprisingly, we found the breathability of the REI Co-op Midweight Half-Zip much better than we anticipated. The midweight synthetic fabric isn't going to be 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. We found that 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 both 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 a far more delicate and usually more expensive wool upper.

Comfort and Fit

We found the REI Co-op Midweight Half-Zip true-to-size, fitting close to our 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 does have 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 abrade or annoy one 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. It's synthetic midweight fabric has proven to us 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, we experienced no seams coming undone, no pilling of the fabric, 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 tumble dried on low. So go ahead and plan to use it as your go-to baselayer all winter, then stuff it into the deepest bowels of your hiking pack in the summer.

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. As mentioned above, 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.

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 we feel it should be a designated mid-layer. The material is also soft, but not so soft that we feel it won't slide over most any other layers you 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, we're quite impressed.

Several features of the Midweight Half-Zip do make it stand out when it comes to layering, none of which we enjoyed more than the thumb loops. When utilized, they can help keep the sleeves in place and not lost in several other layers of clothing. The half zip can also help with breathing a little easier by having a way to dump out a little heat when you can't stop to take off a layer until later. Branding is kept to an absolute minimum, which we generally like to champion. Using this base layer as your top layer won't seem out of place even in 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 reasonsnotto recommend the REI Co-op Midweight Half-Zip - especially for the price - except for those who need the absolute maximum performance that only a wool or wool blend is going to 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.

What Other Base Layers Should You Consider?