The base layer seems like a no-brainer, right? Let’s stick a t-shirt on “Jonny” and get moving! I can’t tell you how many times I’ve seen kids in a cotton t-shirt on the trail, and when conditions turn, they get cold. The key to layering is anticipating your environment and gearing your clothing selections to ensure comfort and safety. Here are a few tips on picking the perfect base layer for your kids’ next outdoor adventure.


You just walked into the kid’s section to find a base layer and there were a hundred different options, different fabrics, colors, and styles. This is what you need to know.

Merino Wool

Merino wool is my choice for a base layer in every season. Why? It’s soft and stretches when you move. That’s important given your kids will be moving constantly and wearing the same shirt for the next few days. It helps regulate body temperature—keeping you cool in hot weather and warm in cold weather—and does a great job wicking moisture. No other fabric can offer such versatility in this range of conditions. Finally, it’s extremely effective controlling order and can be worn for multiple days without drawing the ire of your family. Think about it, you’ll be sleeping next to “Jonny” for the next few days…enough said.

Merino wool is measured by fabric weight using grams per meter squared (g/m2), so you’ll usually see ratings between 150 and 400, meaning 400 g/m2 fabric weight. In the summer months, a fabric weight between 135 and 170 is ideal, usually characterized as featherweight or ultralight. For cooler temperatures or shoulder season activities, a 200 mid-weight merino might be just the ticket.

But, like most things, nothing is perfect. So, there are a few drawbacks to merino wool. Let’s start with price. On average, a merino wool shirt for your kids will set you back $50-80, which is not chump change for a shirt they may only use a few times a year. However, keep an eye out for sales. I’ve purchased all my merino at substantial discounts. Next, merino wool can be less durable than other fabrics, especially in those ultralight weights that are preferable in summer conditions. My kids have had merino wool shirts for several seasons and they still look good, but they’ve picked up a few holes from leaning against rocks or clipping a tree branch. Hey, it’s extra ventilation. Finally, if your kids are anything like mine, mosquitos are a big problem and knit fabrics perform miserably as a bug barrier. To mitigate some of the ill effects of knit fabrics, I use a permethrin treatment, which has been shown to be an effective repellent for mosquitoes and ticks. You can use a spray like Sawyer Premium Insect Repellent for Clothing or send your clothes to insect shield for a longer lasting repellent.


There’s a reason most athletic wear is made of polyester material; it’s cheap, extremely durable, wicks moisture away from the skin, and dries extremely quickly. If you drop into a retail outlet store you can usually find a kid’s polyester shirt for under $10. The polyester fibers are strong and resist abrasion, so your kids will most likely outgrow the shirt before wearing holes in the fabric. Plus, polyester fabrics perform well as a barrier against mosquitos, especially when treated with permethrin. Honestly, nothing can ruin a trip more quickly than a hundred mosquito bites, so you might consider polyester as an insurance policy during those early season excursions. Finally, polyester provides very good ultraviolet resistance, which means you don’t have to worry about sunburn for the covered area.

Now for the drawbacks to polyester. First, when polyester gets wet, it literally saps heat from your body. That might work during a football game, but it’s less than ideal in the mountains where temperatures can vary drastically. Second, polyester is abysmal at controlling odor, so packing a single polyester shirt will test the boundaries of even your closest friendships after more than a night in the outdoors.


Nylon is a synthetic material made from oil byproducts with exceptional durability, which is why it’s used in parachutes. It’s also lightweight, provides exceptional wicking, and dries quickly. Better yet, nylon provides a complete barrier against bugs, so it’s a great option for children, like mine, who have painful reactions to mosquito bites. If you treat nylon with permethrin, it’s an unstoppable combination.

The major downside to nylon as a base layer is the lack of breathability. In high aerobic activities or warm conditions, you kids will suffer. Make sure to look for a hiking shirts with a button front, ventilation across the back, and roll-up tabs on the sleeves. This will allow air flow for cooling, which is important for temperature regulation.

What about Cotton?

I know cotton is the fabric of our lives, and for good reason. It’s comfortable, breathable, and cheap. But, in the outdoors, it is Kryptonite for your little superman. The biggest drawback is how quickly cotton absorbs moisture, hence the reason it’s used in bath towels. When cotton gets wet, the fabric loses all warmth and draws heat away from the body. It also takes an eternity to dry, which is not acceptable, even possibly dangerous, as a base layer.


Okay, so you settled on a fabric. Now it’s time to consider style. Here are some pro tips to improve function and comfort:

  • Long-sleeve shirts provide greater flexibility in the outdoors—warmth and better protection from the elements
  • Quarter zip tops improve ventilation
  • Nylon shirts must have a button front with roll-up tabs for the sleeves to increase air flow
  • Lighter colors are cooler in warm conditions and repel bugs

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