The base layer is quite possibly the most important component of the layering system when dressing for being outdoors in cold weather for an extended time. Does it hurt or help to wear multiple base layers?
In very cold weather, it’s fine to add an extra base layer. Two layers will be able to wick away additional moisture keeping you drier and more comfortable. Base layers should be tight-fitting, so an extra layer may inhibit mobility somewhat. In that case, one thicker base layer is also an option.
Outfitting your winter weather clothing system can be daunting. There are all sorts of opinions floating around about what’s necessary. We’ll try and demystify the base layer’s purpose as well as clarify why two base layers won’t ruin anything.
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Why Multiple Base Layers Won’t Hurt
The layering system has three parts: The first is the base layer which is typically a thin layer (synthetic, wool, or silk) next to your skin. The purpose of any base layer is to wick moisture away from your skin. If your skin gets wet, you’ll start to cool down, which is nice in the summer, but not what you want in the colder months.
Think about it like this, if you have a thicker base layer, that’s an extra bit of insulation for you while still performing the essential task of wicking moisture from your skin.
It works the same if you have two base layers that are equally tight and equally effective. Both base layer garments will perform their duty in this case.
If you have one base layer that is baggy and one that is tight, then you will disrupt the wicking and insulation process.
It’s an unbelievably complex interaction between molecular fabric structures and hydrodynamics. It’s safe to say though that if either base layer you wear doesn’t fit like a base layer should than it will disrupt its primary function.
The question is, is there a reason to double up on base layers at all?
Is There a Reason To Double Up On Base Layers?
The primary purpose of the base layer is to wick away moisture, and provide a bit of insulation. If you add a second base layer, are you just trying to add insulation?
In that case, you should consider adding a mid-layer instead.
The mid-layer’s purpose is to insulate your body and is often made from fleece or down.
The mid-layer is usually a breathable layer so that you can wear it as the outermost layer without making a personal sauna out of your own clothes. (If you want to see how breathable fleece is, check out our post, here)
Make no mistake, a thick base layer can add significant insulation. My ColdPruf thermals (see my recommended gear page to find out more info) are thick, and they are definitely warm even just to wear them by themselves.
There are a lot of factors determining your layering system. If you wear two or more base layers, remember that if you get too hot you have to take that layer off at some point–how easy a layer is to remove may be the difference of you ever removing it.
So all in all, adding another base layer will help you retain some warmth, but it may not be the most efficient, effective, or comfortable way to add that warmth.
What Is the Ideal Clothing Layering System?
To summarize everything we’re talking about, for an effective layering system you need the following.
- Base-Layer made of breathable moisture wicking materials (polyester, wool)
- Mid-Layer made from breathable but insulating materials such as fleece or down
- Outer-shell made from less-breathable materials to block wind and rain.
Regardless of your choices for base layers, insulating layers, and outer layers, the best way to be comfortable in the cold is to think about how long you’ll be outside, and what your activity level will be. In general, the lower the intensity of the activity or the longer the duration outside, the more you’ll need to layer up.
Lower Intensity or Longer Duration = Layer Up
It’s a super easy to test this out before you do your activity by simply going outside and deciding if you’re cold after five or ten minutes. If you feel no cold, then you’re probably dressed appropriately.
Higher intensity activities are a little trickier. The higher the intensity of the activity, the hotter you’ll get, and you risk sweating too much if you’re dressed too warmly.
Higher Intensity = Hold Back a Layer
In this case, if you feel a tiny bit cold right at the start, you will feel comfortable once you’re halfway up that big hill, and you’ll keep the sweating to a manageable level. The layer you should omit should be an insulating layer or an outer layer, never leave out the base layer.
Of course, do keep that extra layer in your pack in case the weather changes or you find yourself staying out longer than you thought. Remember, it’s always better to have it and not need it than need it and not have it.
Do I Even Need a Base Layer?
Unless you plan to spend your whole life in the tropics wearing flip-flops, shorts, and t-shirts, at some point, you’re going to need to think about base layers. For colder weather, it’s the one layer you should almost always have on.
If the weather is calm, and it’s not raining or snowing, you might not need a shell. If it’s just a little cool, but not cold, you might not need an insulating layer, but it’s hard to think of a cold-weather scenario when you wouldn’t need or want a base layer.
In hot weather, you sweat, and your body cools itself through the evaporation of sweat. It’s the same thing in cold weather, but this time, you want your skin to stay dry.
Wet skin will cool your body temperature. It’s the job of the base layers to help pull that moisture from your skin, and therefore they should fit pretty snugly. They don’t have to be Olympic-skier skin-tight, but they need to have contact with the skin to do their job, so they shouldn’t be loose and baggy. Also, you’re going to be putting more layers on top so everything needs to fit comfortably.
On a side note, this is another reason why the layering system is important – if you feel like you’re getting too warm, and starting to sweat, it’s a good idea to remove a layer or two so you can stay dry. That will help keep you warmer in the long run, even if it seems counter-intuitive at first. Always be sure to save room in your day pack in case you need to remove a layer.
Choose the Right Base-Layer Material
One of the few immutable laws of winter outdoor clothing is that you should avoid wearing cotton. On a trip to the mailbox, it’s fine, but if there’s any chance you’ll be encountering water, either in the form of precipitation or perspiration, then cotton is a bad idea. Cotton hangs on to moisture and will work against you in the cold if it gets wet.
Cold = Leave the Cotton in the Closet
The best base layers are made of either polypropylene or wool. They will dry quickly and keep you warm even if they do get a little wet. As for which of these to choose, the two factors to consider are cost and the environment. Polypropylene is cheaper than wool, but because it is derived from fossil fuels, and is essentially a variety of plastic, it exacts a much greater environmental cost – from its production, all the way to the microplastics that get constantly shed as you wash it and wear it.
This study, for example, examined the impacts of microplastics on the environment.
Silk is another option for a thin base layer. Silk is a little less effective at wicking moisture than wool or polypropylene, so it might not be the best idea for the coldest days, but its soft texture makes it a more comfortable (if more expensive) option. In addition, its moisture absorbency and strength are actually on par with wool in many aspects–check out our article on silk as a base layer for more specifics.
You may come across materials such as Capilene or Thinsulate. These are not altogether different materials, but rather brand names for slight variations on polypropylene (polyester is another variation).
Capilene is a product of the Patagonia brand and has an additional component intended to wick more moisture.
Thinsulate is a 3M product used by a number of clothing companies. I mention this not as a way to compare brands, but just to clear any confusion as various names are often casually tossed around in the outdoor community without much explanation.
Thinner Base Layer vs. Thicker Base Layer
Generally speaking, one thin base layer should be all you need (along with the mid-layer insulation and shell layers) unless the temperature drops below 10 degrees Fahrenheit. At that point, you will want to consider either a thicker base layer or two thinner ones.
Because base layers are tight, you may find that wearing two is a slight impediment to your flexibility and movement. For more relaxed outdoor activities like hiking or sightseeing, that might be OK, but for higher intensity activities like running, snowshoeing, or cross-country skiing, two layers might not work. In that case, try a thicker layer to stay warmer.
If neither of these options seems to be working, you may just need to add more to the insulating layer. This is where the real warmth is going to come from whereas base layers are mostly about getting moisture away from your skin. Insulating layers can be as thick and as numerous as you can manage, and if it’s really cold (like Minnesota cold), the more the merrier.
How Many Base Layers Do I Need?
A single base layer is all that is necessary to stay warm as long as you combine your layering with a bulky mid-layer and a waterproof outer shell.
Although an additional base layer isn’t likely to affect your layering negatively, strictly speaking, you’ll get all the benefits of a base layer from just having a single base layer.