The general principle of layering is to maintain a comfortable body temperature, that is one where you are not cold and not too hot either. Its the “Goldilocks” zone.

So how do you accomplish this? The answer is layers. The best way is to have multiple layers rather than one or two layers.

Base Layer.
The base layer is your next to skin layer, it forms the base of your clothing system by trapping warmth close to the skin. Base layers are normally polypropylene, merino wool or a blend of the two.
Polypro is generally cheaper to purchase and they last a long time, however they do become smelly quite quickly.
Merino wool is more expensive and I have found they do not last as long as the polypro however I find them nicer on the skin and I have worn them for 10 days without a wash and they still smelled fine. Merino wool is naturally antimicrobial and fights that odour for a long time.
Now if its warm weather your base layer may be a shirt to keep you cooler and get rid of that heat rather than trap it. Even if it is predicted to be nice weather for the duration of your trip its wise to carry one for the evenings and for sleep.
On a multiday trip I will pack two base layer tops and two base layer bottoms, one for wearing during the day and one set kept dry, stored in my sleeping bag and only put on once I have escaped the elements. I will use this layer to sleep in instead of a sleeping bag liner and if I need I will put on a pair of socks and beanie to complete the next to skin base layer for the night.
During the day your base layer would normally consist of
-Underwear
-Socks
-Merino Pants (weather dependant)
-Merino Top (weather dependant)
-Beanie (weather dependant)
-Gloves (weather dependant)

Where the item is ‘weather dependant’ means that if its a warm day you may want to use your shorts without thermals underneath or a sun shirt instead of a thermal top. Your beanie and gloves finish the layer off if required.

Mid Layer
Your mid layer is the next line of defence in insulating you from the cold, you put it on over your thermal layer to increase the amount of heat trapped on your body.
There are two main types, natural fibres like Merino wool and synthetic fibres like polar fleece.
The synthetic fibre options are generally lighter in this layer such as a mid weight merino zip up is heavier than a fleece in the same thickness. Synthetic 100w fleece layers are small and light, dry quickly and transfer moisture away from the body to evaporate.
A Merino mid layer will be heavier for the reasons mentioned above, it will still keep you warm (though not as warm) if it gets wet. The issue is that it takes a while to dry and stays heavier longer as a consequence.
For mid layers I prefer a 100 weight fleece as its light and versatile, quick to dry and can be used as a base layer and walked in on colder days.
Generally I don’t use this jacket until I get to camp, I run on the warm side and it traps too much heat for me. Even in snow conditions I will normally have just a thermal or thermal and synthetic sun shirt under my rain jacket. Now everyone feels the cold differently and I know people that would have all but their thick down jackets on under their rain jackets and still not sweat.

Insulation layer.
This layer is your main source of insulation, again this is worn over the preceding layers to increase the amount of heat trapped around the body.
Natural and synthetic options are available here again, the most popular being Down jackets and Synthetic jackets.
Down is the best weight to warmth option available, its highly compressible, its naturally lightweight and has been the go to insulation for cold temperatures. It has one negative aspect though, if you get it wet it has no thermal qualities at all, it takes a long time to dry and it forms clumps that need to be broken up to dry the jacket properly. With that one major downside your need to take care to keep it dry. As such I will store this jacket inside the waterproof liner inside my pack.
Synthetic options include thick fleeces or jackets made with synthetic fibres sewn into the facing fabrics. Some manufacturers produce a synthetic version of down and fill jackets similar to a down style jacket.
Personally I use down, and I will keep this in my pack until I have set up camp and changed into dry clothing then stowed away safely in the morning.

Shell Layer
Your shell layer consists of a wind and waterproof jacket and pants. This is your final protection from the elements during the day and, if required, and if its dry, can be put over everything else to trap more heat.
Shell layers are almost all synthetic jackets with a thin waterproof membrane that will prevent water from going through and allow water vapor (sweat) to escape. In theory this process stops the build up of sweat inside the jacket and stops the jacket from “wetting out’. Wetting out occurs when the jacket either doesn’t breathe (let that sweat out) or it cant hold up to the amount of rain its receiving and both the inside and outside are drenched.
Exactly the same theory applies for the pants.
Some jackets are better than others at being able to withstand the volume of rain than others. This process is measured in a waterhead rating test. I have a brief explanation of the ratings here. A reading of 1,500mm is about the base level to be classed as water resistant. Jackets up to and exceeding 10,000mm are available and somewhere in the 7-10k range being a solid jacket for most scenarios.
With all that being said I have not found a jacket yet that keeps up with my warm running body and hasn’t wetted out from sweat after a few hours.

Now that we know the layers and what items they consist of lets look at a couple of scenarios.

1 Cold -1c degrees, clear skies, light wind.
I’ve already done my morning routine and I’m about to get changed before I take down the tent. I will have a merino wool base layer top with a 1/4 zip, synthetic shirt and my 100w fleece over the top. I will then add a merino base layer pant, a pair of synthetic shorts and a mid weight pair of merino socks. My shoes or boots, my rain jacket and a cap. I know ill be cold at the beginning but should warm up enough through walking that I will soon take off my rain jacket. Not long after I will take off the 100w fleece if I am getting warm. Both of these layers will stay near the top of my pack to swap on and off if needed during the day.
When I get to camp the first thing I do is set up my shelter and in this instance that the weather is still clear I will get in and get changed out of my wet or mucky clothes and into my dry base layers, dry mid layer and insulation layer as its cold I don’t want to run the risk of chilling down. In a hut scenario I would do it immediately as the shelter is already provided. If I’ve put on too much its easier to shed a layer than warm one up.

2. 9 Degrees C, Rain, Windy.
I have already done my morning routine and I’m about to get changed before I take down the tent. I’ll have the merino top and bottom, shorts, synthetic shirt, rain jacket and pants and my hat. Its a bit warmer so I wont worry about the fleece as I know I’ll warm up quicker. I will still keep the fleece close to the top of my pack in case I need it.
I got to my campsite and I’ve set up my tent, however before getting changed I’m going to assess a couple of things. Firstly ‘have I wet the jacket through’ if I haven’t I will be able to use it over my dry insulation later. If its dry I will get changed. If its wet I will not want to put it over my dry insulation later so I will collect water for the evening and next morning now and asses if I need to go number 2. Once that is done I can take off all my wet gear and hop into the tent for a quick wipe down and change into all my dry layers.

3 22 degrees C, clear, warm breeze
This is beautiful day, I’ve done my morning routine in my shorts and shirt and that’s pretty much how I’ll stay for the day. It has been cold overnight though about 2 or 3 degrees. I will still keep the rain gear handy and the 100w fleece near the top of my pack.
I got to camp all hot and sweaty but its only 4pm so I will get changed into my other pants and shirt and give my sweaty clothes a rinse with water, wring them out and hang them to dry, the same with my socks and jocks from the day. These days are rare here in Tas, tomorrow it could be cold and rainy. Now I’ll set up and get the tent organised. As the sun dips I will put my thermals on and 100w fleece and maybe my down jacket a bit later if I’m not already in bed.

Having multiple layers allows your to regulate your temperature better that one thick layer which will have you overheating when walking or too cold if you take it off.
The common advice is to start the day cold and warm up as you walk rather than stopping to take off a layer. I don’t mind stopping to regulate layers and it doesn’t really take long to take off a layer and stow it in the pack.

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Tags: base layers, Hiking, hiking equipment, hiking gear, Hiking Tasmania, insulating layers, Layering, merino thermal, mid layers, Overland Track, overland Track tips, shell layers, Tasmania