Thermal clothing and thermal underwear form the base layer of your workwear. Which option suits your work depends, among other things, on how much you move, the cold you work in, the material and the clothing layers you wear over it. This guide helps you compare those choices and shows when a thermal shirt, thermal trousers or a complete base layer makes sense.
What matters during your work?
| During your work… | Pay particular attention to |
|---|---|
| A lot of movement / perspiration | Moisture management, material and fit become more important. |
| Working in the cold / outdoors | Compare material, fabric weight and the layers you wear over it. |
| Cold legs as well | Include a base layer for your lower body in your clothing system too. |
Synthetic, merino or a blend?
The material makes a noticeable difference to how thermal clothing feels while you work. If you move and perspire a lot, synthetic materials are often worth considering because of their moisture management. Merino wool is commonly used in thermal clothing for colder conditions. Blends of different fibres are also available. So do not look only at the material on the label; also consider fabric thickness, fit and the clothing layers you wear over it.
What does g/m² say about the warmth of thermal clothing? g/m² indicates how much one square metre of fabric weighs. A higher number does not automatically mean that the thermal clothing is warmer or better for your work. Material, fabric thickness and what you wear over it also matter.
Your work situation
The same job or sector can place different demands on your base layer from one working day to another. Focus on what you do during the day and the conditions in which you work.
A lot of movement and perspiration | If you walk, lift or move for much of the day, moisture management, material and a close but comfortable fit become more important. A base layer should sit close to the body without restricting movement. |
Working outdoors or moving between warm and cold areas | Temperature, wind and exertion can all change during the same working day. In that situation, not only the base layer matters, but also how it works with your mid layer and outer layer. If your activity level varies considerably, a half-zip can give you extra control. |
Long periods in a cold or refrigerated environment | During prolonged exposure to cold, heat retention becomes more important. Look at the material construction and also consider whether only your upper body or your whole body needs an additional base layer. |
Thermal clothing as a base layer in the 3-layer system
If you work with several clothing layers, thermal clothing sits directly against the skin as the base layer. A mid layer, such as a work sweatshirt or fleece, can provide extra insulation. The outer layer protects against conditions such as wind and rain. Already wearing a sweatshirt and work jacket therefore does not determine what you need as your first layer: it is the combination of activity, base layer and the other layers that determines how the clothing system works.
Comparing thermal shirts
Crewneck or half-zip? The main difference is around the neck. A crewneck has a standard round neck. A half-zip usually has a higher collar and a zip that lets you open the neck. This gives you more opportunity to release heat when you work harder and close the neck again when you move less or start to feel colder.
Compare the material construction and product design below with the work situation you recognised above.
Comparing thermal trousers
Only a thermal shirt, or thermal trousers as well? You do not automatically need to wear a thermal shirt and thermal trousers together. If you work in the cold for longer periods or find that your legs do not stay warm enough under your work trousers, thermal trousers can complement your base layer. Make sure the combination with your work trousers remains comfortable and allows enough freedom of movement.
Further reading if you work in the cold
Cold feet too?
Read which thermal socks suit your work. What are the best thermal socks for work?
Want to combine your base layer properly?
See how the layers in your workwear work together. 3-layer system
Do you also work in winter conditions?
Read more about clothing choices for working in cold and winter weather. Winter conditions require the right work clothing
Frequently asked questions
+What determines how warm thermal clothing is? Is merino warmer than synthetic?
Thickness and construction, fit, activity level and the other clothing layers also matter. Merino wool is commonly used in base layers for colder conditions; synthetic materials are often used when moisture management during active work is important. A merino base layer is therefore not automatically warmer than every synthetic base layer.
+Should thermal underwear fit tightly?
A base layer should fit close to the body, but it should not restrict you. Raise your arms above your head and squat a few times. If the shirt rides up strongly, the waistband digs in or the fabric limits your movement, the base layer is probably too tight.
+What is the advantage of a half-zip?
You can open the collar when you want to release more heat during exertion and close it again when you move less or start to feel colder.
