Thermal Underwear for Work: Stay Warm and Dry | Saniso

Thermal underwear: the short answer

Wear thermal underwear directly on your skin: a close-fitting, quick-drying shirt with long sleeves, plus long johns (long underpants) for your legs. This thermal base layer keeps body heat in and moves sweat away from your skin. Your warm mid layer and work jacket go over it.

At Saniso you can choose between two lines. SKYLINE from STALCO is black and comes in sizes S to 4XL, such as the thermal shirt in size L (S-51314). WOLVERIN from STALCO PERFECT is sold as seamless and comes in combined sizes, such as the undershirt in M/L (S-79102). Saniso B.V. in Zwaag sells the STALCO and STALCO PERFECT brands as a wholesaler and webshop.

Why the layer on your skin decides how warm you stay

The layer on your skin has two jobs: hold on to your body heat and get rid of sweat. A thick jacket cannot fix a layer that stays damp underneath it. That is why the first layer matters most when you sweat at work and then stand still.

SKYLINE is described as the base layer of work clothing, worn under sweatshirts and jackets. It is meant for work in low temperatures and during high physical effort. In short: thermal underwear for outdoor work, worn as a base layer under work clothes.

Dry skin stays warm: what quick-drying fabric does

Every shirt and every pair of long johns in both lines is quick-drying. For SKYLINE, moisture from physical effort is not absorbed but released quickly to the outside. Excess heat can escape too, so you are protected against both cooling down and overheating.

WOLVERIN is built for moisture wicking: it keeps the skin dry and prevents excessive sweating during intense work or training. The fabrics differ:

• SKYLINE: 86% polyester, 14% elastane, 180 g/m²
• WOLVERIN: 55% polyamide, 39% polyester, 6% elastane

Close fit, no bunching under work clothes

A base layer only does its job when it lies against your skin. The shirts in both lines have a fitted cut and a round neckline. The long johns have an anatomical fit and a wide, soft waistband.

Flat seams in both lines help prevent chafing under work trousers or a jacket. The SKYLINE long johns also reduce the risk of the fabric catching on protruding parts while you work.

Who wears thermal underwear for work?

Anyone who works outside in the cold, for example in construction, paving or a warehouse. The product pages describe it for work in low temperatures, during high physical effort and with changing temperatures, so it also suits anyone who keeps going in and out of a warm van or site hut.

WOLVERIN is also described for work or training, so it can be worn for outdoor training in cold weather too.

All shirts and long johns in this range are men's models.

Shirt and long johns: build your base layer

A thermal shirt covers your upper body. Long johns give your legs the same layer: the SKYLINE long johns are made to be worn under work trousers. Both lines have a shirt and long johns, and for WOLVERIN you can put together a complete set.

SKYLINE: flat seams, sizes S to 4XL

SKYLINE is the black STALCO line. Shirt and long johns both come in S, M, L, XL, 2XL, 3XL and 4XL, so you simply take the same size for both. A shirt in size M (S-51312) goes with long johns in size M (S-51326).

• Flat seams, fitted cut, round neckline on the shirt
• 86% polyester, 14% elastane, 180 g/m²
• Largest size 4XL: shirt S-51322 and long johns S-51336

The SKYLINE shirt in size S, S-51310, is a long-sleeve shirt just like the other sizes. The SKYLINE long johns are also stated to keep their antibacterial properties and to prevent wind penetration.

WOLVERIN: seamless, in combined sizes

WOLVERIN from STALCO PERFECT is sold as seamless. It is made with a minimal number of seams. On the shirt those seams are flat, elastic and pressure-free; on the long johns they are flat and elastic. The labels are knitted in instead of sewn on.

The shirt comes in S/M, M/L and 2XL/3XL; the long johns in S/M, L/XL and 2XL/3XL. The largest size in both is 2XL/3XL: the undershirt S-79104 and the long johns S-79110.

Which size thermal underwear should you take?

Thermal underwear should sit close to your body without pinching. The close fit keeps the fabric working against your skin and still leaves room for layers on top.

The product pages do not give a size chart with body measurements. What you can go by:

• SKYLINE: single sizes S to 4XL, the same for shirt and long johns.
• WOLVERIN: combined sizes. Shirt and long johns do not run the same sizes: the shirt comes in S/M, M/L and 2XL/3XL, the long johns in S/M, L/XL and 2XL/3XL.
• Largest size: 4XL is only available in SKYLINE; WOLVERIN goes up to 2XL/3XL.

Not sure which size fits? Contact Saniso before you place your order.

Overview: STALCO thermal underwear at Saniso

Prices as of 6 October 2026, incl. 21% VAT. Always check the current price on the product page.

In short: SKYLINE gives you the widest size range up to 4XL at one price for shirt and long johns, while WOLVERIN is the seamless option in combined sizes.

Frequently asked questions

Should thermal underwear fit tight or loose?

Close, but not so tight that it pinches. The shirts have a fitted cut and the long johns an anatomical fit, so the fabric stays against your skin. That contact is what keeps heat in and moves sweat away.

Do you wear a T-shirt under or over thermal underwear?

Thermal underwear goes directly on your skin, so no T-shirt underneath. Anything you wear goes over it: a sweatshirt, fleece or work jacket. A T-shirt underneath would sit between your skin and the fabric that is meant to move sweat away.

Does thermal underwear keep you dry when you sweat at work?

That is what it is made for. Both lines are quick-drying. SKYLINE releases moisture from physical effort to the outside instead of absorbing it, and WOLVERIN wicks moisture to keep the skin dry during intense work. The SKYLINE shirt also dries quickly after washing or getting wet by accident.

Seamless or flat seams: what is the difference in thermal underwear?

Both are made to avoid rubbing and pressure points. SKYLINE has flat seams. WOLVERIN is sold as seamless: it has a minimal number of seams, which are flat and elastic, and knitted-in labels. You can see this on the seamless undershirt in S/M (S-79100).

Which size do you take when shirt and long johns come in combined sizes?

That applies to WOLVERIN. Shirt and long johns each have their own combined sizes: the shirt S/M, M/L and 2XL/3XL, the long johns S/M, L/XL and 2XL/3XL, for example S-79108 in L/XL. There is no size chart with body measurements, so if you are in doubt, contact Saniso before ordering. If you prefer the same size for top and bottom, SKYLINE uses single sizes from S to 4XL for both.

Can you wear thermal long johns under normal work trousers?

Yes. The SKYLINE long johns are made to be worn under work trousers, and the WOLVERIN long johns are comfortable to wear under trousers. Both have a wide, soft waistband and flat seams, for example the SKYLINE long johns in size L (S-51328).

How do you wash thermal underwear?

Follow the washing temperature on the product page of each line, because it is not the same everywhere:

• SKYLINE shirts: wash at 30 °C
• SKYLINE long johns: wash at 40 °C
• WOLVERIN undershirts and long johns: wash at 30 °C

For all of them: do not tumble dry, bleach, iron or dry clean.

Contact: Saniso B.V., De Corantijn 95, 1689 AN Zwaag · +31 85 488 5920 · [email protected]