October 3, 2025 Igors Tomilovs

Thermal Base Layers for Men, Women, by the Numbers

Contents:

Why +1…+3 °C with wind often feels colder than a dry −5 °C
Materials: merino, synthetics, merino blends
Weights 150/200/260 gsm & knit structure
Membrane + base: how not to “steam”
Ready sets for real-world use
Baltic temperature map
Fit & details
Care without drama
Checklist: +2 °C & wind
Product links

Shop the full range: thermal underwear and base layers, or narrow it to men’s base layers and women’s base layers.

1) Why +1…+3 °C with wind often feels colder than a dry −5 °C

Humidity + convection + evaporation drive heat loss. Wind strips the warm boundary layer near the skin, moist air and wet fabric conduct heat faster, and sweat evaporation steals extra energy from the skin.

Numbers: at +2 °C and 7 m/s wind, “feels like” is around −3…−3.5 °C; at 10 m/s it’s ≈ −4.5 °C. So your base layer needs to be warmer than in a dry −2…−3 °C with no wind.

2) Materials: merino vs synthetics (and merino blends)

Your base fabric determines how fast your skin stays dry and how stable warmth feels when effort and wind change. In Latvia, three approaches work best: 100% merino (theoretical ideal), merino blends (merino + synthetics), and synthetics. Our range focuses on merino blends — they win in Baltic wind.

Merino (100%) — theory, pros & cons

Pros: natural thermoregulation in static/damp conditions, stays warm even slightly wet, skin-friendly, less odour.
Cons: higher price and faster wear, dries slower during high-intensity work.
Note: we don’t prioritise 100% merino; instead we offer merino blends that dry faster and last longer: men’s merino/merino-blend base layers · women’s base layers.

women's merino base layer set

Synthetics (PP/PES/PA)

Fastest moisture transport and fastest drying — perfect for sweat spikes while running or brisk hiking in wind.
Feels cooler in wind and during static periods if the mid-layer isn’t warm enough; you need smart layering (fleece). See fleece mid-layers.
Care: simple, but after hard use rinse/ wash more often to avoid odour. See examples in women’s base layers (synthetics & merino blends).

synthetic or blend base layer

Merino blends (merino + synthetics)

For Baltic conditions the sweet spot is a 40–60% merino + synthetic blend. Moisture leaves the skin fast, while merino keeps warmth and softens the feel in wind.

Best for: hikes with breaks, daily city/commute cycling, “+2 °C & wind” by the sea.
What to look at in our store: men’s merino blends and women’s base layers.

Comparison by criteria

Criterion	100% merino	Merino blend (merino + synthetics)	Synthetics (PP/PES/PA)
Warmth static / in wind	Very good / good	Very good / excellent	Good / medium (needs warm fleece)
Moisture transport	Medium	Very good	Excellent
Drying time	Slower	Fast	Very fast
Wear resistance	Medium	Good	Very good
Skin feel	Very pleasant, “warm”	Pleasant, balanced	Cooler, more “sporty”
Price / value	Higher price	Good to very good	Best performance per €

Quick picks by scenario

+1…+4 °C & wind, 60% static: merino blend ~200 gsm + fleece 200–300 gsm.
Active movement, short stops (+3…0 °C): synthetic/merino blend 170–190 gsm (women — here) + light fleece.
Evening camp, little movement (+2…−4 °C): merino 220–260 gsm + warmer fleece.

3) Weights & knit: 150/200/260 gsm — why “thicker ≠ always warmer”

150–170 gsm — active hikes/runs, short stops, +3…−2 °C, light to moderate wind, under a light mid-layer.
190–210 gsm — Latvia’s “all-rounder” for +5…−5 °C with wind. Holds static warmth well, won’t overheat on the move. Men’s merino 190–210 gsm · Women’s base layers
240–270 gsm — long static time (camp/observation), +2…−8 °C and wind — add fleece.

Knit matters: rib/interlock with micro-loft traps more air and feels warmer at the same weight; smooth jersey moves sweat faster but feels cooler in wind. A brushed back is cosy yet needs a thoughtful mid-layer — see fleece jackets.

4) Membrane (Dermizax / TorayDelfy) + base layer: how not to overheat

The job of a membrane shell is to block rain and wind but let vapour out from within. You’ll see 10k–20k+ water resistance and breathability in specs. Numbers help, but real comfort depends on the system as a whole: base → mid → shell.

“Sauna” under the shell is often not leakage but condensation (dew point) when warm, humid air meets a cold fabric. The fix: correct base + early ventilation.

Vapour gradient that works

Next to skin: synthetic/merino blend for fast wicking — men’s merino blends, women’s base layers.
Mid-layer: warm layer that spreads moisture — fleece 150–300 gsm.
On top — membrane shell: with real vents (pit-zips, two-way front zip) — men’s waterproof shells, women’s waterproof shells.

Fit & ventilation (quick code)

Close to skin: avoid air pockets that turn into cold spots in wind.
Open vents before you overheat: pit-zips + two-way front zip.
Carry a thin spare base tee — swapping at a break works wonders.

No cotton: cotton soaks and cools — it has no place under a membrane shell.

no cotton under shells

5) Ready sets for common scenarios

A. Seaside day-hike, +1…+4 °C, 6–10 m/s wind, ~60% static

Base: merino blend ~200 gsm or bi-layer 180–200 gsm. Men — merino base layers; women — women’s base layers.
Mid: fleece 200–300 gsm or a light synthetic loft.
Shell: 20k/10k+ membrane (Dermizax/TorayDelfy) — men / women.
Plus: a dry spare base set in a dry bag.

B. City/commute cycling, +3…0 °C, gusty wind

Base: synthetic/merino blend 170–190 gsm — women and men.
Mid: fleece 150–200 gsm; actively use vents.
Shell: breathable jacket with pit-zips — men / women.

C. Evening camp, +2…−4 °C, little movement

Base: merino 220–260 gsm (comfort in static & damp). Women — sets here.
Mid: fleece 250–300 gsm or thin loft.
Shell: wind-resistant membrane — men / women.

6) Temperature map (Baltics, wind, hiking/city)

Temp / wind	Activity	Base (gsm)	Material	Mid-layer	Shell (outer — mandatory)
+5…0 °C, 3–6 m/s	walk 60%, static 40%	170–190	merino blend / synthetics	fleece 150–200	men’s waterproof shells women’s waterproof shells
+3…−2 °C, 6–9 m/s	walk 40%, static 60%	190–210	merino blend / merino	fleece 200–300	men’s waterproof shells women’s waterproof shells
+2…−6 °C, 7–10 m/s	static 70%	220–260	merino	fleece 250–300 + light insulation / Primaloft jacket under the shell	men’s waterproof shells women’s waterproof shells
−5…−10 °C, ≤6 m/s	static 50%	200–220	merino	fleece 250 + insulation / Primaloft jacket under the shell	men’s waterproof shells women’s waterproof shells

7) Fit, seams, details

Fit: close to skin, no folds; a fold = a cold channel.
Seams: flatlock construction, moved away from strap/inner thigh friction lines.
Length: top to mid-thigh, bottoms past the ankle — avoid cold bridges.

8) Care without drama (and without odour)

Wash: 30–40 °C; detergent without softener.
Dry: reshape and dry flat; tumble only gentle if the label allows.

Rotation: 2 sets (short & practical)

Formula: one on you, one drying. Next day — swap.

Merino/merino blend: after wearing, hang wide and airy immediately. Let it dry till morning (8–24 h).
Synthetics: often dry in 2–8 h, but leave overnight so “internal” moisture disappears.
Warmth & hygiene: a dry base = warmer feel and less odour.
Fast drying tips: hang right away, airflow > heat; dry merino flat. In a rush? Towel-roll + gentle squeeze + fan.
Wash rhythm: air out merino/merino blends 2–5 wears; wash synthetics more often (every 1–2 wears).

rotation illustration

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Thermal Base Layers for Men, Women, by the Numbers

1) Why +1…+3 °C with wind often feels colder than a dry −5 °C