Quantifying Comfort — Field Notes

01The problem

“Comfortable” is subjective. The lab does not try to measure it whole. It splits it into three:

Thermo-physiological — heat and moisture.
Skin-sensorial — touch.
Ergonomic — fit.

The influencing factors run in a chain: fiber → yarn → fabric → finishing → garment and fit → layering.

Hover or tap a link in the chain.

02The system

Three parts: body, climate, clothing.

Heat gain is metabolic plus whatever the environment adds. It has to balance heat loss, which leaves five ways: conduction, convection, radiation, evaporation, respiration.

Ambient 70 °F Activity resting

Balanced → core temp holds.

The controller is the hypothalamus. The effectors are the sweat glands, skeletal muscle and the skin arterioles.

Environment

Sensors report in, the hypothalamus compares against its set point, and the effectors answer. About four seconds round the loop.

03What gets measured

Two numbers: Rct, thermal resistance, in m²·K/W, and Ret, water vapor resistance — breathability — in m²·Pa/W.

Both come from the sweating guarded hotplate, the “skin model,” under ISO 11092.

Before Ret, a primer. Diffusion:

Concentrated on the left. Left 190 · right 10 · net flow 0/s. Each particle only wanders. More cross rightward because more are on the left, so the crowd flows without anything pushing it. Breathability is just this, through fabric. Click to reset.

Ret is that, through a fabric, on the skin model:

Fabric

Vapour through the sample: —. Ret —. Heat through the sample: —.

Hohenstein’s additions: F_d buffering, K_f sweat absorption, F sweat transport.

Whole garments go on thermal and sweating manikins.

04Scale

Sweat per activity, from the slides:

Activity	Sweat
100 m sprint	0.1 L
90 min tennis	2.0 L
90 min soccer	3.0 L
Marathon	4.6 L
Ironman	20 L

Each dashed outline is the same 2-litre bottle. The Ironman column is ten of them.

05What I checked

Diffusion definition, thermoregulation, heat-balance model, ISO 11092 description: verified accurate.
Sweat table: consistent with published ranges (0.5–2.5 L/hr endurance; marathon ~2.5 L median, up to ~6.8 L) but marathon and Ironman run high. Ironman 20 L is gross production over 10–17 h, not net loss (finishers lose ~1–6% bodyweight). No primary source found; illustrative.
Core-temp graphic claimed severe damage/death at ±4 °F. Hot side is close (heat stroke ≈ 104 °F). Cold side understated: 94.6 °F is only mild hypothermia; life-threatening is below ~82–92 °F.

Core temperature

Danger hatched, safe in teal. Toggle and watch the cold edge move.

06Why this matters to me

[Two lines to come.]

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07Sources

ISO 11092:2014, Textiles — Physiological effects — Measurement of thermal and water-vapour resistance under steady-state conditions (sweating guarded-hotplate test).
Johns Hopkins Medicine, 2019 — marathon sweat and sodium loss study.
Sharwood, K. et al., 2004 — weight changes and performance in Ironman triathletes, British Journal of Sports Medicine.
Cleveland Clinic — hypothermia stages and core-temperature thresholds.
Wikipedia, “Diffusion.”