Kefiw

Archived noindex page. Kefiw's public focus is Property decision help.

Archived page

This older Kefiw page is kept for reference, marked noindex, and removed from the primary sitemap. The current Kefiw experience is focused on property decisions: cost, quotes, damage, buying, selling, owning, and packets.

Go to Property

Clo Insulation · The Layering Math

1 clo ≈ a business suit. Higher activity generates metabolic heat, lowering required insulation.

Required clo = (33°C − Ta) / (8 × met). Pick layers that sum to the target — runners over-dress, desk workers under-dress.

Clo is the insulation unit that turns "what should I wear?" into arithmetic. 1 clo = 0.155 m²·K/W, the insulation of a 1950s business suit at rest in a 21°C room. Required clo scales inversely with metabolic rate (met) — a runner generates 6-8× the heat of a seated desk worker, so a runner at 40°F needs roughly the same clothing as a desk worker at 65°F. Under-dress and the body diverts fuel from performance to thermogenesis; over-dress and sweat soaks layers, destroying their insulation.

Part of: Environmental Stressors

Quick answer

Required clo = (33°C − Ta) / (8 × met). Pick layers that sum to the target — runners over-dress, desk workers under-dress.

What you are trying to do
1 clo ≈ a business suit. Higher activity generates metabolic heat, lowering required insulation.
Best next step
Insulation Logic · Clo Units
Limit to remember
Treat this as a practical aid for the task, not a replacement for professional judgment.

Key points

  • ▸ Required clo formula: (33°C − Ta) / (8 × met), where Ta is air temp in °C and met is metabolic rate.
  • ▸ Met values: resting 1.0, light desk work 1.2, walking 2.5-3.0, brisk hike 4-5, running 6-8.
  • ▸ 1 clo = 0.155 m²·K/W ≈ business suit (pants + shirt + jacket) at rest in 21°C, 50% RH, no wind.
  • ▸ Garment clo values: t-shirt 0.08, dress shirt 0.25, fleece 0.3-0.5, down jacket 0.8-1.2, heavy parka 2.0+.
  • ▸ Indoor default: 0.7-1.0 clo (typical office wear) at 21-23°C, met 1.2.
  • ▸ Outdoor winter: 2-4 clo for rest in below-freezing conditions; runners at the same temp need only 0.7-1.2 clo.

How to

  1. Enter air temperature in °C or °F.
  2. Pick activity state — resting, light, walking, brisk, running — which sets met.
  3. Read required clo.
  4. The suggested stack greedy-packs layers (base + mid + shell) to meet the target.
  5. For variable activity, plan for the lowest met you will experience (the stationary rest break, not the climb).
  6. Wind chill and rain increase required clo by 20-50% — add a shell layer.

Examples

  • 40°F (4.4°C), brisk hike
    Required = (33 − 4.4) / (8 × 4) = 28.6 / 32 = 0.89 clo. Stack: thermal base (0.3) + fleece mid (0.5) = 0.8 clo. Add a light shell for wind.
  • 21°C office, desk work
    Required = (33 − 21) / (8 × 1.2) = 12 / 9.6 = 1.25 clo. Typical office wear: dress shirt (0.25) + trousers + light sweater (0.3) + shoes = ~1.0 clo. Most offices run cool for 1.0 clo — add a cardigan.
  • −10°C standing outdoors, light activity
    Required = (33 − −10) / (8 × 1.5) = 43 / 12 = 3.6 clo. Stack: thermal base (0.3) + fleece mid (0.5) + down jacket (1.0) + heavy parka (2.0) ≈ 3.8 clo. Runner at same temp only needs 0.9 clo.

When to use which tool

▸ Operational Thresholds
  • CYAN · STABLE — 0-1 clo — light indoor or active outdoor; t-shirt + light layer territory.
  • GOLD · GUARDED — 1-2.5 clo — standard cold-weather layering; base + mid + light shell.
  • MAGENTA · CRITICAL — >2.5 clo — deep cold or low-activity; add heavy down, parka, or insulated shell; frostbite risk rises on exposed skin.
▸ Pivot
Cold side handled. Flip to the heat side and verify WBGT for any summer transition planning.
Thermal Failure · WBGT →

Related

Frequently asked questions

› What is 1 clo exactly? Definition

1 clo = 0.155 m²·K/W — the thermal resistance of a 1950s business suit (jacket, trousers, shirt, underwear, socks, shoes) at rest in 21°C, 50% RH, with no air movement. It is a reference unit, not a garment.

› Why does higher activity need less insulation? Troubleshooting

Metabolic heat production scales with met. A runner at met 7 generates ~7× the resting heat output. That heat has to go somewhere — if insulation is too high, it stays trapped, sweat soaks the layers, and the now-wet insulation loses 30-50% of its clo value.

› How do I handle variable-activity days? How-to

Layer for the lowest met you will experience (the rest break), with shed-able pieces for the high-met phases. Modular layering beats one heavy coat: base stays on, mid and shell come off during effort, go back on at rest.

› How should I use this guide with a Kefiw tool? How-to

Use the guide as the plan and the linked Kefiw tool as the check. Read the steps first, try the move manually, then use the tool to compare outputs, catch edge cases, and decide whether the result actually fits your task.

› What mistake do tool guides help avoid? Troubleshooting

Tool guides help avoid using a utility mechanically without understanding what you are trying to accomplish. Most word, writing, and text utilities are fast, but speed can hide context mistakes. Know whether you are solving a puzzle, cleaning copy, drafting a line, or checking a rule.