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Fiber & Material Science · Thermal Data
Thermal Conductivity of Scarf Materials
Measured thermal conductivity (W/m·K) and CLO values for common scarf fibers and constructions — with warmth-to-weight comparisons and specification guidance.
Fiber & Material Science — Thermal Data
How Thermal Performance Works in Scarves
Thermal conductivity (λ, W/m·K) is a fundamental material property — but in textiles, it tells only part of the warmth story. Construction, loft, and still air entrapment are the decisive factors in practical scarf warmth. This guide provides fiber reference data, CLO values by construction, and guidance on how to specify warmth in purchase orders.
Key principle: The primary insulator in all textile products is still air (λ = 0.026 W/m·K). Fibers that trap more air per unit weight — through crimp, fine diameter, or pile structure — produce warmer fabrics regardless of the fiber’s own thermal conductivity value.
TC-01
How Thermal Conductivity Works in Scarves
Thermal conductivity (λ, W/m·K) measures how easily heat flows through a material. Lower λ = better insulation = warmer scarf. In textiles, the fiber itself is not the main insulator — still air trapped within the fiber structure is. Wool’s natural crimp and cashmere’s fine diameter create more air pockets per unit weight than coarser fibers. Fabric construction (pile height, density, thickness) determines practical warmth more than fiber λ alone — a thick lofted acrylic scarf can outperform a thin cashmere one in absolute warmth terms.
Lower λ
= Warmer Scarf
Still Air
Primary Insulator in All Textiles
0.026 W/m·K
Still Air Conductivity (Benchmark)
Fiber + Structure
Together Determine Warmth
TC-02
CLO Values and Practical Warmth
CLO is a unit of thermal resistance used in comfort science. 1 CLO ≈ 0.155 m²·K/W. A typical wool knit scarf provides approximately 0.3–0.8 CLO depending on thickness and construction. A cashmere scarf at the same weight provides slightly higher CLO due to finer fiber diameter and greater air entrapment per gram. These values are measured by sweating guarded hotplate (ISO 11092). CLO values are the most reliable metric for comparing scarf warmth within the same weight class — more useful than fiber λ alone for purchase specification.
0.155 m²·K/W
1 CLO Definition
0.3–0.8 CLO
Typical Scarf Range
ISO 11092
Test Standard (Hotplate)
Higher CLO
= Warmer
TC-03
Warmth-to-Weight Ratio by Fiber
For buyers specifying scarves by warmth and weight, the warmth-to-weight ratio (CLO per gram of fabric) is the most useful sourcing metric. Cashmere and fine merino wool lead in warmth-to-weight. Acrylic approximates wool in warmth-to-weight at significantly lower cost, making it the dominant fiber for commercial winter scarves. Silk is a poor insulator per gram but excels at moisture management and layering comfort. Polyester fills match or exceed natural fibers in warmth only in thick, lofted constructions with significant air entrapment.
Cashmere
Highest Warmth per Gram
Acrylic
Best Synthetic Warmth/Weight
Silk
Lowest Warmth per Gram
Construction
Determines Real-World Warmth
Reference Data
Thermal Conductivity and CLO Data Tables
Thermal conductivity values sourced from published textile science literature. Cashmere data (*) is estimated from fiber diameter and air entrapment modeling; direct measurement values are limited in public literature. CLO values in Table 2 are factory-estimated at standard construction parameters.
Table 1 — Thermal Conductivity by Fiber / Material (reference values)
| Fiber / Material | Thermal Conductivity (W/m·K) | Density (g/cm³) | Warmth-to-Weight | Notes |
|---|---|---|---|---|
| Still air (reference) | 0.026 | — | Benchmark | The true insulator in all textiles |
| Cashmere | 0.025–0.040* | 1.28 | Excellent | *Estimated; fine diameter maximises air entrapment |
| Merino wool | 0.029–0.054 | 1.32 | Excellent | Natural crimp = high air entrapment |
| Acrylic | 0.050–0.051 | 1.18 | Good | Best synthetic insulator; low density |
| Viscose (Rayon) | 0.055–0.071 | 1.52 | Moderate | Dense fiber; less air entrapment |
| Cotton | 0.040–0.071 | 1.54 | Moderate | Higher conductivity than wool; cooler handle |
| Silk | 0.050–0.075 | 1.34 | Low | Poor insulator per weight unit |
| Nylon | 0.260–0.290 | 1.14 | Low | High conductivity; wicks heat away |
| Polyester | 0.150–0.400 | 1.38 | Low–Medium | Construction-dependent; filament vs. staple differ significantly |
Table 2 — CLO Values by Scarf Construction (factory-estimated; ISO 11092 methodology)
| Construction | Fiber | Fabric Weight (gsm) | CLO (estimated) | Typical Use Season |
|---|---|---|---|---|
| Fine knit (3mm thick) | 100% cashmere | 120 gsm | 0.35 CLO | Spring / Autumn |
| Standard knit (5mm) | Merino wool | 250 gsm | 0.55 CLO | Autumn / Winter |
| Chunky knit (10mm) | Acrylic / wool 70/30 | 420 gsm | 0.80 CLO | Winter |
| Woven twill (2mm) | Cotton | 180 gsm | 0.20 CLO | Spring / mild winter |
| Woven (1.5mm) | Silk | 80 gsm | 0.12 CLO | Year-round layering |
| Double-layer knit | Cashmere | 200 gsm | 0.70 CLO | Winter |
Common Misconceptions
Thermal Performance — Myths vs. Facts
Four common misunderstandings about scarf warmth, thermal conductivity, and fiber insulation performance.
Myth
“The fiber with the lowest thermal conductivity is always the warmest scarf material.”
Fact
Thermal conductivity of the fiber itself is secondary — construction determines warmth. A thick, lofted acrylic scarf traps more air than a thin cashmere one and will be warmer in practice. Warmth is determined by total thermal resistance (Rct), which depends on fabric thickness, density, and air permeability, not fiber λ alone.
Myth
“Cashmere is significantly warmer than merino wool.”
Fact
Cashmere’s warmth advantage over merino wool of comparable weight and construction is modest — approximately 5–15% higher CLO value. The perceived softness difference is far more dramatic than the warmth difference. Cashmere’s real thermal advantage is achieving the same warmth at lower weight — not dramatically higher absolute warmth.
Myth
“Polyester is always a cold, non-insulating fiber.”
Fact
Polyester thermal conductivity depends heavily on construction. Polyester filament fabric (tightly woven, little air entrapment) has high conductivity and is cool to the touch. Polyester staple in lofted knit construction (brushed, napped) traps air effectively and can achieve warmth comparable to mid-weight wool at equivalent thickness.
Myth
“Silk is a warm fiber.”
Fact
Silk has relatively high thermal conductivity (0.050–0.075 W/m·K) and low CLO per gram — it is one of the poorest insulators among natural scarf fibers by weight. Silk’s value lies in moisture management, lustre, and light drape — not warmth. Specifying silk for a winter scarf requires significantly heavier construction to compensate.
Frequently Asked Questions
Thermal Performance — Buyer FAQ
Common questions from scarf buyers on warmth specification, testing methods, and fiber selection for thermal performance.
What thermal conductivity value should I look for in a warm scarf?
Lower thermal conductivity = better insulation. Wool and cashmere (0.029–0.054 W/m·K) outperform synthetic fibers at equivalent construction. For practical scarf sourcing, CLO value (measured by ISO 11092) is more useful than fiber λ alone — request CLO data at your target fabric weight when specifying winter scarves.
How is scarf thermal performance tested?
Thermal resistance (Rct, m²·K/W) is measured by ISO 11092 using a sweating guarded hotplate. The fabric sample is placed on a heated plate at 35°C in standard airflow; heat flow through the fabric is measured. CLO = Rct / 0.155. Some factories use simpler comparative methods (ASTM D1518) for routine QC — adequate for relative comparison but not for absolute CLO specification.
Does fabric weight or fiber type matter more for warmth?
Both matter, but construction (weight, thickness, loft) has the larger effect on practical warmth. Doubling fabric weight roughly doubles thermal resistance. Fiber type determines warmth efficiency per unit weight — cashmere and wool are more efficient (warmer per gram) than acrylic or polyester, which matters most for lightweight products where weight is a design constraint.
Why does acrylic perform better than polyester for warmth?
Acrylic has lower thermal conductivity (0.050–0.051 W/m·K) than polyester filament (0.150–0.400 W/m·K) and lower density (1.18 vs 1.38 g/cm³). Acrylic staple fiber also has better crimp and loft than polyester filament, trapping more still air per unit volume. Together, these factors make acrylic the warmest synthetic fiber for knit scarf applications at equivalent fabric weight.
Can I specify CLO value in a scarf purchase order?
Yes, though it requires the factory to have ISO 11092 testing capability or access to a certified textile lab. More commonly, buyers specify fabric weight (gsm), fiber content, and minimum fabric thickness as proxies for warmth. If CLO specification is required for a technical winter product, request the test report from an accredited lab (Intertek, SGS, Bureau Veritas).
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References & Standards
- ISO 11092:2014 — Textiles: Physiological effects — Measurement of thermal and water-vapour resistance under steady-state conditions (sweating guarded-hotplate test). iso.org
- ASTM D1518 — Standard Test Method for Thermal Resistance of Batting Systems Using a Hot Plate. astm.org
- ISO 139:2005 — Standard atmospheres for conditioning and testing textiles. iso.org
- Textile Institute — Thermal Comfort in Textiles and Clothing, Manchester, UK.
- Ashdown Engineering — CLO Values Reference Database for Textile Products.
See this standard applied in production: WeaveEssence factory technical records include test reports and process data relevant to this guide. Contact the technical team for specification-specific documentation.