CLO Value
CLO value is an index of thermal insulation that indicates the degree to which a garment suppresses heat loss from the human body, and the higher the value, the greater the thermal insulation generally is.
Contents6 sections
Definition and Overview
CLO value is a unit that represents the thermal resistance of a garment or combination of garments, that is, the degree to which it hinders the transfer of heat from body temperature. It is used as a guideline for heat retention performance, including the wearing state, rather than the thickness of the fabric itself or the material name.
The higher the value, the more static air it tends to retain, and the less heat tends to escape from the body to the surrounding environment. However, actual warmth also varies depending on the wearer's activity level, temperature, wind, humidity, and the gaps between layered garments.
Texture and Functional Features
Garments that tend to have a high CLO value create an air layer through brushed finishes, pile, filling, down, and similar materials, so they are more likely to have a bulky, soft appearance and texture. On the other hand, surface feel, drape, and breathability cannot be determined from CLO value alone.
Even with the same material or fabric weight, thermal insulation changes depending on the weave or knit structure, degree of brushing, presence or absence of lining, amount of ease, and layering structure. Wind resistance and moisture permeability are separate properties from CLO value, and should be checked together when considering comfort in cold conditions.
Main Applications
CLO value is useful when considering thermal insulation designs suited to the usage environment in autumn and winter clothing, cold-weather outerwear, workwear, outdoor wear, bedding, and loungewear. It is used not only for individual garments, but also for evaluating the entire outfit from underwear to outerwear.
In planning, organize not only the expected temperature but also whether the item will be used outdoors or indoors, for standing work or exercise, and whether protection against wind and rain is required. For applications with high activity levels, excessive insulation can cause stuffiness, so balance with moisture permeability and ventilation features is important.
- Cold-weather clothing intended for low-activity or rest periods
- Autumn and winter outerwear for commuting and everyday wear
- Uniforms suited to the work environment
- Outdoor wear designed for layering
Selection and Handling Notes
When comparing CLO values, check the test method, whether it is a single garment or a clothing combination, and conditions such as underwear and posture. Values obtained under different conditions may not be directly comparable, so do not determine the warmth of a product from the number alone; instead, choose evaluation conditions close to the intended application.
If washing, drying, or compression storage changes the bulk of the filling or the nap direction of the brushed surface, the air layer may decrease and thermal insulation may be reduced. Follow the care label, and if necessary, reshape the item and dry it properly. Shrinkage is not determined by the CLO value itself but varies depending on the materials and processing of the outer fabric and inner materials, so separate confirmation is necessary.
In sewing, the spacing of quilting, the method of securing the filling, and the way cold air enters from the seams affect thermal insulation. For products with filling, consider specifications that prevent sewing misalignment, filling breakage, and shifting, and also check the slip between the outer fabric and lining, as well as feeding during sewing.
Differences from Similar Terms
Thermal insulation is a broad term describing the property of clothing or fabric that makes heat less likely to escape. CLO value is an index that quantifies that thermal insulation as the thermal resistance of clothing. Fabric weight is a standard showing mass per unit area, and heavier fabric does not necessarily have a higher CLO value.
Fill power is an index used mainly to evaluate the loft of down. It relates to the thermal design of down products, but the object being measured differs from CLO value, which indicates the overall insulation of a garment.
Frequently Asked Questions
If the CLO value is high, can it be considered a warm garment?
In general, when compared under the same evaluation conditions, a higher CLO value is an indicator of higher insulation. However, perceived warmth varies depending on wind strength, roominess when worn, perspiration, layering, and activity level. Wind resistance and moisture permeability also need to be checked according to the application.
Can CLO value be determined from fabric weight alone?
No. Fabric weight indicates the weight of the fabric, while thermal insulation depends on thickness, air content, brushing, filling, structure, and the air layer inside the garment. Even with similar fabric weight, CLO value differs depending on structure and construction, so evaluation under conditions close to the intended application is necessary.
Does washing change the CLO value?
If the filling loses loft, down shifts, or the brushed surface becomes flattened, the air layer retained inside the garment may decrease and thermal insulation may change. The extent of the change varies depending on the material and product specifications, so follow the care label and check the condition after washing before mass production.
