Thermal resistance, often expressed as Rct, is one of the most widely used measurements for evaluating textile insulation materials.
Unlike general descriptions such as “warm” or “high-performance”, Rct provides an objective laboratory measurement of how effectively a material resists heat transfer.
For product developers, Rct is a valuable tool because it allows different insulation materials to be compared under identical test conditions.
However, like all laboratory measurements, Rct should be considered together with other performance characteristics rather than as a single indicator of product quality.
Rct measures the resistance to heat flow through a textile material.
The higher the Rct value, the greater the material’s resistance to heat transfer under laboratory conditions.
In simple terms:
Higher Rct = Better thermal insulation.
However, Rct does not measure comfort, breathability, durability or garment performance. It measures only thermal resistance under controlled conditions.
Rct is normally measured according to ISO 11092, often referred to as the Sweating Guarded Hot Plate test.
During testing, a heated plate simulates the heat produced by the human body.
The insulation material is placed above the plate, and the amount of energy required to maintain a constant surface temperature is measured.
The less heat that escapes through the material, the higher the Rct value.
Because the method is standardised internationally, it allows meaningful comparisons between different insulation materials.
Unlike marketing descriptions, Rct provides measurable data.
It allows developers to compare:
This makes Rct particularly useful during material selection and product optimisation.
A high Rct value indicates strong thermal resistance under laboratory conditions.
However, the finished product may perform differently depending on factors such as:
For this reason, Rct should always be interpreted as part of the complete product system.
Rct and CLO describe similar thermal characteristics but use different measurement systems.
Because both evaluate thermal insulation, they are often presented together in technical documentation.
Many insulation manufacturers publish one or both values depending on market tradition and customer requirements.
Understanding both measurements provides a more complete picture of insulation performance.
One of the strengths of Rct is that it allows developers to compare insulation efficiency independently of thickness alone.
Modern microfibre insulation can sometimes achieve relatively high Rct values despite using considerably less material thickness than traditional insulation.
This makes Rct particularly valuable when developing:
where available space is limited.
Rct is one of the primary performance indicators used when evaluating the MEIDA insulation range.
Because MEIDA focuses on achieving efficient thermal performance in relatively thin constructions, Rct provides an objective way of comparing different material weights and product variants.
However, Rct is always considered together with:
This provides a more complete understanding of insulation performance than relying on a single laboratory value.
A CLO value is a standardised measurement used to describe the thermal insulation provided by clothing and insulation materials.
CLO is a unit used in textile insulation to express thermal insulation performance under controlled laboratory conditions.
Not necessarily. The best CLO value depends on the intended application, available space and overall product design.
CLO values are determined using recognised thermal testing methods under controlled laboratory conditions.
They provide an objective method for comparing insulation materials.
Yes. Fibre technology and construction influence thermal efficiency.
Yes. Modern microfibre insulation systems can provide high thermal efficiency without excessive thickness.
No. CLO and Rct both describe thermal insulation but use different units and testing approaches.
Neither is better. Both provide useful information and are often used together.
CLO provides valuable laboratory data, but real-world warmth also depends on garment design, moisture, wind and user activity.
The measured CLO value describes the insulation material, while the finished product performance depends on the complete construction.
Yes. Compression reduces the amount of trapped air available for insulation.
Moisture influences thermal comfort and product performance even when the laboratory CLO value remains unchanged.
There is no universal “good” CLO value. The appropriate level depends on the intended application.
MEIDA Original is designed to provide high thermal performance while maintaining a thin, lightweight construction.
Yes. Gloves often require high thermal performance within very limited space.
Yes. Thermal performance is an important consideration in insulated footwear, particularly where product thickness is limited.
Because thermal comfort also depends on moisture management, air permeability, thickness, weight and overall product construction.
Yes. Together they provide a more complete understanding of thermal insulation performance.
Technical performance data is available in the individual MEIDA product datasheets.
Whether you’re developing apparel, footwear, gloves or bedding, our specialists are ready to help.