What is a CLO rating? How warm is my jacket?
How to understand CLO Values
Clothing is our main and first line of defence against the cold. How well our clothing protects from frigid temperatures depends on its CLO value – a measure of clothing’s thermal insulation.
CLO values date back to when they were developed in 1941 as an attempt to explain the clothing insulation value, and are an excellent guide to assisting in correct garment selection.
CLO values are a great guidance tool, but lots of other factors can come in to play from normal body temperature, gender and amount of movement. However, using a CLO value as guidance is a very good barometer, especially if working in harsh cold conditions.
CLO is a value that describes the degree of insulation provided by a piece of clothing.
The CLO value of 1 is equal to the amount of clothing required by a resting human to maintain thermal comfort at a room temperature of 21 degrees Celsius, or 71 degrees Fahrenheit.
When working in extreme and/or cold environments, it can be difficult to accurately estimate how much warmth and insulation are needed based on just the temperature alone, due to the work being done etc.
A big question we get is: "How do I compare insulation when there are different brands and levels?" So how do you compare insulation in different garments? Remembering the thicker a garment, doesn't necessarily mean a warmer garment.
Understanding the values is the best initial start.
The base is 0, which represents a completely naked, unclothed person. Not ideal for cold conditions.
Example CLO ratings of garments:
- Men’s briefs = .04 CLO
- Sweatpants = .28 CLO
- Thick sweater = .35 CLO
- Winter coat = .70 CLO
Now, compare those to some of the most common thermal liners used in cold weather hand protection, like Thinsulate™ brand insulation, created by 3M.
Thinsulate™ liner CLO ratings:
- C40 Thinsulate™ = 0.7 CLO
- C100 Thinsulate™ = 1.3 CLO
At MI, we offer the world's finest brands and can guide you with your product selection throughout your evaluation process. See our jacket range here as a guidance