Why temperature rating won’t tell you how warm your coat is

The cold weather will soon hit and so begins the search for the right winter jacket.

So how do you know if a jacket is warm enough?

Many people will search for a jacket with a specific temperature rating in mind. But did you know that garment insulation experts will tell you that temperature rating is rarely ever accurate and should not be relied upon to choose your winter coat?

In fact, most major outerwear brands no longer advertise or use temperature ratings for that very reason.

Simply put, there are too many variables that affect how warm and/or comfortable a person may feel.

Warmth is measured by what is called CLO value. But this being said, neither CLO value nor temperature rating can guarantee how warm you will feel, because all of the following factors come into play: 

  • Your level of activity (This plays a major role in how warm you feel!)
  • Your personal metabolism
  • Are you someone who runs hot or cold?
  • What other clothing are you wearing under the coat?
  • Are you wearing one or multiple layers of clothes?
  • Are all parts of the body covered by adequate clothing?
  • Wind speed
  • Humidity level
  • The style of the coat – long or short, high or low neck, hooded or not
  • The construction of the coat – how are the seam lines done and does the shell and lining fabric let in wind or water? (Wind and humidity will make you feel much colder.)  

All of the above will directly affect how warm you feel.

Now as a general rule and the common perception is that the loftier the insulated garment is, the warmer you will be. That would be true if comparing down insulation. But for synthetic or plant-based insulation, this is only true if you are comparing between the same type of insulation within a same brand. Plant-based or synthetic insulations are often built with their own distinct structures or technologies to trap air and reflect body heat. So using the “puff factor” to evaluate the level of warmth between different brands of synthetic or plant-based insulations is comparing apples and oranges. 

An example that also illustrates how puffiness doesn’t always correlate with warmth proportionally is this. Think of insulation padding used in footwear.  The insulation padding in footwear is normally very thin. Yet, not only are your feet where heat loss will occur most rapidly, they also come into contact with the cold ground and snow more directly than other parts of the body. But the insulation padding in footwear is virtually always thinner compared to a coat’s insulation, yet a pair of properly insulated boots can protect your feet just as well as a puffy jacket would your body.  

So how to choose the right winter coat? Carefully consider the list of factors above to evaluate your needs, then select an adequate style of jacket with an effective insulation technology to correspond with your specific needs. Be sure to cover the extremities (hands, feet and head) really well, because heat is lost and felt there the quickest. And we always recommend that you wear multiple layers of clothes under any jacket so you can easily adjust your coverage level as needed. This is the best method to ensure that you stay comfortable and warm throughout the day, as you go through different levels of activity and transition from outdoor to indoor at various times.