Staying Warm – the ABC of Insulation

babyMost of us probably own a thick jacket or coat meant to insulate us from the cold UK winters. Have you ever wondered how insulation actually works though? Why do some garments keep us warmer than others despite their thickness?

Insulation – when it’s done properly – is a little bit of magic, creating a warm, impenetrable bubble around your body.

Basically it takes three things to work:

Seeking shelter

For an item of clothing to insulate you properly it firstly needs to keep the wind out; think of a wind breaker or heavy leather jacket that literally blocks the wind. A survival technique you may have seen on a reality series advocates layering your clothes with newspaper or the like – not to keep you warmer, but to block the wind. Thankfully a proper jacket or coat will do the trick under normal circumstances.


A No Wet Zone

The second important factor is keeping dry – insulation (i.e. maintaining your body heat) can’t work if it’s wet; thereby making you even colder.


Robins Do It


You’ve seen birds puffing themselves up on cold days. What these little feathered friends are doing is trapping warm air between their feathers and bodies. The third element of effective insulation is based on this principal.

When shopping around for a winter coat or jacket it’s important to ascertain whether it will a) keep you protected from the wind b) keep you dry and c) have an inner layer that will trap hot air between itself and your body. If the garment meets the criteria the chances are that it will work perfectly. There is also a measuring system that you can use as a guide:


Clo units

Clothing insulation is measured in clo units with 1 clo equalling 0.155 K·/W. It’s all very mathematical but this table will give you an idea of how it works:




Clo m2K/W
Light shirt with long sleeves 0.20 0.031
Work coveralls 0.50 0.078
Jacket 0.35 0.054
Down jacket 0.55 0.085
Coat 0.60 0.093
Parka 0.70 0.109


As you can see from this table from The Engineering Toolbox, the more insulated the clothing, the higher the clo factor, and the warmer the wearer.


Stay Dry!

Utilise water proof trousers, Jackets and Boots to stay dry when the temperature drops, heat lose can happen 25x faster when wet.

When it comes to staying comfortably snug this winter, make sure your jacket or coat meets all of the above criteria and you’ll be toasty as a puffed up robin.

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