All You Need To Know About Down vs Synthetic Insulation


What’s the difference between down and synthetic insulation? 

Broadly speaking, there are two types of insulation: natural down insulation and synthetic insulation. Both have their pros and cons. Down is lighter and weight-for-weight it’s warmer than synthetic insulation. But down fails to insulate when it’s wet. Synthetic insulation, on the other hand, maintains its insulating power in damp conditions. Here we are exploring the difference between the two, and talking about which is best for your thermal clothing.


What is down insulation? 

Down comes from birds, duck down or geese down are commonly used in clothing. It’s the very finest feathers closest to the bird’s body. These light, fluffy feathers are naturally insulating. They trap air between their loose tendrils helping to prevent heat loss. Neither down insulation nor synthetic insulation actually create heat; they simply effectively maintain the body heat that’s generated. 

The North Face® down found in our insulated jackets is RDS down. RDS stands for Responsible Down Standard. This sustainable down is ethically sourced and fully traceable. This means we know where our down is coming from and that there is absolutely no live-plucking or force-feeding. RDS down is a by-product of the food industry and down has the lowest carbon footprint of any fill material.

What does down fill mean? 

Fill is the amount of down inside the clothing product. It’s usually referred to as fill power, basically because the higher the fill the more powerful the garment is at insulating. Fill power is determined by placing one ounce of down in a graduated cylinder and measuring the volume the down occupies in cubic inches. A greater volume means a higher fill power. The longer the tendrils are the more volume it occupies, meaning the tendrils trap more air and are better at keeping you warm. They are also lighter and more compressible. 


What is synthetic insulation?

Synthetic insulation is usually made from polyester, either raw or recycled. It’s engineered to mimic down’s lofty tendril structure trap warm air for insulation. However, this man-made structure isn’t as delicate as down, so the insulation isn’t as compressible and to get the same insulating power as down you need more synthetic insulation, making thermal clothing heavier and bulkier. But synthetic insulation does maintain its insulating power even in wet or humid conditions. It also dries faster making it easier to wash. The polyester fibres are also more durable than down. 

So, what’s best down or synthetic insulation?

The simple answer is it depends. One is not better than the other in all situations. The decision to choose a down insulated jacket or a synthetic insulated jacket revolves around the conditions you’ll be facing most of the time.


When to use down insulation

Down is weight-for-weight the better insulator, so it’s most suitable than synthetic down for extremely cold conditions. Very cold conditions are usually very dry conditions. Down is the ideal insulation for dry-cold climates and on expeditions and adventures where weight is a defining factor, such as alpine climbing. 

In normal circumstances, down does not perform well in wet and humid conditions. However, at The North Face for our higher-priced and more technical products we use ProDown™. This is a special type of RDS down that has been treated with a durable water repellent (DWR) to help it perform better in damp conditions. Though unless weight and compressibility are important, synthetic insulation is still a better option for damp environments. 


When to use synthetic insulation 

Synthetic insulation is a very versatile insulator. It’s easy to take care of, it keeps you warm in a variety of conditions, including cold and wet environments, and it’s cost-effective. It’s particularly useful in humid conditions, such as those you find in many parts of the UK, the Benelux region and away from the mountains in France, Spain and Italy. 

At The North Face, our preferred choice for synthetic insulation in our thermal clothing is ThermoBall™ Eco. This synthetic is made from recycled polyester and insulates extremely well for its weight. Weight for weight ThermoBall Eco is not as warm as down, but still maintains a high level of insulation. 

On top of all this, aside from the insulation filling, we treat many of our jackets and trousers with a durable water repellent (DWR) to help water bead off the surface, thus helping to keep the insulation drier for longer.