Down vs. Synthetic Insulation

Which do you prefer?

When choosing a warm insulating jacket for winter, or a sleeping bag, we often hear that down is the best option. Why is this? Because it’s the most compressible and warmth for weight is unmatched. So what are the disadvantages? When it becomes wet, it clumps and it does not retain it’s insulation. Once you get it wet, it’s difficult to dry, so it’s not recommend for very humid and rainy environments.

In the mountains, you will find most people prefer down, though despite the debate most people will own one of each, synthetic and down jackets. In spite of opinions it is simply a matter of application.  In extremely wet environments, down simply is not practical.

insulation types

What is Down?

Down is actually the fluffy undercoating that provides warmth for geese, ducks and other waterfowl, and not the feather itself.  Its structure traps air pockets, is breathable and allows moisture to escape. Synthetic fibres are simply man made, usually polyester.

Let’s break down the individual benefits and disadvantages of each.

ama dablam jacket marmot

The Marmot Ama Dablam is an 800 fill jacket for $275

Benefits of Down

For the weight, down is simply warmer than synthetic insulation. There is nothing man made that matches the warmth to weight ratio of down.  It also generally lasts longer, retaining it’s shape and loft well with proper care. It can last for decades.  Also, down is highly compressible, a feature also unmatched by any man made fabric.  It’s ultra-lightweight and highly compressible.

Disadvantages of Down

When down becomes wet, it looses it’s insulating power when it becomes wet and takes a long time to dry out, particularly in humid climates.  Down is also difficult to clean, as great care must be taken to clean it properly.  Harsh, strong detergents and other chemicals can break down down’s natural loft and luster.  You do get more, but you pay more.

Types of Down

There are basically three types of down:

  1. High loft goose down: this is the finest type, with the highest warmth to weight ratio available, and the most expensive
  2. Standard goose down: has slightly less loft but is a little less expensive
  3. Duck down: less fine, however considerably less expensive.

Fill Power

So we often see numbers that describe down insulation. Down is rated according to fill power which is loft quality, and means the number of cubic inches the down will occupy.  That is if one ounce of down takes up a volume of 700 cubic inches, it is given a 700 fill power rating.   This is also a measure of quality.  Down warmth is a direct function of both fill power and amount of fill.  High quality down requires fewer ounces of down than that of a lower quality down, hence less weight.

Mountain Hardwear Ghost Whisperer jacket

The Mountain Hardwear Ghost Whisperer Jacket

For example, the Mountain Hardwear jacket is 800 fill down and retails for $320, and the Marmot Ama Dablam jacket retails for $275.

Read our review of the Ghost Whisperer jacket.

Most outdoor gear manufacturers only use goose down, which has a fill power starting at 500 or 550, and can go as high as 800.  The higher the fill power, the warmer, meaning less cold spots forming – down moving around leaving uninsulated areas.  Generally speaking if fill power is not specified, the fill can be less than 400 or the item contains less than 75% down.

Benefits of Synthetic Insulation

Synthetic is basically polyester threading that is molded into threads to mimic down. The fibres are becoming quite advanced and they rival down in terms of warmth to weight ratio.  The main benefits are resistance to water, and most retain some warmth when wet.  Some will actually repel water.

When synthetic insulation gets wet, the moisture gets trapped in the air pockets between the fibres and not within the fibers themselves, allowing for faster drying.  It is quite a bit less expensive, meaning it will keep you warm for less money, and are easier to care for. Virtually all of them are machine washable and dryable.

They are also completely hypoallergenic – non allergy causing – provided you keep them clean.

Disadvantages of Synthetic Insulation

Like we have already mentioned, synthetic insulation is heavier and bulkier than down, so you need a heavier jacket (more weight) for the same level of warmth.  It won’t pack up as small and generally doesn’t last as long. For example, down jackets and sleeping bags can be compressed for years without any loss of loft or insulation, while in synthetic fibres you will notice a breakdown of loft over time.

You will replace your synthetic fill items much faster than you would your down items.  No matter how well you care for them, you will eventually experience a loss of loft and warmth.

Types of Synthetic Insulation

Below are three different types of insulation, two of them are proprietary, belonging to the company that manufactures them.

Left to Right: Primaloft, Thermoball (The North Face) and Coreloft (Arc'teryx).

Left to Right: Primaloft, Thermoball (The North Face) and Coreloft (Arc’teryx).

Common Synthetic Fills

There are many synthetic fibbers, some of them are: Polarguard, Primaloft, Thinsulate and Thermolite.  One of our personal favourites for synthetic fill is Primaloft.  it is an ultra-fine micro fibre blend that is incredibly soft and lightweight.  This fibre feels the most like down, with it’s down-like softness that adds comfort.  it has the highest warmth to weight ratio of any synthetic insulation on the market.  it’s soft, durable, high loft, very thermally efficient compressible, fast-drying and water resistant.

The Patagonia Nano Puff is filled with Primaloft insulation, available for men and women.

The Patagonia Nano Puff is filled with Primaloft insulation, available for men and women. Cost without a hood is $199.

Patagonia has a large selection of Primaloft-filled insulated jackets, for example the Nano Puff, available for men and women, with or without a hood.

One of the newest on the market is The North Face’s “Thermoball” fibre, which has an excellent warmth to weight ratio, even when wet, and performs a lot like down.  These jackets are quite a bit less than down, for example with The North Face ThermoBall men’s hoody jacket retailing for $220.

The North Face Thermoball jacket

The North Face Thermoball jacket


Generally, down can be worn while standing around and is too hot for when you’re moving.  However, I have worn down while skiing on extremely cold days. Synthetic insulation is better overall while moving because it breathes better, and it is good for layering.  Also you do not want to sweat too much while wearing down because remember, when down gets wet it looses it’s ability to insulate properly.

I will layer a synthetic jacket in the winter while out in the mountains on very cold days, and a down jacket for when I am standing around, on top of all my other layers.

The Bottom Line

So is one fill better than the other? No, it depends on your circumstances and what you are using it for.  For the weight, and compressibility, down cannot be beat for warmth. That being said, it is also a lot more expensive, but lasts longer – so you get what you pay for.

But, if you spend a lot of time in very wet environments, down won’t be a good choice. The fact that synthetic fibre still insulates when wet is a big advantage, as down will pile and loose it’s effectiveness when wet. Synthetic is also easier to clean. it’s a good choice for casual outdoor enthusiasts who only use their gear a handful of times a year and prefer to save a bit of money.

Where to Buy

Down and synthetic fill jackets are available at every outdoor retailer. For the best prices, check out our gear search.

Also read our article on how to care for down jackets.



Alicja is an economist, enjoys climbing, mountaineering, backcountry skiing, cycling and gets out into the backcountry as much as possible. See all of Alicja's Blog Posts