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Igloo Puffer - Down Insulation Blog

Down Insulation Explained: A Guide to Down Fill Power and Weight


Down is one of the most widely-used materials in winter jackets and sleeping bags — and for good reason. The natural duck and goose plumage provide unbeatable warmth while being “as light as a feather”. When you’re shopping around for down jackets or sleeping bags, you’ll come across different numbers and ratings, such as fill power, fill weight, and down to feather ratio. But what do these numbers mean, and how do you know which down product is best for you? In this article, we’ll demystify down ratings so you can make informed decisions about your gear.

What Is Down? The Ultimate Insulation

Down comes from the plumage of birds, particularly ducks and geese. Plumage is the soft, fluffy undercoat found beneath the tougher feathers on the birds' underbellies.

Down has unique properties that make it highly effective for insulation purposes. Down clusters are formed by thousands of tiny fibres that crisscross in every direction, creating air pockets between them. These air pockets allow the down to trap and retain body heat.

As birds mature, their plumage tends to become larger, resulting in increased loft (fluffiness) and a higher fill power rating. We’ll get into the meaning of loft and fill power below.

Down is highly regarded for its warmth-to-weight ratio, meaning it provides significant warmth without adding excessive bulk or weight. Down insulation is also known for its durability and ability to withstand compression, making it a popular choice among outdoor enthusiasts.

These are the reasons why we use down insulation in our puffer jackets and sleeping bags at Bushbuck — it’s incredibly warm, lightweight, and easy to compress and stuff in your pack.

What is Down Fill Power or Loft?

When it comes to down products, fill power plays a crucial role in determining their quality and performance. Fill power measures the loft (or fluffiness) and effectiveness of the down insulation, or how much space it occupies when fully expanded. Sometimes fill power is referred to as “loft”.

The higher the fill power, the better the down's ability to trap warm air and provide insulation. This loftiness translates into improved warmth retention and enhanced thermal efficiency.

Most outdoors gear should have between 500 and 900 fill power. All of Bushbuck’s down puffer jackets contain 800 fill power down, which provides the warmth and performance our customers need in extreme conditions.

What is Down Fill Weight?

Down fill weight is pretty self-explanatory. It refers to the total weight of the down used in the product.

Generally, the more down used in a puffer jacket, the warmer the jacket will be. However, the higher the fill weight, the heavier and bulkier the jacket, so there’s always a trade-off. 

When you’re shopping for a puffer jacket or sleeping bag, we recommend looking for a balance between fill power and fill weight.

For example, the Bushbuck Furnace Waterproof Puffer Jacket only has 160g fill weight, but has 800 fill power down. This means it’s lightweight, not bulky, but still seriously warm. A jacket with 300g of 500 fill power down may provide similar warmth, but it will be heavier and bulkier. 

Fill weight is an important factor to consider and it often comes down to personal preference.

What is Down to Feather Ratio?

The down to feather ratio refers to the proportion of down clusters to feathers used in the insulation. 

As mentioned above, down is the fluffy plumage found beneath the outer feathers of ducks and geese. While feathers provide some insulation, they’re not as effective as down.

The most common down-to-feather ratios in outdoors gear are 80/20, 90/10, and 100%. The first number always refers to the down, while the second number refers to the feathers.

The higher the down-to-feather ratio, the better the performance of the insulation.

However, you also have to consider fill power and fill weight to determine the overall performance of a down jacket or sleeping bag.

Down Insulation Explained - Igloo Puffer 2

What is the Responsible Down Standard (RDS)?

RDS, or Responsible Down Standard, is a certification that ensures ethical sourcing and humane treatment of ducks and geese in the production of down and feathers.

RDS down is sourced from farms that adhere to strict guidelines and undergo independent audits to verify compliance.

By opting for RDS-certified down, you can support sustainable and ethical practices in the down industry and contribute to the overall welfare of animals involved in its production.

At Bushbuck, we only use RDS-certified down.

What is Hydrophobic Down?

It’s well-known that down loses much of its performance when it gets wet.

One way to overcome this issue is by creating durable, seam sealed, 100% waterproof outer layers that protect the down in all weather (like the Bushbuck Furnace and Igloo jackets). 

Another way is by using hydrophobic down. 

Hydrophobic down is down that’s been treated with a water-repellent coating, which helps it to resist moisture absorption and dry faster.

While some people prefer to use down in its natural state, hydrophobic down is popular with hikers, hunters and explorers who are exposed to the elements in the outdoors. 

Hydrophobic down can be beneficial in sleeping bags that may get a bit damp from body heat, or sleeping under a bivvy. 

Hydrophobic down isn’t waterproof, but it can be a gamechanger if you and your gear are exposed to wet conditions.

At Bushbuck, we currently only use hydrophobic down in our sleeping bags as our puffer jacket range uses fully waterproof (or water-resistant) outer fabrics.

Down Insulation Explained - Sierra Sleeping Bag

What’s the Difference Between Duck Down and Goose Down?

You might notice that some down products contain duck down and others contain goose down — but what’s the difference?

Goose down clusters are generally larger than duck down clusters. This means that goose down tends to have a higher loft, which makes it more effective at retaining heat and providing warmth.

Due to the larger cluster size and higher loft, goose down typically provides more warmth for its weight, allowing you to use less down to achieve the same level of insulation.

Goose down is generally more durable and resilient than duck down. Its larger clusters tend to have stronger fibres, making it less likely to break or lose its loft over time. 

While goose down has superior performance, it’s less readily available and, therefore, more expensive. 

At Bushbuck, we tend to use duck down in our puffer jackets and goose down in our sleeping bags.

Duck down still provides excellent performance. However, because sleeping bags are often used in the coldest conditions (overnight) and are sometimes relied on in survival situations, we’ve opted for the extra oomph that goose down delivers.

Down Insulation Explained - Furnace Camo

What's the Best Down Jacket for You?

Hopefully, you have a better understanding of how down insulation works and what to look for when you’re shopping for a down jacket or sleeping bag.

It’s all about finding the right balance of fill power, fill weight, ratio, and water-resistance for your needs.

To give you an idea of what down jacket will be “best” for you, here are some guidelines using the Bushbuck range as examples.

The Weekend Warrior

You’re after a warm puffer jacket to wear in the winter, around the farm, and on the occasional “good weather” weekend hike or hunting trip. You’re after a good quality jacket capable of performing outdoors, but your main priority is warmth and comfort wherever you go.

Best puffer jacket: The Bushbuck Polar X

Down Insulation Explained - Polar X
  • 800 fill power

  • 260g fill weight 

  • 90/10 down-to-feather ratio

  • RDS duck down

  • Water-resistant 

  • Durable canvas fabric 

The Outdoor Enthusiast 

You get into outdoors hiking, hunting, and exploring most weekends. You’re after a puffer jacket that will keep you warm on the move without feeling bulky or weighing you down. As you’ll be exposed to the elements in the bush and mountains, you need a jacket that’s fully waterproof and tough enough for the outdoors. 

Best puffer jacket: The Bushbuck Furnace

Down Insulation Explained - Furnace 3
  • 800 fill power

  • 160g fill weight

  • 90/10 down-to-feather ratio

  • RDS duck down

  • 100% waterproof

  • Durable ripstop nylon 

The Hardcore Adventurer 

You push the limits of outdoor adventure and live for hunting, hiking, camping. You’re regularly exposed to extreme conditions — rain, wind, cold — and need a down jacket that’s ultra-warm, waterproof, and tough. Whether you’re in the alpine zone or on the sidelines at a rugby game in torrential rain, you’re after a puffer jacket that keeps you warm and protected in all weather.

Best puffer jacket: The Bushbuck Igloo

Down Insulation Explained - Igloo 2
  • 800 fill power

  • 320g fill weight

  • 90/10 down-to-feather ratio

  • RDS duck down 

  • 100% waterproof

  • Durable nylon canvas 

This is just a general guide to how different puffer jackets may fulfill different needs. All Bushbuck puffer jackets are made to perform in severe conditions in the great outdoors.

If you’re looking for a puffer jacket for general winter use, look for something that has at least:

  • 600 fill power

  • 150g fill weight

  • 80/20 down-to-feather ratio

If you’re looking for something suitable for outdoor adventures, go with a Bushbuck puffer or one with similar specifications.

What is the Best Down Sleeping Bag for You?

You can apply the same rationale when shopping for down sleeping bags.

The fill weight of sleeping bags will generally be higher than puffer jackets as they’re providing insulation for your entire body — from head to toe. 

When you’re looking for a down sleeping bag, you should consider the conditions you’ll be using it in. 

As with puffer jackets, the fill power, fill weight, and feather-to-down ratio will influence your sleeping bag’s performance. 

However, sleeping bags generally come with temperature ratings (comfort, lower comfort, and extreme) which can give you a clearer idea of how much warmth they provide.

The Weekend Warrior

You’re after a down sleeping bag that you can take on summer camping trips, Great Walk hikes, and the occasional missions in cooler weather. You mostly sleep in huts, but you’d like something you can use in a tent or more exposed conditions as well. Your main priorities are that it’s compact, comfortable, and affordable.

Best sleeping bag: To be honest, you probably don’t need a high-performance Bushbuck sleeping bag. You could go with the Sierra 500 Down Sleeping Bag, but at minimum you’d be look for:

  • 600 fill power

  • 400g fill weight 

  • 80/20 down-to-feather ratio

  • RDS down

  • 0°C to 5°C comfort temperature rating 

The Outdoor Enthusiast 

You’re after a down sleeping bag you can use on a wide range of hiking and hunting adventures, sleeping in huts, tents, and open-air bivvies. It needs to be lightweight, compact, and keep you warm in frosty conditions. 

Best sleeping bag: Bushbuck Sierra 500

Down Insulation Explained - Sierra 500
  • 800 fill power

  • 500g fill weight

  • 90/10 down-to-feather ratio

  • RDS goose down

  • Hydrophobic down

  • 0°C comfort temperature rating 

The Hardcore Adventurer 

You’re looking for a top-of-the-line down sleeping bag that will keep you warm almost anywhere you go — even when the temperatures dip below zero. It needs to be light and compact for carrying in your pack and deliver maximum thermal efficiency. You’re willing to invest in quality gear if it means you’ll be warm, safe, and comfortable in the outdoors. 

Best sleeping bag: Bushbuck Sierra 650

Down Insulation Explained - Sierra 650
  • 800 fill power

  • 650g fill weight

  • 90/10 down-to-feather ratio

  • RDS goose down

  • Hydrophobic down

  • -4°C comfort temperature rating

Warm as Toast, Light as a Feather

There’s a reason down is the most popular insulation in outdoors gear — it’s the best we’ve got. No synthetic insulation comes close to its unique warmth-to-weight ratio.

Hopefully, this article has provided you with all the information you need to make an informed choice when it comes to buying a down puffer jacket or sleeping bag.

Jonathan Carson

Jonathan Carson is a Content Writer and Copywriter at Bushbuck. He's a wordsmith who handles most of Bushbuck's website, marketing copy and oversees our blog, The Campfire. 

Outside of work, he's big on hiking and dabbles in surfing and bouldering. His favourite wilderness area in New Zealand is Nelson Lakes National Park, particularly the Blue Lake, home to the clearest known freshwater in the world.