Wool vs Down vs Synthetic: Which Duvet Filling Is Right for You?

For most bedrooms, wool. If your room runs cold and dry and you want the lightest possible duvet for the warmth it gives, down is genuinely excellent and worth the care it demands. Synthetic makes sense when the budget decides it, and you should know what you are trading away.

The reason comes down to one property, and it is not warmth.

The thing nobody tells you about duvets

You lose water vapour through your skin and your breath all night, without sweating at all. It goes into the thin layer of air between you and the duvet, and what happens to it next is decided almost entirely by the filling.

Wool holds roughly forty times what polyester does.

That matters because humidity, more than heat on its own, is what wakes people at two in the morning. Polyester has essentially nowhere to put the vapour, so it builds up between you and the covers. You surface, push a leg out, pull the covers back, and never quite work out why.

Wool absorbs it into the fibre without ever feeling damp, then gives it back to the room. It is the same reason a wool duvet needs washing far less often, and the same reason it still smells fresh after a year.

Almost every other difference between these fillings flows from that one number.

The four fillings compared

Most people think there are three. There are four, because synthetic comes in two forms that behave differently.

Synthetic: cheap, washable, and a false economy

Hollowfibre is polyester spun with a hollow core to trap air. Microfibre is much finer polyester engineered to imitate down clusters. Both are sold on two things: they cost very little, and you can machine wash them.

Both arguments are weaker than they look.

On washing. Yes, you can wash a synthetic duvet easily. You also have to, because polyester cannot absorb the moisture you put into it every night, so it sits there. Wool holds odour compounds rather than releasing them into the air, which is why airing a wool duvet for an afternoon does more than a wash, and why most owners wash theirs once a year at most. Easy to wash matters a great deal less when you barely need to.

On price. A hollowfibre duvet lasts two to four years, microfibre four to five, because the fibres flatten and become less resilient to repeated washing. At that point they stop trapping air, which is the only thing they were doing. You are not buying a duvet for $99. You are renting one for three years.

Three more things worth knowing, none of them opinion.

It is sold as the hypoallergenic choice and the evidence says otherwise. New Zealand research across 65 duvets, 81 pillows and 65 mattresses in 34 households found synthetic pillows and duvets carried significantly more dust mite allergen than feather ones, about 7-fold and 15-fold respectively. The authors concluded that advising sensitised people to use synthetic bedding does not prevent exposure. A twelve-month study putting paired pillows on the same beds found the same thing again.

It needs chemistry to be safe. Polyester fill does not pass fire testing on its own, which is why flame-retardant treatments exist. Wool passes untreated.

It is plastic, and it stays plastic. Polyester sheds microplastics and does not biodegrade. In controlled composting testing, untreated wool broke down substantially over 181 days while polyester did not measurably break down at all.

Synthetic has a place. A spare room, a student flat, a bed used four weeks a year. For the bed you sleep in every night, it is the filling with the least going for it.

Down: excellent at one thing

Down deserves its reputation. It is the best insulator per gram that exists, and nothing else gives that much warmth for that little weight. A well cared for down duvet can last over a decade. If you want the lightest possible duvet for the warmth it delivers, buy down, and we would rather say so than sell you something else.

Two honest limits.

Warmth per gram is a niche requirement. It matters enormously if you are carrying it up a mountain. On a bed, nobody is counting grams. The property down is best at is the one your bedroom cares least about.

The care is real. Washing one properly takes a gentle cycle, a double rinse and two to three low-heat dryer cycles with breaks to break up clumps. Detergent residue stops the clusters re-lofting and high heat mats them permanently. Most people never wash theirs, which is why most down duvets are professionally cleaned or simply not cleaned at all.

It is also loose fill, so it migrates within its baffles over the years and leaves the middle thinner than the ends.

We covered this properly in the real problems with feather and down duvets, including the one problem it does not actually have.

Wool: the filling that works with your body rather than around it

Wool is the only common duvet filling that does something active. It takes moisture out of the air and gives it back as conditions change, and that single behaviour is behind almost everything else.

The air under the duvet stays drier, which is the difference between sleeping through and surfacing at two.

It needs washing rarely. Wool holds odour compounds rather than letting them sit in the air. Hang it outside for an afternoon and it comes back fresh.

And when you do wash it, it goes in your own machine on a cold wool cycle. Most wool quilts are sold as either untreated or washable, because making wool reliably washable usually means treating the fibres so they do not shrink. Do Not Disturb's are both, with nothing added.

Construction matters more than the fibre. Most wool duvets are loose carded wool, quilted into pockets to stop it moving. Loose fill moves anyway over the years, and a thin patch is a cold patch no matter how much wool the duvet contains in total. Ours is needle-punched into a single bonded sheet, so there is nothing inside that can drift or clump.

On durability, independent compression testing at SATRA in the UK put needle-punched wool and polyester through 80,000 compression cycles. The wool came back with far more of its original thickness. We have been making these duvets unchanged since 2023, and in four years we have not had one fail.

The trade is loft. A wool duvet looks flatter than a down one of similar warmth, and people are regularly surprised when the parcel arrives. Craig in Invercargill swapped his goose down inner for a 350gsm wool one and put it better than we could:

I had my doubts on whether a 350gsm wool duvet inner could compete with my 90/10 goose down duvet inner. I became more concerned given the significant difference in loft. However, tested on the coldest of Invercargill nights the wool duvet inner outperformed the goose down.

Loft you can see and warmth you can feel are not the same thing.

What it actually costs per year

The sticker price is the wrong number.

We have left the wool row incomplete on purpose. We have been making these since 2023, so the oldest in use are four years old and going strong. We could tell you a wool duvet lasts fifteen years. We have not measured it, so we are not going to.

The synthetic rows are the interesting ones. A $99 duvet replaced every three years costs more across a decade than a $419 one bought once, and you sleep worse for all ten years.

Which suits your bedroom?

Warm room, humid room, or you wake up too hot. Wool, and it is not close. This is exactly what the moisture handling is for.

Cold, dry room, and you want minimum weight. Down. Buy the best you can afford and budget for the cleaning.

You want to wash it yourself. Wool or synthetic. Down is possible and rarely worth the risk.

Tight budget. Hollowfibre will get you through. Just price it per year before you decide it was the cheap option.

Worried about allergies. Not a reason to choose synthetic. Bedroom humidity matters far more than what your duvet is filled with, and a filling that manages moisture is doing more for you than one labelled hypoallergenic.

You share a bed with someone who runs at a different temperature. No single filling solves this. Two duvets does.

Where our duvets sit

Do Not Disturb makes wool duvets from New Zealand strong wool, needle-punched into a single continuous sheet rather than loose-filled, in two weights and six sizes. Known in Australia as a wool quilt or doona. Nothing is added to the wool, and they wash at home.

What they are not. They are not the warmest duvet you can buy. Our heaviest is 350gsm, where some brands go to 700. They are not the cheapest. And they do not have the loft of down.

If your room is cold and dry and you want maximum warmth for minimum weight, buy down. For every other bedroom, we think wool is the better night's sleep.

What this means for you

Start with your bedroom, not with the fillings. If it runs warm or damp, the moisture question decides it, and wool wins on a margin of about forty to one. If it runs cold and dry, down earns its price.

And price a duvet per year rather than per purchase. The cheapest thing in the shop is rarely the cheapest thing across a decade, and it is never the best thing to sleep under.

FAQ

Which duvet filling is best overall? For most bedrooms, wool, because it is the only common filling that manages moisture, and moisture is what disturbs sleep. Down is better if you want maximum warmth for minimum weight in a cold dry room. Synthetic is the budget answer and costs more than it looks across a decade.

What is the difference between hollowfibre and microfibre? Both are polyester. Hollowfibre has a hollow core to trap air and is cheaper. Microfibre is finer and engineered to feel like down. Microfibre feels better and lasts slightly longer. Neither absorbs moisture.

How long should a duvet last? Hollowfibre two to four years, microfibre four to five, down a decade or more with proper care. Wool is long-lived. Ours have been in use for four years without a failure, and we will tell you more when we know more.

Are synthetic duvets better for allergies? No. Research consistently finds synthetic bedding carries more dust mite allergen than feather, not less. Bedroom humidity matters far more than the filling.

Sources

• Siebers R, Fitzharris P, Crane J. House dust mite allergen levels in individual bedding components in New Zealand. 2002.

• Rains N, Siebers R, Crane J, Fitzharris P. House dust mite allergen (Der p 1) accumulation on new synthetic and feather pillows. Clinical & Experimental Allergy, 1999.

• Sleep Foundation, How to Wash a Down Comforter.

• SATRA Technology Centre, compression testing to EN ISO 3385:2014, commissioned by Wisewool.

• NZWTA, flammability testing to BS 5852, commissioned by Wisewool.