Which Duvet Filling Is Best? Warmth, Breathability and Allergies Compared
At Simba, we don't make a down duvet, and that was a decision we made after a lot of reflection. Once we'd worked out what we wanted a duvet to do - hold a steady temperature, survive a washing machine, suit people who react to feathers, and not involve an animal product - down stopped being the obvious answer it had been for a century.
So here is an honest comparison of what goes inside a duvet, judged on the things you'll actually notice at three in the morning.
The Two Families: Natural vs Synthetic
Natural fillings means down, the soft clusters growing beneath a duck or goose's feathers, feather itself, or a blend of the two. Wool and silk turn up in more specialist duvets. All of them have been sold for decades on loft: the ability to trap a lot of air in very little weight.
Synthetic fillings are engineered fibres built to do the same job, and this is where the category has changed most. Early synthetics deserved their reputation, flat and lifeless things that went lumpy after two washes. Modern fills are designed specifically as down alternatives and behave nothing like their ancestors. Ours is Simba Renew™, made from recycled bottles, with the fibres combed and folded into soft, airy, down-like clusters.
Warmth Is a Tog Question, Not a Filling Question
How warm your duvet is comes down to its tog rating, and both natural and synthetic duvets are sold across the full range. Buy a 13.5 tog duvet of any filling and you will most likely overheat in June.
Where the filling genuinely matters is warmth-to-weight, meaning how heavy the thing feels for the warmth it delivers. Down earned its reputation here, and we won't pretend otherwise. What's changed is that combed, lofted synthetic clusters now trap air in a comparable way, so a well-built down alternative feels light for its warmth too. If a weightless duvet matters to you, look at the loft and the construction rather than assuming the natural option wins by default.
Breathability, Which Is Where We'd Spend the Money
Insulation and temperature regulation are two different skills, and most duvets only have the first. Down insulates beautifully and then has no answer when you get too warm, because it has no mechanism for shedding heat. You wake up hot and throw a leg out.
We built our Hybrid™ duvets around the second skill. The Simba Renew™ fill sits inside a cotton cover finished with Stratos® cooling technology on one side, which is designed to absorb and release excess heat so your temperature holds steadier through the night. If your recurring complaint is overheating rather than feeling cold, this is the single most useful thing to look for, and it matters more than which family the filling belongs to.
A Duvet Suitable for Those With Allergies
For a lot of households this settles it. Feather and down cause two separate problems: some people react to the feathers, and natural fills are harder to wash at the temperatures that keep dust mites in check.
Synthetic fills sidestep both: there's no feather or down in ours, and because you can put them through a normal wash, you can launder the whole duvet regularly rather than just the cover. That routine does more for dust mites than any single purchase. We'd add the obvious caveat: if your symptoms are significant or stubborn, see your GP, because bedding supports treatment but isn’t designed to replace it.
Low Maintenance Matters Too
Practicality favours synthetic so heavily that it's almost unfair. Ours go in the machine and dry in reasonable time. Down and feather generally need careful washing or professional cleaning, and they take a long while to dry properly, because damp clusters left inside develop an odour you cannot get back out.
Cost runs the same way. Good down is expensive at the till, synthetics are cheaper and easier to replace, and while a well-kept down duvet lasts many years, that longevity depends on you keeping up with demanding care. Wool sits in the middle: it regulates temperature well and resists dust mites, but it's heavy, pricey and rarely machine washable.
Ethics and What "Green" Means Now
Down is an animal product. Responsible suppliers work to sourcing standards, and plenty of people are entirely comfortable with it, but plenty aren't, and a synthetic fill removes the question. Ours contain no animal products at all.
The sustainability picture has also inverted. The old assumption that natural means more eco-friendly doesn't hold when the synthetic option is made from recycled bottles that would otherwise be waste. Add the fact that a washable duvet lasts longer, and durability itself becomes an environmental argument, because the most environmentally-friendly duvet is the one you don't need to constantly replace.
What Actually Works
For most households, a well-made synthetic answers more of the brief: hypoallergenic, machine washable, vegan, more affordable, available with cooling built in, and now competitive on warmth-to-weight. Down still suits someone who wants a natural loft above all else and accepts the price and the dry cleaning.
And don’t forget to get the tog right, because that's what you'll feel. Our comfortable duvets and their recycled-fibre filling come as a 10.5 tog all-rounder, a lighter summer weight, and a 3-in-1 that clips a 3.5 and a 7 tog together so one purchase covers the whole year. Choose the tog for how warm you sleep and the filling for how you want to live with it.
FAQs
Synthetic, in almost all cases. There's no feather or down to react to, and because a synthetic duvet can go through a normal wash, you can launder the whole thing regularly to keep dust mites in check rather than just washing the cover. See your GP if symptoms persist.
Warmth comes from the tog rating, not the filling, and both are sold across the full range. Down has traditionally led on warmth-to-weight, feeling lighter for the warmth it gives, though combed down-alternative fibres have narrowed that gap considerably.
No, and it's a deliberate choice on our part. Our duvets use a Simba Renew™ fill made from recycled bottles and combed into soft, down-like clusters, so they're hypoallergenic, machine washable and free of animal products, with a cotton cover carrying Stratos® cooling technology on one side.
Around 4.5 tog for summer, 10.5 tog as a year-round choice for most homes, and 13.5 tog or above for genuinely cold bedrooms. Our 3-in-1 clips a 3.5 and a 7 tog together, which covers summer, spring and autumn, and winter from one purchase.
Synthetic, comfortably. Ours go in the washing machine and dry in reasonable time. Down and feather usually need careful or professional cleaning and take a long time to dry through, and wool duvets are rarely machine washable at all.
