The duvet affects your sleep temperature more than the mattress does. I test mattresses for a living and I'll say it plainly: most temperature complaints that buyers blame on their mattress are actually caused by the wrong duvet. A 13.5 tog synthetic duvet in a centrally heated bedroom in June is going to make you sweat regardless of how breathable the mattress is underneath. Getting the duvet right is cheaper and faster than replacing the mattress, and it often fixes the problem on its own.
Tog explained simply
Tog measures thermal resistance - how much warmth the duvet traps between you and the bedroom air. Higher tog = warmer. The UK tog scale runs from about 1 (summer sheet substitute) to 15 (unheated room in midwinter). The practical togs for a UK bedroom with central heating: 4.5 in summer, 10.5 in winter, 7.5-9 as an autumn and spring transition. If you run hot, drop one step from the standard recommendation. If you run cold, step up.
The most common mistake is using the same tog year-round, which means either overheating from May to September or undercooling from November to March. All-season duvets (two duvets that button together, typically a 4.5 + 9 that combine to 13.5) give you three options from two products. Practical if you don't want to store separate seasonal duvets.
Filling types
Goose and duck down is the warmest filling per weight. A good goose down duvet feels almost weightless while trapping serious warmth. Down clusters are the premium component - the higher the down percentage versus feather, the warmer and lighter the duvet. Duck down is cheaper than goose and slightly heavier for the same thermal performance. Both last 5-10 years with proper care. Not suitable for allergy sufferers unless the down has been specifically treated and certified hypoallergenic.
Hollowfibre is the mainstream synthetic option. Machine washable, hypoallergenic, cheap to replace. The fibres trap air to create insulation but compress over time, so a hollowfibre duvet that felt warm and lofty in year one can feel flat by year three. I've tested several side by side and the loft drop is visible. The trade-off for easy washing and low cost is shorter useful life.
Microfibre is the finer-grade synthetic. Softer against the skin than hollowfibre, with better drape (the way the duvet moulds around your body) and slightly better temperature regulation. Still machine washable and hypoallergenic. Sits between hollowfibre and down on quality, feel and price.
Wool does something different from all of the above. Wool regulates temperature in both directions - it warms when you're cold and breathes when you overheat. For buyers who struggle with overheating at night or for menopause night sweats, a wool duvet handles the temperature swings better than any synthetic and better than down in most cases. Wool is also naturally hypoallergenic and resistant to dust mites. More expensive than synthetic. Worth the premium for temperature-sensitive sleepers who want one duvet that works across seasons.
Silk is the lightest natural option. Excellent for hot sleepers who want a thin layer that breathes without trapping heat. Less insulating than down or wool, so it's primarily a warm-weather or hot-sleeper choice in the UK climate. Premium priced for the thermal output, but the feel and weight against the body is unlike anything else.
Size and fit
Buy your duvet one size up from your bed. A king-size duvet on a double bed gives both partners enough coverage without the nightly tug-of-war for their share. This is one of the simplest quality-of-life upgrades for couples, and it costs almost nothing extra. I recommend this to almost every couple who mentions sharing complaints, and most come back saying they should have done it years earlier.
Care basics
Air the duvet daily by pulling it back from the bed for an hour each morning. This lets moisture from overnight perspiration evaporate instead of building up in the filling. Shake it to redistribute the filling and prevent the clumping that develops when the same area stays compressed.
Wash according to the label. Most synthetic duvets handle 40-60 degrees in a domestic machine. Down and feather need gentler handling and often benefit from professional cleaning or a large commercial machine. Make sure the duvet is completely dry before using it again, because damp filling loses its thermal properties and can develop mould that's hard to reverse once it sets in.
Verdict
Get the tog right for the season. Choose the filling for your temperature profile: down for maximum warmth per weight, wool for temperature regulation, hollowfibre for budget and easy washing, silk for hot sleepers who want something light. Replace synthetic duvets every 2-3 years when the loft drops. And if you're sleeping hot, the duvet is the first thing to change before blaming the mattress underneath it.
