Your bedding keeps your skin warm while your core cools
You need warmth around your skin to settle comfortably, even though your core temperature falls as you drift into sleep. Turning the bedroom into a conservatory in July is a fairly clumsy way to get there. Bedding creates a small pocket of warmth close to your body, so you can have a cosy bed in a cooler room.
The 2019 review by Harding, Franks and Wisden describes sleep onset coinciding with a fall in core body temperature, while people use bedding to create a skin microclimate of roughly 31 to 35C.1 That is the temperature around your skin under the bedding, distinct from the room temperature. To my mind, a warm duvet is a much nicer starting point than another argument with the thermostat.
Warm feet deserve some attention too. In Ko and Lee's small bed-socks study, six young men slept for seven hours at 23C with and without socks. With socks, they fell asleep an average of seven and a half minutes sooner, slept about half an hour longer, woke fewer times and had higher sleep efficiency.2 Six men, one night each condition, a cool room not a cold one. I'd give a comfortable pair of bed socks a go before spending mattress money.
Heat also moves through the mattress beneath you. A thin comfort layer over pocket springs allows more heat to pass through; a deep foam layer insulates and surrounds more of your body. If you feel cold underneath even with a warm duvet, that difference matters. If you're warm underneath but chilly across your shoulders, check the duvet's coverage first.
Fix the duvet and sheets before spending mattress money
A warmer duvet and warmer-feeling sheets are the first changes to make if your mattress still supports you comfortably. Start with a higher tog if your duvet feels too light for the season. Tog describes insulation; the physical weight of a duvet is a separate comfort preference. I'm autistic, and the weight of a heavy duvet helps me settle, but you don't have to share that preference to want a warm bed.
If you share with someone who throws the covers off while you're pulling them up to your ears, use two single duvets on your double. You can each choose the warmth you need without having the same negotiation every evening. Honestly, matching duvet covers are quite enough togetherness. Check that each duvet covers its sleeper comfortably when they turn onto their side.
Brushed cotton or flannel sheets feel warmer against your skin than crisp percale or polyester. Change those before assuming the whole mattress is too cold, particularly if the worst moment is getting into bed. Percale has its place, but that brisk, fresh-sheet sensation loses some appeal when you're already doing a little dance beside the bed to keep warm.
Bed socks are a cheap thing to try alongside the warmer bedding. For a bed that's cold when you first climb in, use an electric blanket on a timer beforehand, switch it off when you get in and follow the maker's instructions. A hot water bottle is another option for pre-warming a patch of bed; follow its instructions too. There's no need to make the whole bedroom hot just to take the chill off the sheets.
Keep the room comfortably cool and adjust the bed's warmth around that. You want to get under the duvet without bracing yourself, then stay comfortable once you've warmed up. If you start throwing the covers off later, reduce the duvet's insulation before changing several other things at once. It's much easier to work out what helped when you've made one change.
Deep foam and wool make more sense than a cooling mattress
Choose a substantial comfort layer if warmth is part of the reason you're replacing your mattress. Deep memory foam is the stronger option for an enveloping, insulated feel; wool is the more flexible option if you also want comfort through warmer weather. The trade's enthusiasm for calling absolutely everything "cooling" gets a bit tiresome when you're the person wearing socks in bed.
With deep memory foam, you sink into the surface and have more material around your body. That helps retain warmth and gives you the tucked-in sensation some cold sleepers love. It also means turning over feels less immediate than on a springier surface. If you dislike feeling held in place, choose a shallower foam comfort layer or wool over pocket springs, and get the extra warmth from your duvet.
Wool warms to body temperature quickly and buffers moisture. I think it's the better all-season option for someone who feels cold in winter but gets warm in summer. You get a cosy surface without the same deeply enveloping feel as memory foam. Look for wool in the comfort layers, because a mention of wool somewhere in the cover tells you less about the cushioning underneath.
Pocket springs are still a good foundation. The important difference is how much material sits between you and them: a thick top holds warmth differently from a thin top over an airy spring unit. Don't rule out every sprung mattress because you sleep cold. That would be like refusing every coat with a zip because one of them was a rain mac.
The cover changes the first-touch sensation too. Polyester feels colder initially than cotton, and wool feels warmest of those three. Your sheet sits between you and the cover, so consider both together. A warmer-feeling cover is pleasant when you climb in, but the deeper comfort layers matter more to how insulated you feel once you're settled.
For a hot sleeper, much of this advice goes the other way: less enveloping foam and more scope for heat to escape. Take that distinction seriously when reading recommendations. A mattress praised for its cool surface could be exactly the wrong purchase for you, however pleased the reviewer was to stop kicking off their duvet.
Choose for your summer nights as well as your winter ones
Choose a mattress you can live with in warm weather, then adjust the bedding with the seasons. Wool is the more adaptable route; deep foam suits you better if you consistently want an insulated bed. December shopping can make August seem entirely fictional, but you're buying something you'll sleep on through both.
Check whether you need a mattress at all. If yours is level and comfortable but feels cold underneath, add a memory foam or wool topper. That gives you another warm layer without replacing the whole bed. Avoid this route if the mattress has a lasting dip: a topper follows the dip and leaves you with the same uneven support.
Choose the feel before the warmth claim. In a showroom, spend a proper stretch lying as you normally sleep, including turning over. A quick sit on the edge is barely a greeting. Notice whether you like sinking into foam or prefer the easier movement of wool over springs. Extra warmth won't make a mattress comfortable if you dislike the way you lie on it.
Check the depth of the comfort layers. Ask how much foam or wool is above the springs, because total mattress depth includes the support underneath. A deep mattress with a thin top won't feel like one with substantial cushioning around your body. Compare the construction before getting attached to a name with "cosy" in it.
Make a summer plan before buying deep foam. A lighter-tog duvet helps reduce warmth from above, but the foam beneath you still insulates. If you already have sticky nights in summer, wool makes more sense to me. If you stay cold through most of the year and love sinking in, deep foam is a reasonable match.
Read the return terms before ordering. Check whether you can return a mattress for comfort reasons, what collection involves and which conditions apply to bedding protection. I find protectors frustrating when they reduce breathability, but any required protector needs to be part of your decision. Use a breathable one where the terms allow, and judge the bed with the bedding you'll actually keep on it.
Avoid buying more of what already leaves you cold
Skip thin, cooling constructions if you already wake cold, and resist replacing a comfortable mattress to compensate for summer bedding. The temptation to solve everything with one impressive purchase is understandable. I still think a duvet is a better buy when the duvet is the problem.
- A thin top over springs advertised as sleeping cool. That construction lets heat move through the mattress, which works against the warmer surface you're trying to get.
- Polyester sheets and a synthetic summer duvet in January. The sheets feel cold at first touch and the summer duvet offers too little insulation for someone who needs more warmth. Change the sheets and choose a warmer duvet.
- An electric blanket left on high all night against the maker's instructions. Use a timer to warm the bed beforehand, switch it off when you get in and follow the maker's instructions.
- A low bed on a cold floor with nothing underneath. Air is coldest near the floor. Check your bed's height and what's beneath it if the whole sleeping surface feels chilly.
- A new mattress bought to fix inadequate bedding. If the mattress is comfortable and level, try a warmer duvet or a suitable topper before replacing it.
A floor-level bed might look lovely in a carefully styled bedroom photo; the person taking it doesn't have to get in wearing flannel pyjamas. If you're choosing a new base as well, check the finished bed height with the mattress in place. You should be able to sit on the edge with your feet flat.
