A sleeping mat solves the problem most people underestimate on a cold night: the ground. Lying on cold concrete, tiles or earth pulls heat out of you faster than the air ever will, and no amount of blankets on top makes up for an uninsulated surface underneath. A self-inflating or inflatable mat puts a layer of trapped air between your body and the floor, and that insulation — measured as an R-value — is what actually keeps you warm when you sleep on the ground during a power cut, a house evacuation, or a night in the car. The trade-off is bulk and, for inflatable mats, a small risk of a puncture, though a self-inflating foam mat still gives some insulation even flat.
A bivvy bag solves a different problem: the weather. It is a waterproof, windproof shell you climb into, either around a sleeping bag or on its own in an emergency, and its whole job is to keep rain, wind and ground damp off you and the insulation you are relying on. The lightweight emergency versions weigh almost nothing and pack to the size of a fist, which makes them ideal grab-bag and car items, but on their own they provide very little warmth — a night in just a bivvy is about survival, not comfort. Crucially, a bivvy does almost nothing about heat lost into the ground, which is exactly the gap a mat fills.
| Feature | Sleeping Mat | Bivvy Bag |
|---|---|---|
| Main job | Ground insulation — stops the cold floor stealing your body heat while you lie on it. | Weather protection — blocks wind, rain and ground damp and reflects a little body heat. |
| Warmth on its own | Adds real, measurable warmth from underneath, but does nothing to shield you from wind or rain. | Minimal; an emergency bivvy alone is a survival measure, not a comfortable night's sleep. |
| Weather resistance | Wipe-clean surface, but no weatherproofing — it is a base to lie on, not a shell. | Fully waterproof and windproof; keeping water out is its entire purpose. |
| Weight & pack size | Bulkier — a self-inflating mat rolls to about the size of a large water bottle; foam mats are lighter but bigger. | Emergency versions weigh under 200g and pack to the size of a fist. |
| Best emergency use | Sleeping on hard floors at home, in a shelter or in a vehicle where the surface is cold and unforgiving. | Grab bag, car boot and daypack where a last-resort weatherproof shell must weigh next to nothing. |
| Weak point | Inflatable versions can puncture; carry a patch, or choose self-inflating foam for more forgiveness. | Little insulation and no ground protection; condensation can build up inside cheaper non-breathable ones. |
| Price band | Roughly 15 to 60 pounds depending on R-value, packed size and inflation type. | A few pounds for an emergency foil bivvy; more for a breathable outdoor shell. |
Choose a sleeping mat when you expect to sleep on a cold, hard surface — a tiled or concrete floor during a power cut, a night bedded down in the car, or a spell in a rest centre or on a friend's floor after a house problem. This is the piece most people forget, and it matters more than an extra blanket, because heat lost into the ground is heat you can never make up from above. Look at the R-value if warmth is the point, carry a patch kit for an inflatable, and remember a mat pairs naturally with a sleeping bag or blankets on top. For sleeping warm at home during a winter outage, the mat is the higher-impact buy.
Choose a bivvy bag when weight, pack size and weatherproofing matter most and you need a genuine last-resort shell rather than a comfortable bed. An emergency foil bivvy costs a few pounds, weighs nothing and belongs in every grab bag, car boot and hiking daypack precisely because there is no excuse not to carry one. It is the right call for a stranded motorist, a walker caught out after dark, or anyone who needs to block wind and rain fast. Be clear about its limits, though: on its own it keeps you alive rather than warm, and it does little about the cold ground — so pair it with a mat and some insulation whenever you can.
These two cover different halves of a cold night, and the best setup uses both. A sleeping mat handles the ground, which is where most of your warmth quietly disappears; a bivvy bag handles the weather, keeping wind, rain and damp off you and your insulation. For sleeping warm at home during a winter power cut, the mat is the piece to buy first — the floor is the enemy indoors, not the rain. For a grab bag or car, a featherweight emergency bivvy is the smarter first buy, because it costs almost nothing and packs to a fist. Build a proper cold-weather sleep system and you want both, with a sleeping bag or blankets between them: mat underneath for insulation, bag for warmth, bivvy over the top to keep it all dry.
A self-inflating mat from a trusted UK bedding brand — insulates against cold ground and packs down into its own storage bag, no separate pump needed.
An inflatable sleeping mat that packs down to about the size of a water bottle, so it slots into a grab bag far more easily than a bulky self-inflating roll. It lifts you off cold, hard ground, which helps you rest and stay more comfortable overnight. Inflates in a couple of minutes and deflates fast when you need to move on.
A compact emergency bivi bag from Lifesystems that reflects body heat back to keep you warm if you're stranded or injured outdoors. The kind of lightweight insurance that lives in a rucksack for hillwalks and long drives.
A lightweight reflective survival bag that traps body heat to fend off hypothermia in a cold-weather emergency. Packs down small enough to live permanently in a rucksack or car.
The main route into storm, power cut, warmth, water and car-kit guidance.
A practical first plan for lights, phones, food, warmth and checking on people.
Buyable kit picks for the most common UK storm and outage problems.
A printable checklist for cold weather, outages, travel disruption and home prep.