A house is expensive to warm and a person is not. That single sentence is most of British cold weather preparedness, and it is why the scenario cards all say the same thing: pick one room, put everybody in it, and stop trying to heat the building.
This page is how to do that properly, because the difference between a well-chosen sealed room and a badly-chosen leaky one is several degrees and a great deal of fuel.
Heat the person, then the room
Layers, loose, with a windproof outer. Trapped air is the insulation, so several thin layers beat one thick one, and anything tight compresses the air out and stops working. A hat indoors is not silly; the head is a large uncovered surface.
Change out of anything damp immediately. Wet clothing conducts heat away from the body many times faster than dry, and in a cold house it does not dry on its own.
Eat and drink. Staying warm is metabolically expensive, and shivering burns through reserves fast. Something hot before bed does real work. See hypothermia, which is the page this one exists to prevent you needing.
People are heaters. A seated adult at rest gives off roughly 100 watts. Four people in a small room is 400 watts of continuous, free, silent heating, and it is the main reason everybody being in one room works at all.
Choosing the room
Most households pick the living room, and it is usually the wrong answer.
Small wins by a wide margin, because you are heating a volume of air and warming a surface area, and a small room has less of both.
Upstairs wins, because heat you have already spent rises into it, and because the floor below is warmer than the ground.
The number of outside walls matters more than people expect. A corner bedroom with two exposed walls and a window in each loses far more than a box room with one.
Be honest about the bay window. A big single-glazed bay is a hole in the wall as far as heat is concerned, and no amount of curtain entirely fixes it.
Check where the water pipes run before you abandon the rest of the house to the cold. See burst pipes: leaving the whole building unheated in a hard frost is how you swap a cold house for a flooded one.
Sealing it
The cheapest heat is the heat that does not leave.
- Cover the windows at dusk. Curtains closed before the light goes, not after. A second layer, a blanket or a duvet hung over the pole, roughly doubles what a curtain does. Uncover them in daylight if the sun reaches the glass, because free solar gain through a south-facing window is real.
- Hang a blanket or duvet over the door, on the room side, reaching the floor. This is the old idea of a portiere and it works.
- Block the gap under the door. A rolled towel does it. So does a sausage of clothing.
- Block the letterbox, the keyhole and the cat flap in the hall outside, because the hall is now your buffer.
- Shut every door between the warm room and the rest of the house. Each closed door is another still air layer.
- Close the loft hatch and consider insulating it, since it is often a bare sheet of plywood in an otherwise insulated ceiling.
- Block an unused chimney temporarily with something removable and obvious, and write yourself a note, because an open flue is a permanent hole to the sky.
Getting off the floor
The most under-rated item on this page.
A cold floor takes heat by conduction, which is a far more effective transfer than the air managing by convection, and it takes it continuously from anybody sitting or lying on it. People wrap up thoroughly, lie on a thin mat on a solid floor, and cannot work out why they are cold all night.
- Layer underneath, generously. Cardboard is genuinely good and genuinely free. Then a foam mat or a folded duvet, then the bedding you sleep in.
- Aim for more insulation under you than over you. Whatever is over you is uncompressed and lofted; whatever is under you is squashed flat by your own weight and doing much less than its thickness suggests.
- Sofas and armchairs beat dining chairs, and both beat the floor.
- Rugs and carpet on a bare floor make a measurable difference to comfort even before you sit down.
The tent indoors
Pitching a tent inside the room, or building one from a clothes horse and blankets, sounds like a game and is one of the most effective things on this page.
It reduces the volume you are actually heating from a room to a box, it traps the heat that people give off, and it gives children something to be enthusiastic about at a moment when enthusiasm is scarce. A two person tent with two people in it warms up noticeably within minutes.
- Do not seal it completely. Leave the door partly open or a vent panel unzipped. Sleeping in a fully closed small volume raises humidity fast and, in a room with any burning appliance, is dangerous.
- Insulate under the tent as well, on the same reasoning as above.
- Do not put any heat source inside it. Not a candle, not a heater, not a stove. Ever.
Heating it, and the thing that kills
Beyond that, the ranking is simple: an electric heater is the safest thing to run indoors if you have power, a properly installed and flued solid fuel stove is next, and everything flueless is a managed risk that needs real ventilation and constant attention.
Hot water bottles are excellent and carry none of this risk. Fill from a kettle heated however you like, wrap it in a cloth, and put it in the bed twenty minutes before anybody gets in.
The moisture problem
Everybody in one room, breathing, cooking and drying clothes, with the door and windows shut, produces a great deal of water vapour with nowhere to go. The windows stream, the outside wall goes cold and wet, and mould appears in the corners within a fortnight.
Air it hard, twice a day. Everybody in coats, window wide for ten minutes, then shut it. You lose very little from the structure and you dump a lot of moisture. Do not dry washing in the sleeping room. Wipe the condensation off the glass each morning rather than letting it run into the frames.
The full version is on damp and mould, and it is worth reading before the first fortnight is up rather than after.
Through the night
- Everyone in the same room, and small children and older people nearest the middle, away from the outside wall.
- Share bedding rather than splitting it. Two people under one big duvet is warmer than two people under one each.
- Hats and dry socks in bed.
- Hot drink and something to eat before sleep.
- Check on people. Older relatives and anyone unwell, by name, before lights out and again in the morning. Hypothermia indoors builds over days and the affected person will not report it, because impaired judgement is an early symptom.