A house with no heat in a cold climate is not a shelter. It is an exposure hazard with walls. The building envelope slows heat loss — it does not prevent it. In a well-insulated modern home, interior temperature drops approximately 1°F per hour at 20°F outside with no heat source. In a poorly insulated older home, it drops twice that fast or faster. At that rate, a house that is 68°F when the power fails reaches hypothermia-risk temperatures for vulnerable occupants within 12-24 hours. Children, elderly adults, and anyone with compromised circulation or medical conditions reach dangerous thresholds before the general household population does.
This is not a problem that develops slowly. It develops at a predictable rate in a predictable direction and must be addressed in the first hours of a grid-down event during cold weather, not the next day when the house is already cold.
This post covers the heat retention and heat production strategies for a household without electricity, in order of priority: passive heat retention first (it costs nothing and buys time), supplemental heat sources second, and the safety protocols that determine whether those heat sources save lives or end them.
THE PHYSICS — WHAT YOU ARE MANAGING
A house loses heat through four pathways: conduction through walls, ceiling, and floor; infiltration through gaps and cracks; radiation from windows; and ventilation — air exchange between inside and outside. Managing these four pathways is the entirety of passive heat retention. None of it requires equipment. All of it can be done in the first hour.
Windows are the primary radiation loss surface in most houses — a single-pane window loses heat 10x faster than the same square footage of insulated wall. Double-pane windows are better but still significant. Covering windows on the interior with blankets, moving blankets, sleeping bags, or heavy curtains reduces heat loss from the window surface by 50-80%.
Doors — especially exterior doors — lose heat through the door panel, through the frame gap, and through mail slots and pet doors. Rolled towels or draft snakes along the base of exterior doors are simple and effective. Hanging a blanket over an exterior door on the interior adds an additional insulation layer.
Chimney and fireplace flue — an open fireplace flue is a direct shaft from your living room to the outside. If you are not using the fireplace, the damper must be fully closed. A closed damper is an insulated cap. An open damper is a hole.
Ceiling and attic — heat rises. An under-insulated attic is where significant heat escapes in a cold house. If attic access is available, lay additional insulation over the attic floor — sleeping bags, blankets, anything with R-value. This is not a permanent fix but it meaningfully slows heat loss in an emergency.
PASSIVE HEAT RETENTION — DO THIS FIRST
Consolidate the household into one room. The warmest room in the house is the one with the most people generating body heat in the smallest volume. Choose one interior room — interior walls rather than exterior walls on all sides, south-facing if possible. A small bedroom is often better than a large living room for heat retention. Move sleeping materials, food, water, and lighting into this room. Close all other rooms. A closed door between the occupied room and the unoccupied rest of the house is a meaningful thermal barrier.
Cover all windows in the occupied room. Blankets, moving blankets, sleeping bags. Anything with mass and insulating value. Tape edges if necessary to eliminate gaps.
Seal door gaps. Rolled towels, clothing, or dedicated draft snakes at the base of the room’s door and any exterior doors.
Body heat is significant. Four adults in a small room generate approximately 1,500 BTU per hour from body heat alone — equivalent to a small space heater. In a consolidated, sealed room with covered windows, body heat from the occupants is a meaningful heat source. Do not underestimate it.
Layer clothing before supplemental heat. The appropriate sequence is: maximize passive retention, layer up, then assess whether supplemental heat is necessary. Base layer (moisture-wicking), mid layer (insulating), outer layer (wind and moisture resistant). A wool hat eliminates 20-30% of heat loss. Wool socks over a thin liner sock. Multiple layers of dry clothing are warmer than one heavy layer because trapped air between layers is the insulation.
Sleeping warm. Sleeping bags rated to 0°F or below are available for under $100 and are the most effective single investment in cold-weather resilience. Two people sharing one sleeping bag add each other’s body heat to the insulation — warmer than two separate bags. A reflective emergency blanket (mylar) on the outside of a sleeping bag reflects radiated body heat back in — adds 10-20°F of effective warmth at negligible weight and cost.
SUPPLEMENTAL HEAT SOURCES
Wood Stove / Fireplace Insert
A properly installed wood stove or fireplace insert is the gold standard for off-grid home heating. It burns a renewable fuel available on any property with trees, requires no electricity, heats a space effectively, and can be used for cooking. If you have one, use it. If you are building or renovating, prioritize installing one.
Fuel storage: A cord of dry, split hardwood is a serious winter heat supply — approximately 20-24 million BTU, adequate for a full heating season in a moderately cold climate if the stove is the primary heat source. Store firewood covered, off the ground, with airflow on all sides. Minimum 6-month drying time for freshly split wood. Store at least 2-3 cords if a wood stove is your primary backup heat.
Safety: Annual chimney inspection and cleaning before each heating season. Creosote buildup in chimneys is the cause of most chimney fires — preventable with regular cleaning by a certified chimney sweep. Carbon monoxide detector in the room where the stove operates. Fire extinguisher accessible.
Propane Heaters (Indoor-Safe Models Only)
Mr. Heater Buddy and Big Buddy series heaters are the most widely available and recommended propane heaters rated for indoor use. They have an oxygen depletion sensor (ODS) that automatically shuts the unit off if oxygen levels drop — the primary safety mechanism that makes indoor use marginally safer than non-ODS heaters.
“Indoor-safe” does not mean ventilation is unnecessary. All combustion consumes oxygen and produces carbon monoxide. The ODS sensor prevents the most acute oxygen depletion hazard, but carbon monoxide accumulation over time in a sealed room is still a risk. Crack a window or door slightly during operation. Run a carbon monoxide detector continuously. Do not operate while sleeping without additional ventilation.
Fuel: 1-lb disposable propane canisters or 20-lb refillable tanks via the bulk adapter hose. The 1-lb canisters are expensive per BTU — the adapter hose for 20-lb tanks ($25) pays for itself quickly. A 20-lb tank at medium output on a Buddy heater runs approximately 100 hours. Store propane in a detached structure, not in the house — propane vapors are heavier than air and accumulate at floor level, creating explosion risk.
Output: Mr. Heater Big Buddy: 18,000 BTU/hr at high, 9,000 BTU/hr at low. Adequate for heating a medium-sized room to comfortable temperature in moderate cold.
Kerosene Heaters
A quality kerosene heater (Dyna-Glo, Sengoku) produces 10,000-23,000 BTU and is an effective supplemental heat source for a single room. Kerosene is more energy-dense than propane, storable in 5-gallon cans for years with a fuel stabilizer, and available at hardware stores and some gas stations.
Kerosene heaters produce more odor than propane heaters during startup and shutdown. They produce combustion byproducts including carbon monoxide and particulates. Ventilation is required. A carbon monoxide detector is mandatory. Do not refuel a hot heater.
Fuel storage: 10 gallons of kerosene provides approximately 100 hours of runtime on a mid-sized heater. Store in sealed approved containers with a fuel stabilizer — K-1 kerosene stores well for 1-2 years with stabilizer. Do not use red-dyed diesel as a kerosene substitute — it is not the same fuel and produces more particulates and odor.
Catalytic Heaters
Wave catalytic heaters (Camco Wave 3, Wave 6) use a catalytic element to combust propane at lower temperatures, producing radiant heat with lower CO output than open-flame combustion. Generally considered safer than open-flame heaters for enclosed spaces. Require the same ventilation precautions as any combustion heater — carbon monoxide detector mandatory.
Passive Solar Gain
On sunny winter days, south-facing windows admit solar radiation that heats the interior even in cold weather. Remove window coverings on south-facing windows during daylight hours to admit solar gain, then replace them at sunset to retain the accumulated heat. This is not a primary heat source but provides meaningful supplemental warmth at no cost on clear days.
CARBON MONOXIDE — THE CRITICAL SAFETY RULE
Carbon monoxide is produced by any combustion source: propane heater, kerosene heater, wood stove, catalytic heater, generator. It is colorless, odorless, and kills without warning. The symptoms of carbon monoxide poisoning — headache, nausea, confusion — are easily mistaken for flu or fatigue, particularly in a household already stressed by a crisis event.
Non-negotiable rules:
Never operate a generator, gas range, propane grill, or any non-indoor-rated combustion appliance inside the house or in an attached garage. Carbon monoxide from a generator in an attached garage enters the house. People die from this every winter in power outages. It is entirely preventable.
Run a battery-powered carbon monoxide detector continuously whenever any combustion appliance is operating indoors. Replace the battery before it fails. A CO detector that sounds means everyone leaves immediately — no discussion, no investigation from inside the house.
Crack a window or exterior door for ventilation when operating any indoor combustion heater. The indoor-safe rating on propane heaters does not eliminate the need for fresh air exchange. It raises the threshold. Cross-ventilation — a cracked window on each side of the occupied space — is better than a single vent point.
Never sleep without ventilation when any combustion appliance is running. The body’s oxygen consumption drops during sleep, CO accumulates faster in a sealed room, and the body’s response to CO poisoning is further impaired by sleep. If you are heating a room overnight with a combustion appliance: crack a window. Run the CO detector. There is no other acceptable protocol.
VULNERABLE HOUSEHOLD MEMBERS
The temperature threshold for hypothermia risk is different across household members. Healthy adults at rest are typically safe to 55°F ambient temperature with appropriate clothing and bedding. Children, elderly adults, and those with circulation problems, heart conditions, or hypothyroidism may be at risk at significantly higher temperatures.
Children: Children lose body heat faster than adults due to higher surface area to mass ratio. Keep children in the warmest part of the shelter, fully clothed including hat and socks, with adequate sleeping insulation.
Elderly adults: Age-related changes in thermoregulation and circulation reduce both heat production and cold sensation — an elderly person may not feel cold even when their core temperature is dropping. Check on elderly household members proactively; do not wait for them to report being cold.
Medical conditions: Hypothyroidism, diabetes, cardiovascular disease, and several medications reduce cold tolerance. Know the vulnerabilities of each household member and plan accordingly — a household member who reaches dangerous threshold sooner than others may need to be evacuated or relocated to a warmer environment before other household members are affected.
Pets: Cats and dogs tolerate cold better than small animals, reptiles, and tropical fish. Know the thermal requirements of every animal in the household and plan their housing accordingly.
TEMPERATURE MONITORING
A household thermometer — ideally a min/max thermometer that records the coldest temperature reached — is a simple and essential tool for monitoring house temperature during a cold event. Check it every 4-6 hours. Know the temperature thresholds that trigger action: below 50°F, activate all passive retention measures if not already done; below 45°F, activate supplemental heat; below 40°F, vulnerable household members are at risk and may need relocation.
FINAL THOUGHTS
Cold is the grid-down threat that arrives on a schedule you can predict and kills on a timeline you can calculate. It is also the threat that is most completely addressable with preparation — passive retention techniques cost nothing, supplemental heat sources cost $100-300, and fuel storage is straightforward. A household with a propane heater, two 20-lb tanks, a carbon monoxide detector, quality sleeping bags, and the knowledge to use all of them correctly is not significantly threatened by a winter power outage of several weeks’ duration.
Build the capability before the cold comes. The propane heater acquired in November and tested in the backyard is the one that works correctly in January. The one ordered online after the power fails arrives after the crisis passes — if it arrives at all.
For building a wood stove-capable fire safely and efficiently, see Rocket Stove Build in DIY Schematics. For the insulation principles that apply to both shelter and clothing layers, see Improvised Shelter. For the first 72-hour cold weather protocol, see First 72 Hours. For medical management of hypothermia, see Hypothermia in the First Aid section.