Buyer's Handbook
Emergency blankets and bivvies, and what a sheet of foil can and cannot do.
A reflective blanket costs less than a sandwich and folds smaller than a phone. This handbook explains what these sheets, tube tents, and bivvies really do, why the cheap ones leave you damp, and where each one belongs in a car, a day pack, or a home kit.
Reviewed November 2026. We re-check this guide quarterly.
By Dan Whelan, founder of New World Survival
Researched from government agencies, university extension services, and other published sources. See our sources
Start here
A long wait on a cold shoulder, and a packet in the glove box
The highway is closed ahead and nothing is moving. Or the soccer game runs long and a cold rain sets in. Or a day hike takes two hours longer than planned and the sun drops behind the ridge. None of these is a disaster, and each one is easier with something warm and dry within reach.
That is the honest job of an emergency blanket, a tube tent, or a bivvy: a light, cheap layer that blocks wind and rain and holds in some of your own warmth until the wait is over. Videos make them look like a full night's shelter for fifteen dollars. They can help a great deal, as long as you buy them for the job they actually do.
Before you buy
Five questions about where you would use it
Answer these first. They decide between a five-dollar blanket and a sixty-dollar bivvy far more than any brand does.
Where will it live?
A car can carry a real wool blanket as well as a reflective one. A day pack rewards the lightest thing that still works. A home kit can hold sleeping bags, and the reflective sheet becomes a backup or a ground cloth.
How long would you need it?
An hour or two of waiting is what a basic blanket does well. A whole night is different, because moisture from your breath and skin builds up inside a sealed plastic layer. That one answer is what points some people toward a breathable bivvy.
What weather do you actually get?
It does not have to be winter. CDC notes hypothermia can occur even at cool temperatures above 40°F when a person is chilled by rain, sweat, or cold water.[1] Cold rain in spring or fall counts.
How many people?
Most blankets and bivvies are sized for one adult. Tube tents and the larger blankets are sold as two-person shelters. Count the people who ride in that car or walk that trail, and buy one each.
What warm layers do you already own?
A reflective sheet works best over real insulation, such as a coat, a wool blanket, or a sleeping bag, not instead of it. If the car already carries blankets, a few inexpensive reflective sheets round it out. If it carries nothing, start with a blanket and add the sheets. The full price ladder is in the what to buy section.
How it works
A wind and rain barrier with a shiny side
Your body is always making heat and always losing it. NIOSH puts the problem plainly: in the cold, the body begins to lose heat faster than it can produce it.[3] OSHA adds the two conditions that speed that loss: wind, and wetness, even from your own sweat.[2]
Every product in this handbook is a thin, waterproof, windproof plastic sheet, usually coated with a thin layer of metal on one side. That combination does two useful things. It stops wind and rain from reaching you, and the metallic side bounces some of your radiated warmth back toward your body instead of letting it drift away.
What it does not do is insulate the way a blanket or a coat does. A sheet of plastic traps very little air, and trapped air is what keeps heat in. That is why the best use of a reflective sheet is as the outer layer over warm clothing or a blanket, the order OSHA describes in its own first aid steps.[2]
The distinction that matters most
Something to wait in, or somewhere to live
Everything in this handbook is emergency cover: light, cheap, and meant to buy you time until you reach somewhere warm. None of it is a tent, a sleeping bag, or a heated room, and none of it treats a person who is already too cold.
What emergency cover is good at
Short waits, especially when you are wet or in the wind.
- Blocking wind and rain, the two conditions OSHA names as speeding heat loss.[2]
- Acting as the outer layer over blankets. OSHA's first aid steps for hypothermia call for wrapping the whole body in layers of blankets and a vapor barrier such as a tarp or garbage bag, without covering the face.[2]
- Weighing almost nothing, so it is actually there when needed. The American Red Cross lists an emergency blanket in its basic kit supplies.[7]
What it is not
A substitute for insulation, a vehicle, or medical care.
- Not insulation. The Red Cross lists blankets or sleeping bags as their own item, separate from the emergency blanket.[7] CDC and Ready.gov both list blankets for the car kit.[8][6]
- Not a reason to leave a vehicle. Ready.gov's advice is that if you are trapped in your car, you stay inside it.[6]
- Not treatment. CDC calls hypothermia a medical emergency and says a body temperature below 95°F needs medical attention right away.[1]
What this means for your purchase
Buy the reflective layer as the last piece, not the first. A car that carries a wool blanket, a hat, and gloves is better prepared than one that carries ten emergency blankets and nothing else. Then add the light sheets, one per person, because they cost little and pack small. Our vehicle emergency kit page shows where they fit in a full car kit.
The five formats
Blanket, tube, bag, or tarp
For most households, a few basic emergency blankets in each car and pack are the right start. A non-breathable bivvy suits a day pack. A breathable bivvy earns its higher price if you might spend a whole night in it. A tube tent and a tarp are for people who will be outdoors with something to tie them to.
The differences show up in four places: whether moisture can escape, whether it wraps you or covers you, whether it survives being refolded, and what it weighs.
| Basic blanket | Heavy-duty blanket | Tube tent | Emergency bivvy | Breathable bivvy | |
|---|---|---|---|---|---|
| Example | SOL Emergency Blanket, 84 by 56 inches, 2.5 ounces[9] | SOL Heavy Duty Emergency Blanket, 5 by 8 feet, 7.9 ounces[13] | Go Time Gear Life Tent, 8 by 5 feet, 8.7 ounces[12] | SOL Emergency Bivvy, 84 by 36 inches, 3.8 ounces[10] | SOL Escape Lite Bivy, 82 inches long, 5.5 ounces[11] |
| Shape | Flat sheet you wrap around you | Flat sheet, tougher, often used as a cover or ground cloth | Open-ended tube, hung on a cord between two supports | Sack you climb into | Sack you climb into |
| Lets moisture out | Only around the open edges | Only around the open edges | Through the open ends | No. The maker makes no breathability claim.[10] | Yes, by design.[11] |
| Maker's heat claim | Up to 90%[9] | 90%[13] | Up to 90%[12] | Up to 90%[10] | 70%[11] |
| Typical price | About $7 | About $15 to $20 | About $23 | About $25 | About $57 |
Specifications and prices from maker and retailer listings, checked November 2026. These examples show what each format is like. They are not our picks, and we have not published our own comparisons yet.
Emergency blanket
The space blanket most people picture
A thin reflective sheet, about the size of a single bed, sealed in a pocket-size packet. The cheapest ones come in multipacks, and the name brands sell for a few dollars each. A sheet like SOL's is sized for one adult and weighs about as much as a deck of cards.[9]
The limits: it slips off when you move, it crinkles loudly, and the thinnest film splits once it is nicked. It is hard to refold to its original size, so plan on replacing one after use. Keep one per person in every car and pack.
Heavy-duty blanket
The one you can use more than once
A thicker, larger sheet that can be tied up as a windbreak or a rain fly as well as wrapped around you. SOL's version is a 5 by 8 foot sheet of heavier fabric at under half a pound.[13]
It costs several times more than a basic blanket, and it is the one worth folding back into the trunk afterward. It also makes a good ground cloth under a regular blanket, keeping the wet off the warm layer.
Tube tent
A tent-shaped tube on a cord
An 8 by 5 foot tube of reflective plastic. Go Time Gear's directions are to run the cord through it, tie it 3 to 4 feet off the ground between two trees or sturdy objects, and weigh the corners down; with nothing to tie to, it doubles as a blanket or a bag.[12] This is the trending one, sold as a two-person shelter.
The limits: it needs two anchor points, both ends stay open to the wind, and there is no insulation between you and the ground. It is a rain and wind break for someone outdoors, not a tent. In a car, a blanket does the same job with less fuss.
Emergency bivvy
A blanket sewn into a bag
The same reflective material, shaped like a sleeping bag with no insulation. Because it closes around you, it does not slip off, and it seals out wind better than a loose sheet. SOL's weighs under four ounces and lists no breathability claim.[10]
The trade is moisture. A closed plastic bag holds the water vapor from your breath and skin, and over a long wait your clothes can end up damp from the inside. That makes it a strong choice for a day pack and a weaker one for a whole night.
Breathable bivvy
The answer to the condensation problem, at a price
A bivvy made from a fabric that lets water vapor pass out while keeping rain, snow, and wind out. SOL's Escape Lite is listed as breathable, windproof, and water-resistant, with a lower maker claim of 70 percent heat reflection.[11] It is quieter, tougher, and meant to be used again.
It costs roughly three times a basic bivvy, and breathable is not the same as condensation-free; owners in REI's reviews still report some moisture from breath.[11] If you hike in the shoulder seasons or want something you could sleep in, this is the one to look at. For a glove box, it is more than you need.
A plain tarp and a length of cord belong in this family too. A tarp blocks rain overhead better than any of the above, and many households already own one. The Red Cross lists plastic sheeting and duct tape among its additional supplies.[7]
The words on the packet
What the claims actually tell you
The packaging is small and the claims are large. Here is how to read the six you will see most.
"Reflects 90% of body heat"
This is the maker's own number, and the careful listings say "radiated" body heat.[13] It describes how much infrared warmth the shiny side bounces back, not how much total heat you keep. Wind, wet clothing, and cold ground still draw heat away. We found no independent standard behind these percentages, so read them as marketing, not a rating.
"Mylar"
Often used loosely for any shiny film. Go Time Gear sells its tube tent as Mylar but lists the material as coated polyethylene.[12] What matters more than the name is thickness and whether the sheet splits once it is nicked.
"Breathable"
The one claim that changes how long you can stay in it. A breathable bivvy lets vapor out; a plain one holds it in.[11][10] Expect less condensation, not none.
"Two-person"
Usually means two adults can fit under it, close together. Sharing warmth is real, but so is a cramped, open-ended tube. For a family car, one blanket per person is simpler.
"Reusable"
True of heavy-duty blankets and breathable bivvies. A basic blanket can be refolded, but rarely to its packet size, and creased thin film splits more easily. Treat the cheapest sheets as one-use.
Color
Makers sell bright orange so the outside stands out, and olive green for campers who would rather blend in. For a car or a home kit, either works. Pick orange if you hike where you might want to be seen.
Using it well
Warm layers inside, the shiny sheet outside
Start with whatever insulation you have: coats, hats, gloves, a wool or fleece blanket. Then wrap the reflective sheet around the outside, shiny side in. That is the same order OSHA describes in its first aid steps, layers of blankets and then a vapor barrier, leaving the face uncovered.[2]
Keep yourself dry before you keep yourself covered. OSHA notes that wetness, even from sweat, speeds heat loss, and that wet clothing should come off and be replaced with dry clothing.[2] A dry spare layer in the car often does more than the blanket does.
In a car, stay with the car. Ready.gov advises staying inside if you are trapped in your car.[6] If you run the engine for warmth, CDC warns that snow blocking the tailpipe can let carbon monoxide build up quickly inside the vehicle, so clear it first.[5] Our winter driving guide covers the rest.
Open the packet once at home. You will learn how big it is, how it folds, and how loud it is, and you will be calmer the day you need it. Then buy a fresh one for the kit.
What fails and why
How emergency cover lets you down
Most failures are not the material giving out. They are moisture, gaps, and expectations the packet set too high.
Condensation
A sealed plastic bag or a tightly wrapped sheet holds in the water vapor your body gives off. Over hours, the inside gets damp, and OSHA notes that wetness speeds heat loss.[2] Keep your face uncovered, as OSHA's first aid steps advise,[2] which also lets some moisture out, and on a long wait choose a breathable bivvy or keep the reflective layer loose over a blanket.
Wind getting underneath
A loose sheet flaps open the moment you move, and OSHA notes that wind carries heat away from the body faster.[2] Tuck it under you, sit on the edges, or use a bivvy, which closes around you.
Splits and tears
The thinnest film tears easily once it is nicked, and a creased, refolded sheet splits along the creases. Carry more than one, keep them in their packets until needed, and replace any you have opened.
The cold from below
A tube tent or bivvy on bare ground leaves only a film of plastic between you and the cold surface. Put a coat, a car mat, a pack, or a folded blanket under you as well as over you.
What emergency cover cannot do
It cannot treat hypothermia. CDC lists the warning signs in adults as shivering, exhaustion, confusion, fumbling hands, memory loss, slurred speech, and drowsiness, and calls hypothermia a medical emergency: a temperature below 95°F needs medical attention right away.[1] If help is not available, CDC's steps are to get the person into a warm room or shelter, remove wet clothing, warm the center of the body first, and keep them dry and wrapped, including the head and neck.[1]
It cannot make a heater safe inside it. CPSC says never to use fuel-burning portable heaters or lanterns while sleeping in enclosed areas such as tents, campers, and vehicles.[4] A tube tent, a bivvy, or a blanket wrapped around you in a closed car is an enclosed space. Use body heat, warm layers, and the vehicle's own heater with a clear tailpipe.[5]
It cannot replace staying put. Ready.gov's guidance is to stay inside a car you are trapped in.[6] A packet of foil is not a reason to set out on foot.
It cannot cover a face safely. OSHA's first aid steps say to wrap the body, including the head and neck, but not to cover the face.[2]
What to buy
Now that you know what to look for
Below are the honest price ladder and the checks we hold every emergency blanket, tube tent, and bivvy against. Our own comparisons are in progress and will appear here as each one is finished.
Affiliate disclosure: New World Survival earns a small commission on qualifying Amazon purchases at no cost to you. This helps us cover operating costs and keep building new content. We only recommend gear we would put in our own kit. Commission never decides a recommendation.
| Tier | Examples and typical prices | What the extra money buys |
|---|---|---|
| Basic blanket | SOL Emergency Blanket about $7; generic multipacks cost less per sheet | The baseline. One per person in every car and pack. |
| Non-breathable bivvy | SOL Emergency Bivvy about $25 | A closed bag that stays on you and blocks wind better. |
| Heavy-duty blanket | SOL Heavy Duty Emergency Blanket about $15 to $20 | A tougher, larger sheet you can use again, as a cover or a ground cloth. |
| Tube tent | Go Time Gear Life Tent about $23, sold direct | Overhead cover for two people, if you have two places to tie it. |
| Breathable bivvy | SOL Escape Lite Bivy about $57 | Moisture that can escape, a quieter and tougher fabric, and real reuse. |
Prices from maker and retailer listings, checked November 2026. These are examples that show what each tier costs, not our picks. Sales and retailers vary.
Right format
- Blanket for the car
- Bivvy for the day pack
- Breathable for a full night
Right size
- Long enough for the tallest person
- One per person
- Fits where it will live
Built to last
- Resists splitting once nicked
- Sealed seams on bivvies
- A stuff sack it fits back into
Honest claims
- Heat percentages read as marketing
- No promise of a full shelter
- Price matched to what it adds
After you buy
Putting it where it helps
A blanket in a packet is only half a plan. These guides cover the kits it belongs in and the situations it is for.
Vehicle emergency kit
Everything worth keeping in the car, from blankets and water to the tools that get you moving again.
Read the guideWinter driving
Preparing the car for snow and ice, and what to do if traffic stops and you have to wait it out.
Read the guideSleeping warm in a vehicle
Layering, ventilation, and condensation for a night in the car, done safely.
Read the guideWinter storm readiness
Staying warm at home through a storm and an outage, where blankets matter more than foil.
Read the guideHeating and fuel safety
Why fuel-burning heat stays out of tents and closed spaces, and what to use instead.
Read the guideVehicle kit checklist
A printable list for the trunk, with a reminder to replace opened blankets.
Open the checklistAll comparisons
Every comparison, in one place
Each comparison we publish for emergency blankets, tube tents, bivvies, and tarp shelters is listed here as it is finished.
Where this comes from
Sources
- Centers for Disease Control and Prevention. "Preventing Hypothermia," Winter Weather. Accessed November 3, 2026. cdc.gov
- Occupational Safety and Health Administration. "Winter Weather: Cold Stress." Accessed November 3, 2026. osha.gov
- National Institute for Occupational Safety and Health. "Cold-related Illness in Workers." Accessed November 3, 2026. cdc.gov
- U.S. Consumer Product Safety Commission. "Portable Heaters and Camping Equipment," Carbon Monoxide Information Center. Accessed November 3, 2026. cpsc.gov
- Centers for Disease Control and Prevention. "Clear Snow from Tailpipes." Accessed November 3, 2026. cdc.gov
- Ready.gov. "Winter Weather." Accessed November 3, 2026. ready.gov
- American Red Cross. "Survival Kit Supplies." Accessed November 3, 2026. redcross.org
- Centers for Disease Control and Prevention. "Preparing for a Winter Storm," Winter Weather. Accessed November 3, 2026. cdc.gov
- REI Co-op. "SOL Emergency Blanket" product listing. Accessed November 3, 2026. rei.com
- REI Co-op. "SOL Emergency Bivvy with Rescue Whistle and Tinder Cord" product listing. Accessed November 3, 2026. rei.com
- REI Co-op. "SOL Escape Lite Bivy" product listing and owner reviews. Accessed November 3, 2026. rei.com
- Go Time Gear. "Life Tent" product listing. Accessed November 3, 2026. gotimegear.com
- Cabela's. "SOL Heavy-Duty Emergency Blanket" product listing. Accessed November 3, 2026. cabelas.ca
Stay current
We re-check this guide every quarter as prices and products change. The Weekly Readiness Brief is a quiet way to hear when it updates.