Sleep systems for camping: bags, pads and staying warm at night

Your body loses heat in three directions at night: into the air around you, into the ground beneath you, and through moisture in your clothing. A sleeping bag handles only the first. The insulation under you gets compressed to nothing by your body weight, so without a proper pad the ground pulls heat out of you all night regardless of how expensive your bag was.

The practical rule: if you are cold at night, upgrade the pad before the bag. A mid-range bag on a well-insulated pad beats a premium bag on a thin foam mat almost every time.

Most quality bags use standardized EN/ISO ratings with two numbers. The "comfort" rating is the temperature an average cold sleeper stays comfortable at; the "limit" rating is for an average warm sleeper curled up. The big number in marketing copy is usually the limit — or worse, a survival figure.

Buy for the comfort rating, and treat it as optimistic. If you expect nights around freezing, choose a bag rated to 20°F (-6°C), not 32°F (0°C). You can always vent a bag that is too warm; you cannot add warmth to one that is not.

Down packs smaller, weighs less and lasts decades if cared for — it is the right choice for backpacking and cold, dry conditions. Its weakness is moisture: wet down clumps and stops insulating, though modern water-resistant treatments help.

Synthetic fill keeps insulating when damp, dries faster and costs less. It is bulkier and heavier, which matters in a pack but not at a car-camping site. For car camping, family trips and humid climates, synthetic is usually the sensible buy.

Sleeping pads are rated by R-value, a measure of resistance to heat flow. Higher is warmer. R-values are additive: stacking a closed-cell foam pad under an inflatable adds their values together.

As a rough guide: R1–2 suits summer only, R2–4 covers three-season use for most people, and R4 and above is for cold ground, shoulder seasons and winter. If you sleep cold, add one step.

Closed-cell foam pads are cheap, indestructible and instant — but thin on comfort and bulky to carry. They shine as a backup layer or a sit pad, and strapped outside a pack where bulk does not matter.

Inflatable insulated pads are the comfort standard now: three or four inches thick, warm for their weight, and they pack to the size of a water bottle. Self-inflating pads split the difference — tougher and less fussy, but heavier and bulkier than modern air pads. For car camping, a thick self-inflating mattress or a camping-specific air mattress is hard to beat.

Sleep dry. Even slightly damp base layers will chill you at 3 a.m. — change into dedicated dry sleep clothes. Eat something before bed; your body needs fuel to make heat. Fill dead air space in the bag with tomorrow's clothes rather than buying a bigger, colder bag.

A bag liner adds a few degrees of warmth and keeps the bag clean, which preserves the insulation's loft. And vent the bag if you start to sweat — moisture inside the insulation costs more warmth than opening the zipper does.

For three-season car camping: a synthetic bag rated to a 20°F comfort level, a self-inflating pad around R3–4, and a real pillow from home. That combination covers spring through fall for most people and costs far less than chasing ultralight gear you do not need yet.

For backpacking: a down bag with the same 20°F comfort rating and an insulated inflatable pad at R3 or higher. Add a thin foam pad underneath in colder months — it protects the air pad from punctures and stacks its R-value on top.