The short answer: on a cold night the heat you lose downward through the mattress matters as much as the heat you lose upward, and blankets only address the upward half. A caravan bed base often sits directly over an unheated storage void with outside air moving under the floor. If your mattress is thin, or its foam has compressed under your body, there is very little insulating material left between you and that cold. You will feel it as a cold that no amount of duvet fixes.
Conduction is the problem, not the air temperature
Above you, your body warms a layer of air and your bedding traps it. That works well, and adding blankets adds trapped air, which is why it helps.
Below you, none of that applies. Your body weight squashes the material under you flat. Compressed material has far less trapped air in it, and trapped air is what insulation actually is. So the surface below you conducts heat away from your body far more efficiently than the air above you does.
Hikers have known this for decades, which is why a sleeping bag rated for freezing temperatures is useless directly on cold ground without a mat underneath it. A caravan bed is the same problem with better furniture.
Two conditions make it acute in a South African caravan:
- The void underneath. Many caravan beds sit above a storage locker that is vented to outside or simply not sealed. On a Free State or Highveld winter night, that space can be close to outside temperature, and outside can be near freezing.
- Thin, tired foam. The typical OEM caravan slab is 75 to 100mm of 28 to 30 kg/m3 foam. Once it has been slept on for a few seasons it compresses under your hips to a fraction of its original thickness. You are then a few millimetres of squashed foam away from a cold panel.
What actually fixes it
- Restore the material between you and the base. A mattress with a genuinely high-density core does not compress to nothing under your hips, so it keeps insulating material in place exactly where you are heaviest. Ours use 50 kg/m3 SABS-approved high-density foam for this reason among others.
- Add a layer under the mattress. A closed-cell foam underlay or an insulating membrane between mattress and base adds real thermal resistance. The dual benefit is that a ventilating underlay also helps with the condensation problem, which gets worse in winter, not better.
- Close off the void. If the storage space under the bed is open to outside air, sealing or insulating it changes the temperature of the panel you are lying on.
- Use a mattress protector or underblanket, not just more duvets. Anything that adds a trapped-air layer beneath you does more per millimetre than the same thickness on top.
- Do not block ventilation entirely. This is the trap. Sealing the caravan up tight to stay warm raises internal humidity sharply, and that moisture condenses under the mattress. Stay warm from below, keep a vent open above.
| Fix | Effect on cold from below | Effort |
|---|---|---|
| More blankets on top | None. Addresses the other half of the problem | Trivial |
| Insulating underlay between mattress and base | Substantial, and helps with condensation too | Low |
| Replacing collapsed foam with high-density foam | Substantial. Restores material where you compress it most | Moderate |
| Insulating the storage void under the bed | Substantial, and permanent | Higher, may need a dealer |
Does memory foam feel colder in winter?
A fair question, and the honest answer is that temperature changes how memory foam behaves. Memory foam is viscoelastic, meaning it softens as it warms. In a genuinely cold caravan it can feel firmer than it does in a warm room for the first few minutes, until your body heat brings it up to temperature. After that it behaves normally.
That is a feel characteristic, not an insulation failure. If anything, memory foam conforms closely around you, which reduces cold air gaps along your sides. Our Revive Foam Caravan Mattress is our memory foam build and is the one we recommend first, including for winter caravanning. If you would rather have a firm, immediately responsive surface that does not change feel with temperature at all, the Active Foam Caravan Mattress uses the same 50 kg/m3 core without the memory foam layer.
Frequently asked questions
Why am I cold from underneath in my caravan?
Because your body weight compresses the material beneath you, and compressed material contains far less trapped air, which is what insulation actually is. The bed base often sits over an unheated storage void near outside temperature. Heat conducts down and away from you far faster than it escapes upward through bedding.
Will more blankets fix a cold caravan bed?
Only partly. Blankets trap air above you and do help, but they do nothing about heat conducting downward through a compressed mattress into a cold base. If your chest is warm and your hips and legs are cold, adding another duvet will not change it. Add insulation below you instead.
What can I put under a caravan mattress for warmth?
A closed-cell foam underlay or an insulating membrane between the mattress and the base. Choose one that also allows some airflow, because sealing the mattress tight against the base traps condensation, which is a bigger problem in winter when the temperature difference between your body and the base is greatest.
Does foam density affect how warm a caravan bed is?
Indirectly but meaningfully. Low-density foam compresses almost flat under your hips and lower back, leaving very little material between you and a cold panel exactly where you press hardest. A 50 kg/m3 core keeps its thickness under load, so the insulating layer stays where you need it.
Getting cold on winter trips? Start with what is under you. Our caravan mattresses use 50 kg/m3 SABS-approved high-density foam, cut to your bed shape, with a 365-night trial and a 10-year written warranty.
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