I have a cap over the back of my truck and spend many nights a year camping and sleeping in the back rather than setting up a tent. I really like sleeping in it, saves the tent setup effort and gives my truck an aspect of multi-purposeness and self-sufficiency. The cap is fiberglass and the bed has a plastic liner over it.

The only problem is that it's not at all thermally insulated (save the sleeping bag you're in) and my favorite camping is in the mid Appalachian mountain area where the temps at night go freezing as early as now and often get down even much lower. I have spent a night in around-zero weather (30ish give or take) in my 15 deg bag and a fleece union suit and I didn't enjoy it too much and I'm not even that cold sensitive.

So I'd like to go and camp a few more times this year until maybe early December. Is there a portable (so it's not permanent) solution to add some thermal insulation to the inside walls of my truck cap to make it sustain down to about 20 deg outside weather while keeping it around 40 inside. Since the space is not all that large (6' bed on a Tacoma) and the roof of the cap is regular, I imagine my body could warm up the area as long as this prospective insulating solution was in place.

  • Is the bed metal? What is the cap made of? Metal is a fairly good heat conductor, and as such a pretty bad insulator. Heat proofing a truck bed would probably require lining up both the bed and the cap with some heat insulating material. Wood boards would work well, but you could give foam (yoga style) mats a try as well.
    – Nisan.H
    Commented Oct 21, 2013 at 14:25
  • just posted an update: "The cap is fiberglass and the bed has a plastic liner over it."
    – amphibient
    Commented Oct 21, 2013 at 14:27
  • 2
    offtopic, but I used to have a favourite rock that I would keep in the campfire and put in the bed of my truck when it was time to sleep, gives hours of extra warmth.
    – furtive
    Commented Oct 28, 2013 at 23:08
  • 1
    Is there enough headroom to put a freestanding tent inner in the space? Or even get a tent fabric cocoon made for the space that could be tied/clipped to the space. Commented Feb 7, 2021 at 18:46

5 Answers 5


I'd probably go with a foam roll mat under you, as your biggest heat loss well be conduction through the metal bed.

As the space isn't that great, the cap shouldn't need insulation, but this will depend on your sleeping bag.

  • the bed has a plastic liner -- no direct contact with metal
    – amphibient
    Commented Oct 21, 2013 at 21:20
  • 3
    @amphibient: a simple plastic liner is still rather poor insulation. Commented Oct 22, 2013 at 11:43

You might want to look at Reflectix, an thin, well-insulating material used for car windshield shades, among other things. You can get it at any hardware store.

My only concern would be that it's not breathable, but I suppose neither is your cap.

For the floor, conventional camping sleeping pads are probably the best bet.


It makes more sense to insulate you than the whole back of the truck.

Get a foam pad to put under your sleeping bag. You say there is a plastic liner, but a real sleeping pad should insulate much better than the liner.

As for losing heat from the top, get a warmer sleeping bag or just put a blanket over the existing one on cold nights. You've got a whole truck, so carrying a extra blanket or two shouldn't be a problem. With the blankets, you can tune your insulation to the temperature.


go to home depot and get a 4x8 foam insulation board you can cut it to fit the bed of your truck and can remove it and store it until you need it again i think they start at around $20.00 to high end $35.00 also a little buddy heater will warm the rest of your sleeping area most people that's into rv camping use the same thing i will be setting my truck camper on a insulation board to help keep the floor a little warmer and or you can get a army air mattress they work very good

  • One can also use a 12V hot pad and a portable power solution (e.g. Jackery or other), or a second battery setup.
    – Jon Custer
    Commented Jan 23, 2021 at 16:30

One thing to consider, You could use an adhesive thermal insulating liner on the underside of the bed cap, it would be semi-permanent but i don't see it causing any adverse affects if left in place year round.

If the bed liner is one of the one piece plastic liners you could try removing it, adding a layer of Dynamat beneath the liner covering the entire bed and then re-install the plastic liner over the top. This material could be used for the bed and the cap, it is made to dampen sound and insulate the inside of vehicles from heat from the engine bay/firewall but would work equally well at keeping it inside. It comes in various thickness and can be installed yourself pretty easily.

The only down side is if you sleep with the cap on in summer it could get a little toasty.

Here is an image of some installed to give you an idea of its pliable nature.

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