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I'm not homeless, I'm just frugal and trying to drive a lot less.. maybe I'm adventurous. :) Anyways, I've been working , eating and sleeping out of my new Black van. The van is brutally hot during the day even in the so called South Florida winter. It's okay though, cause I drive w the windows open and I don't really spend much time in the van during the day if not driving and when I do it's parked at the beach under a tree (NICE). Anyways, I'm not sure if it's just me or what, but at night the bare black metal that had cooked during the day van, is much colder than my prior highly insulated SUV. Like right now (10pm) it's 73 degrees out side but inside the van the bare metal feels cold.. I'm not complaining at all - I don't mind it. A few nights ago it was just flat out freezing in the van at midnight and just 6 hours earlier you could fry an egg on the roof.

I am wondering, will insulation make my van hotter at night in the summer? I'm not worried about cold as the van will never travel north of Florida in the winter.

Is it my imagination that maybe the van getting super hot during the day and maybe something like Radiative cooling might be making my van cooler at night than if it had not gotten so hot?

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Adding insulation will have two effects: 1) it will make the interior of the van heat up less during the day, and 2) it will also cool off less at night.

Because it is difficult to get as much thermal insulation into the walls of a vehicle as you'd typically have in the walls of a house, this thermal fluctuation issue is present in not just vans but also motor homes and trailers. Useful measures have been devised to help minimize it: the easiest is to install a solar-powered battery that powers a small ventilation fan that you can run anytime it's hotter inside the van than outside. The battery has enough juice to run the fan through most of the night, and it will not run down the main battery in your van. You can learn about stuff like this by talking to a motorhome repair tech or searching on the interwebs.

Another worthwhile thing that's easy to do is to paint the roof of the van white. This will reflect away a lot of the energy hitting the roof during the hottest part of the day and also impair the roof's ability to radiate heat away at night.

If your van has windows, there is a light-colored plastic film full of little holes that you can apply to the outside of the windows to cut down on the amount of light getting into the van through the windows. This film impairs your view a bit but also makes it harder to see into the van from the outside, improving your privacy.

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  • $\begingroup$ Can we conclusively say a van w/o insulation or air conditioning, just vents/fans will be cooler at night? $\endgroup$
    – Hell.Bent
    Commented Feb 4, 2019 at 13:27
  • $\begingroup$ yes, but a small fan will take a long time to exhaust the heat stored in the van. Wiser to keep it out in the first place IMHO. $\endgroup$
    – niels nielsen
    Commented Feb 4, 2019 at 19:17
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Is it my imagination that maybe the van getting super hot during the day and maybe something like Radiative cooling might be making my van cooler at night than if it had not gotten so hot?

Keep in mind that your body is a horrible thermometer.$^*$ Metal conducts heat very well, so the metal is the same temperature as your surroundings, but it feels colder because it can take your heat away faster than other things you would touch (like a fabric seat).

So yes, this part is your "imagination". The van is going to reach thermal equilibrium with the outside air at night. It won't get "more or less colder" based on how hot it got during the day. To suggest otherwise would break the second law of thermodynamics (i.e. the van can't radiate heat away and become colder than its surroundings).

$^*$https://youtu.be/vqDbMEdLiCs

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  • $\begingroup$ Thanks. I was actually thinking of painting the roof with reflective paint and will eventually have two flexible solar panels take up a big chunk of the roof. But saw articles about radiative cooling where heat produces even ice . Also new paints and films that have pores to emit heat. I don't know anything about the science, but wondered if any creative way to harvest all this daytime heat/energy into night cooling... i2.wp.com/misfitsarchitecture.com/wp-content/uploads/2013/02/… $\endgroup$
    – Hell.Bent
    Commented Feb 4, 2019 at 13:36
  • $\begingroup$ @Hell.Bent Questions like that might be better on Engineering $\endgroup$
    – BioPhysicist
    Commented Feb 4, 2019 at 15:24

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