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I live in South Florida where the summer sun has no mercy. I drive a new van and I've taken steps to keep the inside cooler during the day. I live in the van for weeks at a time and need to store things in the van. I don't hang out inside the van from 11am to 4pm unless it's parked in the shade or unless the AC is turned on. At night i have a very large and powerful vent fan and have no issues sleeping in the van even in July and August. However, my goal and concern here is with keeping some items in the van when parked in the sun. I can't afford to run my freezer every day. Items include dry good and things like Herbal supplements, Teas, instant coffee and Olive oil. These are not things that are generally very sensitive to some warmth and humidity.. but I want to see what I can do to offer them a safe storage in my van. Here's what I've done so far:

  1. Install a large aluminum and glass solar panel on my roof, this the space directly above the place i store these things and blocks the sun.
  2. Open large vent opening under the solar panel where heat escapes.
  3. Install reflective mirror vinyl where the solar panel does not cover.
  4. Install reflectix insulation a 1/2 inch below the roof metal
  5. Install a sealed plywood ceiling
  6. Placing said items in an insulated bag
  7. Placing the insulated bag in a highly insulated and sealed Freezer (that is usually off)

These updates make a huge difference, but still the inside of a metal van who's exterior can get so hot you can fry an egg so it's not like the cabinets inside my insulated, air conditioned Cinder Block and Wood house were it's always below 80F.

So I am wondering...

I need to test and confirm this with a thermostat , but any idea how hot it might get inside that insulated bag/freezer in a van set up as described parked in the Florida sun?

Does it sound like these items are going to go bad or worse be dangerous for consumption if stored as describe .. I mean, tea and herbs are dry leaves and roots.. what if the temp inside the bag is 90 F degrees? is it even possible it could be 90F inside that bag?

closed as off-topic by isherwood, Machavity, JPhi1618, ThreePhaseEel, Daniel Griscom Aug 21 at 11:52

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  • "Questions seeking product or service recommendations are off-topic because they tend to become obsolete quickly. Instead, describe your situation and the specific problem you're trying to solve." – isherwood, Machavity, JPhi1618, Daniel Griscom
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I'm going to treat this question as "how do I keep my home cool when it's a tiny home (often vehicles) and solar gain is my enemy"? Because that would be on-topic here.

Solar gain is your enemy

And to be clear, it is an order of magnitude worse than any other source of heat, even ambient temperature.

From the sun's perspective, it casts 100 watts on every square foot - from its perspective - and that includes the top and sides of your van. This is then reduced by your vehicle's albedo, or its reflectivity. Black vehicles have low albedo, and a pure white can have as high as 92%. Also some of the surface heating transfers to the air near the skin of your van, But with 100 w/sf, there's plenty left to heat up your van. Windows absorb almost all of it, and cause the sun to heat up things in the interior of your van, where the heat can't leave.

Get it in the shade

Top of the list is place your vehicle in shade. What am I saying? Top of the list is get out of Florida... Mark Twain once said "the coldest winter I ever spent was a summer in San Francisco" and he's referring to the coast effect. Santa Cruz, Eureka, Portland, Seattle... Seattle still has to deal with solar gain, but only 3 days a year ;) But I digress....

In shade... I'm saying that there's a huge difference between attaching something to the surface of your vehicle and stood off above your vehicle. The difference is airflow beneath it that carries the heat away, which is what makes it shade instead of attempted insulation. Solar panels are a great plan, but you need to stand them off significantly. That will reduce your high speed fuel economy somewhat, because you are also increasing the aerodynamic "wetted area".

You might also consider deployable shades or solar panels on the sunny side - I assume you can select which side of the street to be on. Again don't forget the objective is shade and to create easy rising airflow for the hot air the shades collect, so a series of angled surfaces with gaps between them is just fine. Figure out the sun's angle etc.

Increase albedo

After your shading options are exhausted, you want to make sure everything is lily white, and have the albedo/reflectivity conversation with your coating supplier.

Windows have basically 0 albedo, so you really need to address those - the best option is place them in shade.

Insulate like crazy

Metal is a good conductor of heat, so the car's body will carry heat some distance beyond the area actually in sunlight. Also, even shaded areas are subject to ambient air temperature.

Of course you don't have 24" to give up for a deep layer of fiberglass batt, so you need to go for the most efficient insulation you can obtain, and you need as much as you can possibly have.

Storing temperature-sensitive dry goods

As for storing dry goods, once you've done your best to make your space temperate, your best bet is to put it in some sort of heavily insulated box. We'd also put as much "thermal mass" in there as possible. The best thermal mass known is water (coincidentally). So freeze-friendly water-based things, like commercial ice packs, are a good choice for "thermal mass".

As a bonus, water also has a phase transition (freezing/thawing) at a semi-convenient temperature, and that gives it a huge amount of additional thermal mass if you're willing to cross the zero degree C line, however if you do that, you have to worry about condensation/sweating on your dry goods.

In a perfect world, your well-insulated box would have a small Freon-cycle machine to chill the box furth-- wait a minute. Did you say you have a freezer and you just don't run it? Run it! You have a solar panel for Pete's sake, I bet that panel is "dumping" lots of excess energy you can't store. Use it for this.

If you don't run your freezer much because you have to run your van's engine to power it, then your solar system needs a lot of work. Let's have a conversation about that.

  • "From the sun's perspective, it casts 100 watts on every square foot - from its perspective - and that includes the top and sides of your van." To be clear, the watts per area is a function of the angle of incidence. It's not 100 watts per sq ft of surface area of the van. – JimmyJames Aug 21 at 17:26
  • I think the part about the box is the key here. I'm not sure a freezer is even needed. I wonder if a good cooler, left closed and out of the sun would be good enough to keep dry goods in a safe temperature range. As long as the van isn't tightly closed, maybe. – JimmyJames Aug 21 at 17:33
  • @JimmyJames yes, I mention "from the sun's perspective" twice. I agree sufficient thermal mass could make up for a freon engine, but since he's already got one, and the solar panels too, he just needs the bits to get them to work together. – Harper Aug 21 at 18:04
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    Re sun: I figured that's what you meant but I thought it was a little unclear. I think the OP should get an decent used cooler and a basic remote thermometer. Put the sensor in the sealed cooler. Reset the min/max memory and tape the reader to the underside of the van or something. Leave in a worst case scenario parking spot through the hottest part of the day. Then check the max temp. I doubt ice or anything is needed. It just needs to keep things at room temp. – JimmyJames Aug 21 at 18:18
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I would not worry about tea and herbs going bad but loosing thier flavor or strength. We seal our tea , coffee, cocoa in canning jars in our motor home we don’t run the AC unless we are in it, I would look up solar car window fan. My uncle Lived in Mojave and he had those in his cars the fan kept the inside of the vehicle cool with the unit in the window. (The unit rolls up and is locked in place with the window the opening was secure) this may be the way to go. He started doing this after some papers on his dash caught fire. The fans only last a few years but they were not very expensive.

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