Mylar sheets on top of the roof?

[Kevin Carney]

I'm "this close" to purchasing a Dodge Grand Caravan minivan as a newbie, kind of try things out, vehicle to do some boondocking, and maybe a bit of stealth urban camping. I don't want to mess with the interior, at least not at the beginning, in case I want to trade it in later. So, here's an idea, and I don't know if it's stupid or not. I have several of those cheap mylar "emergency blankets," just sheets of mylar, really. Would there be any advantage when parked in hot sunny weather to laying them on the roof of the van, and holding them down with, say, magnets, as way of diminishing the heat coming into the van through the roof?

 

[Boyntonstu]

With air flowing beneath the sheets, however little (1/2"), you would have it made in the shade!

 

[Trebor English]

Before buying you can rent one for a couple of days.  Your "conversion" has to be simple put it in, take it out.  

If the vehicle has a roof rack the reflective mylar will be separated from the roof by a space.  If a breeze can get between the two it will act like a heat shield.

 

[Kevin Carney]

Maybe I don't understand how this works yet. Since the mylar would be on top of the van, and there are already 93 million miles of space between the surface of the mylar and the source of the radiation, wouldn't the mylar reflect the radiation, rather than transmitting it to the roof surface, even without an air barrier? Or does there need to be air on both sides of the mylar surface? If there needs to be air against both surfaces of the mylar, I suppose a roll of reflectix with the bubble wrap attached would do the trick. Then the problem of securing it needs to be figured out. But it would all still be better than being able to bake potatoes in the air of my living space.

 

[John61CT]

Imagine the micromillimeter layer of Mylar bonded to your steel shell like paint.

Not optimal is it, still lots of radiant heat gain.

But to the extent there is a gap between the Mylar and your steel, that is reduced.

And if that gap has airflow carrying the residual heat away, even better.

It is also helping remove the heat from your vehicle coming from all the other sources.

 

[highdesertranger]

simply put, yes you need an air gap. the Mylar will get hot and transfer that heat to the sheet metal via conduction. highdesertranger

 

[Trebor English]

The catalytic converter gets really hot.  If you park in long grass it is hot enough to light a fire.  The exhaust doesn't start fires because of the heat shield.  There is a thin piece of steel located a half inch away from the hot parts.  Air on both sides keeps the heat shield cool.  Steel is not a good insulator.  The half inch of air keeps the heat shield from getting a lot of heat input and whatever breeze there is keeps the shield cool.  Good insulation could keep the exhaust as hot as possible but we don't really care about that.  The goal is only to keep the grass cool.  The aluminized mylar space blanket over the roof is like that.  The goal is just to shield the roof to keep the roof cool.

 

[rina]

You might want to check this material. Cooltarp
http://cooltarp.com/

 

[Spaceman Spiff]

What color is the roof of your van?

• If roof is shiny white and the mylar sheet is in contact you will see little improvement.  An air gap between roof and mylar will lower the temp of the roof.
• If roof is a dark color and/or flat (non-reflective) the mylar sheet in contact will give about the same temp reduction as a shiny white roof.  Again an air gap will give more improvement.

Not sure about Reflectix, the stuff I have looked at is not opaque; I can see light through it and it gets worse with handling (reflective coating abrades).  If you decide to use it just pop the bubbles in the places you want to put magnets.  IMO the Reflectix won't work as well as a mylar sheet.

 -- Spiff

 

[akrvbob]

I think it would work really well, but I think it will be too fragile. I would use Reflectix myself.

 

[Gideon33w]

You'd be better served by the shade caused by the plywood. But, if you want a good option which will do what you're asking, check my write-up on reflective roof coatings.

 

[CraigL]

The mylar would absorb v little heat, and reflect all infrared. The magnets, however, will be too hot to touch. Its bound to be cooler, for both shade and IR barrier, and cooling via airgap is minimal... But what a no-stealth hassle! The wind, even a little, will find it. Get 70% shadecloth (that withstands most wind) and enjoy the shade.


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[freedomrider]

Aluminized Mylar sheet with an air barrier between the vehicle and the sheeting material.
If you are parked under the sun all surfaces around the vehicle will radiate heat and furthermore the air will convect heat in all directions.  Been noodling this problem on Google today.  Read NASA info about how the International Space Station stays comfortable.

 

[Reducto]

Aluminet is king here, though it is expensive. Burning Man attendees swear by it. It reflects most of the sun but still allows airflow and it's much stronger than a sheet of mylar. It's also great for extending off the side of the van to create a shaded area outside.

If your roof isn't already white, I would do that before messing with coverings.

 

[DannyB1954]

Here in the Southwest, the wind can come up on a moments notice. Even on a nice day we get things called dust devils. Yes the reflective roof will make the vehicle cooler. I did transport refrigeration repair for 30 years. Heat flows through three methods. Conduction, convection and radiation. The Mylar will help with the third one. One disadvantage is people will be able to see you miles away. Just what the heck is that shinny thing anyways?

I built a bed with storage underneath for a Dodge Grand Caravan. It was plywood 13" tall so that milk crates could be used for storage. I fitted it to the contour of the floor. It came out real nice. One could still use the right rear passenger seat. I think the bed was 30" wide, and you could sit on the bed and just barely not hit your head on the roof.

 

[ckelly78z]

I'm not sure you need the mylar or rooftop reflectix, if you have a white tarp. The idea is to have an air gap to allow heat dispersion, and shade the roof. Maybe run a small fan in the air gap on really hot days. I would also make detachable window coverings out of reflectix.

 

[MrNoodly]

I was camped one time in a place where I couldn't face the front of the van away from the sun. I didn't have my vinyl window cover at the time, but I had a 10-pack of the emergency blankets. So I got one out, spritzed the windshield with cleaner, like I was doing the world's crappiest window tint installation, and spread the blanket over the wet glass. Then I used some painter's tape on the corners and a couple of other places to hold it down in case of wind. It didn't do much to cool things down. When I wanted to remove it, it was stuck enough in some places I had to scrape with a razor blade.

 

[HappyLife1977]

I knew id seen these somewhere! And what a price! Not bad! Now if only they made them for moving vans. I think the make them for diff vehicles because I first saw them for smaller cars.

https://www.ebay.com/itm/Universal-...1&pageci=03eb6a70-c87b-4a39-8bd6-a1085a59334f

 

[Cammalu]

That is cool!