How hot will it get inside my van?

[Matt71]

Ok, here's my insulation plan for my van
Walls: 1" Polysi Foam insulation
Ceiling: 2" Foam insulation
Air Circulation: Fantastic-Vent 2250

Trying to decide if I really need air conditioning, but I have no idea how hot I can expect it to get in the can at a given outdoor temperature. For some reason I'm thinking 20 degrees hotter in the van without the fantastic-vent, but I have no idea how much the fan will mitigate that.

Here are the average high temps for the places we will be staying on our trip and how long we'll be in that temperature

28 degrees - 1 day
47 degrees - 1 day
52 degrees - 1 day
61 degrees - 6 days
63 degrees - 8 Days
64 degrees - 7 Days
65 degrees - 14 days
66 degrees - 2 Days
67 degrees - 2 Days
68 degrees - 12 days
69 degrees - 11 days
70 degrees - 27 Days
71 degrees - 15 Days
72 degrees - 38 Days
73 degrees - 22 Days
74 degrees - 35 Days
75 degrees - 61 Days
76 degrees - 2 Days
77 degrees - 20 Days
78 degrees - 20 Days
79 degrees - 9 Days
81 degrees - 11 Days
82 degrees - 16 Days
83 degrees - 1 Day
84 degrees - 10 Days
85 degrees - 3 Days
86 degrees - 7 Days
87 degrees - 4 Days
89 degrees - 2 Days
90 degrees - 1 Day

I'm sure humidity factors in somewhere, but that aside, do you think we'll be in the hotter temps long enough to warrant an air conditioner?

 

[minimotos95]

I think elevation also plays a significant role as the suns radiation increases 4% with every 1000ft gained.

 

[Matt71]

Ok, for now let's calculate for sea level and I can add the 4% per 1000' later

 

[SoulRaven]

I've seen temperature changes upwards of 50° in the sunlight.

When I had a heavily insulated cargo van, by mid afternoon the indoor temperature would be in the 140° to 180° range, and wouldn't cool off to comfortable until just about sunrise. Even with the doors open didn't seem to help, it was like the insulation trapped the heat and continued to radiate it for many hours.

In my humble opinion, if you're traveling in weather that is going to be uncomfortable, insulation or not, I'd have both heat and air conditioning available. You just can't trust Mother Nature, and where you're planning on 80° weather, could turn into 120° weather. Being prepared is a better choice than being miserable.

 

[GrantRobertson]

Here are the average high temps for the places we will be staying on our trip and how long we'll be in that temperature

Matt,

While I am amazed at the level of detailed research you must have done to get those numbers I have to tell you that there are still at least a dozen other factors that are going to affect whether you feel a need for air conditioning, including:

Are the temperatures you listed annual averages or the average for the time of year you plan to be there?

What is the expected humidity?

Will you have something over your roof most of the time. With all the solar you are planning on, I'm guessing yes.

Will you be parking in the shade?

Will you be parking next to trees or plantings that cool off the air? Some kinds of trees and plants transpire a lot more than others. That means they evaporate a lot more water from their leaves. This cools the air significantly. Riding my motorcycle around (when I had one) I have noticed as much as a ten degree drop when riding past well watered groves of water-hungry trees. Drought-tolerant and coniferous trees don't do this nearly as much.

Will your van be actively ventilated all day?

How cool does the area get at night and are you willing to allow the interior of your van to cool off down to the coldest temperature in order to dissipate as much of the stored heat as possible?

How much equipment do you plan to run inside the van? Is there a way you can sink some of their heat outside the van? For instance, mount your inverter and battery charger directly to the floor with no insulation between them and the floor, thus allowing them to radiate their excess heat out through the bottom of the van. (Yes, in the winter, you are going to wish you had that heat, so you gotta balance all the considerations.)

Do you and your wife radiate a lot of heat. Some people seem to be furnaces, whereas others seem to be cool to the touch most of the time.

You seem to be planning to haul a lot of heavy stuff. This will act as a heat sink. Once it heats up in the day time, it will take a long time to cool off unless you have cool air blowing directly over all that mass.

Finally, do you ever sleep? This research must take forever.

My advice is to leave room for an air conditioner in both your van and your budget. Then, if you decide you need it you can pick one up along the way.

 

[jimindenver]

The whole concept to solar oven cooking is a dark sealed box heated by the sun. We had one green van that got so hot inside that we would open all of the doors and wait a few minutes just to let the heat out before we got in. It was nice on those cold early mornings when the sun would warm the van up but we spent the rest of the day outside. Even the roof of a white van just radiates heat down on a sunny summer day.

Now if your figures are averages, watch out. Average where we go is 75 at best, records are in the 90's. By then our trailer heats up like a oven without fans or AC and it is white and insulated. That's why I designed our solar around the ability to run a AC. Normally we can get by with a third of the total watts without that big load.

 

[Matt71]

Grant,
The temps are averages for the month we will be there and are for the closest city. Some of the smaller towns don't have weather stations, so a few times i had to get temps for a few miles away.

I can get the relative humidity from the same place i got the temps, but it might take a while to compile everything.

The roof will be covered with solar panels, probably mounted on plywood.

The amount of shade will vary. The times when we'll be above 80 are kind of spread out. Some days will be in Sequoia National Forest, Arches National Park, Mesa Verde National Park, Denver and the Black Hills

Where we park wil depend on if we're on shore power or not. If we're relying on solar we won't be in shade, but then again we won't have the juice to run the AC anyway if that's the case. Unless we go back to bringing a generator.

We'll probably run the fan all day. The model we plan on using can sense the temp inside the van and adjusts it's speed accordingly.

The areas that are above 80 all get down to about 50 to 55 degrees.

I do plan to vent the area around the power station. Was doing it for the batteries, but venting some of the heat from the inverter sounds like an added befit.

I don't think we radiate much heat. My wife is cold most of the time which is one reason we're following the warmer weather.

I do sleep about 6 hours a day. The research does take a long time, but I like it. It's the first thing I look at every day.

 

[Matt71]

One thing to keep in mind is that the van will have its own AC that might cool things down a bit when we are driving as long as we keep the access to the back open. We'll be driving quite often, but not for extended periods.

Has anyone ever trie putting reflectix on their roof?

Oh and we're 90% certain we'll have a white van

 

[jimindenver]

A word of warning about Denver. I don't care what the average is at any time of year, our summer highs are mid 90's into the 100s. Even now at mid winter we are having record setting highs in the 70's while the average is 44. This is why we go to 10,000 ft to camp, when it's in the 90's up there, it is 105 in Denver. The only time we camped at lower elevations in a heat wave we had hook ups thankfully. I had to drop the awning down as far as possible to keep the sun off the trailer at 6 am.

 

[LeeRevell]

You can take a page from Bob's excellent work on van living, and have a white plywood stand-off panel above the roof. Safari vehicles in sunny equatorial Africa use this technique too - keeps direct sun off the vehicle's roof. Makes a convenient way to mount you PV panels too.

 

[rvwandering]

Good cross ventilation is one of the most important factors for keeping a vehicle cool. Since stealth is not a factor that you have to consider is there a way to add some windows into your plan? Our 25' class C never gets above outside air temperature inside unless we have all of the windows closed. Even then we can quickly bring the temperature down by opening the windows and running the fan for awhile. If we're parked in the sun it feels much cooler inside than it feels outside. Since we mostly dry camp we've never had an air conditioner.

There are usually a few days every year that we're uncomfortable because the temperature is in the 90s and the humidity is high. When it's really hot and we can't find any shade we park with the rear to the south and put reflectix in any windows that are in the sun. Parking so that a breeze blows through helps. Parking by a body of water can drop the temperature too.

 

[akrvbob]

I think those numbers are skewed very low. Having looked at your intenerary I think you are going to be in for a much hotter time than those numbers imply.

The best you can ever hope for with passive cooling is to keep the temperature inside the same as outside. That isn't very hard to do. Passive cooling is parking with the most doors and windows that will open to the north and cover the south wall with shade cloth and the roof with plywood. Have all the windows and fans on. That should keep the temperature the same inside as outside.

Of course if you are in the woods you can park in the shade but there goes your solar. I'll try to post some photos of how shade cloth works for me. I'm in the AZ desert now and it;s in the mid to high 80s every day and the inside of my trailer is the same as the outside temps.
Bob

 

[Ken in Anaheim]

Just a reality check....and I mean ABSOLUTELY no dis-respect...but, you can't take a comfy-air-conditioned-family-room-at HOME environment with you. If that's what is needed ,you can get it AT HOME. But consider...have you ever been un-comfortable AT HOME ? Of course you have. It's an inherent part of being alive. Don't be afraid of what you may (or probably NOT) have to confront in the "real world" as opposed to the place you're inventing in your imagination.
Again, no disrespect. We all go thru the initial period (fear) of trying to plan for ALL contingencies. Then ya realize you've never been successful at that at home or anywhere else....and still survived.
Step forward boldly, fearlessly and you'll experience........LIFE.
KinA

 

[Matt71]

I'm not concerned about being uncomfortable, I'm worried about being cooked, more specifically I'm worried about our cat being cooked if we decide to bringer her with us.

 

[GrantRobertson]

Just thought I would throw in this little tip:

Japanese professor's trick for quickly pumping all the hot air out of your car.

I have tried it on a car and it works like a charm. If you stand by the open window while someone is pumping the other door, you can feel the huge gusts of hot air blasting out of the window.

Now, for a van, I would open the back door a crack (perhaps even blocking it slightly open with something) then use one of the front doors to open and close. You would also likely need to do it about 10 or 15 times instead of just 5, simply because there is a lot more air in a van. If you had two people, you could work both front doors, either in unison or alternating, to get the hot air pumped out even faster. 

 

[Bdog1]

I think your van would be comfortable at 80 in the sun, ( with ventilation) and to the mid 80's in the shade. Humidity over 80% is gonna decrease these numbers. Cats however seem to enjoy it warmer than us.

 

[Matt71]

Well, I broke down and figured out the relative humidity and elevation of everywhere we'll be staying. If anyone thinks they can crunch some numbers with that or if you guys just want to laugh at how crazy I am, I can post them

 

[SoulRaven]

Well, I broke down and figured out the relative humidity and elevation of everywhere we'll be staying. If anyone thinks they can crunch some numbers with that or if you guys just want to laugh at how crazy I am, I can post them

The problem is that even the highly skilled weather men/women get it wrong half the time.  Mother Nature is fickle.  You just have to be prepared for ANYTHING!

 

[Matt71]

I don't need anyone to predict the weather. I need someone to do the physics. If it's 80 degrees outside with 70% humidity and I have a white van with solar panels shading the roof, reflectix in the windows and a fantasticvent on high all day, how hot is it likely to get inside? 10 degrees hotter than outside? 20? more?

 

[Almost There]

I'm not concerned about being uncomfortable, I'm worried about being cooked, more specifically I'm worried about our cat being cooked if we decide to bringer her with us.

All of this math/physics/weather calculation is all about the cat?

Simple answer, on at least a few of the days it will get uncomfortably hot inside the closed van no matter what color it is, no matter the reflectix in the windows, no matter the fan left on.

On those days, leaving the cat locked in the van while you do sightseeing on a schedule that is planned to the half day or better is just plain asking for trouble. People who travel with their pets learn to accommodate the needs of the pet above and beyond everything else in their world. Laundry, groceries, sightseeing, everything depends on the weather and how it would affect their pet....schedule be damned.

Keep in mind that in a lot of states it is against the law to leave an animal unattended inside a closed vehicle. The animal doesn't have to be in distress to warrant a charge being laid.