Cool the inside of a caravan without an AC?

**Danie Odendaal** · Yesterday, 11:42 AM

Some technical clarification on evaporative coolers for caravans that may help with commends in this thread - in principle! The evaporation of moisture in the air supply result in lowering the temperature of the supply air, potentially down to the web bulb temperature of the air. The wet bulb in dry conditions is significantly lower than the dry bulb. It is quite common for the wet bulb to be between 17 ͦC and 23 ͦC in dry months (September / October in Botswana), and the cooler can achieve this if 100% effective. The technology is therefore good for off grid camping, but the devil is in the detail – A caravan/ tent absorbs a huge amount of heat which must be removed, especially during the day and in full or partial sun. To key issues

Considering several factors, the cooling efficiency of the unity must be high to get as close as possible to wet bulb temperature. Industrial coolers are designed to achieve this.
The volume of air must be high, and the fresh air must “replace” the air in the caravan. You need around at 25 to 50 air replacements per hour (that is a lot) for caravans depending on the design of the caravan and the position of the son. To achieve this, the caravan or tent ventilation openings must be open. To push the heated air our with the fresh air supply. (Note that the air supply is cool but high in humidity and absorb the heat inside the “box”. If not ventilated at a high replacement rate it will become hot humid which is not good)

So, this is a workable solution. The technology is proven and used in most buildings we visit every day. It has also been proven for camping vehicles but is not common on shelves to buy. This is an option to consider depending on your camping preferences.
Let’s talk about this.

Danie

**Pieter de Waal** · Yesterday, 11:50 AM

This is actually much more technical than we think and if we do not manage all the factors we will only get half the results.
Let us start with the big tree. I work from home and often in the garage. I have massive trees around the house. My garage with a flat concrete roof is in the shade 95% of the time. With the hot spell we currently have I yesterday measured 26 degrees in the garage. The doors and windows were closed all day. (I will normally ventilate after 6pm) Slipping out to pick up something at about 14.30, the outside temp was 33,5 degrees. Both measured with the car temp reading. If I can reach that difference in a caravan I will be very happy. This proves it is possible without air conditioning.
I grew up on a farm close to Botswana. No electricity, no aircons, no fans no isolation and a corrugated iron roof. (No big trees even.) Before 7 in the morning all windows and doors were closed. Heavy curtains were drawn. After 7 in the evening, everything was opened up. That house used to be heaven with 40 plus degrees outside.

Try and copy as much as possible to your caravan and be surprised.
The small things that will all help:
Find the biggest tree and it must have dense foilage. Park on the south side and slightly to the west. Be in shade from 8 to 3++ ?? Being in a cluster of trees will keep the surrounding ambient lower.
Add isolation to all six sides. Spx closed cell rubber from Sondor is magic. It has the same heat transfer rate as polystirene. I use 6mm. Cheap, weighs almost nothing and easy to work with.
Reflective film on the windows. Note dark is not cool. Ask for the specs and see for yourself the amount of light it will let through. The more reflective the better. It becomes a mirror, you can comb your hair in it.
Fit block out curtains that covers the whole window and frame. Get them close to the body of the caravan to stop ventilation and sort of seal the pocket of hot air in. Vulcro works quite well.
Close the doors and windows by 7 in the morning and keep it closed till 7 at night.
Vent your fridge/freezer properly to the outside. Do not cook inside.
Get a decent fan for inside and even outside. Enhance the efficiency of your own body cooling system. Let it blow directly on you. Wet towel around your neck and a mist spray bottle also works wonders.
Awnings and a false roof can help but only if you have unobstructed ventilation all round. The roof tend to form a pocket of hot air in the top and that destroys all the advantages if there is not at least a slight breeze.

Only after doing as much of the above as you can manage:
Fit the biggest mother of an aircon that you can afford or find the space for. (Not sure about this but keep it below 2 kw as the circuit breakers in camp will trip if you go higher.) Buy one that has a reverse cycle for winter.

If you have to braai, do it closer to the neigbour than to your own caravan.

If you use a tent like me, ventilate, ventilate, ventilate, go for the tree and live with the consequences.

If you are unclear about anything, you are welcome to talk to me.

Drink lots of water

**PRA** · Yesterday, 03:09 PM

Some great additional information here.

**johannes f** · Today, 10:37 AM

Originally Posted by Danie Odendaal

Some technical clarification on evaporative coolers for caravans that may help with commends in this thread - in principle! The evaporation of moisture in the air supply result in lowering the temperature of the supply air, potentially down to the web bulb temperature of the air. The wet bulb in dry conditions is significantly lower than the dry bulb. It is quite common for the wet bulb to be between 17 ͦC and 23 ͦC in dry months (September / October in Botswana), and the cooler can achieve this if 100% effective. The technology is therefore good for off grid camping, but the devil is in the detail – A caravan/ tent absorbs a huge amount of heat which must be removed, especially during the day and in full or partial sun. To key issues

Considering several factors, the cooling efficiency of the unity must be high to get as close as possible to wet bulb temperature. Industrial coolers are designed to achieve this.
The volume of air must be high, and the fresh air must “replace” the air in the caravan. You need around at 25 to 50 air replacements per hour (that is a lot) for caravans depending on the design of the caravan and the position of the son. To achieve this, the caravan or tent ventilation openings must be open. To push the heated air our with the fresh air supply. (Note that the air supply is cool but high in humidity and absorb the heat inside the “box”. If not ventilated at a high replacement rate it will become hot humid which is not good)

So, this is a workable solution. The technology is proven and used in most buildings we visit every day. It has also been proven for camping vehicles but is not common on shelves to buy. This is an option to consider depending on your camping preferences.
Let’s talk about this.

Danie

At last some sanity......

**Pieter de Waal** · Today, 04:18 PM

I see there is interest in evaporative coolers. I can agree that one must have a look at the option. For one it is a lot cheaper than a compressor system. Secondly, if you look at the practicalities there is a place for it.
The biggest issue is the principal of operation. In our hot and humid applications there are serious limitations. In dry low humidity conditions it works quite well. (Northern Cape) In Kruger during the wet months it can still do the trick if you understand these limitations.

When you use it in a closed caravan it will be rather disappointing as it will build up humidity from a fairly high point to a decidedly uncomfortable point and then become rather ineffective. (See the post above with wet and dry bulb temperatures.)

If you change its position where it can suck air in through a window (Preferably with a sort of duct so you can limit the air entering to fresh outside air. It can be a couple of towels supported into a sort of duct shape.) Then it will use the ambient air with whatever humidity and drop the temperature by adding humidity. You then open windows or the door on the other side of the caravan and vent the higher humidity air out. This will take ambient air, drop the temperature, push that through the caravan taking away heat out of the caravan on the other side. The outlet temperature directly after the cooler will be the lowest temperature your caravan can reach. This will be substantially lower than you will get from a closed up caravan.

You can also use it outside by setting up your chairs right in front of the unit. You wiil not be able to change the ambient at all but that cooler stream of air should make a huge difference to your comfort level.