Too hot? How about misting the roof?

[75Bob]

Last year we were in Texas and it was 107 degrees. After a few minutes on High we then turned the ONE A/C unit down to Low the rest of the time we were there. They really don't make them as well as they used to.

[Gene]

The problem is you have an RV with poor insulation and many thermal transfer situations. Two inches (optimum) fiberglass is not much insulation and years of movement plus any
leaks probably have caused clumping of the fiberglass into useless balls and areas with no insulation. The numerous windows and vents cause quick temperature transfer and metal connections between the exterior and interior cause more transfer. Everything in the RV has been storing up heat all day when traveling. This is an uphill fight.

So do the little things that can help unless you want to do a rebuild with modern insulation:

1. Buy some Reflectix. It has aluminum foil on each side with a thin insulating barrier inside. It does make a difference on fans and skylights and windows. It also keeps the bedroom dark at night. Install with Velcro. Stores like Lowe’s sell rolls of it cheaper than RV stores.
2. Clean AC filters regularly.
3. Put out awnings and park with awnings facing the afternoon sun.
4. Put down blinds on sunny side.
5. When arriving at campsite, we put the thermostat down to 55 or 60. It seems to cool faster though I cannot explain it logically. But if it fools us into thinking it is cooler, fine. When the temp. gets down to where you want it, adjust the thermostat.
6. Water will draw off heat from a metal or other surface and a mist on the skin can help and an in-line filter may clean up the water. There are expensive filters sold that remove everything and deionize the water to eliminate water spots and other mineralization. What filter you use makes a difference.
7. Drive uphill. Every thousand feet of elevation decreases temps 3 degrees—sometimes more, sometimes less. Camp in the mountains in summer.
8. Get up earlier when traveling and stop earlier before heat build up gets worse. In a MH the vehicle A/C may not be enough, but running it with vents closed will keep temps lower inside. With a trailer get vent covers for the fans and run the fans while travailing. Have one for exhaust and one for intake.

I remember pulling into a campground in Utah when the temp was 106. i asked for a site with the awning facing west, cranked up the A/C and got it down to 80 or so fairly quickly, but lower took time and sunset. People say an A/C will lower temps 20 degrees, but that is not always the case.

The last resort is to sell the Airstream and get an RV with better insulation. Our Nash is a four season trailer and much easier to heat and cool than our Airstream was. Saves on propane and electric and makes the interior much more comfortable plus much less wear on the HVAC systems. One way we are not as cool, but we are cool.

[fricassee1]

I just painted my roof using Trope-Cool. I picked a gallon of it up at Home Depot. It cooled my 27ft inside by a few degrees. I'm living full time in SW Louisiana and at the moment it's 94 at 9:30 PM. A few degrees may not seem like much but Tropi-Cool made a considerable difference inside. In addition to reflecting back the heat from the roof Trope-Cool is a silicone based paint which when applied to the roof forms a silicone seal. The paint nicely covered all my riveted seams and added a waterproof barrier to them. I've only painted the roof and not the end caps so the paint cant be seen from the ground.

Other things that I do, I cook everything outside and never turn off the A.C.. Once the A.C. is turned off, even for a short period, it can never catch up and overcome the heat. The electric setup at my campground is a 30 amp and 20 amp service, one 30 amp plug and one 20 amp. My Airstream is on the 30 amp and I've run an extension cord (#12 wire size) to the 20 amp outlet so I can use things like my induction cooking top or toaster oven and not blow the circuit breaker in my camper.

[rlphillips00]

I had to replace a two year old Dometic after the condenser quit but the fan kept blowing. I keep a temperature gun around just to make sure I know what’s coming out the vents in hot weather. Those little Dometics seem to be under designed for what people want or need them for. I don’t want to run holes and put spray foam insulation everywhere either, but it would help!

[ltcajh]

In the desert, to fend off heat, the Army has a canvas tarp above the tents. The tarp gets the heat, not the tent. Looks odd, but it works. Is there anything on the market that mimics this other than a carport?

I use an 80% (or so) horticultural net over an outdoor work area. The reinforced plastic tarp was frequently destroyed by wind, but the holes in the net have never caused a wind issue. Think, think.. is there a way to make a setup to cover the camper?

[Gene]

Originally Posted by ltcajh

In the desert, to fend off heat, the Army has a canvas tarp above the tents. The tarp gets the heat, not the tent. Looks odd, but it works. Is there anything on the market that mimics this other than a carport?

I use an 80% (or so) horticultural net over an outdoor work area. The reinforced plastic tarp was frequently destroyed by wind, but the holes in the net have never caused a wind issue. Think, think.. is there a way to make a setup to cover the camper?

With lots of money and servants, you can do anything. Long collapsible poles, reflective netting, guy wires to keep the contraption from falling over, payment to the campground to get permission to erect the cover, that would work. Maybe poles that fit into the sides of the trailer could be used instead.

There is reflective white paint that helps. I have a neighbor who has a Camry with it. The silicone paint referred to above may be the same thing. We have been warned many times not to use silicone sealant on Airstreams because it doesn't seal well on them, so silicone paint may not work well for that purpose.

[ITSNO60]

Originally Posted by ltcajh

In the desert, to fend off heat, the Army has a canvas tarp above the tents. The tarp gets the heat, not the tent. Looks odd, but it works. Is there anything on the market that mimics this other than a carport?

I use an 80% (or so) horticultural net over an outdoor work area. The reinforced plastic tarp was frequently destroyed by wind, but the holes in the net have never caused a wind issue. Think, think.. is there a way to make a setup to cover the camper?

Theres this: https://www.shaderv.com/

[rmatkovich]

Originally Posted by WayneG

Just thought I would throw this out there after the recent heat wave.


My single AC unit is not powerful enough to battle direct sun in the 90's on a 27' motorhome. The indoor temp was 100 when I turned on the AC and I can only get down to about 90 deg. after 2 hours. (Yes I know 2 AC units are better than one, but I only have room for one.


I have a 16' misting setup I use for the kids (young & old) to cool of at events I go to. I run it off the rv water supply through a filter and it works nice with very low water usage.

I wonder what would happen if I suspend the misting tubing a few feet above the RV roof, from end to end?
Would it have enough evaporative power on the skin and around the AC condenser to reduce the inside temperature more than the 10 degrees I get now?

Insert opinion here:

I have a 34' and the air does fine as long as I close off the hall to the bath and the bed room door. After the sun goes down we open everything up to cool for sleeping. We leave the air on low all night and all is well.
Jim:

[WayneG]

At 27' they did not provide for separations in the floor plan and with one bed forward and one rear, someone would get the cool and the other the heat.
This weeks camping is moderate heat, mid 80's but the humidity will be high, the AC should do OK on its own, if I keep it running.

I think my whole roof misting attempt was a bust. Resources & effort vs results was not worth it.
I am looking into one more misting method for the AC unit heat exchanger. If I install a few nozzles around the fan shroud, it may be enough to boost the AC output.
I need to wait until my knee allows me to climb ladders again, but I have the parts to do it.

[Mattirs]

Originally Posted by WayneG

At 27' they did not provide for separations in the floor plan and with one bed forward and one rear, someone would get the cool and the other the heat.
This weeks camping is moderate heat, mid 80's but the humidity will be high, the AC should do OK on its own, if I keep it running.

I think my whole roof misting attempt was a bust. Resources & effort vs results was not worth it.
I am looking into one more misting method for the AC unit heat exchanger. If I install a few nozzles around the fan shroud, it may be enough to boost the AC output.
I need to wait until my knee allows me to climb ladders again, but I have the parts to do it.

With misting the condenser, would't mineral build up on the coils?

Matti
I

[WayneG]

I use a cartridge before the nozzles to reduce minerals clogging the nozzles, that should help with the AC fins also. I also figure the duration the misting is turned on will be minimal, just when the AC cant hold its own

[ITSNO60]

Originally Posted by WayneG

I use a cartridge before the nozzles to reduce minerals clogging the nozzles, that should help with the AC fins also. I also figure the duration the misting is turned on will be minimal, just when the AC cant hold its own

Bringing this thread back to the top as we were camped in Deseret Center last Sunday overnight on our way to the coast and the temperature reached 115-118F depending on who you asked. Our rooftop AC quit on what I surmise was the compressor overload opening due to high head pressure. Meanwhile it got to 96F inside before I finally thought to climb a ladder and spray down the condenser, I could only get to 2 sides but it helped immensely, the compressor stayed running but I would have to climb the ladder every 5 min. We saw the amps drop between 3 & 4 when I'd wet it down then creep back up when I stopped. I got out 2 hoses and I had 2 sprayers which I rigged to put out a steady mist and secured the hoses to various roof structures to keep water going on 2 parts of the condenser. It used a lot more water than a real mister would have used but it's all I had and this was an emergency, (plus water happens to be plentiful at Desert Center due to nearby Lake Tamarisk)

It was a success and within 2 hours the interior was down to 76F which was 39 degrees cooler than the outside! Around 11:00 PM when the temperature outside had dropped to 106F I turned off the water and the AC kept up the rest of the night.

Which got me thinking I will build a mister to carry just for such an emergency. There is a commercially available one with a fan switch https://coolnsave.com/ but I had more in mind just a small one with 3 misting heads and a cartridge that I could install in an emergency with zip ties. It's usage would be so infrequent that I am not concerned about scale buildup.

So I brought the thread back to see what others have built one with. I'm thinking just the small flexible kits from Home Depot like you put on a shade umbrella.