Zennie needs to chill! Painting the roof to keep it cool

Zennie has a metal roof, and boy, does it get hot up there! 😮 On those sunny days in the desert when it’s over 100 degrees Fahrenheit outside, the roof is so hot you can’t touch it without burning yourself. I’m not sure exactly how hot that is, but I’ve felt it too many times!

This heat is a problem, and I’d read that painting your RV roof can make a real difference. So I decided to cool Zennie off a bit by painting the roof with white elastomeric roof paint. Here’s the scoop…

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Why worry about the hot roof?

1. 1. It heats up the inside of the motorhome. If you’re traveling in an RV in hot climates, then keeping it as naturally cool as possible is important. If you’re running an air conditioner, then it will use less power if you’re not absorbing a ton of solar heat through your roof.
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      In my case, I took the AC unit off Zennie because (a) I’m never plugged in, I always boondock, (b) I hate running a generator, and (c) I want to save the weight of both the AC unit and the generator. With no AC, it’s even more important to do what I can to keep it cool. Painting your RV roof white is supposed to reduce the inside temperature by several degrees, and every little bit helps! 🙂

1. 1. I suspect it damaged my solar panels. I installed flexible solar panels directly on Zennie’s roof. This seemed like a great solution – lightweight and low profile. However, when they were sitting in the sun during a big Tucson heat wave, my solar panels stopped working – first one, then a couple of weeks later the other.
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      Now this could be a coincidence, but I suspect that the superheated roof caused some damage to the panels. This could have been due to the heat itself, or possibly to the expansion and shifting of the roof as it heated up. (I’m using a different method for mounting the new panels, to avoid that direct roof contact.)

1. 1. You can’t work up on the roof. During hot weather, I could only work on the roof from 6 to 8am, and after that the roof was so hot it was really painful to touch. Yes, I brought up boards to sit on and mats to lay across open spaces. But the roof radiated heat waves, making it much hotter working up there than on the ground, and there was always some time when I accidentally touched that sheet of hot metal. Ouch!
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      The white painted roof reflects a lot of the sun’s rays, so it doesn’t absorb nearly as much heat, and it stays cooler to the touch. If I need to work on the roof, it’s both safer and more comfortable.

“Cat on a hot tin roof?” Or “Deanna on a hot Zennie roof?”

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What is elastomeric roof paint?

Elastomeric roof paint works well in hot climates, and it’s common for people to use on their homes in the southwest. It’s supposed to be elastic enough to handle expansion and shifting with temperature changes, while maintaining a solid seal on the roof. The white version is popular for its heat reduction properties.

Some types of this paint are especially recommended for use on RVs and campers, where the roof gets jostled around a lot more than a permanent home installation.

Also, some types of elastomeric paint are designed for different types of roofing materials. I looked for one that specified metal roofs, but you’ll have to do your research.

I painted my motorhome roof for the heat reduction, but a side benefit of elastomeric paint is its rain-blocking qualities. If you have tiny pinholes in the roof, the paint can seal them up, so it’s a relatively easy way to take care of minor imperfections and prevent a few leaks.

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Painting your RV roof with elastomeric paint

In New Mexico, I happened to camp near a guy who saw my can of elastomeric paint, and told me he was an expert on it. He said he used to paint roofs around Tucson with this stuff as his job, and gave me some tips on how to do it so that it lasts.

He also pointed out a nearby camper that had strips of white blowing in the wind at the edges of its roof — what happens if your elastomeric paint doesn’t stick correctly!

Here’s what he advised, and my comments:

1. 1. • Surface prep. No surprise here. Just like with any kind of painting, getting the surface cleaned properly is important to making sure the paint sticks well.
      • Paint on dry days. You don’t want the roof to get rained on until at least 24 hours after you paint it, so check the weather forecast before you begin.
      • Start at first light. You want to paint during the coolest part of the day, so he advised me to start as soon as it was light enough outside to see what I was doing. This is in a hot climate – it might not be wisest if you’re in a cooler place. Check your paint for optimal temperatures.
      • Paint in a cool, shaded place. If your freshly painted roof gets hit with full sun and heat before it’s fully cured, this can affect the way it adheres to the roof. Keep it as cool as you can for the first 24 hours, preferably somewhere shady out of the sun.
      • Let it cure 24 hours. You don’t want to take off down the highway until your roof paint is fully cured, because the wind could affect the wet paint, too. He said to wait a minimum of 4 hours, but really 24 hours is ideal. You’re going to the effort of painting the roof, so it would be a shame to have to redo it just because you’re impatient to get on the road!
      • Add another coat every year or two. Different types of paints say they’ll last different durations. The one I bought says it’s good for 10 years. But if you keep painting your RV roof with another a coat every year or two, it should last indefinitely. If you wait until the first coat is flaking apart, you’ll have more work to do on surface prep just to get it back in shape. Adding paint now and then is a lot easier, and will keep the roof cool and dry!

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Painting Zennie’s roof with elastomeric roof paint

So how did this go for me? OK, I guess, but I’m not done. This is still an on-going project! 🙁

I found a quiet free campsite near Los Alamos, New Mexico where I could work, with a nice shady parking spot, and a weather forecast that was dry for a couple of days. One evening I went up on the roof and cleaned everything so it would be ready at first light the next day.

The big morning came, and I got up on the roof with my paint, brushes and roller. The surprise was how thin this paint is! I’d read accounts by other people saying that 2 coats should be enough, and my fellow camper-expert said that often one coat would do it! So I’d been hoping that in 1 or 2 days, I’d be done.

Well, they must have all been using a different brand of paint! I put on one coat one morning, and a second coat the next morning, and the roof still doesn’t look entirely white. It’s pretty white, but you can still see through it, and it’s not the glowing white that I was expecting. I think I’ll need at least 3 coats (perhaps even 4) to get the complete reflective white that should keep things the coolest.

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Project status and questions

After getting those 2 coats of paint on, the summer monsoon season arrived, with rain almost every afternoon. Between the frequent rains and my travel schedule, I haven’t yet had a chance to add the final coat, so a month later, this project is still in process.

Here are a few questions I’ve got that I want to answer as I watch this project over time.

1. 1. • How many coats does it take for total white? I know that with this particular brand, 2 coats doesn’t do it. Will 3 be enough, or will I need to do 4?
      • How much temperature difference does it make? I do know the roof doesn’t get nearly as hot, because I can now touch it on days where I would have burned myself before for sure. How many degrees difference that is, I don’t know. I also need to see how that translates into the inside temperature.
      • Are there any places where the paint starts to lift? I’m trying to follow the advice I’ve gotten, so hopefully this won’t happen, but it is one of the risks when painting your RV roof…
      • How does it work on top of Eternabond roofing tape? I painted over the edges of my Eternabond roofing tape, to provide an unbroken surface from the metal roof to the tape. I know this isn’t really necessary, since the tape is reflective white and waterproof already, but I didn’t want to leave any unpainted gaps. The paint may stick differently to the tape than the metal roof. Another “we’ll see…” item!
      • How does the paint weather over time? This is the big question to answer a year or two down the road. After it’s gone through months of blazing sun, freezing cold, rain storms, hail storms, and the occasional scratching tree branch, how does this hold up?

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For the answers to these and other questions, I’ll write an update later! I’ve got high hopes, but time will tell… 🙂

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Project – Painting the roof
Product – Kool Seal 63-600 White elastomeric roof paint. Kool Seal has a range of different products, so do the research to verify which of them is right for your RV roof type.

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Questions? Comments?

Have you painted your RV roof with elastomeric roof paint? Did it work well for you, or did you encounter any problems? I’d love to hear about your experiences, so please share in the Reply section below. Thanks!

PHOTO CREDITS: Deanna Keahey

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