By Andrew Herrick
Your RV is a solar oven. You may consider it your adorable home-on-wheels, but to the 10,000-degree star burning 93 million miles away from our planet, it’s a heat box, no different than the science project you constructed in 5th grade. That bothers your air conditioner. Your air conditioner has one job: to move heat from inside to outside. But how can your hardworking, loyal air conditioner remove heat if you keep adding it back in? How can you sip a cup dry through a straw if someone else keeps adding water to your cup?
This is often why your “air conditioner doesn’t work.” Your air conditioner may actually be working just fine, but it simply can’t keep up with the tremendous heat gain.
So what’s the second-best thing you can do for your air conditioner? Reduce the heat gain!
(FYI, the absolute best thing you can do for your air conditioner is to keep its evaporator and condenser coils clean and unobstructed.)
Why heat gain is the enemy of your RV air conditioner
Heat moves in three ways: conduction, convection, and radiation. Touch the stove—that’s conduction. Blow on your finger—that’s convection. Feel the heat radiating off the pan— that’s radiation.
Radiation is your biggest enemy. Radiant heat is what makes an asphalt road sizzle at 140 degrees when it’s only 95 degrees outside. The air isn’t making the asphalt hotter, the sun is.
You already intuitively understand this. You stand in the shade on a hot day. So why not give your RV the same break? Park in the shade!
But what about when you’re camped somewhere where your RV is taller than the trees (looking at you, Arizona)? Or what if there are no trees whatsoever (looking at you, Texas)? Fear not. Let me give you three easy ways to reduce your heat gain and keep your air conditioner happy.
1. Keep your roof snowy white
Clean your roof. A clean roof is white and reflective; a dirty roof is brown and hot. You don’t wear a dark T-shirt on a muggy summer day, do you? So why ask your RV to suffer through the same?
If you want to really get into the weeds, you’ll need to know the Solar Reflective Index (SRI) of your RV roofing membrane type. For instance, Dicor Polar White DiFlex II TPO has a SRI of 108 when new and will slightly degrade with age. Lasalle Bristol XTRM PLY has an initial SRI of 109. These are good numbers! In comparison, commercial white EPDM roofing can have an initial SRI of around 94 and a 3-year aged SRI as low as 77.
And, by the way, virtually all darker colors—gray, tan, or black—have pitiful performance in comparison to white. That’s why lighter colors are usually classified as “cool roofs.”
2. Block out your skylights and fans
You already close your window shades when it gets hot outside, but do you cover up your skylights and roof fans? You might be appalled to learn just how much heat can enter your RV through these neglected pathways. (Plus, the direct sunlight can cause your furniture and flooring to fade.) Do yourself—and your air conditioner—a massive favor and either build or buy reflective foam inserts to stuff into your skylights and roof fans.
It is important that the inserts be both FOAM and REFLECTIVE. The foam prevents conductive heat transfer from the hot airspace above, and the reflective foil prevents radiant heat transfer. It bounces most of the sun’s rays back outside. These are the best.
A word of warning! Note that these inserts will increase the temperature of the skylight or fan lid material itself. Most of the time, this will have no harmful effect. But in severe heat, the plastic can actually warp or bubble from the excess heat. If you’re battling truly apocalyptic temperatures, you might want to do away with the reflective foil.
P.S. You’ve heard since childhood that dark colors absorb heat and light colors reflect it. This is true, but don’t be fooled by clear. A clear skylight or fan lid is actually the worst for heat gain, while a dark-tinted lid actually blocks the most heat.
3. Let the RV air out first!
I know, I know. When you finally arrive at your campsite after traveling all day and you open the RV’s door, it’s hotter than heck inside. So your survival instinct is to kick on the air conditioner and let the compressor work its magic.
This is not how you keep your air conditioner happy. It can easily be 100–120 degrees inside an RV after traveling in the hot sun all day. And I’m not just talking about the air. I’m talking about all the stuff inside your RV: furniture, cabinetry, belongings, etc. All this stuff has thermal mass, which stores heat. Your RV is literally a battery for heat. And until you discharge this heat, it will continue to emit from your stuff and warm the air temperature.
You can kickstart this process by opening up your windows, turning on your exhaust fans, and using your air conditioner in Fan-High mode only. Your goal is to ventilate your RV as quickly as possible! The more airflow, the more you’ll “discharge” the heat captured within the mass of the RV itself. Just ventilating an RV for 5-10 minutes can make a massive difference. If you ventilate your RV first, your air conditioner will bring down the room temperature faster. Be kind to your air conditioner, and it will be kind to you.
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Our Class C has a white fiberglass roof, but the satellite dome and air conditioner cover are both black. Would it help to change these to white? It seems that the RV manufactuers use black purely for esthetics based on the color/s of the RV body.
Of course! Anything that you can change to white – do it!! Black absorbs – white reflects.
Use weather hoods on your roof vents. They provide shade for the vent cover, and they allow the vents to be open and exhausting heat while driving (unless you are on dirt roads – the hoods keep the water out, but not the dust).
So we all know that dark colors absorb heat. So why are all the air conditioner shrouds black. You see very few white covers. The same with propane tank covers and battery boxes.
Makes no sense does it! The RV I own now has black A/C shrouds and the first thing I did when I brought it home was lightly sanded the top and sprayed two coats of white enamel paint (formulated for plastics) on top, left the sides black. At least there’s a good amount of reflective color.
Good things to remember
I park with awning facing west and use it to shade wall from afternoon sun.
I have pieces of reflective bubble-wrap cut to size of windows. They install and uninstall in seconds; I store under cushion or mattress.
Look at any RV lot or a busy campground and about 90% of the RV’s are black and gray. It makes no sense to me why the manufacturers would do that and why people would want those dark colors when it’s a chore to keep rv’s cool even with lighter shades. Black is a rich looking color, so that must be their reasoning.
Thank you, Andrew! 🙂 Great advice that probably cannot be said and repeated enough! 🙂 Thanks again, have a great week, and safe travels! 🙂
My Reflectix is cut to cover the exterior of the windows, including the window frames. The frames can transmit significant heat to the interior. The Reflectix panels are held to the frames with heavy duty hook and loop squares for easy on and off.
Yeah, I just don’t get the sudden switch from white trailers and MH’s to darker colors. Sure, they look nice but make no sense. Our aging 2012 Arctic Fox is the old white color – and we love it. Since we do very little winter camping we’re not looking for dark color heat absorption.
Thank you for the info about ventilating first when setting up camp. I hadn’t considered the thermal potential of belongings and the interior fixtures. Makes sense!
Excellent article, thank you. I am most interested in roof options. We live in a Mercedes Sprinter-based conversion van, so we don’t have an RV “roof” to apply a new membrane to such as the Dicor option you referenced. Is there reflective paint available for a van like ours, and what would the SRI values be?