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What’s the second-best thing you can do for your RV air conditioner?

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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Ross Regis
Ross Regishttps://askthervengineer.com/
Ross Regis is a practicing RV design engineer specializing in towables. Jack of all disciplines and master of none, Ross enjoys explaining how RVs work (and sometimes why they don't.) He blogs weekly at AskTheRVEngineer.com.

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K Howland
18 days ago

We travel in a Thor Chateau class C. We have fabricated interior window covers for each window in the RV from REFLECTIX Double Bubble White Reflective Foil Insulation, which we buy at a local hardware. We cut the foil to fit the window, then we bind the edges with duct tape. We even made a cover for the skylight in the bathroom, and stick it to the rim of the skylight with velcro. In addition, we have installed window awnings over each exterior window. We travel primarily in the South. Florida is our home base. When we arrive at our campsite we open the rv (all windows, doors, and roof vents) and let it air out. Then we open the awnings. In about 15 minutes it is cool enough to turn on the AC. We then close the windows and roof vents and enjoy a cool RV interior. When parked, we leave the reflective material in place in the cab. When we leave the campsite to go exploring during the day, we put up the reflective covers. This keeps it cool and when we return the RV is always comfortable.

E Horton
12 days ago
Reply to  K Howland

K Howland,
We do practically the same things. Especially putting the reflective bubble foil in the windows! This is a tremendous help. The only foil we remove is on the entrance side of the camper, not the back side. Even worked great last summer in 109F Austin TX, 4th of July weekend!

Dr. Mike
25 days ago

We have a 45-foot Class A, and when we are in conditions like this, we use a small (16-inch) pedestal fan to move the air around before and during the use of the A/C.

Jeanne H
26 days ago

I have used the reflective silver mesh tarps on my roof in very sunny, warm weather. I had them for the dog shows and thought why not try them on the roof? The mesh allows air flow while the silver reflective material protects from the sun.

KellyR
27 days ago

Ventilating the RV first – I don’ know about others, but down here in Fla.in 90 deg days, RV or car, we open the doors, start the A/C, and stand outside in 90 deg air waiting for the A/C to push the 120 deg air out of the vehicle before getting in.

HT Morgan
27 days ago

Purdue University has developed an ultra white paint that makes roofs. See article below. In doing a project for a church in Key West, we added new metal roof to an addition and used special roof paint from Home Depot. The unpainted side was so hot you could feel the heat through your shoes. On the newly painted side it was comfortable to sit on. Later, I saw this article and thing about paint my RV roof. AC would work much better…
https://www.purdue.edu/newsroom/releases/2021/Q2/the-whitest-paint-is-here-and-its-the-coolest.-literally..html

Parson Pete
27 days ago

Amazing how common sense can be overlooked.

DW/ND
27 days ago

The windshield is the biggest source of hi heat gain. I made shades which installs with snaps on the outside, (I think you can buy that screen like plastic material ready made). I cut four 3/4″ blue foam panels, with an aluminum face, joining them in pairs with aluminized duct tape, to fold them for storage. I slide them under the screen material. Also serves as hail covers in the event of… To intall the screen I have to use a ladder..To unsnap the top snaps, I use the awning rod. Reduces heat about 20-25 deg F.; also saving on the A/C use to later in the day. We have a class A with a huge windshield. Pics available.

Neal Davis
27 days ago

Thank you, Ross! We will try this on our next warm-weather trip. I am excited by the potential benefits from following your advice. Thanks again!

Snoopy
27 days ago

Pretty much the best your AC can do is 20 degrees less than the ambient temperature! Yup its 110 outside in the shade it’ll be 90 degrees inside your RV with ac on, or about that!
Snoopy

Spike
27 days ago
Reply to  Snoopy

On normally built, poorly insulated single pane window RVs, I tend to agree. But a lot depends on how well insulated your RV is. With our very well insulated Newmar (with dual pane windows and a cream base colored exterior) we have been in ambient temps >100F and kept the inside at 70F.

MattD
27 days ago
Reply to  Spike

agree..

Calvin Wing
27 days ago
Reply to  Spike

Yep, we have found the same thing. In fact last summer one of our trips found us in a park with only 30 amp’s available. We have Softstart units installed but they don’t work with a residential fridge plus inverter cycling on and off. So one a/c unit plus fans kept us comfortable for the weekend.
Double glazed Thermal windows + thick roll down shades, insulated curtains, awnings deployed on the West side all on a 39’ fifth wheel with a total square footage of 412 including slides. The only place uncomfortable was the front bath so we closed that door.

Lee A.
27 days ago

The best thing I ever did for my AC was to install the product from RV Airflow. It eliminates the leaky divider that separates the hot and cold side inside the AC and greatly improves the airflow going into the ceiling ducts. I live and travel in Arizona and this product saved me from adding a second AC to my trailer. Even with extremely high outside temps in the summer our trailer stays comfortable inside, plus it cools down so much faster now.

Nanci
27 days ago

Great article! Didn’t think of ventilating the RV first before turning on the AC. Thanks

Bill Byerly
26 days ago
Reply to  Nanci

I agree with you Nanci !

McTroy
27 days ago

We learned the hard way about cleaning the condenser coils. Cost us a new AC unit. Ours was 8 years old and had problems 2 years ago. Took it to 2 different service techs and neither if them cleaned the coils. Instead they quieted the fan. Well that caught up to us this Spring. Now we have a new AC unit, know how to maintain the coils and a white AC shroud. Yea!

Dr4Film
27 days ago

Cover the windshield with a solar cover is the SECOND most thing to do as it is one of the biggest sun radiators more so than the vent covers. Also, having a WHITE roof and all white components help a great deal versus having a colored roof and components on top.

Dan
27 days ago
Reply to  Dr4Film

One of the first things we do when we are setting up.

Ed D.
27 days ago

Excellent “common sense” article Ross. I hope a lot of people heed your words of wisdom.

Seann Fox
27 days ago

RV roof vent covers are a must, as is upgrading your vents to fantastic fan . Open the roof vent, turn on the fan open the windows on the shaded side and the hotter air will be sucked out. Then you can turn on your A/C. Basic science, hot air rises, cold air sinks.

Last edited 27 days ago by Seann Fox
Michael Gardner
27 days ago

Why are most AC covers black? Because black plastic is cheaper than white. Why put the AC inside a black “hot box”? Because it’s cheaper. I replaced my 2 AC covers with white ones.

Tom
27 days ago

You are so right. Never understood black A/C covers.

Tommy Molnar
27 days ago
Reply to  Tom

I think the black AC covers are supposed to look cooler, appearance-wise. Just as silly as some of the newer trailers going to DARKER colors. Probably fine if you camp mostly in colder climates, but you don’t want black in Quartzsite! Like pickup truck manufacturers, every year they have to do something different in order to try to entice new sales.

Jerry
25 days ago

I wonder if I could paint my black exhaust fan shrouds on the roof? It makes zero sense to put anything black on a roof. Replaced my black king tv antenna with white when it failed.

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