“4-Season Ready RVs? Forget It!” – Letter from a Building Science Guru

Hello there! In my Questions From the Road column, I take a crack at answering real questions from real RVers, just like you. You might find your question here! If not, please send me an email!

I love receiving letters from my Readers! Recently, I received an email from a gentleman named “Martin,” and I thought it was so insightful and articulate that I just had to share it. I’ve copy-and-pasted our conversation below with light editing for brevity and clarity. 

Martin read my article about RV sidewall construction and disagreed with my comments on a particular RV manufacturer. I wrote that their construction style was known to be tough, resilient, and weather-proof. Martin disagreed – and that’s where our story begins!

P.S. I’ve decided to redact the names of the RV manufacturers in question. Honestly, I struggled whether this was the right thing to do. Accountability is a powerful weapon, and I agree with most (not quite all) of Martin’s commentary. Ultimately, I decided to hide their identities because A) Martin’s complaints aren’t exclusive to these brands, and B) I don’t sling mud without inviting the other side to tell their story, too.

Martin Writes: 4-Season Ready? Forget It!

“In what world are these RVs 4-season ready? My experience with RV MANUFACTURER A comes down to one major plus and two major faults:

  1. (Plus) Aesthetics. The principal characteristic, benefit, and the only thing that makes them able to extract the …
  2. (Fault) Price. Beyond ridiculous for a camper without enough room to even have a separate shower.
  3. (Fault) Insulation. It has very little effective insulation and is not even remotely ready for “4-season” use in the northern half of the US, let alone for winter ski trips in Canada. The water supply running through the little “garage” behind a flimsy wall will freeze, guaranteed, by about 15F with the unit at room temperature, and this assumes other standard “winter mods” that all owners intending cold use must make.

Remember the standard about not running plumbing inside RV walls? RV MANUFACTURER A is the prime example of doing exactly that in principle, and then pretending that a 5mm piece of aluminum-foil bubble wrap will somehow keep it thawed at isolated low points in cold weather.

These are rigs you have more for lack of required maintenance and durability – and status. As far as thermally efficient, full-time-anywhere units? Forget it. 

I’ve never actually heard of an RV engineer (oh, Martin, you hurt me!) except for roadworthiness and those outsourced for companies that are building $250K+ units (or Prevost, since they are building commercial transport coaches, and for Canadian use). Most RVs, in my experience, are designed by sales managers and marketing departments with a little service tech help on a CAD program. That’s how we end up with those like RV MANUFACTURER C somehow legally portraying a sheet of aluminum foil as being R-30+. Their factory tour was a hoot for any engineer. I thought afterwards that they should just put a sign up that says that everyone is welcome on the tour except engineers.

Andy Responds: I Like a Good Rant!

Hello Martin! I like a good rant. Thanks for sharing your thoughts! I haven’t used RV MANUFACTURER A myself, so I appreciate your feedback. Are you a current or former owner?

You’ve hit on several of my major complaints as well, such as the inflated “R-value” of foil insulation and what qualifies as “4-season.”  

Unfortunately, sometimes I choose to use the “4-season” adjective the same way the industry does, which, as you’ve pointed out, isn’t suited for sustained sub-freezing temperatures. RV MANUFACTURER A isn’t alone in this; very few manufacturers (outside of ice house builders) make anything truly rated for sustained 15-degree temperatures. 

And yes, the level of engineering that goes on at many RV manufacturing companies is … haphazard. Are you an engineer or designer yourself? I’d love to hear some of your experiences and feedback as an RV owner.

Martin Writes Back: The RV Industry Can’t Build the “Perfect Wall.”

My experience with RV MANUFACTURER A has come from trying to help a couple of their northern customers sort out the gap between the claims and the actual performance (how to rectify tendencies to freeze up internal water lines like I mentioned). 

Fortunately for these companies, it’s a minority of customers who deliberately try to use their rigs in winter in the north. I doubt that they have any experienced customers who do that and haven’t installed their own cold mods. They don’t have much choice. These owners are conflicted—they really want to love and believe in a rig they paid that much for and that looks great and lasts well, but there can be some real frustration with just how bad it is in sustained, serious cold.

My grandparents’ RV MANUFACTURER B was like that as well. If Grandma had been cooking and then nighttime temperatures fell into the teens or worse, they might not be able to get out in the morning without help because the radiant transmissivity was high enough to freeze the moisture at their doors to their frames. Colder than that and frost would form on the interior-side rivets.

I sort of stumbled into engineering of the mechanical sort in a backwards fashion, working as an air traffic controller until retirement but having come from a family with a bunch of engineers. I managed to encounter Joe Lstiburek one day, a famous Canadian building-envelope engineer who started Building Science Corp. I was fascinated enough that I went back to school and caught up on some calculus and physics and, after graduation, started limiting myself to building-envelope corrections in design or application.

The RV industry makes fundamental errors most of the time. They still think there is a “perfect wall” in practice (holding all moisture intrusion at bay indefinitely), but in reality they can make it most of the time to the end of the warranty period and that’s what counts. Human builders and machines just aren’t that good. They don’t understand that an uninsulated aluminum frame (no thermal break between interior and exterior wall) short-circuits a large chunk of their insulation value.

I was in a meeting with a niche “4-season” manufacturer a couple of years ago and told them that this one error was killing them in owner complaints about discomfort, freeze-ups, and frost lines on interior walls when temps were still above 0° outside, let alone in deep northern cold. They predictably told me how delamination risk made the change impossible and I asked them how Triple E had been able to do it just fine for years in Canada (where a 4-season claim is a lot less escapable) without problems. They didn’t know but didn’t care that much and have never changed the design.

There were also no actual engineers at this sizable company. They had CAD people. I was in another major brand’s offices in Indiana one day and asked their technical team (also no engineers) if they knew about the bubble-wrap claims scandal in residential construction about 10 years ago and asked why the RV industry would want to invite a similar legal and regulatory crackdown. They seemed remarkably confident in their immunity. The association obviously has some great lobbyists and attorneys instead of great engineering. I think that is really sad for the trade and for consumers.

Andy Responds: I Love Building Science, Too!

How interesting you mention Joe Lstiburek! I’ve been a reader of his for a long time – plus Martin Holladay, Allison Bailes, and other leaders of the building science movement. Yes, RVs don’t look too good when investigated by anyone with a basic knowledge of heat transfer, do they? Unfortunately, the industry has (so far) chosen to install extra air conditioners or bigger furnaces rather than fix the envelope leakage. But as you’ve pointed out, a bigger stick can’t fix every problem!

And again, you’re reading my mind! I’ve posted a few articles on AskTheRVEngineer.com about the foil R-value racket. Unfortunately, most RV manufacturers seem to think it better to “go with the flow” rather than educate their buyers.

Martin Writes Back: Manufacturers Seem Build to the Lowest Common Denominator.

In my experience, the mid-to-lower-end companies that sell 95%+ of the units on the market simply don’t care about engineering that isn’t mandated from above somewhere, and when people don’t care about getting it right if doing so costs anything, then they are going to continue to churn out lowest-common-denominator stuff that isn’t really fixable from an engineering standpoint.

It would be great if consumers actually had a way to fix the underlying design problems but, even less than with buildings, they are pretty much locked in. The poor owners who do figure out what cold mods work aren’t really fixing the underlying problem at all–they’re just finding a way to get by in spite of it.

For commercial purposes, I tell companies to go find a trailer customizing shop that will convert whatever-size cargo trailer they need into:

  • An RV with residential-depth, furred-out wall and ceiling configuration;
  • The requisite dual-pane escape window cut into the side opposite the door and/or an insulated escape hatch to the roof;
  • Cover the exposed metal ribs with a thermal tape like Tnemec’s aerogel-impregnated stuff (not cheap);
  • Layer in mineral wool to fill all cavities (for fire protective reasons) and don’t use a vapor-impermeable wall covering;
  • Add a small heat exchanger for ventilation whenever temperature / comfort allows.

I have no dog in any fight at this stage and am just happy to see consumers get educated and stop giving money to companies who refuse to care enough to build things that actually perform as they claim, and which their customer has then paid for. The manufacturers will feel few other pressures.

I would also love to see Congress or a regulator like the “Energy Star” folks just slap on a requirement for all RVs that a certified third party must document and publish each model’s energy use per cubic foot of interior space for heating and cooling at two standardized temperatures (say 5 degrees and 105 degrees Fahrenheit), and at which all systems must remain functional without any modifications. That would engage the competitive motive and kill most of the false aluminum-foil-with-bubble-wrap marketing. Then consumers would have some real-world numbers to compare across units regardless of their size.

Andy’s Final Thoughts: Vote with Your Dollars!

So, that’s our conversation! Thanks Martin! I hope it was illuminating for the rest of you. I would like to echo one thing Martin said: “Stop giving your money to companies who refuse to care enough to build things that actually perform as they claim.

Believe it or not, there are actually engineers and designers in the RV industry who know the underlying problems and want to build better. But you get what you buy for – and companies will build what you buy. So vote with your dollars, and buy quality!

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