Answers to questions about RV Repair and Maintenance from RV expert Dave Solberg, author of the “RV Handbook” and the managing editor of the RV Repair Club. This column appears Monday through Saturday in the RV Travel and RV Daily Tips newsletters. (Sign up for an email reminder for each new issue if you do not already receive one.) Today Dave discusses the R-value of RVs.
How can I determine the R-value of my travel trailer? —James
According to the Department of Energy, R-value is the material’s resistance to conductive or straight line heat flow. This can be heat flow either from inside the rig to outside in winter, or from the outside to the inside in summer. Simply put, how long can we maintain the interior temperature without needing the roof AC or furnace to kick on and run longer?
It is very difficult to determine the “actual” R-value in RVs. You would need to not only find out what material is used in the panel, but also the makeup such as pounds used in bead board. R-value claims are regulated and monitored by the Federal Trade Commission. The R-value is basically the materials resistance to heat transfer or how long it takes heat to flow through it.
Many manufacturers will advertise R-values in brochures and other marketing materials and some get way out of hand. I have had seminar attendees state that they were told units were four-season units with R-38 sidewalls and R-52 roofs! WOW! That’s incredible, since a 6-inch-thick residential wall only has an R-19 rating. So the sidewall of that unit would have to be more than 1-foot thick and the roof over a 1.5 feet thick!
R-values of some products
While at Winnebago, we did an extensive amount of research on the various building materials and what they contributed for structure and insulation value. Some manufacturers build what we call “stick-and-tin” versions that utilize wood framework and fiberglass insulation – which I call “loose fill” insulation. According to Owens Corning, their best fiberglass product is rated at R-11. at 3.5 inches thick. The typical sidewall of an RV is only two inches thick at most, so the insulation is only about 1.5-inches, which means an R-4.8 rating. The Luaun panel inside and out, plus the outer fiberglass, adds about an R-2. A thicker 4-inch roof would give approximately twice that, at R-13.
Block foam insulation is rated at R-5 per inch. So that’s approximately R-7.5 for 1.5-inch thick sidewall and another R-2 for materials. For years, Winnebago has state R-values of R-9 for sidewall and R-13 for the roof. Keep in mind, this is the 2-pound block foam, which is much more dense versus lighter weight types that would have less insulation value.
Reflectix foil insulation
Some manufacturers use Reflectix foil insulation and claim to increase the R value by more than R-13. According to the Reflectix website, the actual foam material only has an R-1.1 value and can only provide R-14 value when used with R-13 fiberglass. Or it will provide R-6 additional insulation value if there is a 3/4-inch air gap on each side before the inner and outer wall material.
But to answer your question, do your research and don’t take the word of the manufacturer or dealer without facts to back up the claim. Find the thickness of the actual insulation, the type, and density, then you should be able to come close.
If you are looking to use your rig in below-freezing temperatures, there are several tips on cold weather camping that you can find in RVtravel.com articles.
Read more from Dave here.
Dave Solberg worked at Winnebago for 15 years developing the dealer training program, as marketing manager, and conducting shows. As the owner of Passport Media Creations, Dave has developed several RV dealer training programs, the RV Safety Training program for The Recreation Vehicle Safety and Education Foundation, and the accredited RV Driving Safety program being conducted at rallies and shows around the country. Dave is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.
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