insulation R value s

[firedreamer]

Ok , I Need some help with the wide range of Values some of the different manufactures are saying their brand has. I can't see how one will say r-30 in the roof
(Jayco) and another says r-38 (forest rivers Cardinal) when both have only 5" roofs. I'm love the Jayco 38 FLEA as a possible full-time rig but trying to do my research but am a little bewildered. LOL by all the different claims. :-)

[Lady Fitzgerald]

Originally Posted by firedreamer

Ok , I Need some help with the wide range of Values some of the different manufactures are saying their brand has. I can't see how one will say r-30 in the roof
(Jayco) and another says r-38 (forest rivers Cardinal) when both have only 5" roofs. I'm love the Jayco 38 FLEA as a possible full-time rig but trying to do my research but am a little bewildered. LOL by all the different claims. :-)

Open Range's R-38 claim is that the value is "calculated". The only problem with that is the calculations they use for the foil and bubble insulation is flawed. They are confusing assembly R rating with R rating. The only way foil and bubble can receive an R rating higher than R-1.1 is to have a large air space on both sides of the foil and bubble insulation, which Open Range doesn't have.

OR also claims to put R14 fiberglass in the ceiling. The problem with that claim is the glass gets compressed over the ducts and as the roof thickness thins toward the edges. Compress fiberglass insulation has a lower R rating than uncompressed insulation of the same thickness as the compressed insulation.

Jayco also doesn't have an air space on either side of their foil and bubble insulation but they no longer make any R value claims. Instead, they report on inside temperatures of the RV after being exposed to temperature extremes inside a closed test chamber. That is more honest but they fail to mention whether the heat is introduced by convection or if there is any radiant heat, such as what would be received from sunlight, being used for the tests.

I looked inside a 338RETS late last year and it didn't look like even 5" of space between the ceiling and the roof at the living room skylight. Maybe 3".

Inflated claims for foil and bubble insulation has been a racket for years but most vendors no longer make those claims, thanks to government intervention. Sadly, there are still some industries, such as the RV industry, making inflated claims using the assembly R value as a regular R value.

[wags999]

Everything has an R value. Perhaps it could be different insulating materials, wood thickness, ceiling panel thickness and type. No clue if anyone gives how they arrive at the R value they post. I know spray foam insulation has a better R value than fiberglas, not sure if any RV's use spray foam. Interested to hear what others have to offer.