SLEEPING PAD INSULATION RATINGS

[wayno]

http://sectionhiker.com/sleeping-pad-r-values/

If you’re a home owner, you are probably familiar with the concept of an R-Value. If not, it’s a measure used in the building and construction industry to rate the thermal resistance of building insulation under specific test conditions. The higher the R value, the more effective it is.

R value performance testing is done in a 70 F environment with no air movement. As such, it doesn’t reflect many real world conditions where you’d use a sleeping pad, so I highly recommend that you augment any gear selection that you make based on it with field testing.

[madmacca]

OK, I say the article is overly pedantic here.

Technically perhaps it is correct, but I'm not sure it makes a big difference in pad selection. Yes, most pads will be used in colder conditions than 70F, and perhaps with some air movement. But most pads are roughly the same size, and colder temperatures and wind are going to affect them similarly. You have to have a common base for comparison, and I would suggest that an R5 is going to be warmer than an R3 regardless of temperature. Especially as pads are compared on the basis of insulative value, rather than being rated for a particular temperature like bags are.

Also, pads are used mainly to prevent conductive heat loss to the ground (and comfort, of course) - ie. from the parts where your body is in contact with the ground. Does wind affect temperature loss from the bag on top of you? You bet it does! But as the pad functions in the very places where the wind can't get to (ie. under your body), then I'm not sure this really is a major factor.

Thoughts?

[Mark F]

I agree. We all understand that more R means more insulation so the article isn't providing any information apart from the comparison chart. As for the comment about field testing ?! - every time I sleep on a pad I am testing it. From personal observation and reading I think it is safe to say that consensus is that R2.5 is ok to just above freezing, R3 moves you to freezing or just below, R5 is good for snow and really cold conditions.
I don't remember ever coming across an air permeable pad so any issues of air movement are not really relevant.

[wayno]

pads like neoair ive seen people complain about not being warm on snow, since its air inside with a layer of foile in the middle compared to other pads that have foam or insulative fill.
i'm not suggesting these R ratings are the b all and end all on choosing mats, but they may give some indication on how effective they may or may not be in extreme cold.. would you choose the worst rated mat for sleeping on snow? I wouldnt.

[Orion]

When I go camping I use the stated R-value for my pad and the estimated ground temperature to determine the heat flux. If it's more than 20 Btu per hour per square foot then I use a pad with a higher R-value. Doesn't everybody do this calculation?

Yes, I'm being sarcastic.

[Mark F]

Wayno - the original Neoairs were rated R2.5 and like any R2.5 pad are not suitable for frozen ground. The newer Xlites are rated R 3.2, so somewhat better insulation (+30%) but still not a pad for snow (the womens xLite is R3.9). This lifts them to a good 3 season mat. The Neoair XTherms at R 5.9 are one of the most insulating pads available. Note - pads are not warm per se but limit heat loss from a warm body. It really doesn't matter how the insulative effect is achieved, padding or reflective surfaces.