Weight VS R-value

Hi,

My first post on this board! I have a dire question about my choice of gear.

I'll leave for the northern parts of scandinavia on July 28 with an average temperature of 5-12 degrees celcius.

I am doubting between packing my (fairly old) Thermarest Trail Regular mat (r value 5, 1050g weight) or my Exped Airmat 5M (r value 1,7 535g weight). Logically the exped packs smaller (half of the thermarest).

I have a thick synthetic sleeping bag (NORDIC -2 degree celcius comfort).

Do you reckon I'll be comfortably sleeping with those outdoor temperatures on the exped mat rather than the Thermarest?

I hope some of you have experience with this and might be able to answer my question!

Cheers,

Wijnand

I think you are on the edge of your lighter pads range, but the synthetic bag will help just a little to boost it. This is not scientific by any means, just from my past experience. If you can experience colder temps on your trip, or your Thermarest is so much more comfortable, I'd lean that way. It's hard to judge how much R-value the bottom of a compressed synthetic bag has. Here's a little test. Take a relatively flat package out of the refrigerator. Place it under your pad and sleeping bag. See how much cold is coming through both. Try it with your larger pad. Something from the refrigerator should be close to 5 deg. C.

I would be inclined to take the lighter, uninsulated sleeping pad and take my chances with it. If necessary, you could boost the R-value of the airmat a bit by placing some items of clothing you aren't wearing underneath it. The length of daylight hours in Scandinavia in late July should work in your favor, too.

Thanks for the responses. I lean towards picking the Exped. It's actually a great idea to pick an item from the fridge and test that out.

I will be the one to disagree with the others! I am bias, because I sleep exceptionally cold.

You stated that the AVERAGE temperatures go down to 5C. Your sleeping bag's low rating is 2C. The sleeping bag ratings assume that you have an adequate pad. Microclimates while backpacking are often less than the "average" temperatures. As for extra clothes to put under the bag, if you have lots of extra clothes, you are then taking too many clothes. Better to take a better pad. I rarely have extra clothed to put under me - plus extra clothes are really lumpy!

The r-value for a pad twice the weight is more than twice the r-value of the lighter pad.

As far as more sunlight in Scandinavia- does not matter how much sunlight if you end up getting no sleep due to being cold, whether that is 3 hours a night of 8 hours a night.

I would buy a new pad that is between the 1.7 and 5 r-value.

I'm with Daisy on this one.

Your first priority is to take what you need for the worst reasonably-expected conditions. After you do that, reduce weight by gettting the lightest version of what works.

So, in this case, an adequate R-value is your first concern. I camp in those general temperatures, and I find that it's not unusual for a predicted 2C to run toward minus 2C, depending on your choice of campsite and the wind you're exposed to. I tend to go with an r-value of 3-4, unless I know I'm going to sleep on snow - then I want something more toward 5.

You can find such full-length pads that weigh less than 450 grams (the r-5.7 NeoAir XTherm, for example.)

I also am with W_D and Glenn. IMHO, a good night's sleep is well worth a little extra weight. If you're shivering, you won't be sleeping, or at least you'll wake up every half hour. Been there, done that, never again!

AS W_D mentioned, the "average" temp is definitely not a number on which you should base your planning--the lows could easily be 10* above or 10* below that number! (Well, maybe 5*C) I look for the record lows for the dates I'll be there, and pick a number perhaps halfway between that and the average.

As she and Glenn also mentioned, sleeping bag ratings are based on having an adequate pad. For a 20*F (-7*C) sleeping bag rating, the EN13537 laboratory tests use a pad with an R value of 5.

Another option is to take a second pad...a closed cell foam and put the ccf on top of the uninsulated inflatable. That should put you in the 2-3 R value range. And, you will have an indestructible mat that you can sit on in camp.

Personally, I would buy a lighter insulated inflatable if you think your thermorest is too heavy.