Companion forum thread to:

Apparatus for Testing Thermal Insulation Properties

mm to inch conversion for the last figure

44 mm = 1.73 in
29 mm = 1.14 in
18.5 mm = 0.73 in
14 mm = 0.55 in

Thank you so much for putting together this seminal article. For us backpacking nerds, this is fascinating. I am eager to see what comes next.

It is also another reason why BPL is the leader in the field.

The article was simple enough that I understood it! Having been "skunked," or rather frozen, by several pads over the years, I would really like to see some standardization--hopefully your work will bear fruit in the future. Thank you, Roger, for your work and the excellent article!

This article goes a long way towards justifying my recent subscription renewal. I'm certain the follow test reports will complete that task.

Nice work Roger.

Quite digestable for something like me with minimal hard science background.

I look forward to the empirical findings.

Definitely looking forward to more. Even the findings here with the pad thickness are pretty interesting considering that many neoair/other inflatable users don't fully inflate the pad for more comfort.

Superb text and pictures. Your explanations are great. Thanks for your continuing service excellence!

Excellent introduction--looking forward to more.

Roger, are you saying the listed r-value on sleeping pads (eg, 1" thermarest prolite 3, stated R-value 2.2) is based on SI units? Versus building insulation products in the US that use imperial units (eg, 1" of EPS foam board ~ r-value 5.0)? You say SI units gives an r-value about 6X less than imperial units. Does this mean sleeping pads are actually much better insulators per unit thickness than common building insulation (eg, 1" thermarest prolite would be equal to R 13 in terms of US building insulation)?

Sorry, I'm a bit confused.

Edited by DavidDrake on 04/26/2011 19:21:44 MDT.

a

Edited by asdzxc57 on 01/25/2012 18:09:30 MST.

Roger,

This is just plain wonderful! I have sought this info for decades. I don't have an engineering degree and most info I have seen in the past only confused and frustrated me. I can actually understand most of what you wrote here. Empirical work in this area should help to separate myth from reality.

Here are a couple of questions I've had relative to this subject:

How much blue foam would be required to roughly equal the insulating value of 2" of down?

What's a common sense guideline for comparing sewn-threw construction in a down sleeping bag compared to box or overlapping tube construction? For example, would 1.5 " of down which is sewn through be warmer than, say, 1" of down within a box constuction?

Daryl

A fantastic teaser... looking forward to the data sets. BTW, great work, Roger. :)

Hi David

> listed r-value on sleeping pads (eg, 1" thermarest prolite 3, stated R-value 2.2) is based
> on SI units? Versus building insulation products in the US that use imperial units
> sleeping pads are much better insulators per unit thickness than common building insulation

Correct, along with all that implies.

Cheers

> how the end effects are accounted.
Bluntly, they aren't.
But in the field the conditions are highly variable, so attempting to measure R-values of airmats to any high level of precision is both meaningless and futile.

> I assume you will strive to have ambient conditions similar for all tests.
Yes. Can't be exact (see above), but yes.

Cheers

Hi Daryl

> How much blue foam would be required to roughly equal the insulating value of 2" of down?
Um ... I think Richard Nisley might have better figures for that than me.

> would 1.5 " of down which is sewn through be warmer than, 1" of down within a box construction?
Another Q for Richard. As sewn-through constructions are rather more variable in performance, that could be very hard to answer.

Sorry!

cheers

Great work, Roger! Looking forward to the airmat survey.

The "edge effect" sounds like a tough problem to handle. Basically, as I see it, you could lose heat in three areas. The first is right where you are measuring (the bottom). The second is on the sides and the third is on top (but through the mat first). The same is true out in the field. The heat can transfer into the pad, then out to the sides, or back up to the top in the section of your pad that isn't covered by a sleeping bag/quilt. Solving the problem with the sides of the mat seems easy -- just let it happen. If a pad loses some heat to the sides during testing, then it will lose some heat in the real world (unless the camper insulates the edges). Solving the loss to the top of the mat sounds harder. In the real world, part of the sleeping bag/quilt covers it up. But depending on the shape of the mat and the sleeping bag/quilt, some of it is uncovered. To get a good estimation, you might want to measure things with various coverings. Start by laying a good bag over the rest of the mat, then cover only part of it, then cover none of it.

It would be interesting to see how mat combinations work under these conditions as well. As has been reported by many people, if you have an inflatable and a closed cell mat, you are better off putting the closed cell on top. Without the edge effect, I would assume that it would make no difference. I would be curious as to much of the loss is due to the sides of the mat, as opposed to the uncovered top.

a very long time ago in high school, al (a genius) and peter (not quite a genius...) decided that while stuck in experimental filmaking class with the hippie chicks, that we should determine a formula that once the data was entered would tell us (in advance you see. a leading indicator in todays lingo) if the girl was .. "any good".
this project turned out to be a failure for any number of unmentionable reasons, but i suspected from that day that hippie girls would end up being a lot like camping mats, in that in order to tell if it's a good one, you really need to sleep with it.
in the end, sleeping with them is going to be the best way.
a keeper ?
a tosser ?
it only takes a night or two to find out what you need to know.

but peter ! ... you'd have to sleep with ALL the mats....

yes .. that might be a problem. i suppose that the mats that initially didn't look so hot, we could just pass around thru the group.

Good Work Roger. Your always pushing the envelope.

Cheers,
Lawson

Roger, I am not an engineer, so frankly some of the more technical aspects of your article were a bit over my head. But the bottom line is that based on your previous work with BPL, I trust you. Therefore I welcome your new testing apparatus and look forward to future comparison tests.

Slainte! (Irish for CHEERS!!)