Thermal Efficiency of extra wide pads

[Paul S.]

I like room to spread out when sleeping so I’m considering getting an extra-wide pad.  Is there any science to the thermal efficiency of a pad that extends wider than your body?  E.g. a 30-40 inch wide pad

I know for NeoAir reflective insulation I might lose warmth around the edges I’m not covering, but does that apply for all pads?

Anyone else regularly use extra wide pads?

[David Thomas]

Heat conduction to the perimeter of the pad will be very low – essentially no different than in a 20-inch-wide pad if you’re in a sleeping bag.  Short answer: I’d focus on the R-value of the quilt, narrow or wide.  And if a wide quilt gives you much better sleep, HYOH.

In a quilt?  As long as the quilt draped down onto the pad, it seems you’d have the same, roughly semi-circular cross section of meat and air under the quilt.

If the quilt were so large as to drape of the sides of the pad, then maybe it would have a trapezoidal cross section (i.e. extra triangular air passages on each side).  Seems like that could make for more drafts, but it would have to a very wide quilt to do that.

When car / boat / kayak camping, I sometimes bring a 30″ wide pad.  I don’t notice a difference in drafts. It does help avoid wiggling off the pad and allows for more positions – more towards a fetal position – while all of my body is still on the larger pad.  If there’s wet ground or a wet tent floor it is very nice how it keeps more of my quilt dry.

Less of a weight penalty would be if someone made a 20-inch-wide quilt with “rails” along the edge: a thicker cross section just at the edges.  After a few nights of use, I suspect I’d learn to stay on the pad without fully waking and prior to wiggling off the pad.

[Paul S.]

The quilt I’ve been using lately is wide and it can easily drop off the edges of my 25 wide NeoAir.  It’s less about the quilt width and more about wanting to sleep more like I do at home.  When I sleep on my side they can fall asleep hanging off the edge or rest on the cold ground; both less than ideal.

I’m tempting to go for an Exped HL Duo for a super luxurious setup.  It’s about 2 ounces heavier than my All Season, but much more fragile and less warm, not to mention pricey.  I tried one out a year ago as a couple’s pad and it just doesn’t work for two larger people.  The taper from 40 down to 30 is pretty nice for one.

I’m also playing with the idea that I’ll not be very comfortable not matter what so I should just go SUL with a torso NeoAir and CCF at the feet…

[Ben H.]

I would think horizontal baffles would be more likely to conduct heat to the edges thereby cooling you more.  I doubt it makes much of an impact, but I haven’t tried it to know for sure and I don’t think I am willing to sink that much effort into doing the analysis.

Vertical baffles would be better because they would prevent significant flow to the periphery.  Foam would probably be the best.  If you did notice an issue, adding a thin foam mat on top of the air mat would probably rectify the situation.

Dave – The REI Stratus has larger outside baffles to center you on the pad.  I like them.

[James Marco]

I agree, Ben. Especially with the older rectangular NeoAirs, there was a pretty clear difference between having the quilt tucked around you (and leaving the edges free to bleed off heat) and having the whole pad covered. That said, the somewhat extra space under the quilt also required extra body heat to warm it up.

A bag, with the pad inside it, much like the Inertia Xframe though I used a semi-inflated NeoAir, was the warmest over a 5 layer Nightlite CCF pad below both. (System: Marmor SuperStretch 0-a 10F bag, Neoair medium, and Nightlite.) This all happened on a couple occasions when I expected about 20-25F and it got COLD…down to about 10F. Note that the NeoAir uses a IR reflector inside it and having no heat loss (since it was covered by 2″ of down) it warmed up fairly easily. But, you need a long/wide bag to do this effectively. So, a narrow 20″ pad was good. A 25″ pad would not have worked.

I also agree that the Vertical baffles in a pad would work better.

[Paul McLaughlin]

My only experience with a relatively wide pad is a NeoAir Xtherm. Mine is the wide mummy version. Warmest pad I have ever used – and very comfy. I tend to sleep on my side mostly, so I would say some of the pad is exposed (as in not covered by me or my bag) most of the time.

 

Wait – not true – I also have Thremarest Camp rest pads for car camping – like 30″ wide or 28 or something like that – but different since foam filled. Also very warm and comfy. Maybe warmer than the Xtherm, so amend what I said above to make the Xtherm the warmest backpacking pad I have ever used.

[Paul S.]

Sounds like sleeping on an extra wide pad with vertical baffles (e.g. Exped Duo) won’t comprise the effectiveness of the insulation.

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