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Exped Synmat UL 7 felt "cool" under hips at 5-8 deg C
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Matt Purnell

Locale: Brisbane
Exped Synmat UL 7 felt "cool" under hips at 5-8 deg C on 05/19/2013 22:01:55 MDT Print View

I’ve just bought and tried out a Synmat UL 7 medium. Unfortunately it felt “cool” under the hips. I was camped on bare ground with the PU floor of the tent in between. The air temp was somewhere between 5 and 8 deg C. I was car camping, so I was in my warm tent and warm sleeping bag and my body was otherwise warm. On a hiking trip I’d have the same situation, except the tent floor would be silnylon and the air temperature could be a little colder – somewhere between 0 and 5 deg C.

So a couple of questions:

1. Is feeling a bit “cooler” under the hip normal on a relatively thick air mattress? My last mat was a Metzeler Thermo, which one inflated to about 3cm thickness with about two big puffs. I used the schnozzle bag to inflate the 7cm thick Exped – I think I’d pass out if I tried to inflate it by mouth. The mat was fully inflated – a test at home demonstrated that was necessary lest my hips hit the ground.

The sensation wasn’t “cold” – just “cool”. And once asleep this “coolness” didn’t wake me up. I’ve read plenty of BPL testimonials by people saying they’ve had no problems at temperatures lower than I’m reporting. Has anyone else experienced this sensation at these temps and just puts up with it to save weight?

I was wearing only a pair of boxer shorts and a t-shirt. If I was also wearing woollen leggings and nylon pants, might that make much of a difference?

2. How feasible is supplementing the warmth of the mat with a short section of thin closed-cell foam that just goes under the hips? Otherwise it’s the Exped Downmat UL 7 medium for me I think. (I want to stick with Exped because the mat was so comfy.)

However, the weight difference between the Downmat medium (560g) and the Synmat medium (455g) is 105g.

I’d only need a section of foam that’s about 30cm x 52cm. But wouldn’t that approach 95g anyway? For example, a Gossamer Gear large sit pad (25cm x 53cm x 2cm) is 54g (

So, I’m in two minds. I hardly ever camp below 0 deg C, but I get cold easily, my Six Moons Haven tarp + net-tent is airy and “cold”, and I’m planning on replacing my heavy, very warm sleeping bag with a quilt. Should I just play it safe and get the Downmat, or should I supplement the Synmat?

Edited by Treefern on 05/19/2013 22:03:20 MDT.

Randy Martin
(randalmartin) - F

Locale: Colorado
Sleep Clothing on 05/19/2013 22:17:50 MDT Print View

My first reaction is that I would never sleep in boxer shorts and t-shirt. One of the cardinal rules of cold weather camping is to wear at least some of your insulated clothing/base layers to sleep. It not only helps supplement your comfort but also keeps your sleeping bag much cleaner.

I think the idea of putting a small section of thin foam (perhaps dual use as a sit pad or frame sheet) under your hips is an excellent idea in colder conditions.

Todd T
(texasbb) - F

Locale: Pacific Northwest
Synmat UL R-value... on 05/19/2013 22:36:04 MDT Print View

is a little lower than some alternatives. It's a smidge over R-3, which compares to a tad over R-4 for some other popular air pads like the Big Agnes Insulated Air Core. That means the Synmat allows about a third more heat transfer at any given temperature difference, other things being equal. I'm not criticizing the Synmat--I love mine--just pointing out the specs.

Stuart .
(lotuseater) - F

Locale: Colorado
'Cool' Synmat UL7 on 05/19/2013 22:45:49 MDT Print View

There are many ways to lose heat at night, and conduction to the ground is only one of them. You mention that your Synmat UL7 was fully inflated - that's good, as the insulation value is a factor of how full the pad is. Is your sleeping bag accurately rated, and is it new / clean? How well does your tent block wind? Did you eat well before you went to bed, and were you well hydrated? What's your metabolism like? Was your site in a valley, near water, or in another location that could have caused the localised temperature to be lower than in surrounding areas?

First time I took my Synmat UL7 out, I made a lot of mistakes. It was early season, my sleeping bag wasn't rated high enough, I was probably dehydrated, and I pitched camp in a valley close to water. Each time since I've made adjustments, and the mat has been comfortable down to ~3-4C. When it's borderline I will add a 1/8" closed cell pad to add an extra layer of insulation. But when I expect temps below -5C I'll switch to my Downmat UL7.

Just don't expect the mat to be a panacea - you have to be mindful of other factors.

Matt Purnell

Locale: Brisbane
"Coolness" was localized to under my hip on 05/20/2013 00:49:15 MDT Print View

Thanks for the comments so far. Stuart D - yes to all the above. I was car camping, so I was well-fed, well-watered, well everything and using my warm double-walled tent with fabric inner and my sleeping bag rated to -5 deg C. It's not new but it is clean and the reason I sleep in boxers and a t-shirt in it is otherwise I overheat! I had to keep the side zip and the toe-box zip open most of the night. So, my body wasn't cold. But even while feeling otherwise toasty warm, when I lay on my side I could feel "coolness" under my hip, which I'm concluding was either localized heat loss at that point, or my imagination.

Stuart D, when you say "the mat has been comfortable down to ~3-4C", do you mean -3 to -4 deg C, or +3 to +4 deg C?

On a hiking trip (as opposed to this car camping trip) I would be in a "colder" tent, wearing all my layers, and using a quilt. So, if I wasn't imagining things and the Synmat is borderline at the temps I normally encounter (0 to 5 deg C), should I swap it with the Downmat (add 105g), or use a bit of foam under the hips (add ?g)?

BTW, the minimum air temp was likely in the range 5 to 8 deg C with no significant wind chill. The car next to me registered 5 deg C, mine registered 8 deg C, and a thermometer at a nearby house registered 8 deg C.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Exped Synmat UL 7 felt "cool" under hips at 5-8 deg C on 05/20/2013 04:54:14 MDT Print View

UL 7 plus 1/8" foam mat (GG?) down to -7 C. We were warm.

The secret is to NOT camp on a hard smooth surface. If you camp on a lumpy surface (oh the horror!) you can always find somewhere between the lumps for your hips. Then the mat is not so thin.


Matt Purnell

Locale: Brisbane
1/8" foam mat in Oz? on 05/20/2013 06:06:25 MDT Print View

Thanks Roger. Any idea where one can buy a 1/8" foam mat in Australia?

SPIRIDON Papapetroy
(spotlight) - F
Quilt vs sleeping bag. on 05/20/2013 06:25:26 MDT Print View

I was also thinking of a quilt but i have never uswed one yet to see the difference from sleeping bags. My current sleeping bag is Monbel UL super spiral down hugger #3. I think it might feel strange to sleep with my head and arms outside the quilt.

Stuart .
(lotuseater) - F

Locale: Colorado
Temps on 05/20/2013 07:06:04 MDT Print View

@Matt - I meant approximately +3C to + 4C. I tend to think in Fahrenheit after the best part of two decades living in the US, so conversions back to Celsius / Centigrade are a little rough and ready.

I typically take a torso length 1/8" closed cell pad with me regardless of temps, as a little insurance against cold and sharp objects. I ruined my first Synmat UL7 with a large scratch from a dog's claw. He didn't slice the pad wide open, but the pad never held air for more than a few minutes after that.

Roger's advice is good, as always.

Paul Mountford
(Sparticus) - MLife

Locale: Atlantic Canada
Re: Re: Exped Synmat UL 7 felt "cool" under hips at 5-8 deg C on 05/20/2013 07:58:39 MDT Print View

+1 to Roger’s recommendation. On the last few trips I have been a little cool on my Big Angus Insulated Core. I was just chalking it up to me being a cold sleeper in my quilt. On my last trip to Scotland some cold temps were projected, so I also brought a torso length InsuLite 1/8" Foam Pad.

As it turns out, I’m not quite the cold sleeper that I thought I was. I made it through -14 deg C night with my quilt and some extra clothing. My son, who is a warm sleeper, over heated almost every night in his golite 20 quilt. Before this trip, I would not have thought an extra 1/8’th of an inch would have that much of an effect, but it certainly did for my son and I.

Colin Krusor

Locale: Northwest US
UL7 on 05/20/2013 08:58:41 MDT Print View

My synmat UL7 has felt cool under my hips and shoulders at about that temp (0-4 C). On one trip, I remedied that problem by piling a layer of pine duff under the pad to separate it from the cold granite. A thin CCF pad would have worked, too.

Dan Durston
(dandydan) - F

Synmat UL7 on 05/20/2013 09:32:50 MDT Print View

+1 to Colin

Edited by dandydan on 05/20/2013 09:33:26 MDT.

Andrew Martin
(am1982) - M

Locale: PacNW
CCF for cold ground with UL7 or Synmat 7 on 05/20/2013 11:19:28 MDT Print View

+1 Roger and Colin

I've owned and used both the UL 7 and original 7 with snow camping and some winter non-snow camping. These pads will conduct too much heat from the air-cells into the ground unless paired with thin ccf pads. Torso length works OK and full length is even warmer. My guess is that there is enough air circulation inside the UL 7 that the internal air temp is relatively even throughout. The R-value of the combined system must be substantially greater than either component alone given my experience. I've successfully slept in a 30 degree bag with pad+UL7 on snow multiple nights inside a double-walled tent.

Edit: The weight of thin foam can be easily offset in shelter or sleeping bag weight reduction. Matt you are probably safe to assume that a more airy (lighter) shelter or lighter sleeping bag/quilt will be cozy once you pair your mat up with some foam given how warm you were sleeping without foam.

Edited by am1982 on 05/20/2013 11:32:42 MDT.

Dena Kelley

Locale: Eagle River, Alaska
RE "Exped Synmat UL 7 felt "cool" under hips at 5-8 deg C" on 05/20/2013 11:23:11 MDT Print View

Had the same experience with my Big Agnes Q-Core SL this weekend. Went camping in about 20°F weather and the Q-Core was significantly transmitting the cold from the ground. I had brought a Z-Rest to top it with, as I had heard this might happen. I was glad I had it, it made all the difference.

Matt Purnell

Locale: Brisbane
Sources of 1/8" foam? on 05/20/2013 15:29:21 MDT Print View

Thanks all. There's seems to be a clear consensus to supplement the Synmat rather than swap it for the Downmat. I guess this makes sense as the added weight will come in lower than 105g, and the foam will protect the air mattress somewhat, and can be used for other purposes.

Anyone recommend a source for the 1/8" foam? I've seen it here, but the shipping to Australia is crazy.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Sources of 1/8" foam? on 05/20/2013 15:58:42 MDT Print View

You can get 1/4" foam at any Clark Rubber shop, in the form of very cheap camping mats. They may or may not have thinner foam.
I imagine you could get such mats at places like K-mart, Target etc, and at tourist camping places like Kellys as well.
Note that there are light foams and heavy foams. Check carefully. Do not buy open cell foam though: it will not work! Only Closed Cell Foam (CCF).


Matt Purnell

Locale: Brisbane
Re: Sources of 1/8" foam? on 05/20/2013 17:49:15 MDT Print View

Thanks Roger.

Kelly G
(KellyDT) - F
1/8th ccf on 05/20/2013 20:00:08 MDT Print View

+1 on the 1/8th ccf. Used my synmat UL7 for the 1st time, probably got to 40*f, and was cool all over. (I run cold!) Added my GG thinlight and ahhhh, made all the difference.

(Joomy) - M
Re: Sources of 1/8" foam? on 05/20/2013 22:14:30 MDT Print View

I have a local foam and rubber shop ( that sells CCF in all sorts of ticknesses from 6mm or less to 10-15mm. Not sure how it compares to the supposedly very good Evazote stuff from GG and other places but I'm sure it's not very different.

Btw I have also been considering the Synmat vs. Downmat option. I had settled on a Downmat but now I think Synmat + 4-5mm foam might be the better more versatile option too.

EDIT: Btw, Exped themselves sell a 4mm Evazote mat which weighs 390g for 2000x1000x4mm. If they import it you could cut that down to 1000x500x4 for roughly 100g. I might go to my local Exped stockist and investigate this option myself.

Edited by Joomy on 05/20/2013 22:27:52 MDT.

Matt Purnell

Locale: Brisbane
Re: Sources of 1/8" foam on 05/20/2013 22:58:48 MDT Print View

Glad to hear Kelly G that I'm not the only cold fish out there!

Jeremy, I've got a quote for a 2m x 1m sheet of blue EVA30 at 3mm thickness from these guys: $35 including postage. From my calculations this seems to be a very similar material to the Gossamer Gear Thinlight Pad (

I've also found that arts and craft suppliers stock A4 and A3 EVA sheets at 2 to 3mm thickness, for only a dollar or two. For example,

Higher density and hence more weight, but cheap!