When you're camping in cold conditions a warm sleeping bag is clearly a must. Perhaps less obviously essential is the mat you (re)lie on. Yet without sufficient insulation from the bone-chilling ground a miserable night is guaranteed. The modern breed of insulated inflatable mats provide the best warmth for weight, and among the most effective of these are Exped's down-filled range. With the DownMat UL (Ultralight) series Exped have put a lighter twist on their popular DownMat. Big weight savings have been made simply by using lighter fabrics and getting rid of the original DownMat's integral pump. Yet by retaining the same fill weight of 700 fill power goose down, no warmth is sacrificed. But what about durability?

Two models are available: the DownMat UL7, apparently good for -24; and the DownMat UL9, with a quoted bottom limit of -38. Thinking that -24 is quite nippy enough, thank you, I took a UL7 to the Andes. Here we camped high for several nights at a stint, and though we never slept on snow, night time temperatures into minus double figures were low enough to give the mat a proper work out.

Weight and packabilty

Compared with the original DownMat 7, the UL7 is a real featherweight. In size M the DownMat 7 is 845g, while its stripped-back offspring tips the scales at just 587g (my weight; add another 80g for the stuff sack and pump bag). The difference is largely down to the materials: the original mixes 150D and 75D fabrics, while the UL series uses a much thinner 20D top and bottom. Yet with an identical fill weight of 170g of 700 fill power goose down, both models achieve the same measure of insulation, an impressive R-value of 5.9. Down being so compressible, the DownMat UL7 rolls into a compact stuff sack that demands little space in your backpack. It's easily small and light enough to carry on routes where you're planning to camp or bivvy. In size Medium, which at 183x52cm is quite big enough for my six-foot frame, the mat can be compressed to about the dimensions of a 1litre Nalgene bottle, though it's a little broader in the stuffsack provided. When unrolled its square shape may be less space efficient than a tapered design, but I have welcomed the extra legroom it gives.

Blowing it up

The DownMat is not designed to be inflated directly with the mouth, for the obvious reason that condensation from your breath would soon migrate into the down insulation and ruin it. The older, heavier model gets around this problem with an integral pump, but the DownMat UL's solution is simpler and lighter - an external air bag, the horribly named Schnozzel Pumpbag, comes with the product. Plug this into the mat's inflate valve, catch a bladder full of air with the Pumpbag's wide mouthed roll top, then squeeze it into the mat. It's something like playing the bagpipes, minus the dreadful droning. This is marginally more faff than inflating with your lungs, but it's a nifty system nonetheless, and has the advantage that at altitude you're not left breathless. Five or six bags of air are enough to inflate the mat. The Schnozzel doubles as an ultralight drybag or pillowcase. Its tissue-thin fabric might be easily torn, but I don't imagine repairing it would be too onerous.

Comfort and warmth

Kneel on the mat and you'll doubtless feel the ground underneath, invariably a sharp pebble just where you don't want it. But when you lie down and spread the load you're riding high off the floor, floating in luxury on a cushion of air and feathers. Like a thick coat of plaster daubed onto an artex ceiling, the DownMat's hefty 7cm depth smoothes over uneven surfaces, masking niggly stones more effectively than thinner foam or inflatable mats I've used. I'd usually expect to rough it a little when camping, but this is comfier than my mattress at home (and a damn site easier to put on the back of a mule). Even the best down sleeping bag will compress beneath you, compromising its insulation, but because Exped's DownMats hold their feathery filling inside deep inflatable baffles, the loft is maintained. This makes the UL7 impressively warm for its weight. One night in Bolivia my watch in a tent pocket recorded -13, and under clear skies not far short of 5000m I've no doubt it sometimes got colder. But snug and snoring on the DownMat I was completely oblivious to any chill from the ground beneath. For cold weather camping this is by far the best mat I've slept on, and promises to add a whole new level of molly coddling to winter bivvies in the UK too. It is noisy though, creaking and squeeking on the tent groundsheet every time you roll over. To be fair my friend was more bothered by this than I. Perhaps he was just jealous, lying awake shivering on his less snazzy mattress.

Durability

When packing up camp one morning I pulled the mat out of my tent and gently laid it, fully inflated, against a dry stone wall. Big mistake. Though it was simply propped against the rock, the next thing I knew a sharp edge had managed to inflict a 2cm tear. Luckily I'd brought the repair kit (included), and several applications of fabric glue and a small patch had the mat good as new - well almost. Perhaps I was unfortunate, or stupid, but I shall be handling this mat with more care in future, and would not dream of laying it out on stony ground again. The light weight clearly comes at a price. Another wee niggle, and it is minor, is that the fabric has a tendency to pick up grease like suncream, or oil from a sardine can. A gear tester with tidier tent habits might not have noticed.

In conclusion

It's neither as light nor as damage-resistant as a foam mat - and it is vastly more expensive. But if you're out for a prolonged stay in the cold and watching every gram then that very pricey £190 may seem money well spent. The DownMat UL7 insulates so effectively that you could probably get by with a lighter sleeping bag than you might otherwise have had to carry. If you were buying both at once then perhaps you'd even break even on the money. Impressively lightweight, luxuriously padded and susprisingly warm, the downMat UL7 adds a whole new level of comfort to cold weather camps, and packs down small enough for minimalist alpine bivvies. It's the best tent partner I've had in years.

Exped say

DownMat UL7 is the ultra light version of the DownMat 7, 20% lighter yet with identical insulating values. It does not feature an integrated pump but includes the Schnozzel Pumpbag for swift inflation.

• Top: 20 D Polyester, TPU Polyether Film Laminate, Hydrolysis resistant, Honeycomb embossed
• Bottom: 20 D Polyester, TPU Polyether Film Laminate, Hydrolysis resistant
• Fill: 700 fill power goose down
• Fill Weight: 170g
• Temperature: -24 °C
• R-Value: 5.90
• Thickness: 7cm
• Four sizes: XS (52x120cm £145); S (52cmx163cm £175); M (52cmx183cm £190); LW (65cmx197cm £215)
• Weight: S 500g; M 575g; LW 765g

See www.exped.com