With a high R value and relatively light weight, the Exped Downmat Winterlight M seems like a good thing to have during those very cold trips.
The mattress comes with a Schnozzel Pumpbag – it’s a big nylon bag with a roll-top closure at one end and a nozzle at the other that connects to the mattress valve. You fill the bag with air, close and roll the top, then compress the bag to push the air into the mattress. Something like this must be used – instead of our humid breath – to avoid condensation inside the mattress. I’ve been a bit skeptical about arrangements like this but I was able to inflate the mattress several times to a very firm level with only 2 or 3 bags of air so it does actually work. It’s not instant inflation as some of the marketing literature says but it is pretty fast.
On my scale the mattress weighs 478 grams plus 56 for the pump bag or 534 total – about 19 ounces. The thickness is about 3 1/3″. The website specs say R-7 but a tag with the mattress says R-8. The actual R-value is going to depend on inflation pressure and probably other stuff. Compared to my previous cold weather setup of a Thermarest NeoAir on top of a Thermarest RidgeRest, the Winterlight is lighter, thicker, packs much smaller, potentially more comfortable, and potentially warmer (about 2 points higher R-value) so it seems like a win.
I’ve spent 2 nights on the mattress so far and it was plenty comfortable, but I was camped in a grassy field and temps didn’t drop below 50F so that’s not a conclusive test. The top surface is rather slick and my pillow (a stuff sack full of clothes) kept sliding out but there are various solutions for that. Overall, I’m satisfied so far and almost look forward to trying it out with temps <20F.
Nov 3 2015.
Nov 23 2015 update: I slept on the mattress one night at 25F with a layer of leaves under the tent. I didn’t feel any cold from the mattress. Satisfied so far.
The product was purchased with my own money. I have no material connection with any companies, products or services mentioned in this post.