Therm-a-rest are, of course, currently renowned for their innovative camping mats, but in years to come you may look out for the brand when looking for a new sleeping bag, too. Therm-a-rest have been studying the science of sleeping outdoors for over 40 years, and have half of the sleep system sussed, I think you'll agree. So in many ways it makes sense that this January they launched a new line of sleeping bags to compliment their rage of camping mats.
There are plenty of sleeping bags on the market, so what are Therm-a-rest offering that's special? They say 'unique Synergy Link Connectors' (elastic loops that hold the bag to the mat), zone insulation (down where you need it and removed where you don't) and an efficient fit that's comfortable but not restricting. More on all these later, but my initial reaction was: none of these things sound ground-breaking or new.
Then again, as Therm-a-rest say in this little video below, which we got from their new sleeping bag microsite, “the sleeping bag is going to evolve and this is the starting point.” I don't doubt that the range will evolve and Therm-a-rest will bring some revolutionary technology to the table over the next few years. I'm also sure it will be a learning curve. I was interested to see one of the first generation products, and held off judgment till I'd tried one out.
I've had a Navis on test. The lightest bag Therm-a-rest now make, it's designed for those on the move with kit: backpackers, alpinists, cycle tourers and so on. The weight is 610g, and it's designed to offer a comfy sleep at temps from -4 to 7, depending on what kind of jacket you're wearing to bed.
The Navis has no hood
What kind of jacket are you wearing to bed?! Yes, the Navis looks like a normal sleeping bag up to ¾ of the length, then it ends in a simple drawstring. The theory being that most campers have a warm jacket with them anyway, so you can save weight by taking a less full-on sleeping bag and wearing your jacket to bed. If you're not familiar with this kind of sleeping bag, it's not unique, also check out the Nemo Siren 30 for example and the Feathered Friends UL Vireo.
I personally think a hoodless bag is a good, versatile system for lightweight trips. You can mix and match the thickness of your insulated jacket and hat depending on what temps you're going to be sleeping in. For example you can wear a lightweight down sweater in summer, a full on belay parka for winter bivys and everything in between. The temp rating is obviously vague as a lot depends on the jacket - the standard EN test can only be applied to complete bags.
I also think a half or hoodless sleeping bag is more comfortable than a mummy style sleeping bag as you don't feel so hemmed in and don't end up lost in the hood if you turn over in the night. Potential downsides to this system? Well I guess if your warm layers do happen to get wet during the day, you don't have a back up option. And maybe you don't want to sleep in your jacket – it does remove some of the 'just got into bed feeling' if you're still wearing a coat!
There's no down underneath you
How else have they made the Navis light? It's insulated only on the top, ie there's no down right underneath your body. This isn't a new idea, American company Big Agnes have been doing it for over 10 years, and there are others like the Rab Infinity SL. The theory is you have a camping mat underneath to keep you insulated from the ground anyway. Elastic loops hold the Navis onto the mat, and fit any camping mat up to around 60cm wide. Therm-a-rest call these 'Synergy Link Connectors'. It may sound simple, but most other brands feature a sleeve you slip your mat into, or no connection mechanism at all.
I wasn't sure about sleeping in a bag with no down underneath and being strapped in, as I sleep on my side. However I had plenty of room to move around. The bag is too big for me but apparently Therm-a-rest have specially designed it to fit side sleepers – ie with more room at the hip and shoulder if on your side.
There's no zip
There's no zip on this bag either to keep the weight low. It's easy for me to get in and out as there's plenty of room for me - I'm quite small at 5'4”. The shoulderxhipxfoot measurements are 158x147x102cm. The bag is designed to fit people up to 5'10, and is too big for me, with plenty of spare fabric widthways and it comes well over my head (see pic).
I was pleased to hear that Therm-a-rest are planning to add women-specific bags to the range later - when looking at sleeping bags I tend to buy women-specific because they are shorter and therefore more efficient for me both in terms of weight and heat-efficiency – I'm not carrying around more fabric than I need and having to heat up more space than I need.
A downside to the bag having no zips is that you can't drape it around you, or open it up to air it. Nor can you open it up to vent if you get hot. One thing you can do if you are hot though is turn the Navis the other way up and sleep that way, so you have the no down section on top of you.
The down used is 750+ fill power. If I'm looking for an ultralight down product, and therefore prioritising low weight, I'd personally want top quality down (850-900 fill) to keep the weight as low as possible for the warmth.
I also noticed that the fabric is 30 dernier, which seemed a bit excessive to me, adding unnecessary weight. I'd have thought one of the new generation of super strong 10D face fabric would have been better, especially as sleeping bags aren't subject to as much wear and tear as jackets. The Nemo Siren 30 mentioned earlier features a 10D face fabric, and the Rab Infinity SL features top quality Pertex Quantum GL, also 10D.
So I gave Therm-a-rest the chance to explain themselves on these two points, here's the response:
“Thanks for reaching out and giving me the opportunity to answer your questions, because we really did think about all of these in the design process. We chose 750 + fill power down (12.2 liters per ounce), because it provides excellent performance at a reasonable price.
Through our product testing in the cold chamber facilities (one of the only privately operated cold chambers in North America), we've found there is very little performance difference between 800-fill down and our 750+ fill power down, and therefore chose 750+ to keep the price down, and the performance high.
In the design process, we went with a 30D Nylon Ripstop because it was the best combination of value, durability and weight. Our bags were already on the light side of comparable bags so we didn't see a huge need to go with a lighter fabric and have to raise the cost of the bag. (Sidenote: The new women's line in 2014 features a 20D Polyester fabric)".
The Navis has some interesting features. I'd personally prefer a higher down fill power and thinner face fabric on an ultralight bag, but this would up the reasonable £200 price tag – you can find the Navis for £180 if you shop around. I look forward to seeing the range evolve and hopefully trying out a women-specific bag in the future!
Therm-a-rest Navis Sleeping Bag - RRP £200
Temp range: 7—4 degrees c
Fits up to: 5'10”/178cm
Measurements: (shoulderxhipxfoot) 158x147x102cm
Stuff sack: 18x31cm
Fill: 750+ goose down
Shell: 30D Nylon ripstop with DWR
Lining: 30D Nylon