Thermarest Ohm 20 Hoodless Sleeping Bag Review

The Therm-a-Rest Ohm 20 is a hoodless sleeping bag insulated with 900 fill power hydrophobic goose down that weighs 1 pound 6 ounces (652 g). It is box-baffled and has a full-length, two-way side zipper with a draft tube, a puffy draft collar, with a silky 10d nylon/ripstop shell. In warmer weather, the Ohm can be unzipped and used as a blanket or quilt and you can even join two of them together to form a two-person sleeping bag.

Specs at a Glance

• Temperature Rating: 20 degrees Fahrenheit / -6 Celsius
• Gender: Unisex
• Insulation: 900 fill power goose down
• Down Treatment: Nikwax Hydrophobic Down (PFC-free)
• Responsible Down Standard: yes
• Weight: 1 lb 6 ounces (1 lb 7 ounces – actual weighed/652 g)
• Fill weight: 12.5 oz / 354 g
• Length: 73″ (a long 79″ model is also available)
• Girth: 62″ x 56″ x 35″ (shoulder girth x hip girth x footbox girth)
• Packed Dimensions: 6.5″ x 8″
• Stuff sack included: Yes, compression sack
• Storage sack: Yes
• View for complete spaces (including metric conversions)

A Hoodless Sleeping Bag

The Thermarest Ohm 20 is a hoodless rectangular sleeping bag which means you can sleep on your side, back, or stomach without being constricted by a mummy hood. The nylon liner and shell are silky soft and warm against the skin. The bag is insulated with 12.5 ounces of 900 fill power goose down that’s baffled internally, so there are no needle holes in the shell to leak cold air and it can achieve maximum fluffiness (loft).

While the Ohm 20 is rated for 20 degrees Fahrenheit, it has a comfort rating of 32 degrees. The 20-degree rating signifies the lowest temperature where men will remain comfortable, while the 32-degree rating signifies the lowest temperature where women or very cold sleepers will remain comfortable.

Draft Collar

The Ohm 20 also has a thick draft collar, something you mainly find on premium sleeping bags, that wraps around your shoulders, upper back, and neck to prevent cold air from leaking in from the top of the bag and keeps warm air that has been heated by your body from escaping. This is a must-have for a sleeping bag or quilt that you want to use below freezing. The draft collar closes a snap on the side of your neck and there’s a drawcord is used to tighten it. That drawcord is quite long, so you can reach it even when both of your hands are below the draft collar inside the sleeping bag.

Zipper and Draft Tube

The Ohm 20 has a two-way zipper so you can vent the feet by pulling it up from the bottom of the bag if they’re too warm, or the top of the bag if your torso is too warm, or both at the same time. You can also open the quilt completely so that it lays flat so two people can sleep under it, side-by-side. Alternatively, you can zip together two Ohm 20’s and make a complete two-person sleeping bag.

The zipper has a cloth guard along one side which prevents snags, which is another premium feature. There’s also a tube of down insulation, called a draft tube, which folds over the inside of the zipper and prevents cold air from leaking in.

Hoodless Sleeping Bags vs Quilts

How does a hoodless sleeping bag like the Ohm 20 compare to a backpacking quilt and why would you buy one and not the other? Quilts, by definition, are open along the back so that your back is insulated by a sleeping pad (or an underquilt or pad if you sleep in a hammock), while a sleeping bag completely encircles you with insulation and draft protection. That’s the biggest difference between the two.

If you were to unzip the top of the Ohm, you could use it as a quilt, and its extra width would probably do a good job at blocking drafts along the sides of your sleeping pad. But I’d expect that you’d sleep a little colder because the down insulation isn’t as concentrated over your torso as it would be with a quilt with its narrower dimensions. The same would be true if you unzipped the Ohm to use as a top quilt in a hammock. That’s not to say that a hoodless down sleeping bag wouldn’t be usable in those circumstances, but it wouldn’t be as optimized as a quilt.

Quilts have their downsides too, especially when you get below freezing and cold drafts become a bigger issue or you dislike faffing about with a sleeping bag attachment system. I hesitate to say that a quilt will always be lighter weight than a hoodless sleeping bag with the same temperature rating because there are so many different factors that contribute to gear weight. As with anything, which you choose comes down to personal preference and budget.

Personally, I prefer using a hoodless sleeping bag for sleeping on the ground down to about 30 degrees and a quilt when using a hammock. Below 30 degrees, I switch to a mummy sleeping bag and go to the ground, but that’s just me.

Hoodless Sleeping Bag Comparison Table

Recommendation

The Therm-a-Rest Ohm 20 is a super comfortable hoodless sleeping bag that’s ideal for people who prefer the wraparound comfort and security of a sleeping bag but dislike mummy hoods. It has all of the features of a premium sleeping bag, including 900 fill power goose down insulation, a draft collar, a draft tube, and a two-way snag-free zipper, just minus a hood. I think it’s a wonderful off-the-shelf option, although pricey if you prefer the wraparound security of a hoodless sleeping bag over a quilt.

Disclosure: Therm-a-Rest donated an Ohm 20 for this review.