Sea to Summit Spark 15°F Sleeping Bag First Look

I’m excited that I get to test the Sea to Summit Spark 15°F (-9°C) sleeping bag this season. They sent it for review. If you haven’t heard of this bag, it’s an lightweight down sleeping bag made by Sea to Summit. It’s claimed weight is 1 pound 9.7 ounces (730g). At that weight, it is in the weight range of quilts. This is my initial impression after using it for two short trips. Later this year, I’ll post a final review after I get about 30 nights on it.

Unboxing

When I pulled this bag out of the shipping box, I got excited just from the storage bag. Usually, sleeping bags are stored in a cylinder-shaped storage sack, which work well unless you are storing them on an open shelf. The Sea to Summit Spark shipped in a cube. That’s going to stack much better on my storage shelf. I need to find or make other sleeping bag storage sacks in this shape and size to store all my other bags.

The bag comes with an compression sack, which weighs in at 3 ounces (85g). Instead of using this bag, I’ll use a Sea to Summit Ultra-Sil Dry Bag (REI link), which I’ve had great luck with over the years. I got it back in 2009, and it’s still working well. It weighs 1.7 ounces (47g).

There’s also a down test report and care instructions provided in the bag.

As far as specifications, it’s 850+ goose down with a non-PFC dry down treatment. The fabric with 10D nylon with a PFC-free durable water repellent treatment. There’s a YKK #5 zipper that seems to work without snagging. The 15° bag has full box baffles, which helps prevent drafts. There’s also a draft tube along the zipper, and an puffy baffle around the hood. The footbox has a nice shape.

Initial Impressions of the Sea to Summit Spark

One of the first things that I like to do when getting new gear is to put it on my scale to see how the actual weight compares to claimed. Mine is 0.1 pounds less than claimed.

After weighing the equipment, I like to put it on or in this case get inside of it. For me at 5’10” and 190 pounds, it feels plenty roomy. I was able to move around in it just fine. It’s what I’d expect in a sleeping bag. That said, some people did tell me that they found it tight. How constricted you feel in a sleeping bag is always personal, and you should try a bag out to be sure it will work for you. I’ve spent nights in a few bags tighter than this and a few that are larger than this. So for me, it’s the sweet spot.

So far, I’ve slept in the bag on two different trips. The first was a weekend trip on the Upper Iowa River. The second trip was to the Badland, Black Hills, Devils Tower and then Theodore Roosevelt National Park. I didn’t sleep in it the entire time on the SD, WY, and ND trip because I was teaching photography during those trips. When teaching, I slept in a hotel and between workshops, I camped.

Taken together I have six nights in the bag. The lowest temp I had was near 40°F. It was comfortable in the temps that I was in, and overall I found the bag comfortable. So far, I like the bag.

One thing that I noticed switching from a quilt over back to a sleeping bag is that without a draft collar at the shoulders, I do get drafts into the sleeping bag at my neck. But with a quilt, you are wrapping the opening around your neck and letting your head stick out. Overall, it was less drafty than my quilt.

What I Hope to Test

Last year on my bikepacking trip across northern Minnesota, I hit a breaking point with quilts. I had been putting up with them because they were so much lighter than sleeping bags, but on that trip I was uncomfortable on several of the colder nights. Plus, I was tired at night after riding 60- to 80-mile days on gravel, dirt, and forest service roads, and just wanted to climb into a sleeping bag instead of having to first strap the quilt to a pad and getting everything just right. I’m also sick of having to snap the quilt around my neck and cinch it tight.

I looked into sleeping bags after that trip and saw that the newer sleeping bags were only a few ounces heavier for the same temperature range. In this case, I’m switching from an Enlightened Equipment Revelation 20°F, which with the required straps weighs 21.6 ounces. The Sea to Summit Spark at 25.6 ounces is only 4 ounces (113g) heavier.

I want to test if the extra 4 ounces and less hassle makes for a better experience. I also want to test to see if this is less drafty.

The last thing that I want to test is how well the bag does overall for temperature. This is the first new bag that I’ve gotten for myself that uses the new temperature rating system. The lower limit of the bag is 15°, but the comfort limit of the bag is 30°. Having used bags under the older system, I found that the labeled temperature was the temperature that I was comfortable at. So, this will also test if there’s an apple to apple comparison between the older rating system and the new rating system.

Pricing and Purchase Details

Down sleeping bags aren’t cheap, especially quality bags. The Sea to Summit Spark comes in at $549. You can buy it direct from Sea to Summit here or from REI at this link.