Sea to Summit Spark Ultralight 28F - Review 2023

Well-Thought Out Sleeping Bag for the Best Zzzs

The Sea to Summit Spark Ultralight is a well-built model ready to provide the versatility to stay warm in temperatures just above the freezing mark. It’s available in different sizes and temperature ratings. We tested the regular 28℉ version in almost freezing temperatures and found the sizing and rating true to form and function.

Its mummy cut gives a snug fit with a little wiggle room to avoid claustrophobia. The 850+ Loft goose down with heat retention features like draft tubes and oversized collars did a good job of providing conditions for a comfortable sleep in chilly conditions. Despite condensation forming ice crystals inside and outside the tent, body temperature remained ideal when an appropriate amount of clothing was worn.

Regarding packability, the Spark is easy to stuff into its compression sack, and the bag has a relatively small profile when packed. All in all, this is an excellent option for backpackers. Just as well–as long as it’s within budget–a very good bag for any type of camping.

Construction and Design

The Spark Ultralight Sleeping Bag comes with a mummy cut. It provides a snug and cozy fit while cutting down its overall weight. Aesthetically, the outer shell comes in dark gray color while the liner is a bright yellow color block. Baffles also ensure heat retention and prevent any cold spots (more on that in a bit).

Now, we understand that not everyone will like this type of design. If you prefer having extra room to wiggle about and move, we suggest box-shaped sleeping bags like Coleman Green Valley, TETON Sports Celcius, and Kelty Galactic Down 30 Degree.

Construction-wise, this Sea to Summit outdoor bed comes with a 10D nylon shell and 7D nylon liner combination. Nylon is a workhorse for outdoor gear and apparel due to its high strength-to-weight ratio. It’s more durable and the fabric remains lightweight. And since it’s got a ripstop pattern, thicker threads are woven into the fabric to give reinforcement and stop any tear from running big.

Thanks to the anti-snag protection, the #3 YKK 2-way zips, running half-way through, glide without any problem. It comes with large branded pulls, making them easier to use.

The seams have solid stitching without that worrisome separation when stressed. You can move around without thinking if any wrong move will split the seams. The Spark Ultralight from Sea to Summit provides reliable overall construction you won’t typically find in cheaper alternatives.

Features

The hood of Spark Ultralight provides sufficient protection to your head. Heat loss and cold sneaking in isn’t a problem with the draft collar. You’ll also find a drawcord toggle on the left side to calibrate the fit.

The draft tube is also lining up under the zipper, acting as a heat retention agent. Warm air oozing out or chilly wind seeping through this outdoor bed from Sea to Summit is negligible.

Even with a mummy cut, the footbox of Spark Ultralight offers enough room to keep your feet free to move. There’s also ample space for some heavy socks, which you’ll likely need in temperatures below 45℉.

This sleeping bag from Sea to Summit features vertical box baffles on the torso, while the leg area has horizontal sewn-through baffles. Since the shell and lining are not pinched together at any seams, there are no cold spots. There’s extra material serving as walls between chambers for more room for the down to fluff and insulate.

The Drawbacks

On the downside, zip coupling is not possible with this Sea to Summit bag. There’s also no neck pillow or pillow pocket for additional cushioning. Pad loops are missing, so you can’t lash it to your sleeping pad for extra protection from the harshness of the ground and the cold that comes from it.

Escaping the bag once tucked in during the dark of night might also be a challenge. That’s a drawback worth accepting, given the warmth provided by this cocoon.

Fill Power and Warmth 

Sea to Summit Spark Ultralight Sleeping Bags come with ULTRA-DRY 850+ Loft Goose Down. The down fluffs more than 850 cubic inches once released from compression. It works excellently with trapping warm air, promoting better insulation throughout your enclosure.

And since there’s high fill power, it translates to a larger down size (almost as big as a quarter), leading to less fill per cluster and less weight. 

Sleeping bags like the Kelty Cosmic 20 Degree Down and its 600 fill power will require more down to loft a cluster, which means more overall weight.

But goose down still offers better insulation and is lighter than synthetic alternatives like TETON Sports LEEF, and VERZEY Portable. Though they might be cheaper, they can’t compare to thermal retainment that down serves.

Water Resistance

Synthetic fills are popular options that work well, even when wet. Goose down just works better. Thanks to Spark Ultralight’s down has ULTRA-Dry treatment, sleeping in freezing temperatures for three nights with plenty of condensation was doable.

Ease of Use

Since the zipper of this Sea to Summit outdoor bed only runs halfway through, you can’t quickly sneak inside as you would with sleeping bags with full side zips like Marmot Phase and Trestles 30. But it’s still relatively easy to scrawl in than zipless models like Sierra Designs Cloud and Frontcountry. The 2-way zipper allows you to open/close from either end for some ventilation.

Once you’re ready to settle for the night while camping, taking it out of its compression bag and setting it up is a piece of cake. It also fluffs in no time so that you can rest ASAP.

Post-use, packing it is also no problem. Save time without all the rolling. Slowly stuff it into its compression bag, lock the buckles, tighten the traps, and you’re good to go. It’s wise to be gentle when packing, allowing the air to escape gradually rather than bully-pressing the bag into the compression sack.

Overall, this outdoor bed from this Sea to Summit is easy to use and pack up and has a small profile for the temperature rating.

Portability

This bag super lightweight at only 1 lb. and 1.3 ounces. It ranks among the lightest sleeping bags we tested. By comparison, the Western Mountaineering HighLite is 1 lb. and the Marmot Phase 20F Degree Down weighs in at 1 lb. 7.3 ounces. With its balanced performance, Spark Ultralight lives up to its namesake.

It also compresses compactly into a 2.5-liter stowaway bag. You’ll save plenty of room, and lashing it onto your bag won’t be as awkward as its sibling, the larger Ascent Ac1, which packs into a 4.9-liter bag.

Conclusion

Sea to Summit’s Spark Ultralight Sleeping Bag is a high-quality outdoor bed worth the investment. You’ll enjoy both robust construction and reliable performance while staying lightweight.

With 850+ Loft goose down, insulation provides the comfortable coziness you need while camping out. There’s no need to worry about moisture either with its ULTRA-DRY treatment. Take benefits of both box and sewn-through baffles, giving the bag room to loft and trap heat.

This backpacker’s bag from Sea to Summit delivers on its promise regarding thermal retention. Stay warm even when the temperature drops below freezing. With that said, additional clothing or a liner is going to be needed at this temperature. But there’s space for it as long as you match your size with the regular or long edition. The Spark Ultralight is an excellent choice for camping and expeditioning during the fall and early winter season.

Though the price might be on the high-end, the value it returns is priceless. 

Buy this sleeping bag if:

• You love Sea to Summit products
• Want a sleeping bag worthy of its price
• A passionate light packer
• Need versatility in colder climates