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Sea to Summit down sleeping bags, part 1: the 3D NanoShell

This spring season, Sea to Summit has released a groundbreaking new line of down-filled sleeping bags. The Sea to Summit down sleeping bags are so packed with technology, it’s more than we can adequately describe on, so we’ll be examining one technological aspect each day all week. Curious how Sea to Summit’s designers have pushed the envelope with their new down sleeping bag designs? Read on. Today’s topic is the 3D NanoShell, featured in the Alpine Series and Traverse Series bags.


3D NanoShell

Boy, this sounds like an earful, doesn’t it? “3D NanoShell.” It seems like every manufacturer has a different name for their breathable waterproofing and moisture management technologies, but Sea to Summit’s approach here is an innovative one and not just at techy-sounding, trademarked phrase.

See, traditional down bags use coated fabrics to create a water-resistant shell. Water resistance is critical with down-filled sleeping bags, because wet down can’t loft fully and loses its insulating properties. The coated-fabric method is effective at repelling outside moisture, but the problem is condensation. Water vapor leaving your body, in theory, passes through the down insulation and migrates outward through the shell material. For this vapor to escape, it needs to remain vapor… but, unfortunately, it often condenses at the dew point just inside the shell.

Once condensed, this moisture can be absorbed by the goose down, limiting its effectiveness. On a multi-day trip, you can lose warmth on a daily basis as your down sleeping bag accumulates moisture, especially if rainy or otherwise adverse conditions prevent you from drying it in the sun! The bag that keeps you warm on day 1 might be less efficient at doing so on day 3, and downright uncomfortable (or hazardous) on day 6.

This is where the 3D NanoShell comes in. To solve this problem, it is essentially a condensation-management system made up of two components: the NanoShell Face and the 3D Barrier.

The NanoShell Face is a high-density, 20 denier polyester ripstop fabric that utilizes a special Nano (read: extremely small) version of the industry-standard Durable Water Repellent treatment. Optimized for maximum breathability, this is much more durable than a typical DWR treatment, as its tiny particles are attached to the fabric in higher quantities and adhere better. This coating is used in the Sea to Summit Micro series of sleeping bags — without the 3D Barrier — and contributes to the ultralight nature of that series. For the Alpine series and Traverse series, this NanoShell Face is combined with the 3D Barrier to form the 3D NanoShell.

The second component, the 3D Barrier itself, is a layer of siliconized polyester. This material is hydrophobic, allowing vapor to pass through it but not moisture. Once the vapor has passed through the 3D Barrier, it cannot pass back through should it condense; the 3D Barrier creates a shield between this condensation and the goose down insulation.

With this system, the Sea to Summit down sleeping bags prevent moisture from saturating the goose down, thus preventing loss of thermal efficiency. With the 3D NanoShell, you can be sure your sleeping bag keeps you just as warm at the end of your adventure as it did at the beginning!


Check back throughout the week for articles about the innovative construction methods used in these bags, the unique certification provided for down content and fill power, the temperature rating system, and the features included in each of the four lines of sleeping bags.

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