Down insulation is warmer by weight and compresses to a smaller pack size than synthetic, but loses up to 80% of its insulating value when wet. Synthetic fills retain roughly 70% warmth when damp, dry faster and cost 30–50% less. The right choice depends on your climate, trip length and budget — neither material wins in every condition.
How Do Down and Synthetic Insulation Actually Work?
Down traps heat in three-dimensional loft clusters that expand to create dead-air space. Fill power (FP) measures how many cubic inches one ounce of down expands to — 600 FP is entry-level, 850–950 FP is premium ultralight territory. Synthetic insulation mimics this with polyester fibres engineered to mimic down’s loft structure. Major synthetic fills in 2026 include PrimaLoft Gold (used in the Patagonia Nano Puff), Polartec Alpha, and Thermore Ecodown. Neither material category is monolithic — a 900 FP down quilt and a 600 FP down sleeping bag are very different products despite sharing the same fill material.
Down vs Synthetic: Head-to-Head Comparison
The table below compares real products across the key metrics that matter for hiking decisions in 2026:
| Metric | Down (EE Revelation 20F) | Synthetic (NEMO Forte 35F) |
|---|---|---|
| Weight | 650 g | 1,250 g |
| Temp rating | -7°C | +2°C |
| Pack size | 2.5 L (stuff sack) | 5.5 L |
| Warmth when wet | ~20% retained | ~70% retained |
| Price (2026 MSRP) | $395 | $219 |
| Lifespan | 10–15+ years | 5–10 years |
| Best climate | Dry alpine, desert | Wet maritime, variable |
When to Choose Down Insulation
Down is the right choice for dry alpine environments, ultralight builds and multi-week expeditions where every gram counts. The Enlightened Equipment Revelation 20F Quilt at 650 g for its -7°C rating is the benchmark for ultralight hikers — a synthetic equivalent at the same comfort rating would weigh 1,100–1,300 g. Down also has a longer lifespan when properly stored and dried: quality goose down maintains loft for 10–15 years with basic care, versus 5–10 years for most synthetic fills. If you primarily hike in Scandinavia, Scotland, Iceland or the Pacific Northwest where rain is the norm, down’s wet-performance weakness is a meaningful risk unless you use a waterproof stuff sack and dry your bag every morning.
For a full comparison of the best down quilts and sleeping bags currently on the market, the backpacking quilt guide and the ultralight sleeping bag review cover the top options tested in 2026.
When to Choose Synthetic Insulation
Synthetic fills perform reliably across a wider range of conditions and require less careful storage and drying. The NEMO Forte 35F (1,250 g) is the go-to recommendation for first-time backpackers: it handles unexpected rain, compresses in a stuff sack, and costs significantly less than a down equivalent. Synthetic insulation also retains more warmth after washing — relevant for long-distance trekkers who need to launder their sleep system in teahouse washing machines. The Patagonia Nano Puff Hoody (325 g, PrimaLoft Gold) is the best example of synthetic applied to mid-layer insulation: it packs small enough for a hip-belt pocket and maintains warmth even if caught in a rain shower without a shell.
Does Hydrophobic Down Change the Equation?
Many down products in 2026 feature hydrophobic (DWR-treated) down that significantly reduces moisture absorption. Hydrophobic treatments delay — but do not prevent — wet collapse. In a 2022 test by Backpacker Magazine, hydrophobic down retained 70–80% warmth after 10 minutes of rain exposure, versus 20–30% for untreated down. However, after 30+ minutes of sustained rain, hydrophobic down performs similarly to untreated down: both collapse. For genuinely wet conditions lasting more than 30 minutes, synthetic remains the safer choice regardless of DWR treatment.
The Layering Approach: Using Both Materials
Many experienced hikers use both materials strategically. A synthetic sleeping bag or quilt provides a fail-safe for wet conditions, while a down mid-layer like the Nano Puff Hoody is worn in camp. This approach is covered in detail in the hiking layering system guide — particularly relevant for trips that cross multiple climate zones or seasons.
Frequently Asked Questions
Is down warmer than synthetic at the same weight?
Yes, consistently. High-fill-power down (800+ FP) provides 20–40% more warmth per gram than the best current synthetic fills. At the same weight, down will have a lower comfort temperature rating than an equivalent synthetic product — the gap narrows as synthetic technology improves but has not closed as of 2026.
How should I store a down sleeping bag to preserve loft?
Always store down products loosely in a breathable cotton or mesh storage sack, never compressed long-term in a stuff sack. Compression over months breaks down down clusters and permanently reduces loft. Hang it in a cool, dry wardrobe or use a large mesh bag. Wash and re-loft with tennis balls in a tumble dryer once per season of heavy use.
Can I use a down sleeping bag in tropical trekking regions?
Not ideally. Tropical regions like Southeast Asia, Central America and parts of Nepal’s lower elevations combine high humidity with warm nights — conditions where synthetic performs more reliably. For treks above 3,000 m in Nepal, dry alpine conditions make down viable even if the approach is tropical.
Does synthetic insulation lose warmth over time?
Yes. Synthetic fibres break down with compression and washing more quickly than down clusters. After 5–7 years of regular use, a synthetic sleeping bag typically loses 10–20% of its original loft and warmth rating. Down degradation is slower and largely recoverable through washing and re-lofting.
What fill power should I target for a three-season hiking quilt?
800–850 FP is the practical sweet spot for a three-season quilt. At 800 FP, you get excellent warmth-to-weight ratio without paying the premium of 900+ FP fills. Below 700 FP, the warmth-per-gram ratio declines noticeably and you’re paying for extra weight without meaningful durability benefits.