Down or synthetic for a sleeping bag: an objective comparison by intended use
The choice between down and synthetic for a sleeping bag represents a fundamental decision influencing performance, budget, and maintenance requirements. Contrary to popular belief, neither insulation is objectively superior to the other: each excels in specific conditions. Down offers a weight-to-warmth ratio that is difficult to beat (700 to 900 grams for a 0°C comfort rating) and exceptional durability (10 to 15 years), but it becomes vulnerable to moisture and requires a high investment (200 to 350 euros). Synthetic insulation resists moisture better and costs less (70 to 140 euros), but it weighs more (1.2 to 1.5 kg) and lasts for less time (5 to 7 years).
This article objectively compares the two types of insulation across eight key criteria (weight, compressibility, moisture, price, durability, maintenance, ethics, drying), identifies the situations where each naturally prevails, and presents hybrid solutions (hydrophobic down) that attempt to combine the advantages of both.
Comparison table
| Criterion | Down | Synthetic |
|---|---|---|
| Warmth/weight ratio | ++ 700 to 900 g for 0°C comfort | 1.2 to 1.5 kg for 0°C comfort |
| Compressibility | ++ 8 to 12 liters compressed | 16 to 22 liters compressed |
| Moisture resistance | Loses 70 to 90% of insulation when wet | ++ Retains 80 to 90% of insulation when wet |
| Price | 200 to 350 euros | ++ 70 to 140 euros |
| Durability | ++ 10 to 15 years, 300 to 500 nights | 5 to 7 years, 100 to 150 nights |
| Maintenance | Delicate, 48 to 72h drying time | ++ Standard machine, 24h drying time |
| Ethics | RDS certification recommended | ++ Polyester, no animal exploitation |
| Field drying | 48 to 72 hours | ++ 24 to 36 hours |
Advantages of natural down
Goose or duck down is the most efficient insulation in dry conditions, justifying its use in polar expeditions, technical mountaineering, and long-distance thru-hiking.
Weight-to-warmth ratio
Quality down (800 to 900 cuin) requires 250 to 300 grams to achieve a 0°C comfort rating, resulting in a total bag weight of 700 to 900 grams. An equivalent synthetic bag requires 800 to 1,000 grams of fibers for a total weight of 1.2 to 1.5 kg. This 400 to 600-gram difference tangibly changes the carrying experience on a 10-day trek or longer, reducing accumulated fatigue and preserving energy for the climb. Models in the down sleeping bag collection illustrate this weight range for comfort temperatures ranging from 0°C to -30°C. The Aegismax G2 0°C and the Aegismax G5 -23°C are two representative examples at either end of the range.
This performance comes from the three-dimensional structure of the feathers, which trap air in millions of microscopic filaments. Every ounce of high-quality down occupies 800 to 900 cubic inches once lofted, creating exceptional insulation with minimal mass.
Compressibility
A 0°C comfort down bag compresses into 8 to 12 liters, occupying less than a quarter of a 50-liter backpack. This compactness frees up space for water, food, and safety equipment. In bikepacking, a 10-liter bag fits into a saddlebag, whereas an 18-liter synthetic bag requires external attachment. The Aegismax G2 0°C, for example, illustrates this level of compressibility for a 3-season trekking bag.
Durability
Properly maintained down (washed according to protocol, stored uncompressed) lasts 10 to 15 years and 300 to 500 nights without significant degradation. This longevity offsets the initial investment: a 300-euro bag used 40 nights a year for 12 years costs 0.62 euros per night, comparable over time to a 120-euro synthetic bag replaced every 5 years.
💡 To achieve the maximum lifespan of a down bag, always store it uncompressed in a large storage sack between trips. This is the practice that most effectively preserves the loft of the feathers over the long term.
Disadvantages of natural down
Vulnerability to moisture
Down that absorbs 10 to 15% moisture loses 70 to 90% of its insulating power. Wet feathers clump together, lose their airy structure, and do not regain their loft until fully dried (48 to 72 hours). In prolonged humid conditions, a 0°C comfort down bag can effectively drop to only 5 to 8°C, creating a risk of hypothermia if the outside temperature approaches 0°C.
Even without direct rain, condensation inside a tent gradually permeates the down with 50 to 100 grams of water per night, a cumulative degradation over several days without the possibility of drying.
🚫 It does not need to rain for a down bag to lose efficiency. Nightly condensation inside a poorly ventilated tent is enough to alter its performance if the bag is in contact with the walls.
Price and maintenance
High-quality down costs 150 to 250 euros per kilogram for the manufacturer, compared to 15 to 25 euros for synthetic. This difference is reflected in the final price: 200 to 350 euros for a 0°C comfort down bag, compared to 70 to 140 euros for synthetic. Furthermore, down requires a strict washing protocol: a large-capacity machine (7 kg minimum), special down detergent, 30°C maximum, spin cycle at 400 to 600 rpm, and 48 to 72 hours of drying time with tennis balls. A mistake will permanently degrade the loft.
Ethical concerns
Down comes from geese or ducks, which raises questions about animal welfare. The RDS (Responsible Down Standard) certification ensures traceability and the prohibition of live-plucking, but requires verification on the product page. Consumers sensitive to this aspect may legitimately prefer synthetic.
Advantages of synthetic
Moisture resistance
Synthetic retains 80 to 90% of its insulation when wet. Polyester fibers do not absorb water, which condenses between the fibers without drastically affecting their insulating power. A 0°C comfort synthetic bag remains effective down to -2 or -3°C even when soaked, where down becomes far less reliable. This resilience is decisive for bivouacs in Brittany, Scotland, the Atlantic Pyrenees, or any region with high atmospheric humidity. Field drying requires only 24 to 36 hours, half the time needed for down. Models in the 3-season collection include synthetic references suited to these variable conditions.
Affordable price and simplified maintenance
A 0°C comfort synthetic bag costs between 70 and 140 euros, an accessible investment for beginners, families equipping multiple people, or campers going out less than 15 nights a year. Synthetic tolerates standard domestic machine washing at 30 to 40°C, with regular detergent and a spin cycle at 600 to 800 rpm. Complete drying takes 24 hours.
⚠️ Even if synthetic withstands washing better than down, overly frequent washing will eventually break the fibers and pack the insulation prematurely. Once or twice a year remains a reasonable frequency for regular use.
Disadvantages of synthetic
Weight, volume, and durability
A 0°C comfort synthetic bag weighs 1.2 to 1.5 kg for a compressed volume of 16 to 22 liters. The extra weight of 400 to 600 grams and the extra volume of 8 to 14 liters compared to down are noticeable on an itinerary like the GR20 or the Tour des Écrins. Synthetic fibers also pack down after 100 to 150 nights, losing 30 to 50% of their loft. A synthetic bag lasts 5 to 7 years with moderate use (20 to 30 nights a year), about half the lifespan of properly maintained down.
Arbitration based on usage
Choose down if
Conditions are mostly dry (Southern Alps, summer high mountain, arid zone trekking), if weight is an active criterion (regular thru-hiking of 30 nights or more per year, technical mountaineering), if the budget allows for a 200 to 350-euro investment amortized over 10 years or more, and if the rigor of maintenance (washing protocol, uncompressed storage) is feasible.
Choose synthetic if
Humidity is frequent (Atlantic coast, forest, oceanic climates), if the budget is tight below 140 euros or if multiple bags are needed to equip a family, if usage is occasional (less than 20 nights per year), if ease of maintenance is a priority, or if ethical concerns point toward a material without animal exploitation.
Hybrid solutions: hydrophobic down
Hydrophobic treated down (DWR applied to each feather) attempts to combine the advantages of down with partial moisture resistance. The treatment delays water absorption by 30 to 60 minutes, protecting against splashes, light dew, or moderate condensation inside a tent. It does not make the down waterproof: continuous rain or immersion will eventually saturate the feathers. The thermal gain in humid conditions reaches 20 to 30% more insulation retained compared to untreated down, a tangible improvement but insufficient for chronically humid conditions. The additional cost remains moderate: +30 to 60 euros compared to a standard down bag. This option is suitable for practitioners mainly in dry conditions but occasionally exposed to moisture.
Frequently asked questions
Is down really better than synthetic?
Not in absolute terms. Down is clearly superior in dry conditions regarding the warmth-to-weight ratio, compressibility, and durability. Synthetic is superior in humid conditions, regarding price and ease of maintenance. The choice depends on the dominant usage conditions, not a universal ranking.
Can a down bag be used in a humid region with precautions?
Yes, if waterproof protection is strict (waterproof compression sack, appropriate shelter). The risk remains if rain is continuous for 3 days or more without the possibility of drying. In chronically humid regions, synthetic remains safer even with precautions.
Is synthetic worth it despite its lower durability?
Yes, for occasional use (less than 20 nights per year) or in frequently humid conditions. The initial savings of 60 to 210 euros justify replacing it after 5 to 7 years compared to down's 10 to 15 years if usage is moderate.
Does hydrophobic down replace synthetic?
No. The hydrophobic treatment improves resistance to occasional moisture but does not solve prolonged exposure. It is an interesting compromise if usage is mostly dry with occasional humidity. For chronic humidity, synthetic remains the most reliable option.
How should I choose if I do 50% dry trekking and 50% humid camping?
Three options depending on priorities. First option: a down bag with a waterproof bivy cover for humid conditions. Second option: two distinct bags (light down for trekking, synthetic for humid camping). Third option: hydrophobic down as a compromise. The available budget and the priority given to weight will guide you toward one or the other of these solutions.
Does high-quality synthetic (PrimaLoft) compete with down?
On moisture resistance, yes, and even superiorly. On weight and volume, no: the gap persists between 1 to 1.2 kg for premium synthetic and 700 to 900 grams for an equivalent 800 cuin down. Premium synthetics reduce the gap but do not eliminate it.
Conclusion
Down and synthetic have specific advantages without one being objectively superior. Down excels in dry conditions with a warmth-to-weight ratio that is hard to match (700 to 900 g for 0°C), maximum compressibility (8 to 12 liters), and exceptional durability (10 to 15 years), justifying its higher price for thru-hiking and mountaineering. Synthetic dominates in humidity by retaining 80 to 90% of insulation when wet, with an accessible price (70 to 140 euros) and simplified maintenance, ideal for leisure camping and rainy regions despite the real excess weight and shorter lifespan.
The trade-off depends directly on the dominant usage: dry conditions with critical weight favor down, frequent humidity or a tight budget point toward synthetic. Hydrophobic down (+30 to 60 euros) offers a partial compromise for mixed profiles. To identify the insulation suited to your specific practice, the interactive selection tool allows you to quickly target models corresponding to your real-world conditions on our sleeping bag shop.
⚡ Verdict: for 3-season use in dry to semi-dry conditions with a budget of 150 euros or more, 750 to 800 cuin down offers the best ratio of weight-to-insulation-to-durability. For frequently humid conditions or a budget under 140 euros, EN 13537-certified quality synthetic is the most reliable choice.
