A sleeping bag liner is a compact, lightweight addition that punches well above its weight. Slip one inside your sleeping bag and it adds warmth, keeps your bag cleaner, and acts as a hygiene barrier between you and whatever surface you're sleeping on — whether that's a DOC hut mattress or a camp mat in the backcountry. At Dwights Outdoors our lead recommendation is the Peak XV Silk Liner — lightweight, fast-drying, and packable, it's ideal for NZ tramping. We also stock Cocoon sleeping bag liners, a specialist brand with consistent sizing across silk, cotton, and synthetic options.
See our full range of sleeping bags to pair with your liner, or read through our NZ sleeping bags guide for advice on ratings and layering.
Liner Materials: Silk, Cotton, and Synthetic
The material you choose determines the liner's weight, warmth, pack size, and drying speed — all of which matter for tramping in NZ.
- Silk: The lightest option and by far the most popular for tramping. Silk is naturally temperature-regulating, dries fast, and packs to about the size of a fist. It adds roughly 3–5°C to your sleeping bag's rating. Cocoon silk liners are made from 100% natural silk and are robust enough to handle regular trail use.
- Cotton: Soft and familiar, but significantly heavier and slower to dry. Better suited to travel and car camping than backcountry tramping. Cotton liners add a similar warmth boost to silk but at a weight and bulk penalty.
- Synthetic (Thermolite/polyester): The warmest liner option — adding 5–8°C or more to your sleeping bag in some cases. Useful for extending a three-season bag into shoulder-season conditions. Heavier than silk but more affordable, and a solid choice for trampers who run cold.
Warmth Ratings: How Much Does a Liner Actually Add?
Liner warmth ratings are approximate, but as a general guide: silk adds around 3–5°C, cotton adds 3–5°C (with more weight), and synthetic thermal liners can add 5–8°C or more. This means a liner can meaningfully change the usability of a sleeping bag — turning a 5°C bag into a functional 0°C bag on cold nights, for instance. Check individual Cocoon product pages for specific warmth data. Remember that conditions vary: insulation from your sleeping pad, hut draught, and how warm a sleeper you are all influence the result.
Liner Shapes: Mummy vs Rectangular
Liner shape is mostly about fit and intended use:
- Mummy shape: Tapers toward the foot end, matching the cut of a mummy sleeping bag. Stays in place through the night, packs smaller, and is the best choice for tramping where pack weight matters.
- Rectangular shape: More room to move, and can be used as a standalone sheet on warm nights. Better for travel, hostels, and casual camping where packability is less critical.
For multi-day NZ tramping, the mummy shape is the practical choice. If you want one liner for tramping, travel, and hostel trips, a rectangular liner gives you more flexibility.
Frequently Asked Questions — Sleeping Bag Liners NZ
What does a sleeping bag liner do?
A sleeping bag liner serves three main purposes: it adds warmth to your existing sleeping bag, acts as a hygiene barrier between you and the bag (or hut blankets), and helps extend the life of your sleeping bag by keeping it cleaner between washes. In practice, a liner means you can wash the liner frequently — which is easy — and wash the sleeping bag far less often, which is better for the down or synthetic fill. They're also useful on their own in warm conditions or lightweight summer trips where a full sleeping bag is overkill.
How much warmth does a sleeping bag liner add?
The warmth a liner adds depends on the material. A silk liner typically adds around 3–5°C to your sleeping bag's temperature rating. A cotton liner adds a similar amount but feels heavier and takes longer to dry. Synthetic thermal liners can add 5–8°C or more, making them genuinely useful for extending a three-season bag into cooler conditions. Cocoon provides warmth rating information for each liner — check individual product pages for specific figures. Keep in mind that warmth ratings are approximate and vary with conditions, sleeping pad insulation, and how warm a sleeper you are.
Silk vs cotton vs synthetic liner — which is best?
Silk liners are the premium choice for tramping: they are lightweight, pack down to almost nothing, dry quickly, and feel luxurious against the skin. They're the most popular choice among NZ trampers who want packability and comfort without adding much weight. Cotton liners are more affordable and feel familiar, but they're heavier, bulkier, and slow to dry — not ideal for wet NZ conditions or multi-day tramps. Synthetic liners (typically polyester or thermolite) are the warmest option and often the most affordable way to get a meaningful temperature boost, though they pack larger than silk. For most trampers in NZ, silk is the go-to recommendation.
Do I need a liner for tramping huts in NZ?
DOC hut mattresses are shared and not washed between users. A sleeping bag liner is highly recommended for hygiene reasons — it creates a clean barrier between you and the mattress. Many trampers use a liner instead of carrying a full sleeping bag on warmer-weather Great Walks, though for most NZ hut trips a liner is best used alongside a sleeping bag rather than as a standalone. If you're doing the Milford, Routeburn, Abel Tasman, or other hut-based Great Walks, a compact silk liner takes almost no space and meaningfully improves both comfort and hygiene.
What shape liner should I choose — mummy or rectangular?
Mummy-shaped liners are cut to follow the tapered profile of a mummy sleeping bag — they stay in place better through the night and pack down smaller, making them the preferred choice for tramping. Rectangular liners offer more room to move and can also double as a lightweight sheet sleeping bag on their own, which suits travel or summer camping. If you're primarily buying a liner to use inside a mummy sleeping bag on the track, choose the mummy shape. If you want versatility — travel, hostels, car camping, and tramping — a rectangular liner covers more bases.
Can I use a sleeping bag liner on its own in summer?
Yes, in mild conditions a silk or cotton liner works well as a standalone sleep sheet — particularly in huts, hostels, or when car camping on warm nights. A silk liner alone is only suitable when temperatures are comfortably warm (typically above 15–18°C overnight), so it's not a replacement for a sleeping bag on most NZ tramping trips outside of the height of summer. For overnight tramping in NZ, even in summer, having at least a light sleeping bag alongside your liner is recommended given how quickly temperatures can drop, especially at altitude or in exposed huts.
How do I wash and care for a sleeping bag liner?
Most sleeping bag liners can be machine washed on a gentle or delicate cycle in cool water. Silk liners should be washed with a gentle detergent — avoid fabric softeners and bleach, which can damage silk fibres. Cotton and synthetic liners are more robust and can generally tolerate a warm wash. Always check the care label on your specific Cocoon liner before washing. Liners dry quickly on a line or in a tumble dryer on low heat — silk especially dries fast, which is one of its advantages. Store your liner loosely rather than compressed to help it maintain its shape and loft over time.