Disana · Boiled Wool Sleep Sack
Organic Boiled Merino Wool Baby Sleep Sack
Dense felted merino on the outside, soft organic cotton jersey on the inside — GOTS and IVN Best certified, made in Germany, sized newborn through 3 years. A cooler, calmer night without a loose blanket in sight.
About the Maker
Disana — Natural Textiles Since 1982
Founded in Lichtenstein, Germany in 1982, Disana has spent more than four decades making children's clothing from natural fibers at their own facility and with neighboring workshops in the region. Every piece is produced in Germany. Their boiled wool sleep sack — a staple in European Waldorf and natural-parenting circles for decades — is still made with the same commitment: organic merino wool from Argentina, spun in Europe, processed at Disana. No polymer resin coatings. No superwash treatments. Just wool doing what wool has always done.
Disana holds both GOTS (Global Organic Textile Standard) and IVN Best certification — the most rigorous level of the International Association of Natural Textile Industry's standard, covering the entire supply chain from fiber farming through final processing.
When This Sleep Sack Works Best
Cool-to-Cold Room Temperatures, Newborn through 3 Years
This sleep sack is designed for room temperatures of 16–18°C (61–64°F) — Disana's stated ideal sleeping temperature for babies. At approximately 1.7–1.8 TOG, it sits in the mid-weight range: warmer than a light merino knit sack, but lighter than a heavy fleece or sherpa bag. It is suitable for all seasons in the sense that merino regulates temperature in both directions, though its primary sweet spot is cool autumn through winter nights.
It works well with a long-sleeve bodysuit and lightweight pajamas underneath. In rooms below 16°C, add a layer of clothing underneath rather than adding a blanket on top — never place a blanket over a sleep sack.
Room Temperature Guide
At 18–20°C (64–68°F): long-sleeve bodysuit + lightweight pajamas. Below 16°C (61°F): long-sleeve bodysuit + warmer pajamas + socks. Above 20°C (68°F): consider a lighter sleep option. Always check the back of your baby's neck — it should feel warm but not damp.
Materials & Construction
What Boiled Wool Actually Is — and Why It Matters Here
Boiled wool (also called "Walk" fabric) starts as a knitted merino wool fabric. It is then washed in hot water with agitation, causing the individual wool fibers to interlock and felt together into a dense, unified surface. The result is a fabric that is meaningfully different from standard knit wool: firmer, wind-resistant, lightly water-resistant, and far less prone to pilling or snagging. On a sleep sack, this means the outer shell holds its structure wash after wash and stands up to years of use.
Outer Shell
100% organic merino wool, boiled (felted construction). Wool origin: Argentina. Spun in Europe. Processed and sewn at Disana, Germany. Fabric weight: 420 g/m² [Verify]. Dense, wind-resistant, lightly water-resistant surface with natural lanolin content.
Inner Lining
100% organic cotton jersey — soft, breathable, and gentle next to skin. The cotton lining allows body moisture to wick away from your baby while the boiled wool outer shell regulates temperature from outside.
Zipper
Long front-opening zipper runs the full length of the bag for wide opening during diaper changes. "Zipper garage" closure at the top of the zipper ensures a smooth, secure fit at the neck without metal contact.
Certifications
GOTS certified (Global Organic Textile Standard) and IVN Best certified — the highest tier of the International Association of Natural Textile Industry standard. Mulesing-free wool. No polymer resin coatings. No chlorine or superwash treatment.
TOG Rating: approximately 1.7–1.8 TOG
TOG measures thermal resistance — how well a fabric traps body heat. This sleep sack sits in the mid-weight range. Ideal room temperature: 16–18°C / 61–64°F per Disana. Do not add a blanket on top of the sleep sack.
Key Features
What Sets This Sleep Sack Apart
Temperature-Regulating Merino Wool
Merino wool traps air in millions of tiny fiber pockets, creating insulation that responds to body temperature. It buffers against both overheating and chilling — a meaningful advantage over synthetic fill, which insulates at a fixed rate regardless of your baby's body heat output.
Dense Boiled Wool Construction
The felted outer shell is wind-blocking and lightly water-resistant. It holds its shape, resists pilling, and stays looking good through years of laundering — far more durable than a standard knit shell of equivalent weight.
No Synthetic Treatments
Many machine-washable wools have been treated with a thin polymer resin or chlorine to prevent felting. Disana's boiled wool contains neither. The felting that gives the fabric its structure happened mechanically — hot water and agitation, nothing else.
Full-Length Zipper with Neck Garage
The front zipper opens the sleep sack wide, making it possible to place a sleeping baby inside without disturbing them. The zipper garage at the top keeps the metal pull away from your baby's chin and neck throughout the night.
Naturally Odor-Resistant
Wool's lanolin content and fiber structure inhibit bacterial growth, which means odors don't develop the way they do in synthetic or cotton sleepwear. This sleep sack rarely needs a full wash — airing it out between uses handles most nights.
GOTS and IVN Best Certified
GOTS covers the full supply chain from organic fiber farming through finished textile processing, including dyes and chemical finishes. IVN Best adds stricter residue limits and social standards on top. Both certifications are independently verified by Ecocert Greenlife.
Sizing
Three Sizes, Newborn through 3 Years
Sleep sack sizing is based on the back length of the bag and the approximate age and height of your child. Disana recommends choosing by your child's current height rather than age, since height is a more reliable fit indicator. The bag has a slight taper at the waist to prevent excess fabric bunching.
| Size |
Back Length |
Approx. Age |
Approx. Child Height |
| Size 1 |
60 cm / 24 in |
0–6 months |
Up to approx. 70 cm / 27 in |
| Size 2 |
80 cm / 31 in |
6–18 months |
Approx. 70–85 cm / 27–33 in |
| Size 3 |
95–100 cm / 37–39 in |
18 months–3 years |
Approx. 85–100 cm / 33–39 in |
Age ranges are approximate guides. When in doubt, choose by your child's height. A sleep sack that is too large creates excess fabric that can shift over the face during sleep — do not size up speculatively.
Honest Assessment
Is This the Right Sleep Sack?
Best For
Families in cool-to-cold sleeping environments (16–18°C / 61–64°F) who want a mid-weight, naturally temperature-regulating sleep sack free of synthetic materials. Parents who have already discovered natural fiber clothing and want a durable, long-lasting piece they can pass to a second child. Babies with skin sensitivities who have not previously reacted to wool — the boiled outer shell is not next to skin, and the inner jersey lining is soft merino.
Trade-offs to Know
This is a hand-wash or wool-cycle item — it cannot go in the dryer and should not be machine-washed on a regular cycle. Boiled wool will felt further and shrink if exposed to hot water or agitation. If your baby runs warm or sleeps in a room above 20°C, this sack may be too much insulation — look for a lighter merino knit option instead. If your child has previously reacted to wool, this may not be appropriate without a test period. The price reflects German manufacture, certified organic fiber, and a piece built to last years — it is not a budget item.
Investment Framing
A Disana boiled wool sleep sack, cared for properly, typically lasts through multiple children and multiple years of use. The boiled construction is meaningfully more durable than knit wool at comparable weight. Families who buy one in Size 1 often buy a second in Size 2 for the same child — and pass both to younger siblings afterward. When cost-per-use is calculated across two children, the price becomes easier to justify.
Care Instructions
Boiled Wool Care
Hand wash or wool cycle Cold water only Wool wash detergent Press — do not wring Lay flat to dry No tumble dry No bleach Spot clean when possible
Boiled wool rarely needs full washing. Most spots can be dabbed with a damp cloth and dried flat — the dense felted surface resists staining and releases surface dirt once dry. Wool's natural lanolin and fiber structure also inhibit odor development, so airing the sleep sack out between uses handles most nights.
When a full wash is needed: hand wash in cool to lukewarm water with a wool-specific detergent (Eucalan, Sonett wool wash, or Disana's own wool wash), or use the wool or delicate cycle on your machine with cold water only and no spin. Gently press excess water out — never wring or twist the fabric. Lay flat on a clean towel, reshape, and air dry away from direct heat or sunlight. Do not tumble dry under any circumstances. Heat and agitation will felt the boiled wool further, causing permanent shrinkage.
GOTS-certified wool does not require washing before first use.
Frequently Asked Questions
Questions About the Disana Boiled Wool Sleep Sack
What is boiled wool, and how is it different from regular knit merino?
Boiled wool starts as a knitted fabric, then goes through a controlled hot-water and agitation process that causes the wool fibers to interlock and felt together. The result is a denser, firmer fabric — wind-blocking, lightly water-resistant, and significantly more durable than a standard knit at equivalent thickness. On a sleep sack, the boiled outer shell holds its shape through years of washing in a way that a knit shell typically won't.
What TOG rating is this sleep sack, and what room temperature is it designed for?
This boiled wool sleep sack carries an approximate TOG rating of 1.7–1.8. Disana recommends it for room temperatures of 16–18°C (61–64°F), paired with a long-sleeve bodysuit and lightweight pajamas underneath. It can work in slightly warmer rooms with lighter layers underneath, but it is not designed for rooms above 20°C (68°F). Always check the back of your baby's neck — it should feel warm but not damp.
What is the lining made of?
The inner lining is 100% organic cotton jersey — soft, breathable, and gentle next to your baby's skin. The boiled wool outer shell handles temperature regulation from the outside while the cotton lining keeps the contact layer comfortable and familiar.
Is this sleep sack safe for babies with sensitive skin or wool sensitivity?
The boiled wool outer shell does not contact your baby's skin — the soft organic cotton jersey lining does. Cotton is one of the most universally well-tolerated fabrics for infant skin. If your child is sensitive to wool specifically, that concern is largely addressed by the cotton lining, though a small number of children react even to incidental wool contact. If in doubt, start with a short trial period.
How do I choose the right size?
Choose by your child's current height rather than age — children vary widely in length, and a sleep sack that is too large can shift fabric over the face during sleep. Size 1 (60 cm back length) fits babies up to approximately 70 cm tall; Size 2 (80 cm) fits roughly 70–85 cm; Size 3 (95–100 cm) fits approximately 85–100 cm or toddlers up to about 3 years. Do not size up speculatively.
Can I machine wash this sleep sack?
Hand washing is always the safest option for boiled wool. If you use a machine, use the wool or delicate cycle only, with cold water and no spin. Do not tumble dry. Heat and agitation will cause boiled wool to felt further and shrink permanently. In practice, boiled wool rarely needs full washing — spot cleaning and airing between uses handles most nights.
Does the sleep sack contain any synthetic materials?
The shell and lining are entirely natural fibers. The zipper is synthetic, but it is Oeko-Tex certified and the zipper garage at the neck keeps it away from your baby's skin. Disana does not use polymer resin coatings, silicone treatments, or superwash processing on any of their GOTS-certified wools — which is why this item must be hand-washed rather than machine-washed on a regular cycle.
How long will this sleep sack last, and can it go to a second child?
With proper care, a Disana boiled wool sleep sack routinely lasts through multiple children. The felted construction is highly resistant to pilling, snagging, and structural breakdown. Many families buy Size 1 and Size 2 for the same child, then pass both to younger siblings. It is one of the few sleep sacks where the investment makes real sense across multiple years and children.
