{"id":10273,"date":"2026-09-29T08:58:03","date_gmt":"2026-09-29T00:58:03","guid":{"rendered":"https:\/\/kelyland.com\/?p=10273"},"modified":"2026-09-02T09:03:51","modified_gmt":"2026-09-02T01:03:51","slug":"%eb%b4%89%ec%a0%9c%ed%98%95-vs-%eb%af%b8ummies%ed%98%95-%ec%88%98%eb%a9%b4%e3%83%90%e3%83%83%e3%82%b0","status":"publish","type":"post","link":"https:\/\/kelyland.com\/ko\/envelope-vs-mummy-sleeping-bag\/","title":{"rendered":"-envelope vs \ub9c8\ubbf8\ud615 \uce68\ub0ad: \uad6c\ub9e4\uc790\ub97c \uc704\ud55c 5\uac00\uc9c0 \ub0c9\ud639\ud55c \ud604\uc2e4"},"content":{"rendered":"

The envelope vs mummy sleeping bag<\/a> question usually surfaces after a buyer gets burned on a $50K order. “Why does the production run feel colder than the sample I approved?” The supplier’s answer reveals the real issue: “Same shell, same fill weight. We adjusted the pattern to hit the FOB pricing.”.<\/p>\r\n

That pattern adjustment is the whole technical story. The factory cold-room log compares a 190\u00d780 cm envelope bag with 1.0 kg hollow-fiber fill \u2014 no hood, no draft tube \u2014 against a 210\u00d775 cm mummy with 1.2 kg fill, a 3D hood, and an 8 cm draft tube. Shell is identical 210T nylon taffeta with PU coating. Conditions: 20\u00b0C ambient, 60% RH, 0.5 m\/s airflow. The envelope measured a 12\u00b0C<\/p>\r\n

For a private-label buyer, this reshapes the sample approval checklist. The mummy cut reduces exposed surface area by roughly 25% and seals the neck and zipper, which is why a lighter mummy out-warms a heavier envelope. Ask the factory for the mummy sleeping bag ISO comfort rating on the exact pattern they’ll mass-produce. Confirm the draft tube and baffle height in writing \u2014 3 cm for moderate nights, up to 6 cm if you’re speccing a 0\u00b0C synthetic bag. And read the quality tolerance clause<\/a>: if it allows pattern changes after sample sign-off, the cold risk lands on you.<\/p>\r\n

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\"Backpacker
Backpacker unrolling an envelope sleeping bag at sunset<\/figcaption><\/figure>\r\n<\/figure>\r\n

Why an Envelope Bag Leaves Your Shoulders Cold<\/h2>\r\n
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An envelope bag’s open geometry leaks heat faster than extra fill can replace it \u2014 shape fails before insulation gets a chance.<\/p>\r\n<\/blockquote>\r\n

A flat-topped rectangular bag does one thing well: it lets you move your legs at night. When the temperature drops, that same roomy cut becomes a heat-leak machine. There is no hood, and the neck opening spans the full width of the bag. Warm air rises straight out of that opening, and the body keeps paying to reheat the dead air space around the shoulders.<\/p>\r\n

The cold-room data makes the penalty concrete. A standard 190\u00d780 cm envelope bag with 1000 g hollow-fiber fill, no hood, and no draft tube measured a comfort limit of 12\u00b0C under controlled conditions (20\u00b0C ambient, 60% RH, 0.5 m\/s airflow). Drop below that and the sleeper wakes up cold \u2014 usually at the shoulder line first.<\/p>\r\n

The Open Geometry Problem<\/h3>\r\n

Compare the envelope’s exposed shoulder zone to a mummy cut and the difference is roughly 30% more surface area. That extra volume fills with dead air that body warmth must heat before the insulation can retain anything. A mummy’s taper removes that volume entirely, so the fill sits against the body instead of floating over a pocket of cold air.<\/p>\r\n

The envelope also has no way to seal the heat loss path. No neck cinch, no draft tube \u2014 just a wide open collar and a zipper channel that runs the entire length of the bag. Cold air infiltrates along the zip teeth, and warm air exits through the shoulders. A missing draft tube is one of the most common causes of cold spots on rectangular bags, and it never shows up in product photography.<\/p>\r\n

Why Adding Fill Fails<\/h3>\r\n

Some factories respond to the warmth complaint by adding hollow-fiber fill across the chest. That raises the material cost and packed weight, but it does not solve the geometry. The extra insulation lands in a zone that already has coverage, while the shoulders, neck, and zipper channel stay exposed. The bag gets heavier and pricier without gaining meaningful comfort.<\/p>\r\n

The factory cold-room sample log shows a 1.2 kg envelope bag still loses more heat than a 0.9 kg mummy bag<\/a>. Pattern shape alone delivered a 5\u00b0C comfort improvement before any additional fill was added. This is why the sleeping bag shape heat loss comparison matters more than fill weight on a spec sheet \u2014 and why the mummy sleeping bag ISO comfort rating, not the marketing label, should drive your sourcing decision.<\/p>\r\n

The sleeping bag factory we partner with in Zhenjiang runs CE, BSCI, and ISO 9001:2015 certified lines and produces 1.5 million units a year. Every envelope pattern tested through that facility fails the same way below 12\u00b0C: shoulders first, regardless of fill weight.<\/p>\r\n