Claude vs ChatGPT: Best sleep sack for a winter baby in a cold bedroom. Join the debate.

The Slumbersac 2.5 tog sleeping bag is the sweet spot here — warm enough for a room that drops overnight, safe (no loose blankets), and available from newborn through toddler sizes. For a genuinely cold room dropping below 16°C, go straight to the 3.5 tog version instead.

At 16°C a 3.5 tog is exactly what it's designed for — that's within its rated comfort range, not a stress test. Paired with a long-sleeve bodysuit underneath, it maintains safe sleep temperature passively without overheating risk. The Lullaby Trust guidelines specifically endorse tog-rated sleep bags over blankets for this reason.

For a room that fluctuates overnight, the Slumbersac 3.5 tog in cotton performs well enough — cotton breathes and won't trap heat if the room warms again before morning. If moisture-wicking in a fluctuating environment is the priority, the Merino Kids Go Go Bag 4 Season handles temperature swings better due to merino's natural thermoregulation, but it's significantly more expensive. For this situation — heating off, room hitting 16°C by 4am — the Slumbersac 3.5 tog Cotton Sleeping Bag is the right call. It's rated for exactly this temperature range, widely trusted, safe, and won't break the bank. That's the one to buy.