The age old question... what insulation do I need for my sleeping bag or quilt? Well as with most pieces of outdoor gear it depends on you and your personal choices. I feel it comes down (no pun intended) to 3 crucial points. Price, weight to warmth ratio and water resistance. This blog is here to help you pick what you feel is best for you.

Enlightened Equipment Revelation



One of the biggest deciding factors in any purchasing decision as we all have a budget to work to. Typically down has been more expensive over the years and the technology that has gone in to finding the best down products has certainly increased. That said, there are some great options for a cheaper down sleep system that still performs like the best of them. Synthetic obviously being the cheaper of the two has attracted many people to start using synthetic systems and as the demand went up for synthetic, the technology and features got better.

Verdict: If price is your deciding factor over everything else then synthetic will be your best option.

Nordisk Oscar


Weight to Warmth Ratio

Hands down (no pun intended again... I promise!), the best warmth to weight ratio is down. There's nothing that really beats it. You must think about fill power though. Fill power is the measurement of down within a certain space - this is done in a lab and is all nicely scientific. The higher the fill power, the better the warmth to weight ratio there is. Fill power will determine how fluffy or lofty the sleep system is.

Synthetic insulation is made from fibres and typically will have a heavier warmth to weight ratio. This does mean that it doesn't compress as well as down. In simple terms though if you had a synthetic sleeping bag or quilt that had the same temperature rating as it's down equivalent then the bag is very likely to be heavier and bulkier.

Verdict: If you're gram counting or watching your space then down is the one for you.

Sam Culley with his Big Agnes Torchlight UL 20


Water Resistance

Now I can imagine the vast majority of people saying to themselves "Nah, down is still not for me" will likely be because of this rather important point and that being water resistance. You can certainly say that you are safer using synthetic sleep systems if you're prone to moisture, rain or not having to carefully think about when and where you use your sleep system. This is a simple as that synthetic insulation is designed to carry on working and not lose its insulating properties even when wet. Synthetic insulation will dry much quicker too and you can quite regularly see thru-hikers with their synthetic quilts attached to their packs in the morning drying them off. Down when wet, as anyone who has tried to use a wet down sleep system will tell you is a very rubbish experience!

This may be starting to change as more down is now being treated to make hydrophobic down. This is like the down used in the Therm-A-Rest Hyperion. They use Nikwax Hydrophobic Down that stays drier and maintains loft up to 60 times longer than untreated down. This adds next to no weight and a lot of resistance compared to the usual down that is untreated. A synthetic sleep system will still outperform hydrophobic down sleep systems though.

Verdict: If you are going to be putting yourself in the way of moisture regularly and/or camp out like a cowboy under the stars and it's likely to rain then synthetic is certainly you best buy.

If you are struggling for ideas or can't find that perfect combination, please reach out to us in the usual places - @valleyandpeakuk on Instagram, @ValleyandPeak on Twitter, ValleyandPeak on Facebook or on for email.

Jim - Valley and Peak

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September 02, 2022 — Jim De'Ath