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I took a winter camping trip to the Cairngorms spending two nights in temperatures that dropped to minus 12C and struggled to get above freezing during the daytime. I combined a Firelight 750 with an Exped Downmat Winterlite and was very cosy.

Down Quality and Construction

• Highest quality down available – 970 Fill Power (US Method)
• Minimum Box-wall baffle construction
• Slant Box-wall baffle construction on warmer models

Lightwave's Firelight series of sleeping bags use one of the highest quality of down we've seen, at 970 Fill Power (US Method), in order to get this rating manufacturers need to skim the very best down from the rest and this makes these bags more expensive to produce, but this is reflected in the performance – more about this later.

Like most quality sleeping bags the construction is 'box-wall', this method largely eliminates cold spots compared to the alternative 'sewn through' construction which is simpler but much less effective. Lightwave use the box-wall construction method even in their lightest Firelight model, the Firelight 150, which weighs just 395g!

An even more effective construction method is called 'slant box-wall', this is where the seams that create the box-walls are offset from each other, so if the bag is compressed the seams do not line up between the inner and outer shell, thus reducing the potential for cold spots.

We like that as the Firelight models increase in insulation the feature set improves as appropriate to the temperatures the bags will be used in – so, while the 150, 250 and 350 models have box-wall construction throughout, the 450 and 550 have slant box-wall on the top surfaces and standard box-wall on the base. The 650 and 750 models have slant box-wall on both the upper and lower surfaces.

Feature Set

• Full length zip on all models
• Zip offset from the side to the top of the bag & is easier to use
• Neck baffle on all but the two lightest bags
• Box foot with highly water resistant shell around foot area

The most striking feature you'll notice on the Firelight bags is the zip that's offset to the top of the bag – this really works to make access easier, you don't have to reach quite as far to get at the zipper making it easier to zip and unzip. All the zippers are two way so you can vent from the bottom should you need to.

The foot of the bag is constructed as a box to give room for your feet and the entire lower section of the bag is covered in Pertex Endurance fabric which has such a good water resistance rating that its virtually waterproof – the bag isn't waterproof of course because of the seams not being taped – however this feature is very useful because the most likely place to get a sleeping bag wet is in the foot area – this happens because tent walls aren't vertical and your feet tend to press against the fabric during the night. The addition of Pertex Endurance fabric here protects the bag from excessive condensation.

As well as these key features the Firelight bags incorporate a decent hood, zip baffles in all but the 150 model, and double zip baffles in the warmer bags: 550, 650 and 750 models.

Performance

• The 750 model easily achieved its ratings
• Zip doesn't snag Bag doesn't feel restrictive, its slightly larger than other bags in its class

It's nice to be able to confirm a sleeping bags rating and I am very happy to do so in this case, the Firelight 750 I used in the Cairngorms has a comfort limit rating of minus 14C, and to my mind it achieved this easily – here's why; I'm a cold sleeper which means that I usually feel colder than the average person and always take a sleeping bag with a Comfort Rating suited to the temperatures I'll be experiencing – rather than using the Comfort Limit rating which is for the so-called average bloke.

The 750 Comfort Rating is minus 7C but the temperatures dropped to minus 12C so I should have been decidedly cold, as it turned out I was really cosy with just the usual baselayers and socks on.

EN ratings for sleeping bags are notoriously difficult to pin down for warmer bags because the EN test centres don't upgrade the sleeping mat for colder test environment rendering the sleeping bags compromised.

One thing I noted was that the zipper didn't snag – there is an anti-snag baffle, but in my experience these don't always work every time, the Lightwave one looks every bit as inadequate as others I've seen, but the zip doesn’t snag. Not sure how they've achieved that – but well done!!

It's always difficult estimating the size of a bag but the Firelights are more generously sized than other bags with comparable weight to performance ratios. I laid some competitor bags on top of the Firelight to check this and to varying degrees the Firelights were slightly wider in the upper body and shoulder areas. It’s still very much a mummy style bag – it has to be to secure the performance stats, but there's just that bit extra room compared to the very lightest competitor bags.

The inner and outer nylon shells are – well, nylon – they have the same feel as other bags in this category, softish but they can't compete with heavier brushed fabrics.

In Summary

A sleeping bag is a big ticket item and the Lightwave Firelights are at the expensive end, but what you are getting is a lightweight bag of exceptional quality – at the cooler performance end the Firelight 150, 250 and 350 compete with similar weight bags yet are slightly roomier and don't compromise with a short length zip. At the warmer end features like slant box wall construction and double zip baffles raise the performance above its peers.