The advantages of a bivvy sleep system – low weight, low volume and quick to set up – make them a clear favourite of ultra-distance bike racers, although if you’re blessed with stable weather (not common here in Scotland) then the view from your bivvy bag in the morning is still hard to beat without the added pressure of a clock ticking. Different brands take different approaches to their construction, with various materials, sizes and closure systems to give trade-offs between the eternal trio of weight, durability and price.

Despite these differences, bivvies tend to perform the same job: to provide waterproofing from the outside and to allow water vapour produced by your body to escape from the inside, leaving the job of insulation to your sleeping bag, clothing and mat. S.O.L. (Survive Outdoors Longer) offers something different with the Escape Pro Bivvy, by attempting to combine that weatherproofing with insulation – a potential game changer for those wanting to pack as light as possible.

S.O.L already offers various products using reflective-backed fabric to provide weather resistance and insulation: I’ve been carrying one of their ultra-light emergency bivvies as back-up for the last few years, both while working as a guide and on personal rides. I’ve only had recourse to use it a handful of times, and thankfully never for myself, but the insulation properties of the reflective fabric are noticeable, so surely it makes sense to apply that technology to a bivvy?

Although it is the most robust (and heaviest) of their offerings, in reality the Escape Pro occupies a middle ground between an emergency use shelter, and a full-featured mountaineer’s bivvy bag. At 0.5lb/222g, it really is light, and when packed is about the size of a 32oz/1L Nalgene bottle. Some of those weight savings are a result of its relatively small size, which I’ll mention again later. The seams are taped, there is a short zip on the right hand side to aid access and escape, and a basic draw cord around the opening – no bug mesh – allows the hood to be cinched up tight around the face: standard features for a lightweight bivvy without adding excess weight or bulk. At $125 (UK rrp £150) though, it costs a lot more than its competitors, which can often be had for half the price.

The interest lies in the fabric: SOL advertises the orange colour as being helpful in an emergency – this is true, although they claim that the Escape Pro is a legitimate “ultra-light shelter” rather than an emergency bivvy, and that colour might become a disadvantage if you’re planning to stay stealthy. The outer is soft and quiet – no plastic feeling here – and the inner is covered with a micro-porous, reflective coating that SOL claims increases in breathability as humidity in the bag rises: so far, so good.

The very first thing that I noticed on using the Escape Pro was its size when laid out. SOL themselves don’t provide its dimensions, but I measured the bag at 70” long and 30” wide (203 x 76cm). It’s on the small side, to the extent that I can’t fit my NeoAir mat and sleeping bag inside it without feeling restricted and compressing the down in my bag, thereby losing a lot of insulation and any advantage from the reflective fabric. I had to keep my mat on the outside, getting it wet and leaving it vulnerable to punctures. Otherwise, it performed well for a lightweight bivvy during several nights of showers. It ticked the first box nicely by keeping moisture out, and cleared condensation better than other lightweight bivvies that I’ve used, although not perfectly. As I’ve said, Scottish conditions are often challenging for a bivvy, as the atmosphere is humid, and on a chilly autumn night condensation will appear anywhere and everywhere. The Escape Pro didn’t breathe as well as my eVent bag in those sorts of conditions, leading to a damp bag and further loss of insulation, but it was better than the 2.5 layer fabric in my older, cheaper AlpKit Hunka.

Other than doing its job as a bag cover, I was curious to see how the fabric coped with multiple uses – the much flimsier Emergency Bivvy will be shredded after just one casualty incident. The face fabric in this case seems durable enough, but the reflective coating is more fragile – it showed signs of wear after a handful of nights, and the storage bag (made from the same fabric) has wear marks simply from rolling about in the camping kit box in my van.

We’re really wondering how warm it is though, aren’t we? SOL claims that the bag’s material will reflect up to 90% of your body’s heat back to you, which seems optimistic. The manufacturers of the fabric, Sympatex, suggest 75% heat reflection, and even more helpfully give a figure of 3.6∞C for heat loss reduction. I don’t see the value in trying to comment on that claim without the backup of a lab and some reliable measurements. What I will say is that the efficacy of reflective blankets is well accepted, and a hand inserted into the folds of the fabric gave the same instant feeling of reflected warmth – anecdotal evidence suggests that this is a warm bivvy bag. The extent to which that allows the user to shed other insulation and pack lighter will be entirely dependent on conditions and the individual, but 3.6∞C is going to be enough to notice. Because the test period was in autumn, temperatures weren’t high enough to allow me to test it as a standalone bag, which is a shame because I feel that that’s where the Escape Pro could come into its own. Using a lower-profile summer mat and insulated clothing could turn this bag into a racer’s dream, offering enough insulation to get by for a short sleep without a full size sleeping bag.

So we have a fairly expensive but very lightweight/fragile bivvy that performs well in milder conditions, adds some insulation but runs on the small side. Is it useful?