Sleeping bags are a relatively big-ticket item in your personal outdoor equipment and something that you have for some time - I’m on to only my third bag in over 40 years of moderate use and my first one is still usable, albeit patched with duct tape! So, it is a choice you want to make wisely and there’s quite a bit to choose from: mummy or rectangular shape, short or long zip, down or synthetic fill, sewn through or baffled construction, 2, 3 or 4 season, and then there is confusing fill power and weight, temperature ratings and a wide choice of brands. If you are loyal to a brand, that solves the later dilemma, but what of the other choices?
Comfort Rating - Indicates the temperature at which cold sleepers/women might feel comfortable.
Lower Limit Rating - Indicates the temperature at which warm sleepers/men might still feel comfortable.
Temperature Ratings are measured in lab simulations of how a sleeping bag should be used, with a sleeping pad placed under the bag and the occupant wearing base layers. This protocol doesn't account for variations in people's sleeping pad and clothing, body types (warm and cold sleepers), weather conditions, the food people eat and more. So consider them indicative only.
Looking at my bag choice over the years, they have all been down filled, and mummy shaped with a hood giving optimum warmth for their weight. They have had a short, long and now back to a short zip. In a 3/4 season bag, a long zip gives greater versatility for summer and indoor use for the ventilation it offers and being able to open it out into a quilt, although it does add grams. There has been a trend toward lighter weight and more compressible bags in my choice. Some of this has been attributable to advances in materials but mostly to my desire to be more minimalist.
As a guide there is a bit of stuff that I have to carry and can’t skimp on, so it made sense to me to reduce the weight and packed size of my personal gear including my sleeping bag to keep my pack weight and volume manageable. For overnight hikes to the locations we visit in spring through autumn I have found my latest choice up to the task. While I have come to consider my sleeping bag as something to compliment my clothing system to keep me warm, I have rarely needed to wear more than a thermal layer, socks and a beanie. I am a warm sleeper though, add a silk liner, and another trick is I don’t go to bed hungry!
So, to my choice of a Sea to Summit Spark SP2 which is under 500g and has a truly tiny packed size. It has a temperature rating described as 4°C comfort rating woman / -2°C lower comfort rating for men, which you should find adequate for our trips. I find the mummy shape quite narrow and constricting and would prefer something wider in the foot and a long zip but at the expense of added weight. So many trade-offs!
For comparison, we have the Macpac Escapade 350 for hire with the same temperature rating. It has a roomier shape and a full length side zip and foot zip that weighs just under 1kg and has a proportional packed size.
Good luck with your choice.