Home > 2009.08

A Bag For Three Seasons – Three Season Sleeping Bags

Not too hot, not too cold, just right. Three-season sleeping bags are warm enough for cool fall evenings without being too hot for milder summer climbing trips. Here are some things to consider before buying a sleeping bag.

For most Canadian climbers, three season bags offer the best combination warmth, low weight and seasonal versatility. They are warm enough for cool fall evenings without being too hot for milder summer climbing trips. Anyone climbing in serious winter conditions or only during the warmest summer weather may want a more season specific sleeping bags, but the majority of climbers will be better served with one of these three season bags.

First of all, you will have to choose your fill type. Down and synthetic insulation both keep climbers warm on cold nights, but down is lighter and more compressible than a similarly warm synthetic bag. Unfortunately, down quickly loses its insulating properties when damp. And once wet, down requires drying times that are often longer than the actual climbing trip. In wet conditions, synthetic bags excel; moisture does not radically affect their performance and wet synthetic bags dry out much faster than down.

Here are some other points worth considering when buying a sleeping bag:

Down Fill Power

Down bags rate the quality of the insulation with a number representing the down’s lofting power. These numbers usually start at 550 and go all the way up to 800+ fill power and refer to the volume that one once of down can fill. The greater the loft, the less down is required for achieving a particular warmth rating which in turn results in a lighter bag. High lofting down, however, is difficult to extract and therefore more costly than lower lofting down.

Shell Material

Traditional nylon or polyester shells are lightweight, relatively inexpensive, highly breathable and perfect for cold dry conditions. If there is a possibility of moisture or frost during a climbing trip, a water resistant or waterproof breathable shell is a better option. Water resistant fabrics retain almost all the breathability of conventional nylon shells but are better at resisting moisture. Finally, there are bags with waterproof breathable shells and sealed seams that are almost impervious to wetness. These are great for open bivies in exposed conditions but may not be breathable enough in warmer temps. Internal condensation may also become a problem with these shells as perspiration may condense on the inside of the bag due to the reduced breathability.


Down is highly compactable and less affected by extended storage in small compression sacks than synthetic insulation. That said, neither type of bag should be stored in a compressed state, as the insulation with be crushed, reducing warmth.


For long-term use, down is hard to beat; synthetics lose their loft and insulating power more quickly.

Temperature ratings

These ratings are an estimate of how warm a climber will feel sleeping in the bag when using an appropriate insulating ground pad. Unfortunately, the differences in personal metabolisms, gender differences (women sleep colder than men do), rest, hydration and clothing worn when sleeping, affect the bag’s warmth. Use the temperature ratings as a guide and choose warmer or colder bags based on personal experience.


Climbers on smaller budgets should strongly consider synthetic bags as they often cost less than one third the price of high quality down bags.

Antelope MF – $580
Western Mountaineering

Insulation 850+fill power down. Weight 1,105g

This luxurious bag is stuffed with exceptionally high lofting down for excellent insulation in colder temperatures. Western Mountaineering uses a MicroLite XP shell fabric, which repels moisture without compromising breathability. A generous down filled collar prevents drafts while the form-fitting hood traps valuable heat. For warm weather versatility the Antelope MF comes with continuous baffle construction allowing climbers to shift the down better temperature control.

EcoPro 15 – $180 (-7.6C)
Insulation UpCycle EcoPro synthetic insulation. Weight 1,474g
Built with recycled shell fabric and recycled insulation, the EcoPro 15 delivers environmentally low impact warmth in wet and cold conditions. A draft-sealing collar adds comfort on cold evenings while the shingle-like insulation construction prevents heat loss through the seams. Two different and easily identifiable drawcords allow fumble-free adjustments around the face and neck -no more scrambling to poke your head out to survey the morning weather. Finally, a small external Velcro-style pocket securely stores small necessities.

Ibis WB 500 – $440 (-7C)
Insulation 750 fill power down. Weight 1,195g

The Ibis WB 500g protects the down insulation from frost and condensation with a highly water resistant shell fabric and patented welded baffle construction. The welding eliminates sewing-needle holes that compromise traditional water resistant and waterproof fabrics. This construction makes the Ibis WB 500g perfect for exposed bivies or extended days trapped in a leaky tent. Weatherproofing is further enhanced by double Velcro-style sealing zipper flaps, but this added protection also slows down exits. Other useful features include a midsize interior pocket and two different and easily distinguishable drawcords for separate hood and collar adjustments.

Merlin – $310 (-10C)
Mountain Equipment Co-op
Insulation 800+fill power down. Weight 1,005g
Filled with 800+ fill power down, the Merlin is an exceptional minimalist bag for climbers moving light and fast. By eliminating the neck yoke and using a featherweight recycled polyester shell, the Merlin weighs in at a just over 1kg. This stripped -down construction does not, however compromise, warmth thanks to the generous amount of high quality down. A small internal pocket provides storage for contact lenses or a headlamp while the narrow pattering eliminates heat robbing dead-space.

Peggy SL – $353 (-9C)
Big Agnes
Insulation 800 fill power down. Weight 1,020g

The Peggy SL uses Big Agnes’s innovative pad-sleeve to trim overall weight and prevent drifting off the sleeping pad. The system makes sense. By securing the sleeping pad in a sleeve on the bottom of the bag, Big Agnes removes insulation that would normally be crushed when sleeping and reduces weight without compromising warmth. A full draft collar seals against cold air and the water resistant surface treatment extends use in damp conditions. Big Agnes also adds an internal pillow-pocket which can be used with a jacket or Big Agnes pillow.

Re Meow -$200 (-7C)
The North Face
Insulation climashield HL Green synthetic insulation. Weight 1,220g

Using a recycled shell fabric and recycled insulation, the Re Meow delivers versatile warmth in an eco-friendly format. An efficient draft collar minimizes heat loss and extends the comfort range in colder than expected temperatures. A small external zippered pocket holds a headlamp while the glow-in-the-dark zipper-pull ensures easy escapes for midnight nature calls. The included compressions stuff sack effectively reduces the bag’s volume allowing it to fit into most midsize packs.

Shield 3 Season – $620 (-9C)
Insulation 800 fill power down Weight 1,050g

For cold, wet and exposed bivys, it’s hard to beat the protection offered by the Shield 3 Season. Mammut uses a waterproof and breathable shell fabric and avoids any seams on the top of the bag. Seams on sides and bottom are bonded for waterproofness and an innovative rain visor protects the face from the wet and cold. One-third zips on both sides of the bag reduce weight and when partially unzipped, allow climbers to cook and read while remaining protected from the elements.

Wallcreeper 650g – $345
Insulation 750 fill power down. Weight 1,100g

The Wallcreeper is an incredibly versatile sleeping system that also works as an insulating overcoat around base camp. Armhole side zips allow climbers to wear the Wallcreeper and still operate a stove or read a book, while the drawcord bottom closer eliminates the need for boot removal when lounging around camp. If the conditions get nasty, simply seal the bottom and zip the armholes for an effective barrier against the cold.-GA

Check out the latest buyer's guide:

The best end-of-season deals on climbing gear for 2023

Act quick because like the fall weather these deals won't last long