Comparison review: Winter Down Sleeping Bags Who did you get a warm, calm sleep even in the extremely cold winter mountains?

Of course, winter sleeping bags (sleeping bags) are indispensable when spending nights in the harsh cold, such as in a tent in the winter mountains.

Restoring your exhausted body with a warm and comfortable sleep can have a major impact on your next day's behavior. On winter mornings, the inside of the sleeping bag is so comfortable that you can't even get out of it.

On the other hand, mountains are all year round, but if you spend the night with inadequate bedding, you may be unable to sleep due to the cold, wake up multiple times in the middle of the night, or in the worst case scenario, you may end up with hypothermia. In that sense, sleeping bags are expensive, but it is one of the gears that you need to choose carefully.

So, what kind of sleeping bag should I choose? Since it is used for freezing low temperatures, it is only natural that it has high heat retention. If you're camping or sleeping in a car, you can just carry something warm even if it's a little bit bigger. However, this is not the case when used for mountain climbing. The question is how efficiently and without compromising this warmth, it becomes possible to achieve its convenience and safety.

As an aside, the down padding used in winter sleeping bags has specifications that are comparable to those of poorly sophisticated high-end down comforters, allowing you to enjoy the ultimate sleeping comfort even in the lower reaches.

So, this time, in order to find a product that can be absolutely trusted in the winter outdoors, we have compared and examined the winter models from the three most popular domestic manufacturers that Japan is proud of.

Both sleeping bags are models that are expected to be widely used in most severe winter mountains, with a 2,000m class domestically. I was surprised by the spirit of making products, not only in terms of heat retention, but also in the details of the product-making spirit that is created from the user's perspective.

table of contents

• About the items we compared and tested this time
• Test results and spec comparison table
• Impressions of each model
• Detailed reviews of each item
• summary

Sleeping bags compared this time

Here are the three models we compared this time. It is a well-known three major brands of authentic outdoor and mountain climbing sleeping bags. There are many excellent models overseas too, but in Japan, these three companies are so strong that they cannot enter the market, making them a brand with a high level of reliability in basic performance.

That's why don't you want to compare which of these three is better (or worse)? That's the theme of this comparison test!

Although it is called a winter sleeping bag, there are various models depending on the quality and quantity of down, but the current usage environment is that it is a model that can be used well in mountains during the harsh winter (2,000m class south of Tohoku), so we have picked out a lighter model that can be used for mountain climbing with a limit of around -10°C.

• ISUKA AIR 630EX
• mont-bell alpine down hugger 800#1
• NANGA UDD BAG 630DX

Test environment

The test period lasts for two seasons from 2018 to 2019, and is in the harsh winter in Hokkaido. The environment is used in tents, sleeping in the car, or outdoors in strong winds. When I sleep, I wear a base layer, fleece, a down jacket, and a base layer and trekking pants.

I also tried to sleep in my sleeping bag when I went to bed, in order to verify the comfort of my sleeping bag at home. In total, you'll be sleeping in your sleeping bag for about two months!

The following five points were set as indicators for review of the evaluation items.

• Thermal insulation...needless to say, this is the most important item in a winter sleeping bag. Of course, it doesn't mean that just warm is fine no matter how heavy it is. Furthermore, this is merely a comparison between the models this time, so it cannot be said for all models in the brand.
• Weight: I want to keep the weight down as much as possible when I use winter mountain equipment that is bulky. However, this also balances with heat retention, and it's not just that it's light enough.
• Comfort: Check how comfortable you are sleeping. It can be a bit distracting when it becomes extremely cramped to achieve both weight and heat retention.
• Portability (storageability): Just like the above weight, it is something you should not miss from the perspective of carrying it around.
• We check how close the user is to the actual situation, such as functionality, water repellency, ease of use, and ability to respond to poor conditions.

Test results and spec comparison table

If you find it difficult to see the table because it is lightweight for smartphones, click here

Impressions of each model

ISUKA AIR 630EX

This is ◎

• Excellent heat retention
• touch
• Fit
• The zipper is very smooth

This is △

• The hood is shallow
• Storage size and weight

In a nutshell, it's "simple and robust." This model focuses on sleeping comfortably, and is packed with high heat retention and simple functions, making it a model that can be used safely even in the harsh winter.

The supple texture on the inside and the 800FP white goose down, which has excellent padding, not only allowed you to sleep well until the morning even during field tests at 15 degrees below zero, but also provided an exquisite sleeping experience that is comparable to a high-end down comforter.

In my personal opinion, it is the best of the three models in terms of heat retention. In particular, there was a lot of down sealed inside my feet, so my feet were still slurping until morning. From here, I think that the manufacturer's specifications, "minimum operating temperature -15°C," is probably close to the "limit temperature" according to the EN standard.

Unlike the other two models, the U-shaped shoulder warmer that wraps around the neck is not a drawstring type, but the soft fabric fits well so you won't be bothered. Personally, I think I prefer not having a drawcord to it as simple as it doesn't get in the way.

In addition, the draft tube located on the zipper part firmly prevents cold air from entering the zipper. The zipper with a mitigation reduction function generally works well, but since there was no biting at all, I felt that there was still room for improvement.

The waterproof test showed excellent water-repellent properties of the outer material, and although it continued to apply water in the shower for about 3 minutes, it did not show any penetration into the down. However, once the down got wet, it became sluggish afterwards, and I felt it would be difficult to use it on the field.

The hood is the shallowest of the three models, and the entire head is not the type that can fit completely inside, so when used outdoors in strong winds, the cold that the head and face inevitably suffered from.

The price is the highest this time, but overall I think it's a sleeping bag that has the heat retention, comfort and functionality that matches it. As expected from Japan's proud brand, ISUKA. This model was a model that I would confidently recommend.

mont-bell alpine down hugger 800#1

This is ◎

• Stretchability
• Storageability
• light
• Water repellent performance on the surface

This is △

• Fit around the neck
• Zipper biting

It's the cheapest of the three models, so to be honest, I was quite disrespectful at first, but to put it simply, it was a good idea to be disappointing. It's truly cost-effective.

The first thing that surprised me was the high insulation properties. The sleeping bag, which is packed with 800FP EX down, boasting high resilience, was not as good as ISUKA, but it felt warmer than Nanga, which has the same temperature mark. This subtle difference seems to be more about the quality of the down, but rather the overall feel of the various mechanisms that prevent the intrusion of cold air, such as the high density outer fabric "Balistic Air Light", the neck baffle around the neck, and the "double draft tube" that is attached to hold a zipper.

Above all, Montbell's unique "spiral stretch system" allows even authors who have trouble sleeping with poor sleeping positions to move comfortably inside their sleeping bags, providing a unique sleeping comfort. I had plenty of time to change clothes inside my sleeping bag, and I wear cross-legged clothes, so I can wear my sleeping bag even when I'm not sleeping during the cold season. This is also warm and easy to use.

The included staff bag also uses the same spiral stretch system as the sleeping bag, which not only reduces stress when storing, but also changes shape to fit into the dead space inside the backpack, making packing very easy.

Unfortunately, the chuck bites frequently. In particular, when closing the zipper from inside the sleeping bag, the bite occurs once in three times, and if you force it to close it, there is a risk of damaging the fabric, so the more you do it carefully, the longer it takes and I feel very stressed.

Overall, it is lightweight, cost-effective, and has unparalleled comfort, such as stretching functions, but I have the impression that it is not as good as the other two in terms of sleeping comfort and the detailed parts construction.

NANGA UDD BAG 630DX

This is ◎

• touch
• Large hood
• Water-repellent down
• Smooth zipper that is hard to bite
• Storage size

This is △

• Thermal insulation
• Cold air from the zipper

Speaking of Nanga, it's a very grateful "permanent guarantee." With this system, users will be trying to cherish it for the rest of their lives. The UDD BAG 630DX has been released by Nanga. DX down made from white duck down from Europe washed in Japan. This UDD is a water-repellent down that is treated with a super water-repellent finish, and is made into a water-resistant down that "passes through moisture but does not absorb water."

I'm concerned about the water resistance, but first, I'll talk about heat retention. The insulation was satisfactory at the specified temperature range (up to -10°C). It also has a great mechanism to prevent cold air from entering, such as the neck area and draft tube, and the large hood warms the head, making it a great piece. However, when comparing the temperature exceeded the limit and in harsher environments such as low temperatures of around -15°C and strong wind conditions, it is also true that this comparison was the easiest to feel the cold air. I've been feeling the cold air coming in, especially from the zipper and the feet. There may be a difference in quality down quality, but I was surprised that it felt colder than the same Montbell based on the EN standard.

Now, regarding the water resistance, it's a concern, when you submerge the down underwater, it will instantly rise. After repeating it several times, the result was the same, and the entire down was a little wet, but it didn't become slurpy. The other two models were not only shining after repeating them a few times, but rather became shaky, so I was surprised by the results. Of course, wet down will lose its heat retention, so if you use a UDD that repels a little moisture and moisture, it is unlikely to lose its heat retention even if used in harsh environments for a long time.

The zipper is a luminous type with a light-emitting design that reduces biting. It's very helpful that it's excellent visibility even in the dark. Bite reduction also works well. In reality, if you close the zipper with force without stretching the fabric, it will bite at a certain rate.

Although the heat retention of the three models is slightly inferior, it is one of the things that has an unparalleled charm, such as the ease of use and security of the water-repellent down, the fine details including the luminous zipper, and the reliability of the life-saving warranty system.

Next page: Go to detailed reviews of each item

On the previous page, we introduced a ranking of the models we compared, a list of ratings and specs, and recommendations based on them. From here, we will explain what criteria were used to evaluate the evaluation, and why it was evaluated in that way.

Detailed reviews of each item

Thermal insulation

The heat generated in the sleeping bag is likely to move from warm to cold and rise. The key to keeping warm air away is how effective heat retention is achieved through the sleeping bag, which does not let this warm air escape and is also an insulating layer from the outside air. For this reason, the quality of the down, the FP, and the structure of the sleeping bag are important factors. More detailed information about this is explained in detail in this article .

For the three models this time ISUKA and Montbell 800FP goose down, Nanga uses 770FP duck down. What we found out from this comparison is the difference in the amount of down between ISUKA and Montbell the difference in down quality and other differences in heat retention between Montbell and Nanga

We also went inside the sleeping bag for about an hour when the wind is strong outdoors (maximum instantaneous wind speed is 13.0m/s) to verify its windproofness and heat retention. It would normally be inside the tent so it would not be directly exposed to wind, but I did it as a field test.

As a result, ISUKA has excellent windproof and heat retention on the body, but the shallow hood means there was a lot of cold air coming from the head. In comparison, the Montbell 's deep hood protects the head, keeping the body warm and windproof, making it easy to withstand for an hour without any problems. Meanwhile, Nanga felt a cold air throughout his body and after an hour he also got cold, causing him to become far from comfortable.

weight

In order to ensure heat retention, it is absolutely necessary to increase the amount of padding, and the heat retention performance and weight are proportional. Mountaineering equipment is best to have a compact and lightweight design, but this balance is difficult for winter sleeping bags, which require heat retention. Regarding the three models this time, I think all of them are significantly lighter for their heat retention. Among these, the Montbell Alpine Down Hager 800#1 is actually measured at 924g, which is less than 1000g in this class.

Comfort

Of course, it's warm inside the sleeping bag, but you'll want to sleep comfortably. Looking at the materials for the interior walls of the sleeping bag, ISUKA and Nanga fabrics were very soft and comfortable to the touch. The Montbell dough has a crisp and slightly stiff look, and the loudest sound that occurs when you turn over in bed was also the loudest. I don't think it's at a level where I can't sleep, but I was curious about it. However, the stretchability is amazing, and even the author, who has a bad sleeping position, was able to sleep well.

The fit was great by ISUKA While the other two models tighten the neck with a drawcord, the ISUKA 's U-shaped shoulder warmer fits perfectly, making the neck warmer warmer warmer. Additionally, its unique 3D structure aligns with the body, making the whole body fit firmly to the sleeping bag, and it felt like there was the least wasted space that caused the loss of heat retention. the other hand ​​the Montbell seems to be slightly less comfortable compared to the other two.

Portability (storage)

Nanga is the most compact in terms of storage size . Next is Montbell . On the other hand, ISUKA was the biggest . While it has excellent heat retention, there are some areas where we have to compromise on weight and size.

On the other hand, storing down sleeping bags is surprisingly difficult, and some items can require a considerable amount of effort. In order to reduce this burden, each manufacturer has also put in great effort into the included staff bags. In that respect, Montbell staff bag was extremely excellent. The same spiral stretch system as the sleeping bag is used, so if you push the sleeping bag inside, the fabric will stretch, reducing the strain when storing it. The wide entrance is also a great feature. It also changes the shape when packing, and when rolled up, the shape becomes long and thin when rolled up. This is so grateful that it fits perfectly into the dead space inside the backpack. Also, the staff bag has two drawcords attached, making it very easy to compress. After all, a model with two drawcords is very convenient.

Functionality

First, about the zipper. To be honest, each manufacturer has made efforts to prevent biting, but there is no zipper that won't bite at all. For all models, if you close the zipper from the inside, there is a higher chance of it getting bitten. Of these, ISUKA was the least biting, and the movement when opening and closing was very smooth. In addition, Nanga 's zippers are made of phosphorescent resin, making them extremely visible in the dark. This was a very helpful feature.

Next is the water repellency of the surface. We conducted two tests to verify the water repellency.

One thing is to apply water from the shower to the sleeping bag, and after 3, 5, and 10 minutes, we evaluated the water repellency of the outer material and the intrusion of water through the zipper. Another thing is to completely submerge the sleeping bag into the bathtub and evaluate whether it is actually useful when the down is submerged in water.

As a result, when I continued to put the shower on and compared three minutes later, the Nanga was generally wet, while the other two models did not allow water to enter the down until five minutes later. I think this water repellent is extremely excellent. In particular , water infiltrated into the down after 10 minutes, but most of it was from the zipper and the outer material continued to have water repellent properties. We can be extremely trusted with the water-repellent performance of Polcatex, which boasts "the world's highest level of water-repellent properties." All three models were unable to prevent water from entering through the zipper. This may be a future challenge.

Next, we found out that the sleeping bag was submerged in the water stored in the bathtub. Nanga was by far the most water-repellent down performance. Even when I submerged my sleeping bag in the water it quickly rose up, and it was hard to sink the whole thing. Although I repeated it several times, the results were the same and I didn't get too shriek until I was down. After about three minutes, the entire sleeping bag of the other two models submerged under the water, completely slurping.

If it's a little water repelling, it seems that it will work well with water-repellent fabrics from Montbell and ISUKA, but if there is a chronic moisture or moisture situation, the UDD BAG 630DX class of super water-repellent down is sure to be safe.

summary

There were various evaluation items, but what we need for winter sleeping bags is probably mainly heat retention and light weight. Through this investigation, if I were to use it in a 2000m-grade winter mountain, I would like to sleep comfortably, but if I'm looking for lightness and portability, I the ISUKA AIR 630EX . I think I can manage the cold, but if I'm looking for lightness and portability, the Montbell Alpine Down Hager 800#1 . It would be good to say that people who value cost performance.

On the other hand the Nanga UDD BAG 630DX , tests suggest that in terms of heat retention, the equivalent of the two models compared this time, the UDD BAG 810DX, which is one higher class (or the AURORA light 600). Depending on your individual sense, the temperature range is somewhat strict based on the above, and is recommended as a model to use for long mountain trips over several nights.

Finally, through this test, I realized once again that, of course, heat retention is the most important thing when choosing a sleeping bag. A non-warm sleeping bag is useless with any other features. It's best to set a temperature range that meets your goals, and then choose things and priorities that can be compromised, such as lightness, compactness, comfort, other detailed functions, and parts. It's not a cheap purchase, so you should choose carefully. We hope this test will be helpful when choosing your sleeping bag.

We also recommend this article about sleeping bags.

• Warm your body from the core with the perfect sleeping bag (sleeping bag) - How to choose and 8 recommended items -
• How to choose a winter sleeping bag (sleeping bag) to make your winter tent comfortable and 8 recommended ones
• Comparison Review: Ultra-lightweight 3-season sleeping bag - A spectacular battle with a range of great items that are extremely light and warm -
• What to throw away and what to take? How to choose the best sleeping pad (mat) and 3 recommended pieces

TAC

Lives in Hokkaido. When it's a holiday, I can't stay still at home, so I do some kind of activity. I immerse myself in mountain climbing, fishing, camping in the summer, snowboarding and smelt fishing in the winter. I'm also a fan of this site and am looking forward to sharing the appeal of gear. We would like to review this from the perspective of not only mountain climbing, but also from a variety of activities.

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