Sleeping bags (sleeping bags and sleeping bags) are essential for a comfortable sleep while staying in a tent. Unlike typical camping sleeping bags, climbing sleeping bags are made lightweight and compact, providing maximum comfort and warmth while minimizing the burden of carrying.
When climbing mountains that carry food and clothing and shelter, everyone would want to choose a sleeping bag that is as warm as possible and more compact. Choosing the best sleeping bag based on a balance between insulation and portability and a limited budget is a concern that many hikers face, and it is also a difficult problem to choose tools. Sleeping racks are expensive tools that compete for one or two of the equipment, so you cannot be allowed to fail.
Outdoor Gearzine has featured several times in the past on how to choose a sleeping bag and recommended models, and among them, one of the sleeping bags selected in the Best Hiking category is the Isca Air Plus series. The Air Plus series is undoubtedly the best sleeping bags that we have used up until now, and not only has ample heat retention, but also uses comfortable sleeping, ease of use, and high quality materials, and has a balanced, high-level performance, such as lightweight and compactness, making it easy to flexibly accommodate a wide range of seasons and activities, and is a model that can be used by both beginners and veterans.
This time, we will be introducing more in detail about the Air Plus series, and a lot of information about what they are good and recommended. I have also been the ambassador for Isca on Instagram because I was also accused of Isca's items more than ever. We'll be secretly bringing you some secret stories that are not listed in the catalogue, which we've heard from Iska.
The Air Plus Series sleeping bags are made by a manufacturer that knows everything about Japanese mountains, and are lightweight and compact, yet can be used by anyone regardless of the user, and are breathable, ensuring a comfortable sleep during mountain trips.
table of contents
- Main features of the Isca Air Plus series
- 5 reasons why I use the Air Plus series
- Part 1: High-quality white goose down, with a focus on the parts that cannot be expressed using FP numbers.
- Part 2: Excellent breathability that won't make you feel stuffy when sleeping
- Part 3: Optimal size design based on the model to make you look bulky
- Part 4: Essential features installed in the right place by the model.
- Part 5: A simple zipper, smooth and non-biting slider
- About the "minimum operating temperature" that Iska set after actually using it
- Conclusion and summary: Air Plus is an all-rounder sleeping bag that can be used by anyone
Main features of the Isca Air Plus series
Isca is a Japanese outdoor manufacturer founded in 1972. With over 50 years of history, Iska mainly sells sleeping bags (sleeping bags), staff bags, rain bag covers, spats, soft coolers, and more.
The Air Plus series created by Isca is the flagship model at the top of the down sleeping bag lineup.
The Air Plus series is a model that realizes the concepts of "light", "small", and "warm" at a higher level, and uses high-quality white goose down with 820FP (fill power), and the 30g down has over 2 million filaments and extensions, allowing a large amount of air to be stored, providing excellent insulation.
The fabric is made of 10 denier ultra-thin ripstop nylon, and is made of "super water-repellent" fabric, which has achieved the highest rating of grade 5 in the JIS standard. Although it is made of highly water-repellent fabric, it boasts high breathability, reducing stuffiness while sleeping. The three-dimensional shape has a 3D structure that gives room to the chest, the largest cross-section of the body, and the small round shape on the back side wraps around the body, and a large amount of down is enclosed at the feet that are prone to cold, and the inverted trapezoidal shape that follows the shape of the feet creates a mummy-shaped sleeping bag that fits the body without waste.
The Air Plus series, which has a lineup of four models, has a shoulder width design that changes to suit the temperature range used, making it suitable for bulky wear. This sleeping bag also incorporates the best attached functions and structure to shut out the cold air depending on the model, and uses Iska's technology to its full potential.
5 reasons why I use the Air Plus series
Let me start by introducing the reasons why I love the Air Plus series. Based on two of the "Air Plus 450" and "Air Plus 630" that I have actually used, we will tell you what's good about it.
Part 1: High-quality white goose down, with a focus on the parts that cannot be expressed using FP numbers.
The down used in the Air Plus series is white goose down.
The "wings" that are enclosed in down products, including sleeping bags, are collected from waterfowls, and are mainly duck down and goose down. Both are waterfowls, but the quality of the down is very different.
Image provided by ISUKA
In comparison, goose down has a larger down ball than a duck down, allowing it to maintain a high loft (bulging). The down inflates and stores air, creating dead air and providing insulation. When using the same amount of down, down balls with a larger goose down each one can maintain a higher loft and provide better insulation.
When I asked Iska about the difference between goose down and duckdown, it seems that there are differences in not only heat retention but also durability. Compared to duckdown, goose down is more flexible, with less likely to break the feathers and wing shafts, and is more durable because it deteriorates less due to use. I never thought much about the deterioration in performance caused by use of the product before purchasing, but when I think about it, sleeping bags are expensive tools, so once you buy them, you'll want to use them for a long time. Even if the cost of initial investment is high, it seems that the durability will reduce costs in the long run. If you are thinking of purchasing a sleeping bag, I would definitely like you to be aware of whether it is a duck down or goose down. You'll notice that when you touch it, it's not only durable, but also completely different in flexibility.
The down used in Air Plus has changed its FP (fill power) value, which represents the quality of the down, from 800FP to 820FP since September 2024. There have been no changes to the original down product, but after repeated inspections, the inspection results showed that the quality was 820 to 850 FP or higher, and the description was changed because it was not below 820 FP.
Fill power is one of the criteria for evaluating down performance, and represents the resilience of down 30g under certain conditions. The higher the FP number, the better the performance, and the same weight can fill more space. Isca's downs are measured using the world standard IDFL (International Down And Feather Laboratory).
It seems that the quality of the measured down is unlikely to be consistent, and there are variations in the quality of the enclosed down. Down is a valuable natural material, so it's difficult to get it from the same quality. Furthermore, it seems that the manufacturer will determine whether the minimum or maximum value is indicated in the published specifications for the included downs. Unfortunately, most manufacturers do not disclose whether the lowest or highest value is listed, so we cannot determine.
When you touch it, you can see that it uses fluffy, high-quality down. I immediately felt a gentle warmth when I placed my hands.
Air Plus has published a 820FP value that can be guaranteed to ensure quality inspections of downs, and 820FP is the minimum number that can be guaranteed, and in reality it is said that downs of 820FP or higher are included. Just by touching Air Plus, you can see that high-quality down is used. Once you enter your sleeping bag, the supple down will instantly adhere to your body and warm you.
Part 2: Excellent breathability that won't make you feel stuffy when sleeping
The high breathability is unclear based on the specifications of the official website. Although rainwear and other items are numerically expressed as breathability, they are rarely indicated on a sleeping bag, so you won't know until you actually try it.
The author believes that the most recommended point of Air Plus is its high breathability. Iska's sleeping bags have taught me that while heat retention is important for a comfortable sleep, it is also important to avoid stuffiness (breathability).
The secret to the high breathability of the Air Plus series is the quality of the down, its internal structure, and the fabric used. Natural goose down has moisture control performance, and adjusts to a moderate humidity when stuffiness occurs. Furthermore, mesh material is used for the partition walls inside the sleeping bag, so it is designed to prevent the humidity from being biased.
Made from extremely thin, "super water-repellent" fabric of 10D (denier)
The fabric is made of ultra-thin ripstop nylon with 10 denier. The water-repellent fabric has been awarded the highest grade 5 in the JIS standard, and only fabrics that have been awarded "super water-repellent" are those that have been awarded the "highly water-repellent" fabric. In addition to down, the fabric is made from the finest materials.
The fabric used in the Air Plus series has been changed from the notation "15 denier class" to "10 denier." The original fabric was made of 20 denier for the warp and 10 denier for the weft, so the fabric was written as "15 denier class" in the middle, but it has been changed to the thinnest 10 denier notation. The warp thread is made of 20 denier yarn, and the lip structure further enhances tear strength despite its thin fabric and is also wear-resistant.
Goose down is not processed because it has a high natural water repellent properties.
Down sleeping bags are compact and offer high insulation (heat retention), but their weakness is that they are weak to wetting. If down gets wet, the wings will collapse, making it impossible to secure the loft, and its heat retention will decrease.
Many down sleeping bags have DWR processing (durable water-repellent treatment) on the down to protect it from getting wet, but the goose down used in the Air Plus series has natural water-repellent properties, so by sealing it in it without processing it, it is said that it reduces performance and improves durability. Artificially processed water-repellent functions cannot be maintained forever. When considering the long term, the goose down used in the Air Plus series is highly durable and water-repellent.
Iska also seems to be very particular about breathability, and it is a must to prevent functional degradation caused by "wetting" when used in harsh mountainous areas. In that case, it becomes necessary to use a sleeping bag cover. Taking into account that attaching the cover will cause some "smoothing", the bag is designed to provide a high "breathability" and is made with carefully selected materials.
Part 3: Optimal size design based on the model to make you look bulky
Even though Isca's sleeping bags are of the same series, the shoulder width design has been changed depending on the grade.
The Air Plus 450's shoulder width is 78cm, as it is not intended for use in low-temperature environments, as it is less likely to wear when sleeping, so the shoulder width of the Air Plus 450 is 78cm, but the winter model, which is intended for use in harsh environments, has a maximum shoulder width of 84cm, making it suitable for wearing when wearing clothing. (Air Plus 630 has shoulder width of 80cm)
Although other sleeping bag manufacturers have different shoulder widths for regular and long sizes, as far as I can see, Iska is the only one who changes the size depending on the grade of the same series. It's a small thing, but I can sense the commitment to making the sleeping bags is that they have not compromised to maximize the heat retention of the sleeping bags, and the specifications are changed depending on the grade.
Only 2cm, but 2cm. This difference in design creates a large effect, and even when multiple sleeping bags are actually used in harsh environments, it will no longer interfere with the lofts (bulging) between the sleeping bags, bringing out the heat retention of the down to the fullest.
Part 4: Essential features installed in the right place by the model.
The Air Plus 450 is positioned for three seasons, and the Air Plus 630 is positioned for four seasons. These models differ in structure and ancillary functions, and we have taken care to ensure that the most suitable functions are included in each usage situation.
For example, the Air Plus 450, which is enclosed with down, has a "box structure" and the Air Plus 630 has a "trapezoidal box structure", both of which do not impair the heat retention of down, but the trapezoidal box structure is the most excellent heat retention structure that can reduce heat loss by shifting the stitching positions on the inside and outside.
Image provided by ISUKA
Not only that, the shoulder warmers and hoods have different specifications, and the Air Plus 630 has a hood tube that reduces heat dissipation from the head, and a distinctive "U-shaped" shoulder warmers that softly cover the neck.
The Air Plus 630 has down sealed around the hood, preventing cold air from entering.
The shoulder warmer used in the Air Plus 450 is tightened with a drawstring, so it feels a little oppressive, but the Air Plus 630's "U-shaped" shoulder warmer does not feel oppressive and wraps around the neck.
There are some preferences regarding the structure of the shoulder warmer, but for me, the Air Plus 630 is easier to handle as there is no need to squeeze the drawcord every time you enter or leave.
Part 5: A simple zipper, smooth and non-biting slider
It's stressful that the zipper will chew on the fabric when you come in and out. Isca's sleeping bag zipper does not chew the fabric and can be opened and closed very smoothly. The zipper was a simple one that didn't seem particularly clever from the appearance, so I checked with Iska and found out that the reason it's difficult to bite into the fabric is threaded along the zipper to prevent it from getting into the fabric.
Thread is threaded through the dotted red line to prevent the fabric from biting.
I didn't notice it at all until I heard it, but if you look closely, you can see that the thread is threaded along both sides of the zipper. The design is designed to make it easier for users to use because it doesn't seem to be visible.
It's so smooth that it opens on your own when you sleep
The zipper can be opened and closed smoothly without any stress, but it's so smooth that it opens when you sleep and move. Be careful not to tighten it firmly all the way up and secure the Velcro in the zipper garage every time, so before you know it, a gap will form before you know it.
About the "minimum operating temperature" that Iska set after actually using it
Many sleeping bags currently on the market are presented with reference temperature ranges based on the same standards by third parties called European Norms (EN) 13537. This test is conducted in an environment where a thermo mannequin is placed in the sleeping bag in an environment with a temperature of 20°C, humidity of 64%, and wind speed of 0.35m/s, and three indicators are calculated: "comfortable operating temperature," "lower limit temperature," and "limited temperature."
Rather than listing the test results for European Gnome (EN) 13537 as published values in the catalog, Isca's sleeping bags calculate and publish their own minimum operating temperature based on accumulated data and experience. However, this cannot be accurately compared to other manufacturers that display test results for European Gnomes, so when we asked them why, they found out that the mannequins that come into the sleeping bag during the test use mannequins with the skeletons of ordinary European people, and as they are different from Japanese figures, the test results alone are not sufficient. Another thing is that even if the same amount of padding (down) is used, there have been cases where inspection results have been largely different depending on the material of the fabric. One example I was taught was that a highly waterproof sleeping bag gives test results with better heat retention. However, when a person actually enters a sleeping bag, it does not feel that the heat retention is high, and the test results do not show the discomfort caused by stuffiness caused by increasing waterproofing, so in addition to testing European gnomes, Iska also conducts its own tests to calculate the minimum operating temperature.
Rather than just displaying the results of European gnome tests, we also carry out our own tests to suit the Japanese environment, and calculate them based on accumulated data and experience. It shows the commitment of the creator.
However, I understand that neither the European Gnome test results nor the independently calculated numbers are guaranteed, and I think it is safe to use as a reference criterion for choosing a sleeping bag with some spare time.
Understanding the minimum operating temperature set by Isca from experience using the field
Even though these numbers are calculated from accumulated data and experience, what is the reality? That's something you're curious about. To check this, I used the Air Plus 450 & 630 and summarise my own conclusions after sleeping in various environments, and it was difficult to use the product alone in an environment with the lowest operating temperatures announced by the manufacturer.
I felt that the minimum operating temperature published by Isca was a number that has a similar meaning to the "lower temperature" used in European Gnome (EN) 13537. In addition to the Air Plus series introduced this time, I also use two Isca sleeping bags, but the experience is generally the same.
If you're not sure which model to choose
The Air Plus series comes in a total of four types depending on the operating temperature range.
Since cold tolerance varies from person to person, I would like to use this conclusion as a reference only, but in environments close to the minimum operating temperature, I couldn't say that I could feel the cold even when I went into a sleeping bag and sleep comfortably. However, that's not the case when it cannot be used in an environment with a minimum operating temperature or below. Depending on the situation, it is entirely possible to stay comfortable by wearing winter clothing, taking measures such as coverings and underwear. To check the usage limit, I used it in an environment lower than the minimum operating temperature, but if I'm actually using it, I'm sure I can choose a sleeping bag with a little more room, based on the minimum operating temperature.
In terms of Air Plus 450 & 630, specifically, the Air Plus 450, which has a minimum operating temperature of -7°C, can be used comfortably at around -3 to 5°C, and the Air Plus 630, which has a minimum operating temperature of -15°C, can be used comfortably at around -10°C.
Conclusion and summary: Air Plus is an all-rounder sleeping bag that can be used by anyone
In the mountaineering and hiking world, where UL (ultra light) culture is becoming more popular, tools specializing in lightness have been created to compete with each other. There are models with no hoods left to make them lighter, and sleeping bags with cut back on the back, but these are items that can be used by experts who have gained experience and have a thorough understanding of their "comfort zone."
When it comes to sleeping, it's not the right thing to sacrifice comfort. In harsh environments, "warmth" is justice. We do not recommend lowering the specifications of your sleeping bag to reduce weight. (I have also experienced countless nights where I failed to choose a sleeping bag to reduce the weight of the bag, and endured the cold.)
Even for UL-oriented authors, I agree with the idea that "lightness is great," but it is also true that there are not many tools that are "light and comfortable." We recommend "Air Plus" made by Iska as a sleeping bag that can be used easily and safely by anyone with any experience.
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Yosuke C
People who act with just one backpack with the motto of "as light as possible" so that they don't get inconvenient.
From spring to autumn, I chase after char deep in the mountains and go fishing in the mountain stream. We walked the mountains in search of spectacular views that cannot be seen from the ground. Camping to be healed by the bonfire. Snowboarding is a floating mountain with a mountain of silver. A freelance writer who has been enjoying the outdoors for over 20 years and enjoying the outdoors in his own way all year round. Based on my experience writing articles for more than dozens of outdoor web media, I will be sharing my own experiences and tools that I have been using.