Scroll through the bottom of this post or navigate here:
As most of you already know, I've been publishing guides to insulation for years now. You can find the full list at the bottom of this post.
In addition to these guides, I've also continuously been conducting this study to answer most of our questions about the temperature ratings. This post is still updated on a regular basis.
I hope it turns out to be helpful for you!
If you're interested to see the results only and skip the thought process behind this study, navigate accordingly:
Let's clarify one thing before we get to the nitty gritty of insulation.
And I don't think that they're incorrect. There are tons of fluid parameters that are difficult to measure if not impossible.
Not to even mention the subjective nature of the feeling of warmth.
Having said that...
I think it is possible to provide approximate values for an average person making some strict assumptions around layering and weather conditions.
Which is what you'll find out in this post.
I'll be evaluating the context of this study in two parts:
- Down jackets,
- Synthetic insulated jackets.
Let's start.
Understanding the Working Principle of Down Insulated Jackets
Down quality and down amount are the two most important things when it comes to the ultimate warmth provided by any down insulated garment.
You'll mostly come across this as fill power and fill weight respectively.
Because the word "down" is typically referred to as "fill" within the language of down pieces.
Let's take a look at the former first.
Fill Power
Fill Power represents the fully expanded, end volume of a 1 oz down (goose or duck). It's in cubic inches.
For example, a 800 FP (fill power) down will end up getting 800 cubic inches when it's fully expanded.
Because the insulation occurs by trapping air within the vacant spots of down, followed by having that air heated using our body heat as the source.
So, the higher the volume of trapped air (which is directly proportional with Fill Power), the more air will be heated & work as insulation as a result.
Fill power.
In the end, you'll feel warmer inside the jacket you're wearing.
This number varies anywhere from 500 to 1000, although the majority of quality brands (such as Arc'teryx, Patagonia, Feathered Friends, Outdoor Research, Marmot, REI Co-op, Enlightened Equipment, Rab, Black Diamond, Mountain Equipment and Mountain Hardwear)...
...mostly use down between 650 FP and 850 FP.
As you'll see, there are outliers, though. A notable one would be Feathered Friends Eos, which is equipped with a whooping 900 FP down.
Now before we get to fill weight, speaking of fill power...
...warmth actually isn't the only thing that it affects.
Other roles of fill power
It has additional three important roles:
- Loft retention during movement: Higher FP down will retain its loft with minimal loss during movement. The lower the FP, the larger the loss in this department.
- Higher impact on end warmth: Compared to FW (fill weight), FP has a larger impact on the warmth the insulated jacket provides.
For the sake of minimizing confusion and keeping this as clear as possible, I decided to place equal importance (weight) on fill power and fill weight when calculating FP * FW values (which you'll come across as you read on).
...although I did include these effects when calculating the temperature ratings of jackets within their first year.
After all, FP * FW is not the only factor considered while laying out the temperature ratings.
Tens of parameters are assessed, and the values put together at the end are the final results, including the few extra effects of fill power.
- Durability of insulation capability
- A jacket with a higher FP down minimizes its loss of insulating power over time. You'd be able to use a 850 FP down jacket for decades, and it'd feel almost just as warm as the first day you put it on.
- A jacket with a lower FP down, on the other hand, might not and probably will not prove nearly as durable. In my experience, jackets equipped with 650 FP down will probably feel noticeably colder after, say, 2-3 years.
If you, on the other hand, are like me and not planning to use your jacket for more than a few years, then this might not be that important to you after all.
By the time it starts to lose its insulating power noticeably, you'll have gotten yourself a new piece anyway.
- Compressibility: A jacket with a higher FP down will offer a smaller packed size.
Here's a video that also does a good job explaining fill power:
Moving on to our other major factor...
Fill Weight
Fill weight is the total amount of down the jacket is equipped with.
Some other resources might claim that fill weight is much less important than fill power when it comes to warmth, but that's far from reality.
In terms of warmth, fill weight is very, very important. Almost (in some conditions it even is) just as important as fill power.
Because, just like fill power, fill weight also directly affects the total amount of air trapped within the vacant spots of down.
Warmth Calculation
So...
Like I said, fill power and fill weight are the two most important factors when it comes to warmth.
In many cases, on a larger scale, assuming both jackets are equipped with the same amount of equally capable synthetic insulation, it is possible to make very close estimations by multiplying them when comparing warmth ratings of two different pieces.
For example...
- Feathered Friends Eos offers 105 grams of 900 FP down.
- 105*900 = 94,500
- Outdoor Research Transcendent offers 116 grams of 650 FP down.
- 141*700 = 75,400
Since 94,500 is significantly greater than 75,400; it's safe to say that the former will be noticeably warmer than the latter.
On top of that, because Eos offers a higher FP down,
- it'll stay almost equally warm even after decades,
- it won't lose its insulation during movement,
- and is more compressible.
Now...
There are reasons why this mostly won't work on a smaller scale (more on these later, under Other Factors heading).
Comparing two jackets with, say, 125,000 and 120,000 FP * FW values.
Understanding the Working Principle of Synthetic Insulated Jackets
Synthetic insulated jackets imitate the working principle of down insulated jackets.
They're equipped with artificial insulators, rather than natural down obtained by geese and ducks.
Some examples to the names of these artificial insulators can be given as Coreloft and PlumaFill.
Comparing the temperature ratings of synthetic insulated jackets is more difficult.
Because, unlike fill power parameter in down jackets, there isn't a common denominator to compare different types of synthetic insulators in an analytical way.
Maybe except one parameter?
CLO value
CLO value is the insulation power of an insulation setting.
For example, this value is 0.92 for 1 oz (28.35 grams) of a dry PrimaLoft One for one square yard.
The important thing here is that unlike fill power, CLO is not a characteristic that is unique to one ounce of the material.
As you see in the example above, it isn't independent from the area of insulation (square yards).
So, a higher CLO actually points out to the insulation capability of an insulation setting as a whole. It does NOT necessarily mean that the insulator being used is any more capable than an insulation setting put together with a weaker insulator.
Given the right amount of thickness, any insulator can achieve desired CLO value. It's just going to end up being heavier.
So, metaphorically, you can think of CLO value in synthetic insulated jackets as FP * FW value in down insulated jackets.
Unfortunately, obtaining the CLO value for commercial products is absolutely impossible.
Having said that...
We can (and we do) use a made-up parameter to CLO/oz/yd² to replicate FP in down jackets.
Honehstein Institute certified. A quick recap here: As you see, synthetic insulators lose minimal insulating power when they get wet. Down, on the other hand, loses a lot of it.
But unfortunately, a new problem arises here. A fair amount of manufacturers come up with their unique insulators - such as Coreloft, PlumaFill, Octa, Stratus, FullRange, etc.
And just like CLO values, they're unwilling to reveal the CLO/oz/yd² values of their insulators too. Which are the numbers we would need to determine the warmth.
I asked Arc'teryx and Patagonia Customer Services myself about this, and came back empty handed.
Having said that...
During my research, I did come across some useful information that I can leverage. For example, as it turns out, the CLO/oz/yd² value for PrimaLoft One is 0.92. It's also 0.79 for PrimaLoft Sport and 0.74 for PrimaLoft Eco.
However...
These values aren't certain or completely trustworthy by any means. They aren't the results of scientific studies. I didn't detect them in any other place rather than forums, Reddit, or contacting manufacturers myself.
In the end, I put what I could find together and did my best to make an estimation. Fortunately, this calculation using the numerical value CLO was not the only information I had in my hands.
I had two additional (at least equally helpful) data: trying them out myself when I could, and gathering offline user experience.
Warmth Evaluation
So, in the end, I used at least two of these three items to estimate the overall temperature rating of an insulated jacket:
- Analyzed them scientifically (as explained earlier),
- Trying them out myself when I can,
- And/or gathering offline user experience.
And mostly all three above.
In addition to insulation types and amounts (which is what I covered so far), there are also other factors that impact the warmth of an insulated jacket.
Other factors
Let's talk about the most important and most common examples of these factors.
In most cases, these are considered minor next to insulation specific qualities. But they do have a noticeable effect, and combined together, they might come close to affect the warmth as much as the insulator capability and amount.
- Bagginess,
- Length,
- Outer fabric,
- Distribution of insulation.
Bagginess
I also talked about this more in my my Arc'teryx Thorsen vs Therme vs Camosun post.
Baggier cut of Cerium SV helps with its incredible warmth.
Briefly, the amount of trapped air increases as the jacket gets baggier. So more air works as insulation, and ultimately you're kept warmer.
There certainly is something as "too baggy", though. After some point, more inner volume only holds the warmth back.
Length
This has two effects.
First one is that the amount of trapped air, which is explained above.
And second, in colder weather, it becomes much harder to warm your legs and feet than your torso and arms.
This is why a jacket with a longer hem length will feel warmer. And the difference is pretty noticeable.
Outer fabric
Outer fabric is actually much more about weather resistance, but it also affects warmth a little bit.
As explained earlier, no down jacket is able to offer top notch weather resistance since they get clumped and lose their loft when they get wet. Either from your sweat or from weather conditions. Doesn't matter.
Having said that, it's still possible to prevent it to a certain degree. Some products offer a more fragile face fabric, while others can bead water more efficiently. These are directly proportional to face quality and DWR coating.
DWR is a coating.
It's basically sprayed on to the surface of these jackets as a finish. It stands for Durable Water Repellent - which means that water will be repelled under wet conditions instead of soaking into the fabric.
DWR also decreases dry time.
It's a good thing these jackets are coated in DWR, but pay attention to the fact that DWR is a coating - meaning that it will wear off over time.
Which is why you might want to invest in a DWR spray such as this one for after treatment.
As you see, there's a strong correlation between FP x FW and temperature ratings, but not more than, say, 80%. I explained why this happens here in this post of mine.
For face fabrics, I'd list them like this:
Perfex Quantum Pro = Arato 30 > Perfex Quantum > Arato 10 = Drilite Loft 40D > Arato 7 = Drilite Loft 20D > others.
For synthetic jackets, outer fabric affects the warmth noticeably less.
Fill distribution
Some products of my favorite brand Arc'teryx are guilty of this. Take Firebee AR (read my review), for example. Nothing is wrong with the insulation at the back, collar and torso. They feel perfectly warm.
Whereas the insulation in arms, especially in lower arms, are seemingly slightly inadequate, which in the end affects the warmth feeling a little bit.
Results: Temperature Ratings
Down jackets lose insulating power noticeably when its wet out. Synthetic jackets don't. This is why the dry weather assumption was made for both of them.
This is why, I'd recommend synthetic insulated jackets for folks located in damp areas.
Down jackets
All Arc'teryx down insulated products are also equipped with a fair amount of synthetic insulators in addition.
This is why you'll see them rank higher with lower FP * FW values.
In addition, these synthetic insulators are placed strategically at high wear areas (like under arms, shoulders and back) to increase the life time of the insulation.
This is not only a great advantage in theory, but it also works perfectly fine in practice as well.
#Sidenote: Winter Parkas are not included in this table. Check out the table under Full List Heading to see where they're positioned.
Approximate lowest temperatures you can wear each down jacket in the market without feeling uncomfortably cold are...
| °F / °C | Fill Power | Fill Weight (grams) | FP x FW | Face Fabric |
|
|---|---|---|---|---|---|---|
Arc'teryx Ceres SV (Men's) | -15/-26 | 850 | 240 | 204,000 | Arato 30 | |
-10/-23 | 850 | 225 | 191,250 | Arato 7 & 10 | ||
-5/-20 | 800 | 227 | 181,600 | Perfex Quantum Pro |
| |
-5/-20 | 850 | 162 | 137,700 | Arato 7 & 10 | ||
-2/-19 | 700 | 280 | 196,000 | Drilite Loft 40D |
| |
3/-16 | 800 | 182 | 145,600 | Perfex Quantum Pro |
| |
5/-15 | 700 | 179 | 125,300 | Drilite Loft 20D |
| |
7/-14 | 750 | 140 | 105,000 | Perfex Quantum |
| |
8/-13 | 900 | 105 | 94,500 | Perfex Quantum |
| |
8/-13 | 750 | 130 | 97,500 | Arato 30 | ||
12/-11 | 700 | 141 | 98,700 | 3.6 oz 50D polyester | ||
14/-10 | 600 | 177 | 106,200 | 1.4 oz 30D polyester | ||
14/-10 | 850 | 120 | 102,000 | Pertex mini ripstop nylon |
| |
16/-9 | 700 | 133 | 93,100 | 30D Ripstop Nylon |
| |
17/-8 | 850 | 102 | 86,700 | Arato 10 | ||
19/-7 | 800 | 104 | 83,200 | 1.4 oz 20x30D polyester | ||
26/-3 | 700 | 109 | 76,300 | 2.2 oz polyester | ||
26/-3 | 650 | 116 | 75,400 | 20D ripstop nylon |
| |
28/-2 | 800 | 85 | 68,000 | 10D ripstop nylon |
| |
30/-1 | 800 | 81 | 64,800 | 10D nylon |
| |
Marmot Ares (Men's) | 32/0 | 600 | 102 | 61,200 | 1.2 & 1.8 oz polyester |
|
40/5 | 850 | 52 | 44,200 | Arato 7 |
As you see, there's a strong correlation between FP x FW and temperature ratings, but not more than, say, 80%. I explained why this happens here in this post of mine.
These are only approximate values assuming:
- you only have a shirt under and no shell over,
- during daily use (strolls, power walks etc at most - no high output activities),
- with enough wind to cause an umbrella to twist in your hand,
- and when it's dry out.
If you think you run warmer or colder than the average person, then shift temperature ranges accordingly.
Synthetic insulated jackets
If a jacket is insulated primarily with down and secondarily with synthetic insulators, then that's counted as a down jacket, and is listed above.
The reason that they're counted as down is because most down jackets out there are already supported with synthetic insulated at high wear areas.
Approximate lowest temperatures you can wear each down jacket in the market without feeling uncomfortably cold are...
| °F / °C | Insulation | Insulation Amount | Face Fabric |
| Discount Availability |
|---|---|---|---|---|---|---|
Arc'teryx Dually Belay Parka (Men's) | -7/-22 | ThermaTek | 92 g/m² | 30D Nylon |
| |
3/-16 | Coreloft Continuous | 90 g/m² body and arms, 65 g/m² hood and under-arms | N80p-X Gore-Tex 2L |
| ||
5/-15 | Cirrus | 233 g | Atmos ripstop |
| ||
Arc'teryx Kappa (Men's) | 7/-14 | Coreloft Continuous | 140 g/m² | N70p Gore Thermium |
| |
8/-13 | PlumaFill | 135 grams in body, 90 grams in arms and sides | 10D Recycled nylon ripstop | |||
10/-12 | Coreloft Continuous | 120 g/m² body, 80 g/m² under-arms, 60 g/m² hood | 30D Tyono | |||
10/-12 | VerticalX | 60 g | 20D x 30D Nylon ripstop | Cell | ||
19/-7 | Coreloft Continuous | 65 g/m² | Arato 10r | |||
21/-6 | PrimaLoft Silver Active | 60 g | Stretch nylon | Cell | ||
23/-5 | Stratus | 60 g | Atmos ripstop |
| ||
23/-5 | Coreloft Continuous | 60 g/m² | 20D Tyono | |||
24/-4 | Coreloft Compact | 80 g/m² body and arms, 60 g/m² hood | Fortius Air 20 | |||
24/-4 | PlumaFill | 65 g | Perfex Quantum | |||
24/-4 | Ventrix | 60 g | 40D x 30D + 20D Nylon |
| ||
28/-2 | PrimaLoft Gold Insulation Eco | 60 g | 22D Polyester | |||
30/-1 | Primaloft Gold Active | 50 g/m² | 20D Nylon ripstop | Cell | ||
32/0 | FullRange | 60 g | 33D Nylon ripstop | |||
43/6 | Octa Loft | Cell | Fortius Air 20 | |||
50/10 | Coreloft Compact | 40 g/m² | 20D Tyono |
|
As you see, there's a strong correlation between FP x FW and temperature ratings, but not more than, say, 80%. I explained why this happens here in this post of mine.
These are only approximate values assuming:
- you only have a shirt under and no shell over,
- during daily use (strolls, power walks etc at most - no high output activities),
- with enough wind to cause an umbrella to twist in your hand,
- and when it's dry out.
If you think you run warmer or colder than the average person, then shift temperature ranges accordingly.
Arc'teryx & Patagonia only
As most of you know, these two are my top two brands, which is why I decided to devote a table entirely to their own.
| °F / °C | Insulation |
| Discount Availability |
|---|---|---|---|---|
Arc'teryx LEAF Cold WX Parka SVX (Men's) | -40/-40 | Down |
| |
Arc'teryx Ceres SV (Men's) | -15/-26 | Down | ||
-10/-23 | Down | |||
Arc'teryx Dually Belay Parka (Men's) | -7/-22 | Synthetic |
| |
Arc'teryx Thorsen Parka (Men's) | -7/-22 | Down | ||
-6/-21 | Down | |||
Arc'teryx Centrale (Women's) | -5/-20 | Down | ||
-5/-20 | Down | |||
Arc'teryx Therme Parka (Men's) | -2/-19 | Down | ||
0/-18 | Down | |||
Arc'teryx Camosun Parka (Men's) | 0/-18 | Down | ||
3/-16 | Synthetic |
| ||
3/-16 | Down | |||
Arc'teryx Patera Parka (Women's) | 5/-15 | Down | ||
Arc'teryx Kappa (Men's) | 7/-14 | Synthetic |
| |
8/-13 | Synthetic |
| ||
8/-13 | Down | |||
10/-12 | Synthetic | |||
Patagonia Vosque 3-in-1 Parka (Women's) | 10/-12 | Down | ||
12/-11 | Down | |||
14/-10 | Down | |||
Arc'teryx Magnus Coat (Men's) | 14/-10 | Down |
| |
17/-8 | Down | |||
19/-7 | Down | |||
19/-7 | Synthetic | |||
23/-5 | Synthetic | |||
24/-4 | Synthetic | |||
24/-4 | Synthetic | |||
26/-3 | Down |
| ||
28/-2 | Synthetic | |||
32/0 | Synthetic | |||
40/5 | Down | |||
43/6 | Synthetic | |||
50/10 | Synthetic |
Read more about this chart here in my Insulated Outerwear Temperature Ratings Guide.
These are only approximate values assuming:
- you only have a shirt under and no shell over,
- during daily use (strolls, power walks etc at most - no high output activities),
- with enough wind to cause an umbrella to twist in your hand,
- and when it's dry out.
If you think you run warmer or colder than the average person, then shift temperature ranges accordingly.
Also check out my Arc'teryx Favorites and my Patagonia Favorites.
If you're interested in down jackets only, see my Best Down Jackets post.
Full list
Full temperature rating list of all high quality insulated jackets.
Approximate lowest temperatures you can wear each down jacket in the market without feeling uncomfortably cold are...
| °F / °C | Insulation |
|
|---|---|---|---|
Arc'teryx LEAF Cold WX Parka SVX (Men's) | -40/-40 | Down |
|
Arc'teryx Ceres SV (Men's) | -15/-26 | Down | |
-10/-23 | Down | ||
Arc'teryx Thorsen Parka (Men's) | -7/-22 | Down | |
Arc'teryx Dually Belay Parka (Men's) | -7/-22 | Synthetic |
|
-6/-21 | Down | ||
Arc'teryx Centrale (Women's) | -5/-20 | Down | |
-5/-20 | Down |
| |
-5/-20 | Down | ||
Arc'teryx Therme Parka (Men's) | -2/-19 | Down | |
-2/-19 | Down |
| |
0/-18 | Down | ||
Arc'teryx Camosun Parka (Men's) | 0/-18 | Down | |
3/-16 | Synthetic |
| |
3/-16 | Down | ||
3/-16 | Down |
| |
Arc'teryx Patera Parka (Women's) | 5/-15 | Down | |
5/-15 | Synthetic |
| |
5/-15 | Down |
| |
7/-14 | Down |
| |
Arc'teryx Kappa (Men's) | 7/-14 | Synthetic |
|
8/-13 | Down | ||
8/-13 | Down |
| |
8/-13 | Down | ||
10/-12 | Synthetic | ||
Patagonia Vosque 3-in-1 Parka (Women's) | 10/-12 | Down | |
10/-12 | Synthetic |
| |
12/-11 | Down | ||
Arc'teryx Magnus Coat (Men's) | 14/-10 | Down |
|
14/-10 | Down | ||
14/-10 | Down |
| |
16/-9 | Down |
| |
17/-8 | Down | ||
19/-7 | Down | ||
19/-7 | Synthetic | ||
21/-6 | Synthetic |
| |
23/-5 | Synthetic | ||
23/-5 | Synthetic |
| |
24/-4 | Synthetic | ||
24/-4 | Synthetic | ||
24/-4 | Synthetic |
| |
26/-3 | Down | ||
26/-3 | Down |
| |
28/-2 | Synthetic | ||
28/-2 | Down |
| |
30/-1 | Synthetic |
| |
30/-1 | Down |
| |
32/0 | Synthetic | ||
Marmot Ares (Men's) | 32/0 | Down |
|
40/5 | Down | ||
43/6 | Synthetic | ||
50/10 | Synthetic |
These are only approximate values assuming:
- you only have a shirt under and no shell over,
- during daily use (strolls, power walks etc at most - no high output activities),
- with enough wind to cause an umbrella to twist in your hand,
- and when it's dry out.
If you think you run warmer or colder than the average person, then shift temperature ranges accordingly.
As you see, there's a strong correlation between FP x FW and temperature ratings, but not more than, say, 80%. I explained why this happens here in this post of mine.
Supporting documents
Some manufacturers don't reveal vital product information such as fill weight or even fill power at times.
This is why I had to make some calls and send some mails to access them. I thought that it could be helpful for some of you guys to share the written documents with you.
Unfortunately I'm unable to report the results of verbal communication that took place through phone calls.
