The Arc’teryx Proton LT Hoody is a synthetic active insulation mid-layer designed to be breathable and highly durable. It has a full-length zipper, two handwarmer pockets, one chest pocket, and an adjustable waist and hood. This 13.2 oz (375 g) jacket retails for $299.
- face fabric durability
- air permeability of insulation and fabric materials
- comfortable fit
- quality of materials, design, and construction
Where to Buy:
The original version of the Proton LT Hoody received a Highly Recommended rating from our Alaskan contributor, Max Neale, in 2018. He called it the “highest rated all-purpose active insulation jacket” that he tested for his Synthetic Insulated Jacket State of the Market Report.
The newest (2019-2020) version of the Proton LT Hoody features a new face fabric, lining fabric, and insulation. In addition to claims of superior air permeability and insulation, Arc’teryx boasts that the face fabric is 60 times more durable than "the industry standard" (whatever that means).
This review is a collaborative effort between Ryan Jordan and Andrew Marshall, and also draws upon the experience of several other product testers, including:
- Max Neale (mentioned above)
- Dave Swink (a Backpacking Light Wilderness Adventures Trekking Guide)
- Members of the Backpacking Light community who responded to a user survey about active insulation jackets
Thus, this review is comprehensive in nature and is classified as a Performance Review (read about the differences between Performance and Limited reviews here). It draws on the experience of several users across a wide range of environments for an extended period of time (Summer 2019 through Winter 2020).
In this review, we will attempt to answer these questions:
- Does the updated Proton LT Hoody’s performance justify its price tag?
- How much utility does this jacket have for ultralight backpackers?
- How does the Proton LT Hoody stack up against other jackets in the active insulation category?
- durable, air-permeable face fabric
- synthetic insulation
- stretch fit and recovery
- anti-slip main zipper
- helmet-compatible insulated hood
- trim fit
- redesigned in 2019-2020 (new materials)
- claimed: 13.2 oz (375 g)
- measured: 13.8 oz (391 g)
- face fabric material: 84% nylon / 16 % elastane (woven)
- liner fabric material: 100% nylon (woven)
- body: 80 g/m polyester
- hood: 60 g/m polyester
- MSRP: $299
The Arc’Teryx Proton LT Hoody is an active insulation jacket, and we will review it within the context of this category.
Active insulation is clothing that meets the following criteria:
- It offers meaningful insulating properties (some degree of loft);
- It is breathable, i.e., it allows for moisture vapor transmission through the fabrics in response to vapor pressure gradients; and
- It is air permeable, i.e., it allows for air movement in a direction perpendicular to the plane of the fabric in response to convective movement of air resulting from an interior bellows effect (e.g., active motion) or exterior air movement (e.g., wind).
The primary differentiator between active insulation garments and traditional insulation garments is that active insulation garments are more air permeable. This allows the garment to expel excess heat and/or perspiration while wearing the layer during high-output activities in cold temperatures.
High-loft insulating clothing that falls into the active insulation category is usually defined by highly air-permeable face and/or lining fabrics, in contrast to most shell fabrics, which are aggressively calendered, coated or laminated to windproof layers, or otherwise not very air permeable (and often, less breathable).
The classic active insulation jacket of the modern era is the now-discontinued Marmot Driclime windshirt. Similarly, the Buffalo Systems Teclite Shirt, which has a microfleece lining and a highly breathable Pertex shell is a gold standard in Europe. Similar constructions are available from Paramo and others in Europe. The US market has become more recently defined by garments using high-loft insulation, such as the Patagonia Nano-Air (and Nano-Air Light) series of jackets.
The key benefit of active insulation may not be obvious or apparent until you've spent some time wearing an active garment: it offers comfort over a wider range of conditions and minimizes the need for constant layering adjustments.
The Arc’teryx Proton LT Hoody utilizes a proprietary face fabric they call "Fortius Air 20" (presumably, the "20" designation denotes the fiber denier, not the CFM measure of air permeability, as some other media outlets have suggested in their reviews). It's an uncalendered, tightly woven nylon/elastane (84%/16%) blend with a chemical durable water-repellent (DWR) treatment finish. These factors contribute to higher air permeability (and breathability) than face fabrics used in traditional high-loft insulated jackets. This is easily noticeable simply by sucking air through the fabric.
Calendering is a process by which a fabric is pressed through heated rollers. Heat and pressure effectively weld individual fibers together on one side of the fabric, reducing its porosity, increasing its downproof-ness (the propensity for insulation fibers, whether down or synthetic, to migrate through the fabric's pore structure), increasing its water resistance, decreasing its effective thickness, reducing its tear strength, and decreasing its breathability.
On the other side of the equation is this - active insulation face fabrics are less water-resistant and wind-resistant than traditional calendered fabrics used on windshirts and puffy jackets. To what degree this is a shortcoming depends on your intended use of an active insulated jacket. It’s also worth noting that just as with other types of fabrics, active insulation face fabrics differ in terms of air permeability, breathability, water-resistance, wind-resistance, and durability. These differences spring from material and design choices made by the manufacturers.
One way to quantify a fabric’s air permeability is measuring the volume of air that can be moved through a fabric in a given amount of time (in units of CFM, or cubic feet per minute). It’s commonly measured using ASTM D737-18 (Standard Test Method for Air Permeability of Textile Fabrics). Face fabrics used on active insulating layers typically offer CFM values in the range of 20 and higher; calendered fabrics used in traditional high-loft insulating layers typically offer CFM values of less than 5 (and often, less than 1.0).
Arc'teryx touts the durability of Fortius Air 20, and we'll certainly explore that claim.
Active insulation garments utilize more loosely bundled fibers designed to trap some heat while allowing most of the moisture from your vaporized sweat to pass through. (See our notes on porosity above). The upshot is a garment designed to keep you warm and dry during activity, but one that is usually not sufficient as a sole source of insulation while being inactive in camp - at least not in temperatures below freezing.
Active insulation garments are seldom insulated with down because down is poorly water-resistant. But some companies use other natural fiber insulation material, such as wool, in their active insulation garments.
Coreloft is one of Arc’teryx’s proprietary synthetic insulations. It is a loosely bundled polyester filament insulation with mixed-sized hydrophobic large-denier fibers. The benefit of large-denier fibers is that you can use a more loosely-woven (e.g., higher porosity and pore size), non-calendered face fabric in your garment without allowing insulation to escape (i.e., with individual filaments migrating through the fabric pores). In addition, large-denier fibers are more durable (resistant to breakage and collapse) than fine-denier fibers.
Coreloft Continuous and Coreloft Compact are types of Coreloft insulation. As its name implies, Coreloft Continuous can be thought of as one long fiber tangled into itself to make a “sheet” of insulation (long-staple insulation). It has a slightly higher loft (per weight) than Coreloft Compact but is less compressible.
Coreloft Compact is the short-staple version of Coreloft. It's more compressible (in part because its fibers are highly crimped) and slightly less lofty (per weight) than Coreloft Continuous (source: Arc’teryx). For the same insulation weight, Coreloft Compact would allow for a more trim, less bulky jacket than one made of Coreloft Continuous.
Member's Only Content
- Performance Assessment
- Description of Field Testing
- Dates & Seasons
- Environmental Conditions
- How Many User-Days?
- Use Case Scenarios
- List of Performance Criteria
- Air Permeability/Breathability
- Weather Resistance
- Fit and Comfort
- Fit Issues
- Drop Hem
- Adjustment Mechanisms
- Finish Quality
- Description of Field Testing
- What’s the Best Use Case for a Proton LT?
- How Does a Proton LT Integrate with a Layering System?
- Issues of Note
- Compared To
- Arc’teryx Proton LT Hoody vs. Patagonia Nano-Air Hoody
- Arc’teryx Proton LT Hoody vs. Patagonia Nano-Air Light Hoody
- Arc’teryx Proton LT Hoody vs. Arc’teryx Proton FL Hoody
- Comparison Table
- Comparison Summary
- Who Should Consider This Product
- Who Should Not Consider This Product
- Recommendations for Improvement
Member's only version is 6,500 words and includes 21 photographs and/or illustrations.
While the updated Arc’teryx Proton LT Hoody is not the perfect jacket for every scenario (or for every wallet), we believe it to be category-defining in terms of fit, durability, and air permeability/insulation balance.
Its ability to expel body heat and moisture in cold temperatures - even when zipped completely and with the hood up - is its strongest feature. Its high-quality construction stands out even amongst a pack of well-executed jackets, and its design, fit, and finish are undeniably aesthetically pleasing.
While not as ideal for temperate shoulder-seasons or mild winters as the Arc'teryx Proton FL Hoody or the Patagonia Nano-Air Light, we’ve found it hard to beat for moderate to high levels of exertion in cold temperatures. Its performance, when combined with best-in-class durability, makes the Arc’teryx Proton LT Hoody deserving of our Highly Recommended rating.
- Listen to our podcast about synthetic insulation.
- Watch the Synthetic Insulation Webinar to learn in-depth knowledge about how synthetic insulation works, and how you can use that knowledge to make informed decisions about what gear to choose.
- Learn how to use active insulation as part of an inclement-weather layering system in Ryan's Inclement Conditions Masterclass.
- Patagonia Nano-Air Light Hoody First Looks Review
- Patagonia Nano-Air Light Hoody Performance Review
- Patagonia Nano-Air Hoody Review
- Arc'teryx Proton LT Hoody (2018 Version)
DISCLOSURE (Updated November 7, 2019)
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