Don in his Montbell U.L. Thermawrap Jacket on a climbing trip along the Mogollon Rim, Arizona
The Montbell U.L. Thermawrap Jacket is dedicated to no frills lightweight performance. At 8.0 ounces (227 grams) it is one of the lightest synthetic fill garments on the market. The U.L. Thermawrap uses a 1.8 oz/yd2 (1.5 oz/yd2 in the sleeves) proprietary synthetic insulation, Exceloft. I found the jacket to be warm for its weight and comparable in loft to heavier garments using Primaloft One insulation. The shell is an extremely lightweight 15 denier Ballistic Airlight nylon. Based on use over the course of the summer, the shell is completely windproof and reasonably durable. The Thermawrap is a simple jacket with no pockets, a full zipper, Chameece micro-fleece lined collar and elasticized cuffs. Montbell also offers the U.L. Thermawrap in a vest style (see our review here) which weighs 5.2 ounces, with an MSRP of $99.
- Super light, full zip jacket (8.0 ounces, Men’s Medium)
- Extremely light Ballistic Airlight nylon shell is windproof and reasonably durable
- A minimalist, no frills, no pockets garment
- Full zip for temperature regulation and moisture control
- Exceloft insulation. Good warmth for the weight. Retains loft well when wet
- Moderate storm protection, seams will soak through in moderate rain
- Tightly woven Ballistic Airlight nylon shell not as breathable as other nylon fabrics
• Garment Style
|Fully zippered jacket|
• Fabric Description
|15d Ballistic Airlight nylon|
• Insulation Description
|1.8 oz/yd2 (60 g/m2) Exceloft, 1.5 oz/yd2 (51 g/m2) Exceloft in the sleeves|
• Other Features
|Chameece micro-fleece lined collar, stuff sack|
|8.0 oz (227 g) for Men’s Medium, 9.2 oz (261 g) for Men’s XL (manufacturer specification 8.2 oz (232 g) for size M)|
|0.3 in (0.8 cm)|
• Model Year
|$129.00 Manufacturer’s suggested retail price.|
Over the summer I took the U.L. Thermawrap on numerous high mountain backpacking and climbing trips, and a summer trip north of the Arctic Circle to Gates of the Arctic National Park. When the jacket first arrived, my XL size jacket seemed so light that I was skeptical of its warmth. But I wore it down to 40 °F on several occasions and was warm with another light layer beneath the jacket. Its windproof shell was a blessing in Alaska and kept me warm when I might otherwise have needed two layers and much more weight for the same level of protection. Despite being pleased with its warmth, it is still a lightweight jacket, and with only 0.3 inches of loft, it is not a four-season garment. When temperatures get near freezing, the Thermawrap requires significant assistance from other layers if you are resting or around camp. I found a lightweight vest ideal to boost the warmth of the U.L. Thermawrap.
The super windproof shell fabric is not as breathable as some more loosely woven nylon and polyester shell materials. During some high exertion activities I did get a bit clammy in the jacket with the zipper closed. Not surprisingly, the full zip is a great asset for temperature control as well as moisture buildup. I wore the jacket while hiking in the early morning at high altitudes at approximately 45 °F. I was able to stay cool while hiking uphill with the jacket unzipped, and warm on ridges, passes and rest stops with the zipper closed.
In Alaska, I wore the jacket during several heavy rains with temperatures in the 50s. I stayed completely warm each time even when the jacket had absorbed considerable water. The Exceloft insulation performed very well in home tests as well. I completely soaked my jacket, wrung it out mildly and saw no measurable loss of loft. The Thermawrap’s lightweight, sewn through construction does make it vulnerable to rain. Although it comes with a standard DWR, after 10 minutes of moderate rain, I experienced wet shoulders where water came through the seams. A lightweight wind shell with DWR treatment worn over the Thermwrap would dramatically improve storm resistance, and indeed Montbell has designed the U.L. series as inner layer garments.
The U.L. Thermawrap is a no frills jacket. I found the 2 3/4 inch high, micro-fleece collar very comfortable and warm when fully zipped. The Ballistic Airlight nylon held up well over quite a bit of use, including some scrambles and moderate abuse from rocks on climbing trips. Overall fit and articulation is excellent. The sleeves are plenty long on the extra large size even for a tall (6’4″) reviewer. The jacket does not ride up when the arms are lifted to shoulder height. It stuffs nicely into the included stuff sack and makes a great pillow.
As a garment on the cutting edge of lightweight gear, the $129 price tag is a good value. Although the overall warmth to weight ratio is below some other garments in this category, the U.L. Thermawrap weighs in several ounces below most of its competition, making it a tempting choice for those who need the absolutely lightest gear.
Recommendations for Improvement
I wouldn’t change the ultralight focus of the U.L. Thermawrap, and would not want to add any features that would increase its weight. We realize that the U.L. Thermawrap jacket is not designed as rain gear, and it won’t keep you dry as long as some other jackets in this category. Still, we think its storm resistance could be improved for almost no additional weight with a better DWR.