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Montbell U.L. Thermawrap Inner Vest REVIEW

Synthetic, no-frills, ultralight insulating vest.


by Doug Johnson | 2004-11-17 03:00:00-07


montbell ul thermawrap inner vest - field shot
Doug in his Montbell U.L. Thermawrap Inner Vest on a backpacking trip up the Enchanted Valley, Olympic National Park, Washington

At 5.2 ounces (147 grams), the Montbell U.L. Thermawrap Inner Vest is among the lightest synthetic insulation vests on the market. It comes with a Chameece micro-fleece lined collar, elastic openings at the waist and arms, and a full length YKK zipper. It lacks other features such as pockets and a drawstring waist (features that would add to its weight but not its insulation performance). This is a single-minded garment that provides maximum synthetic warmth at a minimum weight.

The Thermawrap Inner Vest uses a 1.8 oz/yd2 proprietary synthetic insulation called Exceloft which is quick drying and loses very little loft when wet. The Ballistic Airlight shell is extremely lightweight and is both water resistant and windproof, further adding to the utility of the vest.

In Brief

  • Super light, full zip vest (5.2 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, soaks through in sustained rain
  • Slightly loose fitting garment - consider sizing down


• Garment Style

Fully zippered vest

• Fabric Description

15d Ballistic Airlight nylon

• Insulation Description

1.8 oz/yd2 (60 g/m2) Exceloft

• Other Features

Chameece micro-fleece lined collar, stuff sack

• Weight

5.7 oz (162 gm) for our size L sample (manufacturer's specification: 5.2 oz (147 g) size M)

• Loft

0.3 in (0.6 cm)

• Model Year

Spring 2004


$99.00 Manufacturer's suggested retail price


montbell ul thermawrap inner vest - 2
The Montbell Vest creates a snug, comfortable seal around the arm

I took the vest on numerous backpacking and climbing outings in the Northwest and the Guatemalan highlands over the summer and early fall. In these settings, it is typical for me to rely on a down vest and varying thicknesses of long-sleeve tops as my only insulation. At first I was wary of the warmth of the Thermawrap Inner Vest due to its light weight and thin 0.3 inches of loft. While the vest was not as warm as a higher loft down vest, I was very surprised by the warmth of the Montbell. In temperatures down to 45 °F and layered with a wool top, I found the vest to be quite warm and comfortable. Further, its windproof shell kept my core warm and allowed me to layer it over a windshirt when necessary. This saves time over a fleece vest where I would need to peel off the windshirt and put the vest underneath.

The full zipper of the Montbell vest increased its versatility as I was able to open the vest to stay cooler during times of higher exertion. The elastic armholes created a snug, comfortable seal around the arms, sealing in warmth. Further, the high collar warmed my neck and prevented warm core air from leaking out the neck opening.

The Thermawrap Inner Vest performed wonderfully when layered in a three-season clothing system. Its weight makes it an excellent layering piece below a thicker synthetic jacket for four-season use.

Storm resistance

I wore this jacket, layered with a long sleeve wool top, during several Washington and Guatemalan downpours. Although the DWR will resist a drizzle, a heavy rain will soak through the shoulders and back in about 10 to 15 minutes. However, I found that even when it was soaking wet, the Exceloft insulation still kept me warm and lost little loft.

To further check the storm resistance of the Thermawrap Vest, I soaked the jacket at home and wrung it out. By my measurements, the insulation had lost less than 10% of its loft and was still reasonably comfortable to wear. Wearing the wet vest, I went to sleep in a synthetic sleeping bag. When I woke up the vest was nearly dry. I feel very comfortable relying on the Montbell vest during adverse and stormy conditions.


montbell ul thermawrap inner vest - 3
The Montbell Vest packs down small and light

The U.L. Thermawrap Inner Vest is a simple vest. It has no pockets or drawstring waist. However, it does have a Chameece micro-fleece lined collar which is warm and very comfortable against the skin. It uses a full-length YKK zipper with anti-snagging Cordura backing. It also has elastic at the arm holes and waist. In other words, it has features that aid its performance without adding any extraneous weight. The vest comes with a well-made Airlight stuff sack for easy packing.

The fit of the vest is loose. I normally wear a large but a medium vest would have fit me better than the size large I tested. However, even the large vest fit snugly at the waist and arms due to elastic-reinforced openings.


If you need one of the lightest insulating garments on the market, the U.L. Thermawrap Inner Vest is a reasonable value at $99. Although not as warm for its weight as a lightweight down vest, the Thermawrap's insulation retains much of its warmth when wet. This is a minimalist garment focused on weight reduction. If you want features like pockets and a drawstring waist, there are vests on the market for less money and with more features and durability - they also weigh more.

Recommendations for Improvement

We don't recommend adding features that would increase the weight of the vest. We would like to see Montbell adjust the sizing to a trimmer fit that will easily layer under larger garments. Also, a more effective DWR coating to shed water a little longer before soaking through in a storm would add to the attraction of the vest.


"Montbell U.L. Thermawrap Inner Vest REVIEW," by Doug Johnson. (ISSN 1537-0364)., 2004-11-17 03:00:00-07.