According to the manufacturer's website:

PRODUCT DESCRIPTION

According to Duofold, the Varitherm line "represent the ultimate standard for products that combine thermal protection and moisture management". Basically high-tech long underwear, they combine moisture management with thermal protection. Varitherm fabrics are supposed to wick moisture away from the skin being made with a hollow core polyester fabric that moves water vapor while also trapping air to create the wicking thermal barrier. Further details can be found in my Initial Report and Field Report.

OVERALL IMPRESSION

As I noted in my previous reports, I find the fit nicely snug - not too tight but (thankfully) not baggy either. Even after four months of regular use, the arms and legs stay where they belong. Neither the sleeves nor the leg cuffs ride up their respective appendages. Often I find the sleeve cuffs of long underwear tops stretching to the point where they don't stay down around my wrists. This has not happened to the Varitherms, something I appreciate. I often wear the underwear (tops anyway) as my external layer. That means I will also often be in the situation where I've warmed up to where I push the sleeves up my arms to help provide some cooling. Despite this tendency to have the cuffs near my elbows much of the time recently, they still fit snugly around my wrists. I attribute this to the fabric's "360 degree stretch" capability - the whole sleeve is staying snug versus a more traditional approach that looks to the sleeve cuffs to keep them in place. Similarly, the tops stay tucked neatly into the waistband of the bottoms and neither travels such that I end up presenting the infamous "plumber's crack". Finally, the fabric is resisting almost all pilling (some minor fabric pills can be seen in the crotch and underarms), colors have not faded and the fabric has not displayed any tendency to retain body odor.

TESTING CONDITIONS

Testing since my last report continued to in the western Connecticut foothills (elevations to 2500 ft/762 m) and the southern Massachusetts Berkshires at elevations to 3000 ft/914 m with temperatures ranging from a low of 15 F/-9 C to highs of 70 F/21 C. I also spent a week backpacking in Arizona's Grand Canyon where the elevations ranged from 7100 ft/2164 m down to the canyon floor a mile (1.6 km) lower (1900 ft/580 m) and temperatures ranged from 27 F/-3 C at the rim to 67 F/19 C on the canyon floor. Wearing the Varitherms, I hiked as much as 13 miles (21 km) in a day including a 10 mile (16 km) trek that took me nearly 4000 ft (1219 m) up. This was not simply a stroll in the park. With 26 lbs (12 kg) of gear, food, water, and fuel on day one (dropping to 12 lbs/5.4 kg on the trip out), I was often sweating but never soaked and the Varitherms dried quickly whenever I was stopped. Except for a morning dip in Navajo Falls and an afternoon getting pelted with spray from Mooney Falls while working my way down the cliffside "trail" chains & ladders, the Varitherms never got dripping wet. Even after the waterfalls, the Varitherms were dry in under an hour - helped no doubt by the very low humidity, but impressive nonetheless.

While I tended to layer when camping here in the Northeast, I simply wore the tops as the only torso layer in the Canyon. On cool days and while on the rim, I wore the bottoms under nylon pants. Later while camping down inside the Canyon I left the bottoms in my pack. When I stopped hiking or the cool evening wind picked up, I simply donned my rain jacket (Frogg Toggs) over the Varitherms and was never chilled. It seemed like a perfect approach to layering; lightweight simple and wind/waterproof. 

FINAL THOUGHTS

When I started this test I was interested in the Varitherm's comfort, performance, durability and washing issues. As I've reported in my Field Report, the Varitherms are super-comfortable and have kept me warm and dry in conditions ranging from the dry desert of Arizona to the cold wet rain and snow of a New England winter. They haven't pulled, snagged, torn, abraded, or lost stitching integrity and they've not bled colors or gotten the baked in "funky" smell that polypro garments often do after long use. This was very impressive considering I spent 9 days wearing them non-stop  in the Canyon without any real washing (soap being a big no-no down in the Havasu Canyon watershed). 

In completing a BGT test, I tend to judge the success or failure of the item using the "would I buy it myself" touchstone. In this case I have purchased a set of Silkweights (crew & turtleneck) for myself and a set of Midweights (top & bottoms) for my son. In a word then, Duofolds are a "success".

I'd like to thank BackpackGearTest and Duofold for the opportunity to test these base layer garments.