Field Report for Red Ledge AO81 Thunderlight Parka
and AO83 Thunderlight Full Zip Pants
Alan Dixon, BackpackingGearTest
Summary of Thunderlight Field Performance
By field measurement the Thunderlight Parka has some of the lowest
moisture accumulation of any rain shell on the market. If you are
working hard and generating a lot of heat and sweat this is the shell
you want. The Thunderlight Parka will keep you dry from the inside as
well as the outside. The Parka has a generous fit and almost every
design feature one could want while still keeping weight under 13
ounces. It is not surprising that the Thunderlight Parka won
BackpackingLight.com's Trail's Best Award.
In my high exertion field tests, the Thunderlight Parka accumulated
the least moisture of any shell tested waterproof or non-
waterproof. The Thunderlight Parka accumulated less moisture than
GoLite's Bark, a non-waterproof windshell. This was due to the
excellent ventilation design (core venting pockets and pit zips) of
the Thunderlight Parka. The Parka's shell material, while not as
breathable as some of the newer polyurethane coating technologies was
sufficient to reduce moisture accumulation in non-vented areas such
as forearms and upper back. In comparison, tests a fully waterproof
shell generated so much moisture that I had sweat dripping out to my
sleeves by the end.
As measured in the BackpackingLight.com's Test Lab, Red Ledge's TH4
fabric's 14% breathability was in the same range as GoLite's GoDri
shell. In comparison, Frogg Toggs shell has a breathability of 45%
and Montane's Pertex Tri-Activ and Rain Shield's Propore shell
fabrics are in the range of 90%. See BackpackingLight.com's
Breathability Specifications & Testing.
The only significant improvement to the Thunderlight Parka would be
to use a lighter and more breathable shell material like Pertex's Tri-
Activ. With this fabric, weight would be reduced to around 10 ounces
and breathability would improve. With this change the Thunderlight
shells would be close to the ideal rainwear and would probably
outperform most windshells for moisture accumulation. One could use
them as both rainwear and windshells saving a bunch of weight.
Overview of Thunderlight Field Testing
This was a very dry fall. I had little chance to test the
Thunderlight Parka and Pants in the rain. Tests in my shower at home
confirmed what I already suspected, which was that the raingear is
What interested me more was the breathability of the Thunderlight
shell material, especially under high exertion activities like
running or hiking steeply uphill. As such, I set out to test
Thunderlight rain shells under controlled field conditions to
determine just how wet I would get working hard. I did this testing
in conjunction with an article I wrote for BackpackingLight.com, High-
Exertion Moisture Accumulation in Rain and Wind Shells.
More Detail on the Field Testing
In a 6-week period I did 20 field tests with various shells to try
and understand and quantify how moisture accumulates in shells under
high exertion activities. Two of these tests were done with the
Thunderlight rainwear provided by BackpackingGearTest.
In each of the field tests I weighed the amount of water in my wool
undershirt (baselayer) after about 50-55 minutes of controlled
exercise (measured by the percent of my maximum heart rate). I also
recorded the temperature, humidity and wind speed for each test. I
feel that this is a more accurate way to compare garments than the
usual "soaked my baselayer" or "bone dry while working hard" reports
one usually gets back from the field as hikers either curse or extol
their waterproof/breathable shells. The data from these field tests
are presented in BackpackingLight.com, High-Exertion Moisture
Accumulation in Rain and Wind Shells LINK to Data Table.
Most testing was done within 3 miles of a major airport. Tests were
started on the half hour and run for approximately 52 minutes. The
mid-test hourly readings at the airport were used for temperature,
humidity, and wind speed. Test course was a little over 6 miles out
and back mostly flat with a few small hills. Run times varied from
50-55 minutes depending on wind speed, how fresh I felt, my level of
caffination, and general inclination. Measured and subjective this
equates to an exertion level of about 80 to 85 percent of my maximum
heart rate. My wool baselayer was weighed before the run and within 3
minutes of completing the run on a digital postal scale accurate to
0.1 ounce. The difference was reported as accumulated moisture.
Results of Thunderlight Field Testing
The Thunderlight Parka uses a multi-vented shell design with both
core venting pockets and pit zips. This proved amazingly effective in
venting excess moisture out of the shell. In field moisture
accumulation tests it outperformed GoLite's Bark, a non-waterproof
microfiber polyester windshirt. In a 52 to 55 minute, 7.5 mph run (80-
85% of my maximum heart rate) under similar field conditions (48-53
degrees F, and 45% relative humidity), the Thunderlight Parka
accumulated 3.9 ounces of moisture and the GoLite Bark (windshell),
in 5-degree cooler temperatures, accumulated 5.2 ounces of moisture.
In a control running test the same wool baselayer without a shell
accumulated 1.1 oz of moisture.
In a brisk (4.5 mph) 53 minute walk, temp 58 F, RH 29%, the
Thunderlight Parka accumulated only 0.8 ounces of moisture. One would
have a hard time telling this amount of moisture from a completely
Fit and Function
The Thunderlight Parka has about every design feature one would want
on a rainshell (see features in BackpackingLight.com's Raingear
Roundup tables) but the best design feature of the Thunderlight Parka
is its excellent ventilation. I believe that the Parka's core venting
pockets and pit zips complement each other. The forward momentum of
running or hiking fast forces cooler, drier air into the shell
through the front facing core vents. With the a neck zipper a bit
open and pit zips wide open, the incoming air exits at your neck and
armpits creating a chimney effect that allows warm humid air to rise
upward and out. This keeps the front of your base layer dry.
Fit on the Parka and pants are a near perfect for me. Mobility of
head an arms and legs was almost unrestricted. There was plenty of
room to withdraw my hands into the sleeves for protection. The
Thunderlight Parka and Pants are somewhat noisier and stiffer than an
uncoated microfiber like the Silmond on GoLite's Bark or even a
silicone encapsulated microfiber fabrics like Epic or Encapsil. It
was still pleasant enough to run or walk in these garments. My only
gripe is that it would be nice to have a brim on the hood and that
the hood's drawcord be elastic instead of rigid nylon cord. The 3.2
oz nylon fabric should provide durable resistance to abrasion and
In summary, the Thunderlight Parka and pants are an excellent choice
for durable, waterproof, breathable, and fairly lightweight rainwear.
The Parka is well ventilated enough that it could probably do double
duty as a windshell in many circumstances. The Thunderlight Parka is
probably the best all round choice on the market for a shell that
will handle almost anything you and the weather can dish up. At the
$50 street price for the Thunderlight Parka nothing even comes close.
The AO83 Thunderlight Full Zip Pants at 11.1 oz (men's med.
advertised wt. 8 oz) are still solid performers and a great buy at
the $30 street price. But the pants will have solid competition from
other manufacturers in both weight (Marmot's PreCip pants are 3-4 oz
lighter); and performance (given the limited breathability of the TH4
fabric some of Montane's pants use fabric that is 6x more
breathable and are lighter).