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Integral Designs Andromeda Strain

Integral Designs Andromeda Strain


by the Product Review Staff | 2002-07-04 03:00:00-06

Manufacturer’s Website:


Size: Standard - Regular

  • Temperature Rating: +40 deg F
  • Total Weight: 30 oz (29.2 oz - measured)
  • Fill Material: 4 oz/sq yd Primaloft Sport
  • Shell Material: Pertex Microlight (1.4 oz/sq yd) ripstop
  • Lining Material: Pertex Microlight (1.4 oz/sq yd) taffeta
  • Length: Fits up to 5' 11"
  • Chest Girth: 62"
  • Hip Girth: 56"
  • Foot Girth: 38"
  • Colors: Black, Crimson, Electric Blue, & Spruce
  • MSRP: $170

General Description

The Integral Designs Andromeda Strain sleeping bag is a synthetic-fill, mummy-style bag with a +40 deg F temperature rating. It stands out from other synthetic fill bags on the market by virtue of its use of Primaloft, a highly compressible insulation that retains much of its insulating value when wet.

At $170, the Andromeda Strain is similar in price to other high-performance synthetic-fill bags. It is a feasible purchase for the mainstream backpacker looking for a sleeping bag for warm, damp conditions.

Fit, Styling, Aesthetics

Weight and Fit

The actual weight of the bag we reviewed (in regular length and standard girth) was 29.2 oz. The bag provides an average amount of wiggle room with interior girth for testers in the range of 5'6" to 5'9" and 110 to 175 pounds, even while wearing long underwear and fleece clothing. Our testers found these dimensions to be large enough for layering a lightweight down jacket as well without inhibiting the jacket's loft.

Integral Designs offers the Andromeda Strain in short (fits to 5'5"), regular (5'11") and long (6'4") lengths, as well as standard girth (62" chest, 56" hip, and 38" foot), broad (67-68" x 56-60" x 38-45"), and overbag (72" x 66" x 48") styles. These options are available in all of Integral Designs' down and synthetic-fill bags. We found this array of fit options the best on the market for fine tuning a sleeping bag for a particular body type.


The insulation used in the Andromeda Strain is 4 oz/yd2 Primaloft Sport (with a specification of approximately 1" of loft). The bag has one layer of Primaloft in the top and one layer in the bottom of the bag. This 50-50 distribution of insulation between top and bottom does not maximize warmth. In this arrangement, half of the bag's insulation is compressed under the sleeper, wasting half of the bag's loft. A better loft distribution for a warm-weather bag would have been 1.2 to 1.5 inches of loft in the top layer and 0.8 to 0.5 inches on the bottom layer. However, there is one advantage of even loft distribution: the sleeper who rolls around at night won't chill himself when the bottom of the bag suddenly becomes the top!

The actual loft in the new bag as we received it was only 1.7" (the average loft measured at eight locations throughout the bag, but far from quilting seams). This is less than the claimed 2.0". After three months of moderate use, the bag's total loft decreased to about 1.3", where it has remained ever since, even after several more months of use. It is interesting to note that both upper and lower layer loft loss was equal. We guess that the loss of loft is from compression in a stuff sack during our trips (we packed the sleeping bag into the stock silnylon stuff sack and stored it uncompressed between trips).

Insulation shift is controlled by a very few quilting seams. We found the quilting pattern to be sufficient to control insulation shift while sparse enough to eliminate significant cold spots.

Other Features

The shell and lining are both made with Pertex Microlight (1.4 oz/yd2), with a ripstop shell and taffeta lining. The lining, in particular, was noted to be "silk-like" by the testers and one of the most comfortable next-to-skin materials we've ever tried. The lining seemed to "wick" moisture well and keep the skin dry and comfortable. We found the shell material to be highly breathable. We found the bag retained little moisture (perspiration) even in cold conditions.

The bag has a full-length zipper that is easy to use. We encountered no problems with zipper snagging or zipper failure.

The bag's simple hood is easily operated with an elastic drawcord from within the bag. Our testers found that its simple design was insufficient to provide a snug and warm fit around their heads when cinched shut.

Product Performance

We tested the Andromeda Strain over a period of 9 months and 40 nights, in temperatures ranging from 26 degrees to 55 degrees, and with a variety of clothing combinations. Here is a summary of our results:

  1. Wearing only long underwear, our testers found that the approximate temperature at which the bag was comfortable was closer to 50 deg F than the claimed 40 deg F. This corresponds to the actual loft measured in our bag (1.7" to 1.3" during the testing period), and it agrees well with currently accepted formulas for predicting temperature ratings based on loft of the upper layer.

  2. Wearing warmer clothing typical of three-season backpacking, such as long underwear, shell clothing (jacket and pants), a lightweight insulating jacket (synthetic or down fill), and warm socks/hat/gloves, the bag could be used comfortably down into the upper 30s. All testers agreed that at these temperatures, long underwear bottoms and shell pants were not enough to keep legs warm. Thus, near- and sub-freezing conditions typically required, in addition to the 3-season clothing ensemble described above, a lightweight (100 or 200 weight) fleece pullover or jacket and 200-weight fleece or lightweight synthetic-fill pants.

  3. The shell material does not resist external moisture. This is especially true after a few nights of previous exposure to large amounts of water (during a spray test with a sprinkler). However, Pertex Microlight is one of the most breathable shell materials on the market, and our testing crew agreed that it is an appropriate material for a synthetic bag, because it allows the sleeper to "dry out" wet clothing (worn) or a damp sleeping bag through the night simply by evaporating moisture. All of our testers noted that the Andromeda Strain was tops in drying damp clothing. They tested this by wearing damp or wet clothing to bed and weighing the clothing and sleeping bag in both the evening and morning. In these tests, it was very rare for the bag to retain more than 10% of its own weight in moisture by morning, even when clothing worn to bed was very damp. Exceptions occurred when the bag was used in conjunction with a Gore-Tex bivy sack or in conditions where humidity was 90% or greater while inside a closed tent.

Intended Use

We believe the Andromeda Strain is a good choice for backpacking in temperate, damp environments. Summer in the western Olympic Mountains of Washington State or in the Western Cascades of British Columbia, or late Spring on the Southern Appalachian Trail are all ideal times and places to use such a bag.

Some of our testers also used the bag for early Summer and early Fall alpine snow and ice climbing in combination with (usually damp) clothing. We also found this an appropriate use of the bag.

In comparing the Andromeda Strain to other synthetic bags on the market with a similar weight, we found that most bags in this weight range had similar amounts of loft. There are a few exceptions (most notably, those made with Polarguard 3D and Polarguard Delta). These bags had 25% or more loft for the same weight. However, these bags were not nearly as compressible as the Andromeda Strain, and most used heavier shell materials.

Recommendations for Improvement

Our testers would have liked to see the Andromeda Strain offered in hoodless versions and with the option of either no zipper or a half-length zipper. Such options would save several ounces for the minimalist hiker who wanted the advantages of a synthetic bag without the frills.

In addition, we think that a bag with more overall loft, especially more loft in the top section, and less (or possibly none) in the bottom section would be a much warmer bag. And, after all, this would not significantly increase the bag's weight -- indeed it might reduce it.


The Andromeda Strain was a solid performer in our field testing. It is a great choice if you think either you or your bag are going to get wet. It was tops for drying out wet hikers and their clothes overnight and retained only minimal moisture in the process.

However, the bag's specifications (loft and temperature rating) were not quite up to the manufacturer's claims. Sadly, the same can be said of many other synthetic and down sleeping bags on the market. Please see "Sleeping By Faith: Bag Temperature Ratings," also in this issue.

If Integral Designs made a bag with 2" of actual total loft, and the loft distribution was altered to provide more on top, we think the bag would be a winner in the synthetic category. Because the bag is designed for moderate temperatures and by its nature should be lightweight, we appreciated the use of Pertex Microlight in the shell and lining, but we would have liked to see a lighter, half-length zipper as the standard option.

Final Grade B

A good design and quality materials and workmanship are the Andromeda Strain's strong points. The bag excels in wet conditions and weather that is not too cold. We think the Andromeda Strain could be an even better and warmer bag with a bit more loft, better distribution of loft, and a better fitting hood.

Integral Designs
5516 - 3rd Street S.E.
Calgary, Alberta
T2H 1J9 Canada
Phone: (403) 640-1445
Manufacturer’s Website:


"Integral Designs Andromeda Strain," by the Product Review Staff. (ISSN 1537-0364)., 2002-07-04 03:00:00-06.