A TEST OF THE HENNESSY HAMMOCK IN AN EXTREME COLD WEATHER ENVIRONMENT PROBABLY THE ONLY HAMMOCK NORTH OF THE ARCTIC CIRCLE a Review by Ben Reynolds

It’s indisputable. 
Hennessy Hammocks could well be the best in the world.  Light, durable, comfortable and excellently engineered… perfect for warmer areas of the world, right?  Well, you will have seen from the website that ever evolving design solutions are attempting to expand the boundaries of the hammock inhabitable world, from calm low lying areas and comfortable lower latitudes, to where the silent killer reigns supreme…. cold.   So, it was with Hennessy Hammock’s Explorer Ultralite Asym, along with elements of the insulated Superstructure that I found myself in Northern Norway in order to test whether the cold can be defeated by this intruder from the tropics. 
 
 THE TEST
 
CONDITIONS.  The system was tested in the area of 68º 33’ 37.12’’N by 16º 58’.54’’E, east of Harstad, Norway.  Initially mild temperatures prevailed, fluctuating around freezing, which resulted in freezing rain, sleet and snow.  Though this is not the extreme cold that was later encountered, it was far more testing due to the freeze-thaw effect and moisture content of the air which accentuated the cold.  Minimum temperature encountered was - 18ºC (0ºF) still air and estimated at -30ºC (-54ºF) with wind chill.  Maximum precipitation encountered was 7.5cm (3 inches) of snow in 6 hrs. Click here to read the entire review.

...CONCLUSION.  The Hennessy Hammock insulation system is capable of supporting a lone traveller in extreme cold weather environments down to -12ºC (10ºF) in the format tested.  This was dependent on the sleeping bag used and a bag with a lower comfort zone than that used in the test will similarly reduce the -12ºC figure.  This figure will also be reduced by: (1) adding insulation to the Under Cover e.g. spare clothing/suitable vegetation, (2) use of the Over Cover, and (3) a solution to cooking which would also heat the living space...However, for those comfortable operating in extreme cold the system works in all respects other than the method in which one can cook, but there must be solutions out there. 

Thanks to Ben for his detailed and informative review!

AN ENCOURAGING LETTER
This is the guy that started me on the idea of the
4 SUPERSHELTER INSULATION SYSTEM.

The hammock is so excellent. It is now one of my most valued possessions. The problem is that your hammock is so revolutionary that it has made the sleeping bag OBSOLETE, along with the tent, pad, pillow, mosquito net, SPACE BLANKET, groundsheet, jungle hammock, bivy bag, cot, etc...
Now just take it the one step further to make it complete... Pardon me for giving more advice, but wouldn't manufacturing an insulation "system" as an optional co-product be beneficial for everyone? You will make more $$, but more importantly, us consumers will be more comfortable. At least do an experimental prototype and let me know personally how you did it.
Sorry for being so opinionated... as I go and cut up my sleeping bag.

In any case, thank you for creating the single best outdoor product ever. This is high praise-coming from a Venezuelan native, born and raised in a hammock culture. C. F.

Wild child stayed warm at 4,000ft

INTRODUCING HENNESSY SUPERSHELTER
A COMPLETE 4-SEASON SOLUTION FOR CAMPING COMFORT

Check out our new 4-season Solution video! In stock and ready to ship.

Pressure to Produce
Hennessy Hammock users have been continually encouraging us to come up with a Hennessy designed solution to the insulation issue. Hennessy Hammock users have generously shared many of their ideas with us. We have received many letters and photos of insulation ideas for the hammock which range from super-simple, ultra -low-tech inflated garbage bags and bubble wrap to more beautiful and ingenious high-tech solutions such as down quilts with differentially radiused baffles which would likely retail for more than the hammock if they ever went into production.

The reason it has taken us so long to come up with our solution was the pressure to keep up with demand for our hammocks. The few breaks we have had resulted in short blasts of design creativity experimenting with ideas and materials then back to hammock production before we could finish the process.

We wanted a system that could retrofit all of our latest a-sym models so that no one had to buy a whole new hammock just to get the improvements. We were looking for something that did more than just keep your back warm. We were also looking for a solution which solved more than one problem in one temperature range. We wanted something that could keep the whole hammock warmer and capable of handling temperature extremes without adding extra bulk to your pack. It would also be good if it could improve protection in horizontally wind- driven rain. And then, while we're at it, let's make it ultralite, compact and affordable!

Put this new insulation system on to the Hennessy Hammock and we'll call the whole thing the Hennessy Supershelter!

Tom and Ann:

Got the undercover/pad and Snakeskins and they are both GREAT! They arrived on Thursday. I set it up last night although it was only in the 40's; I figured it would give me an idea as to the pad's effectiveness..I am a cold sleeper who sleeps with a quilt on top(The discontinued Golite Fur), a GoLite Coal Parka under my torso and I was warm! Happy! Happy! Happy!
Thank you so much for designing another great product..I'll be the envy of the other Hennessy owners on my upcoming hikes in Wisconsin and Michigan..eh eh eh..I love cool, new gear..especially when it weighs next to nothin'!

Thanks again, Linda Voll.

Tom.

I was given the SuperShelter system a year ago as a gift and it is the best. For starters your customer service is number one. I had some issues setting it up the first time out. Yea I should have done it in the back yard but just winged it. I called your company with my cell on the trail. I ws shocked when you called me back within 15 minutes personally and explained what I was doing wrong. I had no more problems. After more than a year of heavy use it held up great. Going to order a new underpad before next winter. Considering the use and abuse of my Explorer Deluxe and the SuperShelter system it has proven extremely durable but everything has limits. I am very hard on gear and have owned my hammock for two years now sleeping inside the thing for weeks on end. The system alone keeps me cold-back-free down to about 35. Toss in my jacket and sometimes a poncho linr and I have taken single digits with a proper sleeping bag. But that is just me. Everyone is different. Once weathered a heavy snowstorm inside my SuperShelter. The wind proof bottom cuts the wind chill perfectly. Even in the summer I use the silnylon bottom. Keeps the bugs off the bottom of the hammock.

The overall comfort of the hammock is outstanding and I just want to thank you personally for making such a great product and your fantastic customer service. Thanks again for those hammock camping tips. They came in useful.

Sincerely, Kevin Renkavinsky

The UnderCover WEIGHT: 7 1/2 oz., double ended StuffSack weight - 1 oz.

We decided to go to a full outside cover for several reasons. The addition of a single layer of fabric, sealed at the perimeter, would create a double wall over the full area of the hammock bottom, which means that a layer of warmer air is trapped between the hammock and the cover fabric. A full outside cover with silnylon coating would greatly improve windproofness and waterproofness. We designed in extra cutting and sewing to produce a contoured tailored cover because it is less weight than a folded rectangular piece of fabric. Then we suspended the UnderCover under the hammock with elastic tensioners to hold it close to the hammock

STAYING WARM OVER A BROAD RANGE OF TEMPERATURES The biggest advantage of our 4 Season insulation system is the ability to add extra insulation and radiant reflecting materials when the temperatures drop. Lightweight item such as a second layer of foam, spare clothing, towel, socks, etc. can be placed above the UnderPad. Heavier item, such as your coat should be placed under the UnderPad. Dry ground litter, when available, such as leaves or grass or moss can also be spread under the UnderPad When even more insulation is needed.

INSTALLATION To install the UnderCover onto the hammock, simply thread the suspending ropes through the holes at each end of the UnderCover and thread the side elastics through the holes in each side of the UnderCover, of course keeping the entrance of the UnderCover at the same end as the entrance as the hammock.

HOT AFTERNOON / COLD NIGHT If the insulation system is not needed during the day, it can be moved out of the way to one side of the hammock by detaching one side elastic of the hammock from the UnderpPad and UnderCover and lifting the hammock out of the UnderCover. It will stay off to one side and you will hardly know its there. When it cools off, just thread the side elastic back through the UnderPad loop and the side hole of the undercover.

KEEPING IT ALL TOGETHER Once the Undercover and Underpad are installed, I suggest leaving the system on the hammock. This makes set-up and break-down a breeze and also protects the somewhat fragile pad from damage. I just stuff it all into my pack compressing the foam UnderPad a lot if my pack is full or less if there is more room. We reccommend lashing all of the attachmenty points so that they cannot come loose when collalpsed into your pack.

The UnderPad WEIGHT: 5 1/2 oz.
First experiments used down and lofted synthetic insulation, but lofted insulation needed a quilted covering, which only added to the production time, cost, weight and bulk. We chose the open cell foam because lofted down or synthetic insulation would compress to half its loft when compressed by the tension of the UnderCover. However, the tension of the UnderCover is not strong enough to compress the loft of the open cell foam pad.

NEW CONTOURED SHAPE PAD We also developed a process to build a contoured open cell foam pad which did a very nice job of matching the shape of the anatomy of the occupant. Open cell foam has the ability of being able to stretch and mold to shape and it will also compress laterally.

WIDER AT THE SHOULDERS Using open cell foam allowed us to manufacture a tapered pad which was 29" wide at the shoulders for the Expedition and the Backpacker and 36" wide at the shoulders for the Explorer models. This solved the problem of your arms hanging off the sides of those narrow 20" closed cell foam pads. The UnderPad is designed to be long enough to keep your feet on the pad but does not extend above the shoulders as I believe a pillow or fleece will do a better job of keeping your neck and head correctly supported and warm.

LESS BULK The compressibility of the open cell pad is another advantage which will be appreciated by any backpacker. The Backpacker UnderPad is an ample 66” long by 29” wide, yet can compress down to less than 25% of the bulk of a open cell foam pad. 5” diameter by 8” long!

EMERGENCY SPACE BLANKET An Emergency Space Blanket is considered a very important part of this insulastion system. It is highly effective, lightweight, cheap and replaceable. Think of yourself as a hot dog in a foil wrapper on a cold windy day at the baseball game

SNAKESKINS I find it a lot easier not to use SnakeSkins with the insulation system. I think that the compressed open cell foam puts too much pressure on the snakeskins and is too much of a wrestling match to get it into your pack. If you do decide to use the snakeskins with the UnderPad removed, the UnderCover will still fit inside the SnakeSkins if one size larger SnakeSkins are used. Fold and roll the UnderPad carefully and store it in the stuffsack.

The OverCover WEIGHT: 3 oz.
Originally the OverCover was offered as an optional accessory because only a small percentage of campers will be spending time camping in dry, subfreezing temperatures. However,some reports are coming in saying that the OverCover is being used in above freezing temperatures with great satisfaction as it keeps interior temmperatures about 10 degrees warmer inside the hammock enclosure with noticably reduced condensation.

INSTALLING OVERCOVER The OverCover is placed over the hammock netting with the air hole at the head end of the hammock. The OverCover is secured under the perimeter of the UnderCover. To install the OverCover, thread the elastics at each end of the OverCover through the holes at each end of the UnderCover and hang elastics onto the hook of the fly tensioner. Next, thread the hammock side elastics through the side openings on the OverCover. If the UnderCover is already installed, make sure the side elastic is threaded through the Over Cover first and then the UnderCover. Fresh air is available through the air hole near the occupant's face. Changing position in the hammock acts as a bellows and automatically pumps fresh air through the air hole. Condensation which may form on the inside of the breathable OverCover will be absorbed and will wick through the uncoated fabric and evaporate through the dry air moving between the OverCover and the rainfly. The OverCover may also be released on one side and the loose half can be tucked between the netting and the OverCover on the opposite side to expose half of the netting and still block the wind from one side.

Letter from SuperShelter User

Tom.

I was given the SuperShelter system a year ago as a gift and it is the best. For starters your customer service is number one. I had some issues setting it up the first time out. Yea I should have done it in the back yard but just winged it. I called your company with my cell on the trail. I ws shocked when you called me back within 15 minutes personally and explained what I was doing wrong. I had no more problems. After more than a year of heavy use it held up great. Going to order a new underpad before next winter. Considering the use and abuse of my Explorer Deluxe and the SuperShelter system it has proven extremely durable but everything has limits. I am very hard on gear and have owned my hammock for two years now sleeping inside the thing for weeks on end. The system alone keeps me cold-back-free down to about 35. Toss in my jacket and sometimes a poncho linr and I have taken single digits with a proper sleeping bag. But that is just me. Everyone is different. Once weathered a heavy snowstorm inside my SuperShelter. The wind proof bottom cuts the wind chill perfectly. Even in the summer I use the silnylon bottom. Keeps the bugs off the bottom of the hammock.

The overall comfort of the hammock is outstanding and I just want to thank you personally for making such a great product and your fantastic customer service. Thanks again for those hammock camping tips. They came in useful. Sincerely, Kevin Renkavinsky

"Total Satisfaction!"

I purchased my first Hennessy Safari Asym Hammock back in January of this year. Living in South Carolina, I had several opportunities to use it in February and March when the weather was not too cold (i.e lower than freezing). Total Satisfaction!  Seem to remember many vows of never sleeping in a tent again during those initial nights.  However, several weeks ago, I decided to give it a try on a backpacking trip with the Boy Scouts.  Being the CubMaster for the Pack associated with the Troop, the Boy Scouts needed some additional adult leaders for their "most strenuious backpacking trip of the year" up Mt. Mitchell in North Carolina.  During the second night of our trip, at an elevation of 6,000 feet, we were hit with what was supposed to be a "potential light dusting of snow".  That night, I experienced first hand how this hammock holds up in extreme conditions to include 30-40 mph winds, rain, sleet, between 6-12" of snow, and temperatures of 5 degrees F with windchill.  Surprisingly - Total Satisfaction!  Other than what one might call "periods of excessive rocking", I stayed relatively dry and warm!

I used my North Face bag rated at 20 degrees with a Thermarest RidgeRest foam pad.  I slept in a pair of  milano wool thermals.  As the sleet started coming down, I decided to experiment with using an old military issue solar blanket.  I placed it under my foam pad and wrapped it completely around my sleeping bag.  This kept me nice and toasty.  Unfortunately, the outside of my sleeping did get a little damp from the condensation that was collecting on the foil. 
The downside was I had several adjustments to the rain fly to make throughout the night due to the unexpected high winds and my lack of experience in using the gear.  In addition, in the morning, the half-hitch knots that I used to tie the hammock to the trees were covered in ice and frozen solid.  I poured the last of my hot morning coffee to melt the ice and loosen the knots.  After that, I had the entire hammock balled up in my pack within 2 minutes.
Given the weather conditions, I slept very well and stayed warm through the night.  On our 8 mile trek out in the snow, I kept hearing comments from the scouts - that they had never seen anyone with a tent hammock before, especially in the snow and how they were going to have to get "one of them hammocks"!  - Jim Towler

Always check your gear before you go!

Always test your gear close to home before you start out on your trip, especially if you're setting our for some cold weather camping. Everyone has a different metabolism (in the winter, some folks sleep with the windows open, some with the heat turned all the way up) and everyone needs to find the right combination of sleeping bag and insulation -reflector pad, closed cell foam pad or car windshield reflector.The hammock fly can be tied down close to the hammock like a tent. Even in the winter, the mosquito netting serves a useful purpose. The fine weave of the mosquito mesh blocks out about 90% of the wind and provides a calm space inside the hammock, even when the fly is not fastened down as low as possible. For winter camping, you should think of polar fleece clothing, mittens, gloves & booties.

Test Results - Winter Camping in Hennessy Hammocks
Hennessy Hammock participated in a gear test with BackpackGearTest  which tested the Ultra Light Backpacker 1.5 Hennessy Hammock and also tested several radiant reflecting materials and other strategies for staying comfortable at low temperatures.

Radiant Reflector Theory (as I understand it)

First you need a radiating heat source which is your body. Opinions differ, but somewhere between 19 and 50 per cent of your body's heat is radiant. Then you need a radiant reflecting surface like highly polished space blanket material or aluminum foil. But most importantly, you also need a dead air space between you and the reflector. This is where those invisible little wiggly red arrows radiate from your body across the dead air space and bounce back off the reflective surface which causes a warming sensation, as if you had some kind of heat source under you. The closer the reflective surface is to your body without touching you, the more efficiently the radiant reflector will work.

Without that dead air space, your body will be directly against the radiant reflector and your body will conduct much of its heat right through the radiant reflector with very little benefit from the reflector.

The First Experiment: Emergency Space Blanket

An emergency space blanket was tested as a lightweight radiant reflector. The most important feature of a space blanket is it's ability to bounce back radiant heat that would normally be lost through the sleeping bag insulation compressed beneath your body. When used inside the hammock. it was found to be extremely noisy whenever the occupant moved. It also had a tendency to shift and was difficult to adjust beneath you. When the space blanket was placed over your sleeping bag in the hammock, large drops of condensation would form on the underside of the space blanket within 3 to 6 hours. When the space blanket was suspended under the hammock, there was much less noise and and no adjustment problems. When the space blanket was adjusted properly and close fitting to avoid drafts, a high percentage of the radiant heat that would normally be lost was reflected back to make the compressed insulation of your sleeping bag even warmer than the uncompressed insulation above you.

The Condensation Factor While the space blanket reflector does a pretty good job of keeping the bottom of the hammock warm and windproof, I still consider the space blanket as emergency equipment only. The downside of this solution is that when warm, moist air surrounding your body contacts the radiant reflector cooled by the lower temperature air moving under the hammock, condensation will occur. For temperatures below 50 degrees, you will probably require additional insulation.

One solution is to flip the space blanket over after a few hours putting the droplets of condensation attached to the space blanket on the outside where they will evaporate in the breeze. The real solution is to put some insulation under the space blanket to minimize condensation and that's covered under hammock Pads in the paragraphs below.

To use the hammock as an emergency heat reflector, just put it under the hammock and tie the two corners at each end up over the ridge line with a small reef knot. One of the guys at EcoChallenge Borneo showed me this trick and the space blanket fit like a diaper - you won't believe how well it works!

Hammock Pads
The next step in the search for the perfect pad was for a lightweight radiant reflector with attached insulation to prevent condensation build-up inside the hammock. We are also looking for a pad that does not interfere with the comfort of the hammock, does not pop out from under you in the middle of the night and provides comfort, efficiency, light weight and low cost.

Hammocks need a different kind of pad than a tent. Pads for tents are usually 20”-24” wide and thick enough to provide softness against the hard ground. Pads for hammocks do not need to provide any softness because the hammock is softer and more comfortable than any pad.

A pad for a hammock should be wider than a pad for a tent because a hammock conforms to the shape of your anatomy and the pad needs to insulate more of your body area than a tent pad. Ideally, the hammock pad would be as thin as possible so as to not interfere with the comfort of the hammock and provide enough insulation for the seasonal conditions. Thick foam or inflatable tent pads are designed to lay on a relatively flat surface. When used in a hammock, they are bent into compound curves which act like a loaded spring causing the pad to pop out from underneath you when given the first opportunity. This is most inconvenient when you wake up at 3 AM with a cold shoulder or hip and realize that the pad is sideways and that you will have to unzip your sleeping bag and sit up – losing valuable body heat – find the pad and wrestle it back under you. Then you have to zip up the bag and try to get warm again and back to sleep.

Auto windshield heat reflector pad

There are several types of auto windshield reflector pads. Some are folded cardboard with foil on one or both sides, some are a double layer of bubble wrap with a layer of aluminum foil laminated to each side and my favorite has 1/8” polyethylene foam with a piece of space blanket laminated to one side only.They come in all different sizes depending on the size of vehicle windshield. They will roll up to almost 2” in diameter and are around 4.5 oz. One nifty trick is to put this pad inside your sleeping bag so that it will stay aligned to your sleeping bag. If it does need a little adjustment, it is inside the bag and you can adjust it without unzipping your bag, losing body heat or waking up too much.

Tom’s experiment with Reflectix, windshield reflector pad, and fleece

I spent a couple of nights in the bush in September 2001 to experiment with reflector pads. Temperatures were in the mid 40s F (7ºC). None of this was very scientific, but the results were impressive. I used a 40" wide x 60" long piece of REFLECTIX tapered at the foot to 18" wide, a double layer of bubble wrap with aluminum foil laminated to both sides available (in different widths) from Home Depot, and an AUTO WINDSHIELD REFLECTOR PAD – 1/8' of polyethylene foam laminated to space blanket material. Comes in different sizes depending on the size of your windshield/body. I’ve heard that Wal-Mart has the biggest ones made for big trucks.

I sewed a piece of heavy fleece to the reflective side of the windshield pad but wearing a fleece suit would be as good or better. The fleece is important because it is fairly uncompressible and contains tiny air spaces necessary for radiant heat to pass through before it is reflected by the pad back to your body. Heat intensifies and, to me, felt like I was laying on some kind of solar cooker turned down to "warm". If your body is directly on the pad without the air spaces, you get the insulation benefits, but not the radiant benefits.

It was so comfortable that I did not need to be inside my bag so I just lay it over me like a quilt. Quilts seem to work well because they usually don't fall off because of the shape of the hammock. This was the most comfortable cool night I can remember.

Conclusion: Reflectix is an insulation manufactured mostly for the construction industry. It is used as a radiant insulating barrier in walls and wrapped around hot water heaters for additional insulation and also recommended as insulation for camping tent floors and insulation for hot and cold food containers. It is constructed of a double layer of bubble wrap with a layer of aluminum foil laminated to each side. It is around 5/16” to 3/8” thick and weighs about the same as foam pads of the same thickness.

The reflectix has several drawbacks. The raw aluminum will tarnish after a while, reducing it's efficiency. It is bulky and not as efficient as as the same thickness of foam and radiant reflector combinations. It's biggest problem is the heavy aluminum foil which is laminated to both sides. While it does reflect radiant body heat quite well, it also acts as a heat sink and the aluminum foil will suck heat out from under you wherever the aluminum foil is exposed to the cold air.

The windshield reflector pad is a much better solution to the problem. The closed cell foam is a better insulator than the bubble wrap and less bulky. The thin micro coating of aluminum reflective material is protected under a plastic coating, eliminating any tarnishing or any tendency to suck away body heat like the Reflectix did.

The dead air space between you and the reflector is an essential factor in the formula for radiant effficiency. If you sleep inside of your sleeping bag, the compressed sleeping bag insulation under you should have enough dead air space to allow the radiant pad to operate effectivelly. If you sleep directly on top of the radiant pad with your sleeping bag fully opened and laid over you like a big quilt, fleece material is probably the best way to get that dead air space between you and the reflector pad. For winter use, the fleece pants and fleece top make more sense since they are usable both day and night. Of course, fleece booties and fleece cap would really top it off. When wearing fleece clothing, you slip around quite nicely on the pad.

A windshield reflector pad facing up on top of a 3/8 inch thick urethane foam pad should take you down to around freezing. Ultralite backpackers will cut the full size 3/8 foam pad down to 36 inches long and keep the full length reflector because there is less weight and pressure on the pads under their legs. Total weight of this set-up is about 11 oz.

So far, this is the extent of our search for the perfect lightweight radiant reflector pad. The automobile windshield reflector pad offers attached insulation to prevent condensation build-up inside the hammock. It is flexible enough and does not interfere with the comfort of the hammock, nor does it pop out from under you in the middle of the night. Used in combination with additional foam pads of less than 3/8" provides comfort, efficiency, light weight and low cost.

Feedback: Gear Report from Rob - the long winded.  (I call him “toasty” now)
Hennessey Hammock (original) - The love fest continues. Someday I might upgrade to the ultralight to save a pound; otherwise the perfect shelter. WM Aspen bag, Jagbag liner. Reflector: Recently Tom Hennessey has been discussing strategies for staying warm in the HH. One item he mentioned was a windshield reflector with fleece sewn on one side. The fleece provides a non compressible barrier, creating the airspace needed for the reflector to work. Not being the sewing type, I hot glued fleece to a truck windshield reflector. On the first night, I had some trouble getting into my silk liner while staying on top of the reflector. The second night, I skipped the liner and slept directly on the fleece. Both nights I piled the unzipped sleeping bag around me like a quilt. Toasty the whole time. Rob

Feedback: Better than any tent...
I have good news for any Hennessy users who are contemplating using their hammock in cold (well, cold for me) weather. I went with my sons' Boy Scout Troop on a hike/campout in the Jefferson Wilderness in Oregon. Temperature Sat, night dropped to 20ºF. I am ecstatic to report that I slept better in my HH Expedition than I have in any of my tents, at any temperature. Hated to have to get up Sun. morning, I was so comfy.