Winter mid

Hi Tjarrd,

Its a tough call.

If I am out in over 10f and know I will be somewhere where wind will not be an issue (I.e. spindrift) I will leave the inner at home but if
Above treeline or its below 10f I am taking the inner.

I spent maybe 10 nights in a 3 man tunnel last winter with 2 buddies and there was a very noticeable difference in warmth when using the inner.

I know folk mention you can build snow walls but that's not always practical.

I go the route of bivy over inner. In addition to the "easy of bodily functions" the bivy also provides wind and draft protection (at least with a quilt) and a few degrees of warmth. A straight net inner seems of little value to me.

Edit. Thanks Stephen. Missed that important word (solid inner).

Malto,

Tjarrd mentioned he has a solid inner.

The walls slope inward

If snow collects on the outside, it tends to push the walls in sideways, making the effective length and width less, although you can hit the walls from the inside and the snow tends to fall off correcting the problem

Maybe a mid isn't best if there's a lot of snow falling, better to have vertical walls (where they meet the ground) like a tunnel tent

Floorless – occasionally, if it was raining, I have just peed sort of sideways where the entrance door is.

Tjaard,

I think you did a good job of summarizing the pros/cons of conventional winter mids with and without an inner. There is an additional mid option that you didn't mention. I use an Epic fabric SL5 (breathable & 40 oz) plus an integral silnylon sod cloth (20" silnylon & 11.3 oz) for winter use. The Epic fabric eliminates most of the condensation and the sod skirt eliminates most of the forced convection.

In 20+ mph winds I can’t feel any air movement in the shelter but, I took a thermal image of my insulated Keen Growlers (32F) and you can see the heat move slightly sideways (15.5F) in the ambient (1F) conditions immediately after entering the shelter.

15 minutes after entering the shelter

After 1 hour only slight RH increase

The breathable walls and the top vents create a 16 F vertical stratification.

I tested to see what affect my Coleman Extreme, at high setting, had on the temperature.

The Coleman Extreme was great for cooking dinner but almost worthless as a tent heater.

Only 10F heat increase from Coleman Extreme but it melted the frozen ground to increase the humidity.

On another cold/snowy day the temp was 3F.

A radiant heat source (black wood stove or small propane heater) test.

59F at shoulder level with 4,000 BTU radiant heat source

Low humidity

79F at shoulder level with 6,000 BTU radiant heat source

If Roger Caffin made an optional IR head for his stove, the combination would be extreme cold weather tent heater Nirvana. Roger… hint… hint!

Nighttime relief in cold/bad weather:

Chamber Pot (I've actually used a zip lock bag)

Billy

hey Richard,

Thanks for your information. Interesting and useful to see.

You mention that the Epic SL5 eliminates most condensation. Is that really correct?

My limited experience with double wall, non mesh tents, below 0F was in a 2 man 'mountaineering style' tent.

That tent suffered from a lot of condensation ,inside the inner tent.
I would imagine (with no experience ;-) that the much larger volume SL5, without the added warmth of the outer tent, would have a lot more condensation issues.
Also, my Epic windshirt, is one of the least breathable ones I have.

Is the fact that wind is blowing across the surface of the tent perhaps the reason for the high breathability you experienced?

PS, this is all just out of interest, as I am not going to buy a new tent! Just trying to decide which combo to use.

Tjaard,

My thermal image testing indicates that: the two LARGE vents at the apex of this EPIC shelter and the large tent surface area combines to set up a substantial non-forced convective flow through the EPIC fabric and out the vents. I would anticipate that a different tent shape, size, or vent orientation would yield different results. Thermal image 14 in my post best pictorially illustrates the strong non-forced convective flow.

I SUSPECT that with your existing SL3 and fabric/Cuben inner tent, a minor mod to the inner would significantly reduce the condensation. Minor mod: add two open mesh vents to the apex of your inner to vertically align with the vents on the SL3. This assumes that your inner fabric is equivalent in air permeability to most conventional tents. If you add a closeable flap to each open mesh vent, you are ideally set to compare the two alternatives in various conditions. The air flow pattern is also going to vary based on what you do to the lower edges of the SL3 (open, buried, or snow wall blocked).

Richard,
What App are you using to do that analysis? It looks very cool.

Ryan

I have a Hilleberg Unna inner ( reg solid one) that I have used in real cold conditoons inside both a GL SL 5 and inside a Golite Utopia 4 and I have found that it works very well. Still all the advantages of floorless, but with a nice inner that does not take up much more room than a bivy would.

I also often use a Tigoat bivy if the temps are not frigid. Before using the Unna inner, I had used a Bibler bivy during real cold weather in SL 5 and the Utopia. But for the same weight ( actually less, as the Unna inner weighs 24 oz) I much prefer the room of the Unna. Plus in a pinch, my wife and I can sleep in the Unna.

Hi Stephen,

Any photos of the Unna inner inside the Sl5?

Does the sod cloth have to be made of a waterproof fabric, or can it be breathable? Especially for a non-breathable fabric mid (e.g., a standard SL3)

James,

Either fabric type is fine for a sod skirt.

Richard,

Interesting data and images.

Tjaard,

I've used an SL3 without an inner and other non-mid tents with a solid inner such as a Scarp 2 down to -10F.

"-Not having a floor makes it easy to take the night time pee break in bad weather"
If you have an inner tent which allows room for a decent vestibule or even inside gear storage, then pee breaks or cooking aren't much more difficult.

"-solid inner tents collect a lot of frozen condensation on them, which can then fall on the sleeping bag, since I wouldn't use bivy."
The condensation is going to fall from somewhere though. :)

"-an inner tent is one more piece complicating set up"
Often, you can leave the inner attached.

I keep going back and forth between using an inner and not. I think I prefer the inner because I consider the above problems resolvable, and the advantages you mentioned to be worth it. I also like have an enclosed space where I can lay out gear and clothing without worrying about accidentally laying stuff on the edge of the groundcloth in the rain or snow.

"-an inner tent is warmer and keeps wind and spindrift out
– this inner tent is about the same weight, maybe even less than 2 bivies"

Stephen M:

Sorry for not getting back with an answer for you on the Unna solid inner in. GL SL5. I do not have any pics of it- but I could set it up and take some if you would like.

It is real easy to put the Unna inner in the SL 5; all you do is run a cord ( I used mason cord) from the top of the inner to the hanging top loop in the SL5. Then there are so many attachment points already in the SL 5 because it takes its own nest. I just tied some bungy cord loops to some of those and then ran cord from the elastic /plastic connection points on the Unna out to those. And then ran cord from the bottom of Unna stake points out to both stake loop points in the back and then to inner nest connection points for the front of the Unna. It works real well and only takes up less than half of the SL 5. I put it in the back half- but could easily be put on L side.

You can either attach the inner each time ( easy to do); or can leave it in place and set it up all in one just like the Hillebergs can.

Here are some pics of that:

Looks good Stephen.

In my experience with winter tents (down to -5 F.) I've found that most of your condensed vapor ("vapour" for you of the British and Commonmwealth persuasion) WILL freeze to the inside of the fly and often to the lower, waterproof portion of the inner tent walls.

Ain't no way to get around that short of a woodburning tent stove, well banked
to burn all night.

Good mid-to-top ventilation cuts this "fly frost " down by as much as 30%.

Basic answer: "DEAL WITH IT"

nm

Part snow trench, part tent can let one use a very small mid with several people. Chairs and cooking platforms of snow can be made.