Tent Warmth Survey

Zero factor.

I've never thought of a tent as having any sort of a warmth factor. If it is warm, then that is a sign that it is not ventilated correctly. Basically, a tent's function is to shed precipitation and wind. If a tent has correct ventilation (not too much or too little), then your sleeping bag will let you get the right temperature for sleeping, and condensation will be virtually absent.

–B.G.–

I went with a double wall for my winter choice because it would be warmer. So yes that was a big factor in my decision. Living here with the windy Lost Coast and the rainy Coastal Ranges were also a deciding factor. Condensation City,USA.

I like a tent to protect me from cold things such as breezes and spindrift snow, but beyond that I don't count on it for much warmth. It's more efficient to keep warm via your sleeping bag/pad than your tent. So a few ounces of extra down in the sleeping bag would go further than a few ounces of extra tent material.

With that said, tent inners could be made from light fabrics that are no heavier than the widely used no-see-um netting. A fabric like EightD (or is it TenD now?) weighs about the same as netting (0.7oz) and presumably would be warmer. It's affordable too, so it may be a good choice for a solid inner fabric.

A tent or tarp plays an important part in my sleep system by preventing convective heat loss. So yes, for me it is important in the northern Rockies.

I find that a shaped tarp such as a trailstar does a good enough job of protecting me from wind gusts. I also use a sleeping bag instead of a quilt, so that cuts down any drafts that do find their way under the sides of the trailstar.

For 3 season camping in Colorado, the trailstar + bag setup works great. If I head out to desert areas (like canyonlands), I prefer to bring a fully enclosed tent, less so for warmth and moreso to block dust blow-ins.

I don't own a single tent that provides any warmth whatsoever. But I do have lots of sleeping bags and bivys that do.

And I bet I've spent a thousand nights wishing my tent was cooler. And that noseeum mesh didn't kill every breeze under 10 MPH.

"And I bet I've spent a thousand nights wishing my tent was cooler. And that noseeum mesh didn't kill every breeze under 10 MPH."

Agreed when I lived in SoCal, same experience.

Even my Hexamid adds some warmth as long as it's not too windy.

I don't consider warmth when I buy tents, although I would if I intended to use a 4th season tent a lot in that 4th season.

I do consider usable interior height. That's my #1 factor.

I camp mostly in the ADK's of NY. Temps run from about -25F to about 100F over the couse of a year, with some extreme days being worse.

My tarp does well down to about 25F, stopping most breezes/winds and convective heat loss. My 4 season tent is an Exped Sirius. At 30F it maintains about a 10-15F temperture differential between inside and outside air. Yes, we get some condensation on the outer fly.

Generally speaking, an open sky is quite cold. I have heard of reports down to -70C or more. Mostly this is due to radiant heat loss, though. General convective loss is helped by stopping most winds/breezes. So, taking a 40F bag down to 30F is OK in a small tightly enclosed tarp shelter. You will notice the difference when you exit the tarp in the morning. Condensation is always a problem in such shelters, though.

A double walled tent, such as the Sirius, has an inner breathable liner and is good to about 20F with a 40F bag. This presupposes a good pad. (I use a nightlite and neoair in combination or about an R4.7 or a bit higher due to lofting in the bumps where I don't compress them.)

I have used this tent in June (late spring/early summer) but found that it was too warm for comfort. I always have both vents wide open, so, this is not a summer tent. Mainly I use this for base camping/car camping due to the ~6pounds of weight.

The tarp I use is larger and weighs a bit more than 17oz. It allows me and my partner to sleep in an A-Frame type setup, or, lean-to depending on the temp. A Diamond setup is sort-of a compromise, so there are several pitching options availble. July and August, I often bring a mesh tent for bugs with a partner. It weighs about 16oz. There are no notable condensation issues, except the tightly enclosed A-Frame pitches. All waterproof layes will have some condensation under some conditions…

Basically, I would consider my use, be it summer, spring/fall or winter and purchase a tent with a warmth factor fugured in accordingly. BTW, I have spent several years camping, so have refined my requirements beyond the average, I believe. But, as always, they are MY requirements, not yours.

I've never bought a tent with warmth as a main reason, but my Stephensons 2R is the warmest tent i've ever used. And i've used quite a few. I think the fact it is almost a 'sealed in' construction is the reason.

I've measured temperature inside and outside tent.

In tent is 5 or 10 F warmer than under stars when it's clear due to radiative heat loss I believe. All tents are about the same – 1 fabric layer blocks IR but 2 layers isn't any better.

Or, you can find a sheltered spot under a tree and get the same.

And convective heat loss is less. I've noticed with edges raised a few inches off ground, the wind speed inside the tent is pretty much zero. I have tried to measure but my wind speed meter only goes down to about 1 MPH. So, I think any tent is about the same. A raised tarp would help a little – you always have Roger's chart of wind speed vs height above ground – where you are the wind speed is pretty low regardless.

Double walls will trap body heat inside tent. You have a second skin of air that provides a little insulation. But your body produces so little heat, maybe 50 Watts, and it gets spread out over large tent area, I don't think that makes much difference. I consider the inner wall just a barrier to remind you not to touch the condensation on the inside of the outer tent.

Recently I was camped out in the open during a storm that had 45+mph wind and heavy rain. Frost in the morning. Sure was still, warm and dry in the tent. Not the case when I experienced similar conditions in my Double Rainbow. Too much ventilation. Could not get out of the wind. Yes I realize that the weight for warmth could be better managed with insulating clothing. And I would go that route if I was not expecting to spend a fair amount of time in camp. Different goals, different tools.

"Double walls will trap body heat inside tent. You have a second skin of air that provides a little insulation. But your body produces so little heat, maybe 50 Watts, and it gets spread out over large tent area, I don't think that makes much difference. I consider the inner wall just a barrier to remind you not to touch the condensation on the inside of the outer tent."

I used to use the Sirius without the inner tent body sometimes. I will note, for the record that there was a 5-7F degree difference under the same night time temp…with and without the inner body. Unfortunatly, I did not have anything besides my gadget watch to measure humidity or air speed. This leads me to believe that while IR may be somewhat important for heat loss, so is convection(a specialized form of conduction, really.) Roger would have his own thoughts on the subject, of course, but I suspect that he would agree that there is more than a negligible difference between a single layer tent and a double layer tent. Indeed, he is designing his "winter" tents as double layer tents with a breathable inner. As you say this needs to be adjusted by internal tent volume/surface area. A small double layered tent will warm up well with a 70watt (the more accepted figure) heat source. However, a large 10 person tent will not.

Yes, what Ken said. I don't really expect a three season shelter to add much in terms of indoor air temperature. A certain amount of air exchange is after all needed to remove humidity. But beyond a certain point the breeze is just sucking the heat out of you. So I prefer some amount of control over the rate of air exchange taking place. In high winds, I want the option of closing things up a bit.

Then again I mostly hike in the northern Rockies where overnight temps can be cool even in the summer.

So its; I want this, I want that. I guess that's what keeps shelter designs interesting.

The wide range of user control over ventilation is a huge plus in Rodger's summer tunnel tent design IMO.

"I will note, for the record that there was a 5-7F degree difference under the same night time temp…with and without the inner body."

Okay, maybe so, especially for small tent.

If the area of the tent is 8 square yards, then a liner would weigh maybe 6 ounces. If you added 0.5 ounce of insulation to your torso you'd get about the same temperature increase.

70 Watts? What's your source for that? I'm curious what the best number for that is. And what is the Watts/square meter? (i.e. what's the area of a body?)

Most of the nights I've spent in tents have been too warm, actually.

Florida doesn't have much of a cold season; this was one of the factors that originally moved me over to an hammock, come to think of it. The under-insulation "problem" that most folks have with hammocks is a plus for me ~8 months out of the year. When night time temps are above 70 F, I find that tents are just too stifling for me to get a good night's sleep. Unfortunately, I need an enclosed area to fight the bugs; the mosquitoes and ticks down here are voracious for pretty much that entire time.

So, a bug netted hammock wound up being a good call for me. I get cool air convections underneath the hammock, helping to keep my body temp "just right" for those warmer nights. On cooler nights (between late October and early March), I bring an underquilt.

If I had been camping somewhere cooler for most of the year, I might have stuck with tents. Unfortunately, they just don't work for me down here during most of the year.

Jerry,
"A human will output from around 70 Watts to 870 Watts, depending on the amount of physical activity undertaken." This was taken directly from Wikopedia a few minutes ago and is a fairly accepted figure. Note that the lower figure was used. I am guessing this would be correct for a sleeping or inactive person, on average. I would guess about a 25% varience would be still considered "normal" though.

Watts/sqm is a bit more difficult. There area a lot of different values and it differs for men and womwn. According to one source it is listed as 1.7m2 According to another about 1.75m2. According to wikopedia it is 1.73m2. In fact they list several ways to derive this number. But for heating value in a confined area, such as a tent, it really doesn't matter. The entire heat eventually ends up in the tent, except for whatever is lost through the floor depending on conduction primarily, with only 5-10% radiant heat loss. Depends on how well you insulate your pad for the conditions, too. Though you could make the argument that this would be returned to the tent after a couple hours due to warming of the ground.

Actually, the inner tent to the Sirius weighs about 3 pounds. The problem with adding lots of clothing comes in because it won't all fit into a bag. I can use long johns and slip my down jacket/insulated pants on at night, but more only compresses the down…similar to laying on it. It really doesn't help beyond a certain point because the bag is pulled tight. Anyway, it is one of the things I look for in a tent. Warm tents vs cool tents. Not really a deal breaker, but one of the things I look for. Along with straight-in (no turning around) access, covered entrance, wind blocking, and ventilation capability.

…

Well this really scientific survey suggested the following:

About half of you said that warmth is not a factor when selecting a tent and were more concerned about keeping cool enough in the tent. Those expressing this opinion tended to live or backpack in warmer climates.

About half of you said that warmth is a factor to consider, depending on where/when you might be backpacking. This group tended to live or backpack in cooler climates.

No big surprises here but I found it interesting nevertheless.

Thanks for responding.

Mike,

Your experience with the Stephensons tent supports their tents' name "Warmlight".

If I was to put a name on the tents I have made I think I would want something that conveyed small, warm and light.

Daryl

In spring, summer, fall the warmth of my tent wouldn't be a factor. But in winter it would. Usually a tent can be warmer by minimizing the air gap around the bottom of the tent and closing a fly vent. But there is a trade off of increased condensation from having less ventilation. This is in the northeast primarily. Many times in the warmer temps of spring/summer/fall you can't get a tent cool enough.

My three season shelter selection is to create a microclimate (eliminate wind or weather). Winter shelter however is all about additional warmth. I have noticed that it plays a more important part in 3 person tents than 2 person tents. With 3 people in a 3 person tent a nice double walled tent is easily 15 degrees warmer than the outside if not more. With 2 people in a 2 person tent it hasn't seemed to do quite as much, still helps a bit though.

Three people in a sung three person tent = true winter bliss

Theoretical calculation:

According to wikipedia R value article, a skin of air has an insulation of 0.11 Km2/W. Adding an inner tent would add 2 skins so 0.22 Km2/W.

Maybe a tent has a surface area of 8 square meters (35 inch high, 70 inch wide, 7 feet long – those dimensions are easy to calculate – half cylinder but about the same as typical small tents).

One person is 75 Watts.

Temperature difference across inner tent is 0.22 Km2/W * 75 Watts / 8 square meters = 2 degree K = 3.7 degree F

2 people would be twice that

But the tent will leak some air so it would be less

And the tent would flap around which would disrupt the skin of air so it would be less

And some heat will go down through the floor so it would be less

Inner tent make it 5 degree F warmer inside – maybe. 10 degree F – I don't think so

I routinely measure inside and outside my tarp with edges raised a couple inches off ground and it's 5 or 10 degree F warmer inside than outside. Different places outside can easily differ by 5 degree F. Measuring the heat difference of inner tent would be tricky – easy to confuse with unrelated differences.

1 question and 1 thought,

Does humidity have any impact on your calculations Jerry?

And, with 3 people snuggly inside a 3 person tent in the winter you pretty much have a sea of goose down that stands about 18" tall. That could be why I feel like it is easily 15 degrees warmer inside that tent.

On the other hand.

The math of all this is where you are going to lose me, but is it really an area calculation? I would have thought it would be a volume of space inside the tent that you were trying to heat with the body?

"Temperature difference across inner tent is 0.22 Km2/W * 75 Watts / 8 square meters = 2 degree K = 3.7 degree F

2 people would be twice that"

I wasn't far off when I said 3 people is 15 degrees warmer… 11.1=15 whats a few degrees amongst fellow backpackers ;)