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  1. #1
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    Lightbulb tent temp: fly no fly

    Is there a guideline on how much warmer it is in a tent with a rain fly vs not? Trying to decide between a zpacks duplex and a big agnes fly creek. The duplex is lighter and has more room, but I usually carry minimal clothes, so the main consideration is the temp diff.
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  2. #2
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    i wouldn't say there's a "guideline" as how much warmer with fly....

    too many factors play into it-----is it windy? is the tent in the shade? is the campsite in a holler where the cold will descent? etc. etc.....

    and of course, one's own body heat along with maybe someone else being in the tent....

  3. #3
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    Don't know. But I can definitely feel the temperature difference from inside to outside on my conventional, double wall one person tent (MSR Hubba). If I had to guess, maybe five degrees warmer inside?

  4. #4
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    Not enough difference for me to change any clothing or equipment.

    thom

  5. #5
    Some days, it's not worth chewing through the restraints.
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    Well, without the rain fly, it will certainly be a lot colder in the rain...

    Or are you asking if a double-wall tent is warmer than a single-wall? If that's the case, I haven't noticed a difference. It's warmer inside the tent primarily because the wind isn't robbing any heat from you. Tarptent sells a liner for the rainbow and claims it adds 5 degrees temperature difference. Not significant to me, and any ounces spent on another clothing layer would be more effective.

  6. #6

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    Quote Originally Posted by Deadeye View Post
    Well, without the rain fly, it will certainly be a lot colder in the rain...

    Or are you asking if a double-wall tent is warmer than a single-wall? If that's the case, I haven't noticed a difference. It's warmer inside the tent primarily because the wind isn't robbing any heat from you. Tarptent sells a liner for the rainbow and claims it adds 5 degrees temperature difference. Not significant to me, and any ounces spent on another clothing layer would be more effective.
    This brings up how I think. It's really not a question of fly vs no fly---as all waterproof tents have a rain fly. It's really more a question of single wall tent vs double wall tent.

    In their video Zpacks says (of the Duplex) that "Any condensation will run down the wall and out to the downward sloping screen rather than down to the floor" etc.

    This is where it's tricky, very tricky---and you hope like heck their advice is correct. In the right conditions ALOT of condensated water will form on the inside of a fly---and the double wall inner canopy will shunt this water off you and your gear and down the canopy sides. A single wall like the Duplex has no double wall protection. Every shake and gust and you brushing up against it can/will/might/might not/certainly will---get you and your gear wet.

  7. #7
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    There are highly specialized winter-/mountain tents that are double wall and designed in a way to save warmth, and are very good at this.
    One secret is the distance between outer and inner being a certain amount (about 2 inches) and being the same measure all over the tent. This makes the air gap between inner and outer a perfect insulation.
    The general design of said mountaineers tents is such that they are not useful in rain and would do no good for hiking.
    So as others have stated here, the main difference is the fly blocking off the wind, especially important for tents that have an inner that has more mesh than canvas.

    I have a dedicated tent for winter hiking, an Exped Venus II and it makes all the difference against the MSR Hubba Hubba NX summer tent. I'd estimate the difference at 5-10 between the two tents.

  8. #8

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    Quote Originally Posted by Leo L. View Post
    There are highly specialized winter-/mountain tents that are double wall and designed in a way to save warmth, and are very good at this.
    One secret is the distance between outer and inner being a certain amount (about 2 inches) and being the same measure all over the tent. This makes the air gap between inner and outer a perfect insulation.
    The general design of said mountaineers tents is such that they are not useful in rain and would do no good for hiking.
    So as others have stated here, the main difference is the fly blocking off the wind, especially important for tents that have an inner that has more mesh than canvas.

    I have a dedicated tent for winter hiking, an Exped Venus II and it makes all the difference against the MSR Hubba Hubba NX summer tent. I'd estimate the difference at 5-10 between the two tents.
    The highlighted quote is very confusing. I exclusively use a 4 season winter tent---a "mountain" tent---and it is designed exactly as you say with the distance between the outer and the inner being about 2 inches and being the same measure all over. And it's the best tent I ever had for long RAINSTORMS---.

    No good for hiking?? Not useful in rain? It's my backpacking tent and as mentioned---awesome in a long mountain rainstorm. Please explain.

  9. #9
    Some days, it's not worth chewing through the restraints.
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    I didn't quite get that one either. As long as you're willing to carry the weight, a mountaineering tent (Hilleberg tents, for example) is a rock solid shelter for any season, any weather.

  10. #10
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    Sorry for my confusing English.
    This is the mountaineering (expedition) Sumitomo tent we were using, and I was referring to:
    Sumitomo.JPG
    This tent provided perfect insulation against wind and cold, how heavy and severe either might be.
    But it had no vestibule you could cook in, had not canopy to protect the entrance against rain, had no bugnet, and was not even waterproof. The flap around the whole perimeter of the fly was wide and very sturdy so you could pile snow and rocks around it.
    On the other hand it had a toilet opening in the floor...
    Not sure about the weight, but we carried it easily together with all the other mountaineering stuff.
    Might have had 2 to 3 kilos maybe (remember it estimating at half the weight than my Salewa, which was a bit over 4 kilos).
    Last edited by Leo L.; 12-19-2019 at 15:03.

  11. #11

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    There are lots of single wall mountaineering tents that are engineered for 4th season use and trade waterproofness for breathability and weight. Because rain is a non-issue on a cold high altitude climb, the fabric isn't designed to withstand a long rainstorm. Great in ice/snow/wind. Awful in rain.

    Bibler makes several examples of this (Firstlight comes to mind).

  12. #12

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    Quote Originally Posted by CalebJ View Post
    There are lots of single wall mountaineering tents that are engineered for 4th season use and trade waterproofness for breathability and weight. Because rain is a non-issue on a cold high altitude climb, the fabric isn't designed to withstand a long rainstorm. Great in ice/snow/wind. Awful in rain.

    Bibler makes several examples of this (Firstlight comes to mind).
    Thanks for the input. I know all about what you're talking about cuz several years ago I bought a "state of the art" single wall Integral Designs MK3 tent (now mercifully discontinued) as it was highly praised by several winter experts.

    BIG MISTAKE. In a long and heavy winter rain the thing leaked in 9 separate places and twisted my medulla and brainstem back to the safe and secure folds of Hilleberg tents. Oh and I used two tubes of McNett's seam grip on the thing with no results.


  13. #13

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    Sounds about right. It's a very purpose oriented design choice. Great for a high altitude climb but totally wrong for your use.

  14. #14

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    Quote Originally Posted by CalebJ View Post
    Sounds about right. It's a very purpose oriented design choice. Great for a high altitude climb but totally wrong for your use.
    I was hoodwinked by experts and previous owners. When I mentioned the leaks they said I must've got a lemon. In part they were right---it's yellow.

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    You've convinced me that The big agnes may be right for me. For me, I would prioritize these things in this order: dryness, warmth, weight, space. It'd be nice to have the space and lighter tent, but not as much as the other two factors. I have a copper spur UL2, but its a tad heavy and I'm giving it to my son. The duplex is lighter and roomier, but I am fanatic about keeping gear dry.
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    I guess it may help to add usage is late spring in southern new england on the AT and northern new england on the AT in summer
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  17. #17
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    Quote Originally Posted by joefryfry View Post
    Is there a guideline on how much warmer it is in a tent with a rain fly vs not? ... so the main consideration is the temp diff.
    Quote Originally Posted by joefryfry View Post
    You've convinced me that The big agnes may be right for me. For me, I would prioritize these things in this order: dryness, warmth, weight, space. ... I am fanatic about keeping gear dry.
    Quote Originally Posted by joefryfry View Post
    I guess it may help to add usage is late spring in southern new england on the AT and northern new england on the AT in summer
    Quote Originally Posted by Cheyou View Post
    Not enough difference for me to change any clothing or equipment.

    thom
    THIS^^^
    Forget warmth as a factor in selecting a tent - especially in order to go lighter when selecting a sleeping bag or insulative clothing - and even more so in northern New England. The R value of a layer of nylon is essentially zero - it's not insulation. And any slight gain in temperature will disappear if conditions require ventilation to avoid condensation. You should select a tent based upon water and wind performance, structure and space, and entry requirements for its anticipated use. Yes, there are trade-offs and compromises to be made, but they are more along the lines of fabric choices, interior volume, free-standing vs staked, etc. vs weight and price. Warmth really isn't a factor.

    A tent may be 5F warmer, but only under conditions when condensation is not an issue. Mostly, they increase warmth because they protect you and your bag from drafts and direct contact with ambient air, settling dew, etc. But, the warmer a tent is inside relative to the outside air, the more you will fight condensation - especially in a single wall tent. The less ventilated you keep your tent, the warmer and more saturated the air (both atmospheric plus water vapor expelled breathing) inside the tent becomes. Then, when it's humid out as it often is in the eastern mountains, as the temp falls at night the low mass tent fly fabric cools almost instantly with the outside air temp, and the moisture in the relatively warmer air inside the tent condenses on the cooler tent fabric. It is unavoidable. When the ambient air is relatively dry, it isn't generally a problem provided there is suitable ventilation. The advantage with a double wall tent (including tents with netting inner walls) is that the air passing between the two tent layers will more easily absorb the water vapor that passes through the permeable inner tent, and the inner tent will shield you from direct contact with any condensation on the fly. Single walls tents don't have this advantage, so they must be more directly ventilated (peak vents, door/side flaps open, etc.). Even then, there are atmospheric conditions when condensation is unavoidable with any tent - and it's always worse with a single wall.

    Also remember that for planning purposes as far as temperatures go, you have to factor in elevation and mountain micro-climates. In northern NH, we usually get our first frost in late August, but I've seen morning frost in Jefferson, NH, in the middle of summer. Expect a few cold mornings (30's) in the northern mountains at some point even in summer. Pay attention to the higher summits forecast when in the Whites. Select a sleeping bag accordingly.

    Regarding the climate north of Glencliff, NH (NH and ME): We only have two seasons up here - July and Winter. Summer is the two weeks on either side of July 15th. Seriously, factor in to your plans that any given day's temperature will typically vary +/- 10 from the average high and low temperatures, with extreme variances possible up to +/- 20F. My summer setup in northern New England is a 35 WM Caribou and BA Copper Spur tent. And once September hits the Whites, that setup can be marginal - I've seen 20's in mid-Sept in the mountains up here.
    Last edited by 4eyedbuzzard; 12-20-2019 at 19:54.

  18. #18

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    Quote Originally Posted by 4eyedbuzzard View Post
    THIS^^^

    A tent may be 5F warmer, but only under conditions when condensation is not an issue. Mostly, they increase warmth because they protect you and your bag from drafts and direct contact with ambient air, settling dew, etc.

    But, the warmer a tent is inside relative to the outside air, the more you will fight condensation - especially in a single wall tent. The less ventilated you keep your tent, the warmer and more saturated the air (both atmospheric plus water vapor expelled breathing) inside the tent becomes. Then, when it's humid out as it often is in the eastern mountains, as the temp falls at night the low mass tent fly fabric cools almost instantly with the outside air temp, and the moisture in the relatively warmer air inside the tent condenses on the cooler tent fabric. It is unavoidable.
    Bold highlight pretty much explains condensation---"when it's humid out as it often is in the eastern mountains" and "It is unavoidable" pretty much hits all important points.

    Peter Clinch also describes tent condensation in one of my older WB posts---

    https://www.whiteblaze.net/forum/sho...=1#post2141516

    There's one other thing regarding "protecting your bag from drafts"---a lesson I learned the hard way back in 1981---

    One cold winter night I was too lazy to set up my tent so I just flopped down on the ground on a pad and zipped up my down bag and tossed and turned all night in the cold. Why? Because a biting wind blew right thru the geese. This never happens in a good tent where no breezes are allowed. The lack of air flow in the winter---the cause in part of condensation---is also the way to stay warmer in a goose down bag---much warmer.

  19. #19
    Some days, it's not worth chewing through the restraints.
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    I agree with all the 4eyed Buzzard & Tipi said, but frankly for the seasons you're talking about, it's not a big deal. Any decent tent that keeps you dry will work from spring to fall. It's only in winter that it's a major concern. I use a single wall tent (TarpTent Rainbow) for three season use, and I love fresh air, so I vent it well and have no condensation issues. I'm going to try it this winter to see how well it handles sub-zero temps, but I usually use a double wall tent in winter.

  20. #20

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    Quote Originally Posted by TNhiker View Post
    i wouldn't say there's a "guideline" as how much warmer with fly....too many factors play into it
    ^^^that, but if you want a point of reference, here's my new MLD Solomid XL and my friend's new Nemo Kunai(he will be out in these conditions regularly, 40+mph winds and whatnot, while they're a rarity for me).
    The Solomid is just a tarp, while the Kunai is a double wall 4 season tent.
    We both had thermometers attached to our packs, which were inside our respective shelters. Shortly after making camp, his read 28F, while mine read 20F.
    20191218_022151.jpg

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