Pertex Quantum, condensation and a sleeping bag

[horizon]

Whoaa there, nsew! All questions answered!

1. I'm using the Fellpacker because it has a polycotton inner (to compare it to a polyester inner) and is light enough to carry. The flysheet is highly suspect but that's isn't in the experiment. I took the material from the label but am inclined to agree with you that it isn't polyester. What bearing would that have on condensation?

2. Mat is a standard Thermarest. I don't know the R factor. Ground sheet material is same as the flysheet.

3. Camping location was on an open hillside campsite in a rural location four miles from the south Cornwall coast.

4. Sleeping bag is a cheapo synthetic but adequate-for-purpose bag and for the purposes of the experiment has a nylon outer shell to compare it to a cotton one to see if condensation occurs.

5. AFAIK both thermometers are working perfectly but checking will take place.

6. Clothing was Aldi ski underwear (100% polyester), light polyester fleece, woolly hat (polyester) and thick socks.

Warmth wasn't/isn't really an issue unless something I am doing/using to keep warm causes condensation, which at present it doesn't. The equipment (and its quality) will change as the trials continue.

[nsew]

Whoaa there, nsew! All questions answered!

1. I'm using the Fellpacker because it has a polycotton inner (to compare it to a polyester inner) and is light enough to carry. The flysheet is highly suspect but that's isn't in the experiment. I took the material from the label but am inclined to agree with you that it isn't polyester. What bearing would that have on condensation?

2. Mat is a standard Thermarest. I don't know the R factor. Ground sheet material is same as the flysheet.

3. Camping location was on an open hillside campsite in a rural location four miles from the south Cornwall coast.

4. Sleeping bag is a cheapo synthetic but adequate-for-purpose bag and for the purposes of the experiment has a nylon outer shell to compare it to a cotton one to see if condensation occurs.

5. AFAIK both thermometers are working perfectly but checking will take place.

6. Clothing was Aldi ski underwear (100% polyester), light polyester fleece, woolly hat (polyester) and thick socks.

Warmth wasn't/isn't really an issue unless something I am doing/using to keep warm causes condensation, which at present it doesn't. The equipment (and its quality) will change as the trials continue.

1. No idea.
2. Some of the Thermarest’s have a lowish R rating ~2 to 2.5. This is fine when the ground has warmed up, but you’ll be uncomfortably cold from the underside outside of those times. A cheap roll mat underneath the pad works wonders at those times. They can be cut to about 3 or 4ft to minimise bulk and they’re great for comfortable breaks.
3.Ive always calculated that anything within 5 miles of the sea is a high humidity area. Where the air mass that sits above the sea or large areas of water encroaches on land. Winds and breezes that come and go in the night will further affect humidity changes.
4. A sleeping bag is the number one consideration for self sufficient travel, before everything else. I have moved to a two bag system (a very light bag combined with the other for temps below +5deg) Light efficient bags aren’t cheap unfortunately.
5. Place together in various temperatures.
6.Polyester is excellent in that it keeps you dry when you perspire. Doesn’t thermo-regulate very well though. The more you pay for poly layers, the better they’ll typically perform. They whiff the next day.
7.The Met Office app is superb for all the weather/climate readings.

I’m travelling so info isn’t as complete as I’d like. Lucky you in Cornwall.

[pjclinch]

1. I'm using the Fellpacker because it has a polycotton inner (to compare it to a polyester inner) and is light enough to carry. The flysheet is highly suspect but that's isn't in the experiment. I took the material from the label but am inclined to agree with you that it isn't polyester. What bearing would that have on condensation?

Cotton is a special case for moisture as it soaks in to the fibres (why it's popular for towels), but even taking that in to account I imagine you'd find more difference between particular fabrics according to their manufactured structure than the chemical composition of the fibres that make them up.
Perhaps more to the point, stuff you're looking at tends to have surface coatings that will affect its performance when dealing with moisture.

Flysheets tend to have full coatings of either PU or silicone elastomer which should be what the water sits on, rather than the fibre weave. Inners (and fancy sleeping bags) will tend to have a DWR coat which tends to make droplets form rather than soak in (you can get coatings which break the surface tension on droplets so water does soak in, these are good on warm weather clothing where you want evaporative cooling more than water resistance).

Texture may well play a part, generally expressed by the denier rating of the fabric, though I'm not going to speculate how!

But, exec summary, I wouldn't get too hung up on if it's polyester, nylon (polyamide), polycotton or what. I think you're just saddling yourself with extra variables that are variable enough within themselves that they're not useful information.

Pete.

[horizon]

I wouldn't get too hung up on if it's polyester, nylon (polyamide), polycotton or what. I think you're just saddling yourself with extra variables that are variable enough within themselves that they're not useful information.

Pete.

Thanks for your feedback. I agree - I'm looking at variables now that I didn't even know existed! What I'm really hoping to find is one or two obvious variables that will mitigate condensation without causing other problems.

One obstacle is actually getting sufficient information from tent manufacturers that is useful, believable and comprehensive enough. Here is one paragraph taken from Vango's own blurb about their Tempest tent:

Featured with the innovative Venturi Vent, allowing fresh air to flow throughout the tent, increasing comfort and helping to reduce condensation.

and (same tent):

Breathable Polyester Inner - Allows condensation to pass through, for a comfortable night's sleep

To which my reply to the second quote is "So obviously not then...". Or did they just mean (regarding the Venturi Vent), throughout the outer flysheet?

I get the impression that we're meant to take everything on trust and just get on with it. When you dig a little deeper though, then yes, you get mired in complexity. My current question is, "How breathable is breathable polyester?".

[nsew]

The fly is vented. Doesn’t mean it’s a breathable material. Means it has vents. The inner is breathable so the moisture you create by breathing, sweating and farting passes out of the living space and meets the waterproof fly. The vents allow air to pass through the tent, minimising condensation build up. If the air outside the tent is saturated then the venting should be closed. There isn’t a tent made that eliminates condensation. Your job is to manage it and that’s what we’ve been banging on about. To no avail it appears.

[horizon]

The fly is vented.

At firsr I thought it meant the inner was vented but it appears that the space between the (waterproof) fly and (breathable) inner is vented (which makes sense)

To no avail it appears

You'll be pleased to know that I won't be posting further on this topic but I am grateful for the comments so far.

[nsew]

https://hilleberg.com/eng/faq/i-want-a- ... densation/

I want a tent with no condensation

There is no such thing as a “condensation-proof tent.” Condensation is something that can happen in any tent to varying degrees. In general, if the temperature inside the tent drops below the dew point temperature (the temperature at which air becomes saturated with water vapor), then moisture will condense on the walls. Similarly, if the humidity outside the tent is higher than inside and there is no air-movement – i.e. no wind – then there will be some condensation. Temperature plays a role, as well: you are more likely to experience condensation in cooler weather, especially in higher humidity situations. In addition to the degree of moisture in the air and the temperature, storing wet equipment in the vestibule or in the tent itself can also contribute to condensation in a tent. Condensation can also be affected by different body types, sleeping bag type, how much heat you produce and the like. This is why it sometimes might seem odd that one person has a tent with more condensation than another.

Vents in the tent will help, but only if the moist air that is being vented out is being replaced by slightly drier air from outside. When the humidity outside is higher than inside the tent, then this is naturally not the case, and the air coming through the vents will actually increase the condensation.

Conditions when it is very humid and a bit colder – such as in the fall or on cold summer days – are especially prone to condensation. Think of the inside of your car in the morning when it is cold, or the outside of a beer glass once the cold liquid is poured inside it. Unfortunately, some degree of condensation is part of the laws of nature. In a smaller tent, any condensation will be more apparent than in a larger tent both because of the smaller space and because the walls – and thus any condensation – will be closer to you. A larger tent has more air to circulate within it, and the walls (and any condensation) will also feel further away from you.

We also make tarps and even with these, under certain circumstances, you can experience condensation underneath the tarp. This is despite the fact that tarps have excellent ventilation, something that is so often regarded as the most effective remedy against condensation. But even here, in conditions as described above, one can wake up to a ceiling of wetness that is at times incomprehensible.

The bottom line is that in conditions where any moist air inside your tent – or under your tarp – is not able to be replaced by drier, warmer, air, there will be some condensation.

In our tents, the outer tent material (our Kerlon fabrics) is fully waterproof and is there to keep water – rain and snow – out. These fabrics do an exceptional job at this, but they are neither breathable – a term that refers to the ability of a fabric to allow moisture vapor to pass through it – nor air permeable. Thus, any moisture vapor trapped under such a fabric will likely condense onto the inside of the outer tent, as you sometimes see in the vestibule. In fact, when we first introduced the extended “GT” vestibules on some tents in the early 80s, we encountered something that we called the “GT-syndrome.” People were not used to having such large vestibules, and they would see the condensation collecting on the inside of the vestibule. Then, rain drops would hit the outer tent and knock loose droplets of condensations, so it appeared as if rain was going straight through the tent wall the vestibule. This was not the case, of course; it was merely condensation releasing from the walls.

Our inner tents, meanwhile, are built from a highly water repellent, highly breathable, and air permeable fabric. This fabric keeps the condensed water out, and allows warmer, moister air to escape, reducing condensation inside the inner tent. In addition, all of our tents are constructed to hold the inner and outer tents apart at an optimal distance to further fight possible condensation.

However, with the humidity in your breath and warmth of your body, or from any wet gear in the tent, or, of course, from the ambient dew point temperature, there is still a chance for some condensation to collect on the inside walls of the inner tent. Despite the inner tent material’s high breathability, in some conditions the walls will be the coldest spot in the tent, and condensation will collect on the coldest spot.

[horizon]

Thanks for the link.

BTW, the reason I've decided to stop posting on this is that, as pjclinch says, there are two many variables. For instance, I think that the breathability of the inner tent is important but there is (AFAIK) simply no way of knowing how breathable it is. I started this thread with a condensation issue that happened in a Robens tent; but I have no idea whether their polyester inner is less breathable than a Hilleberg or more breathable than a Vango (polyester will vary in breathability depending on how ithe actual polyester fabric is constructed). Throw in all the other environmenlal factors and a person's willingness to tolerate (or, as you say, manage) condensation and you have a bit of a mare's nest.

But it has given me food for thought and, as I said above, I'm grateful for all the comments and feedback.

[pjclinch]

I get the impression that we're meant to take everything on trust and just get on with it. When you dig a little deeper though, then yes, you get mired in complexity. My current question is, "How breathable is breathable polyester?".

I think you're over-thinking it... again!

Breathable Polyester Inner - Allows condensation to pass through

is a fabulous piece of marketing-speak, a bit like selling you a bike with "round wheels for smooth rolling": i.e., it's true, but it's what everyone's doing so you'll get it anyway.
Though having said that, it's wrong. Breathable fabrics (and just about any woven fabric is breathable unless it's had a non-porous coating poured over it, because of all the holes in the weave) don't let "condensation" through, they let moist air through. Condensation is moisture that has already condensed in to droplets; what they really mean is "allows moist air to pass through so when the water vapour condenses in to droplets it's out of your way"

Until you get in to the realm of "breathable waterproof" pretty much anything you'll use for this job is breathable enough. You'll notice that "breathable" only became important in the wake of Goretex et al, because these fabrics are significantly less breathable than a simple woven fabric like a very thin synthetic ripstop used for a tent inner.

So not only don't worry about it being polyester (or not), also don't worry if Brand X tell you it's "breathable", because it will be (given companies have been gormless enough to make Goretex rusksacks in the past, so wet things would magically dry out inside them, someone, somewhere will have decided a waterproof inner was a really smart idea, but I doubt anyone mainstream would be daft enough today).

Another misunderstanding is it's widely assumed that a woven fabric with a DWR coat is less breathable than the plain fabric because if you go for a run in a coated top it feels clammier than an uncoated one. In actuality the holes aren't significantly smaller so air (including water vapour) will pass through okay. The difference is that vapour that has already condensed in to droplets (or sweat that hasn't actually evaporated) will be trapped. The DWR prevents it soaking in, the energy isn't there to evaporate it (why it condensed in the first place) so it sticks around as damp. Whether that's better or worse than soaking in to the fabric and being wet that way is, I suspect, something of a sixes vs. half dozens sort of game.

But don't worry. If condensation was such a big problem that lightweight camping with it was untenable then it would have been given up a long time ago.

Pete.

[horizon]

You'll be pleased to know that I won't be posting further on this topic

Well not for a few months anyway. That was back in August so I thought it was time for an update (all the comments received so far notwithstanding).

Just got back from a quick overnighter (cycle camping) on a local campsite. Friday was a warm day here so lots of humidity in the air. Friday night plummeted to around 1 deg C so the dew went crazy - outside of flysheet was streaming with condensation. All in all a good night to test out some theories.

So: double sleeping bag (two-season synthetic on the outside), cotton inner tent, polyester flysheet, no venting, internal temp around 5 - 6 deg C. Snug, warm and dry all night, no condensation inside the tent or on sleeping bag.

I'm very happy with that but I'm not suggesting it proves anything. I think that when people talk about experience, they mean trying out different things over and over again until you get a sense of what works best. I'm still in that process.

[horizon]

FWIW, another update!

I've just come back from 11 nights camping on the Costa del Sol (and inland) using a polyester tent and that sleeping bag - yes, a Rab Ascent 700 on the Costa del Sol.

I was pleased to have it, the nights did get cold, it was light, compact (I was backpacking) and cosy. And yes, it was overkill but I don't have another suitable down bag - 500 gms fill would have been great and for most people no doubt 300 gms fill.

And now for the condensation on the bag: it happened on two nights. I'm now pretty sure that this is body heat/moisture and that the Pertex beads the condensation. A quick shake and dry and the bag was fine. The Pertex still felt cold to the touch on the outside of the bag and there was pretty much no other condensation in the tent (some on the inner side of the flysheet).

I somewhat apologise for my obsession with this problem but for me it was a complete surprise and for which there appeared to be no clear explanation. But I think i understand it better now.

[pjclinch]

I somewhat apologise for my obsession with this problem but for me it was a complete surprise and for which there appeared to be no clear explanation. But I think i understand it better now.

As well as understanding the process better, are you happier with the idea that you can have a decent length of tour, get some unavoidable condensation and not have the sky fall in?

Pete.

[horizon]

I somewhat apologise for my obsession with this problem but for me it was a complete surprise and for which there appeared to be no clear explanation. But I think i understand it better now.

As well as understanding the process better, are you happier with the idea that you can have a decent length of tour, get some unavoidable condensation and not have the sky fall in?

Pete.

I think I am slowly getting my head round the idea that everything I thought I knew about camping has now been turned on its head: moisture comes from within the tent not from the outside and down will inevitably get wet.

This thread was about Pertex and I think this is the nub of the problem: it most likely does have a DWR and allows condensation to bead rather than soak in. I've found that a quick shake and a very short drying time is therefore all that it requires. All my sleeping bags in the past (a real rag bag) obviously lacked this (i.e. they soaked up surface condensation, to their detriment). If I have a spare moment I will check to see what Rab (and the others) say about this. I cannot be the only cyclist/backpacker/hillwalker who has experienced this but possibly for most serious outdoors people it is a well known phenomenon.

[pjclinch]

If I have a spare moment I will check to see what Rab (and the others) say about this. I cannot be the only cyclist/backpacker/hillwalker who has experienced this but possibly for most serious outdoors people it is a well known phenomenon.

Everybody gets it at some point once you've enough camping nights under your belt.
And at first one gets worried, but then if stuff is basically working you come to realise that things don't have to be perfect, just good enough, and part of why you've paid for good gear is that good gear can take it.

Pete.