Pertex Quantum, condensation and a sleeping bag

[horizon]

<big snip>
Getting it exactly right might not be easy!

I suspect you're over-thinking it.

I wouldn't be the first! (Quick Google tells me there are quite a few others out there.)

Two things I agree with:
1 Generally speaking, condensation exists in an outdoor environment and some will inevitably have to be tolerated.
2. Cycle camping kit (both traditional and modern) is robust enough to cope.

However my experience with the Rab was both new (I have never knowingly experienced condensation in the tent to that degree) and unacceptable - on the coldest nights, the bag was at its wettest; it just wasn't what I would call pleasant or even challenging, just pretty awful. So at this stage I'm happy to try and do something about it. And by the way, this wasn't the result of a climate change-induced mega-storm or a trek across the frozen wastes of Scotland in the winter: this was a very normal summer night in southern England, a balmy day followed by a clear, still night.

So far, thanks to the replies on here, I've deduced that an over-warm sleeping bag has conspired with a clear, cold night and a water-resistant sleeping bag shell to create abundant surface condensation on the bag. And I can contrast that with zero condensation in similar conditions using different equipment and practice.

So for me there is still much to play for (and to be grateful for, regarding the replies on here).

[nsew]

1. Cooler sleeping bag (as advised)
2. Layering to appropriate level of warmth (i.e. not too warm) (as advised)
4. Highly breathable inner tent (also recommended)

All good with the proviso that you shouldn’t layer with cotton clothing or use a cotton liner. Cotton doesn’t wick sweat away but absorbs which will increase the feeling of discomfort and cold.

3. No ventilation (keeping internal temp higher than dewpoint) (as suggested)

Only batten up the hatches if you consider the relative humidity is greater outside than in (it likely was on the previous trip). Venting towards the top of the tent works best because warm moist air rises. You always want it “drier” inside the tent than out.

[nsew]

Regarding layers;

Too many and the warmth generated by your body won’t infiltrate the down and it won’t loft, ie insulate, ie work. It is your metabolism that heats a sleeping bag. Better to remove any layers inside the bag while warm. Single base layers (one’s that regulate heat and wick moisture away) can be kept on because they’re effectively another layer of skin.

[nsew]

If the down in the sleeping bag is flat, put it in a tumble drier on a low or medium heat. Take it out after a minute or so to check the outer material can handle the heat. Do this a few times. The down should loft. If it doesn’t then its dirty and clogged and needs a proper clean. Expensive.

[pjclinch]

However my experience with the Rab was both new (I have never knowingly experienced condensation in the tent to that degree) and unacceptable - on the coldest nights, the bag was at its wettest; it just wasn't what I would call pleasant or even challenging, just pretty awful. So at this stage I'm happy to try and do something about it. And by the way, this wasn't the result of a climate change-induced mega-storm or a trek across the frozen wastes of Scotland in the winter: this was a very normal summer night in southern England, a balmy day followed by a clear, still night.

Back to my Black Isle anecdote, where we had an absolute shocker of a condensation event 24 hours after a normal night. Same tent, same venting, same bags, same pitch, similar wind and temperatures, no rain. If I'd had to bet money before we went to bed on whether the condensation would have been significantly different I'd have noted everything was pretty much the same and... lost the bet. You can just get the odd freak night, and unless you get the same thing happening a lot I'd hold that as at least a possibility.

Pete.

[horizon]

Back to my Black Isle anecdote, where we had an absolute shocker of a condensation event 24 hours after a normal night. You can just get the odd freak night, and unless you get the same thing happening a lot I'd hold that as at least a possibility.

Pete.

I do take your point on that. I'm not too worried about the odd (in both senses) event but because it was new to me, I did want to find out more. Also, the possibility that it was body heat/moisture (as opposed to breath and ambient condensation) was new to me as well meant that I've had to rethink what ohers may have taken for granted. And it was a very new, quite expensive sleeping bag ...

[nsew]

However my experience with the Rab was both new (I have never knowingly experienced condensation in the tent to that degree) and unacceptable - on the coldest nights, the bag was at its wettest; it just wasn't what I would call pleasant or even challenging, just pretty awful. So at this stage I'm happy to try and do something about it. And by the way, this wasn't the result of a climate change-induced mega-storm or a trek across the frozen wastes of Scotland in the winter: this was a very normal summer night in southern England, a balmy day followed by a clear, still night.

Back to my Black Isle anecdote, where we had an absolute shocker of a condensation event 24 hours after a normal night. Same tent, same venting, same bags, same pitch, similar wind and temperatures, no rain. If I'd had to bet money before we went to bed on whether the condensation would have been significantly different I'd have noted everything was pretty much the same and... lost the bet. You can just get the odd freak night, and unless you get the same thing happening a lot I'd hold that as at least a possibility.

Pete.

An exposed peninsula virtually surrounded by water. A quick glance at the Met Office app for Cromarty, Highland shows the wind / breeze regularly spinning around from one direction to another in the space of a few hours, sometimes a full 180deg in the space of an hour. Humidity also ranging from 50deg (wind/breeze off the mainland?) during the afternoon to 95deg (wind/breeze off the Sea?) in the early hours.

Clearly a lot can happen in the space of a nights sleep while we’re oblivious to the world, especially on an exposed peninsula.

[pjclinch]

An exposed peninsula virtually surrounded by water. A quick glance at the Met Office app for Cromarty, Highland shows the wind / breeze regularly spinning around from one direction to another in the space of a few hours, sometimes a full 180deg in the space of an hour. Humidity also ranging from 50deg (wind/breeze off the mainland?) during the afternoon to 95deg (wind/breeze off the Sea?) in the early hours.

Clearly a lot can happen in the space of a nights sleep while we’re oblivious to the world, especially on an exposed peninsula.

A lot of my camping over the years has been out of a sea kayak or canoe, mostly Scotland but occasionally Norway. Practically all exposed, often on small islands or skerries, never mind peninsulas. And that Black Isle camp is still a stand out "where the hell did all this water come from?" event wetter than anything bar the "we're inside a cloud and the groundsheet is afloat" stuff.

Pete.

[andrew_s]

Something that hasn't been mentioned that is of relevance is radiative cooling.

The air is mostly transparent to infra red, so all the heat radiated towards the sky is lost, and space is very cold, so on a clear night you get nothing back, so the ground, and your tent outer, get colder, making a good surface for condensation and dew to form on.
On a cloudy night, the clouds absorb heat radiated from the ground, and radiate it back downwards, so the ground doesn't cool, and there's no dew and little condensation.

You can avoid the tent cooling as much, and reduce condensation, by pitching underneath something so the view of the sky is largely obstucted.
Trees aren't always available, and pitching under them has other drawbacks (all-night drips, sap, falling branches), but it's worth weighing everything up and making use of cover on occasion.

[nsew]

Something that hasn't been mentioned that is of relevance is radiative cooling.

The air is mostly transparent to infra red, so all the heat radiated towards the sky is lost, and space is very cold, so on a clear night you get nothing back, so the ground, and your tent outer, get colder, making a good surface for condensation and dew to form on.
On a cloudy night, the clouds absorb heat radiated from the ground, and radiate it back downwards, so the ground doesn't cool, and there's no dew and little condensation.

You can avoid the tent cooling as much, and reduce condensation, by pitching underneath something so the view of the sky is largely obstucted.
Trees aren't always available, and pitching under them has other drawbacks (all-night drips, sap, falling branches), but it's worth weighing everything up and making use of cover on occasion.

Especially so when bivvying - and easier to achieve. In my experience a well designed spacious tent with a single occupant and decent gear can withstand any amount of condensation build up - as long as everything’s closed up. A cold clear night also typically provides the massively welcome benefit of morning sun. It all adds to the knowledge bank and makes for camping out being a significant part of any bike journey.

[nsew]

Going through photos from my last journey abroad. Maybe pushed the envelope a little too far on this occasion but prepared for with footprint deployed, tent fully closed, clothes packed away in dry bag, electronics in waterproof bag buried in pannier etc

[nsew]

There was even a sign pointing the way

[horizon]

On the subject of moisture in down, weigh your sleeping bag after a period of use then give it a good tumble dry; you may be surprised how much lighter it will then be.

Fortuitously, I weighed the bag I took away for the "experiment" (a different bag) before I went. I weighed it on my return after the two-night trip. Unsurprisingly after such a short time it wasn't much different, if at all, but I am now drying it out properly to see if the weight changes, even slightly.

Well I've weighed it after drying it for a week (hung up indoors with plenty of air circulation) and no change. I didn't expect much difference due to the conditions being favourable but it's something I am going to bear in mind for the future.

[horizon]

I've got some short trips coming up so I am going to experiment and hopefully report back.

So here is the first report:

And here's the second one. The only change is the sleeping bag from down to synthetic and you will see that I've also noted the inside temperature (I used two thermometers):

Sleeping bag: three season Hollowfibre synthetic with nylon outer shell and inner polycotton
Flysheet material: polyester
Inner tent material: polycotton (35% cotton 65% polyester)
Temp outside: 7 deg C (clear night, heavy dew)
Temp inside the inner tent: 15 deg C
Ventilation: none
Innerside of flysheet: totally wet from condensation
Clothing: full
Condition of bag overnight/in morning: no condensation (i.e. dry)
Inner tent: no discernible condensation (i.e. dry)

[nsew]

I've got some short trips coming up so I am going to experiment and hopefully report back.

So here is the first report:

And here's the second one. The only change is the sleeping bag from down to synthetic and you will see that I've also noted the inside temperature (I used two thermometers):

Sleeping bag: three season Hollowfibre synthetic with nylon outer shell and inner polycotton
Flysheet material: polyester
Inner tent material: polycotton (35% cotton 65% polyester)
Temp outside: 7 deg C (clear night, heavy dew)
Temp inside the inner tent: 15 deg C
Ventilation: none
Innerside of flysheet: totally wet from condensation
Clothing: full
Condition of bag overnight/in morning: no condensation (i.e. dry)
Inner tent: no discernible condensation (i.e. dry)

I assume you’re using the ~30 years obsolete Saunders Fellpacker mentioned in another thread, which had a flysheet made of polyurethane coated nylon. A heavy budget material that was practically useless after a short period of outdoor use due to its tendency to crack and ease of tearing. A 3 season Hollowfibre bag with a polycotton inner suggests about 2kg of near useless weight unsuited to anything other than car transport and couch surfing. I want to believe your thermometers are accurate and that information is of some interest to me. You have previously flatly refused to answer basic questions about what mat you are using and it’s R factor, where you are pitched (site location) and well, basically every question you’ve been asked. What the hell is “full clothing”? A three piece suit with a boiler suit over the top? That and your wellies and welding gloves? I’m off for a lie down.