Silpoly and condensation

[LowTech]

I just picked up an inexpensive silpoly tarp and have been fortunate enough to have some humidity, which gives us some dew/frost, and a full day of on/off rain, which will give us a few more of those dew nights.
So anyway, the first thing I noticed is that this tarp collects condensation on the inside big time. In fact this morning it was frozen condensation.
Is this normal for silpoly, or just something about this tarp? My silnylon tarp never did this that I can recall and if it did not anywhere close to what's happening w/ this one.

"Sent w/o me knowing"

[sideshowraheem]

Silpoly is supposed to not "absorb" as much water/moisture as SilNylon, for that reason a lot of people opt for it more often in wet/humid conditions. Hard to say without more information on the conditions but its likely that it was just a scenario of site selection and weather conditions that wouldve resulted in condensation regardless.

If you want a real deep dive, the gear nerds and backpackinglight as always have you covered - https://backpackinglight.com/forums/...rp-durability/

[goobie]

In those conditions, without a breeze to move the moisture away, you're going to get condensation regardless of tarp material. Opening up the tarp, think porch mode, can help some.

[MacDuff]

The traditional winter hot tent was made out of Egyptian cotton a tight woven,lighter than heavy canvas material , very vulnerable to mildew damage if not dried out before storage .The material would shed most the rain but more importantly allow moisture created inside the tent to transfer through the walls outside . Sunforger has a light canvas that has since replaced Egyptian cotton which is hard to get any more . This being said I can only find one manufacture even close to this and this is their pitch at almost 15 lbs . Please add any information you feel appropriate to this discussion Rhombus Hammock Hot Tarp | Lonewolf902 Canvas Hot Shelter for Hammock Camping

• SOFT AND BREATHABLE CANVAS FABRIC - We used pomoly's unique blend canvas as tent material. Based on 70% cotton and 30% polyester, this fabric provides comfortable softness and good air permeability. These features also help to reduce condensation inside the tent.
• Capacity / Seasons 1-2 Person / 4 SeasonTent FabricCanvas (30% Polyester + 70% Cotton)Waterproof1500mmTarp SizeSuqare (14.7 x 14.7ft / 4.5 x 4.5m)Weight14.5 lbs / 6.6 kgJoint TreatmentSeamedColorKhakiStove JackHigh Temperature Resistance

[joe_guilbeau]

Polyester hardly absorbs water, unlike nylon as mentioned. Because of this feature condensation is not absorbed, and therefore lays on the tarp material.

A steeper pitch will allow condensation to roll down the sil-polyester fabric and a slacker pitch will not allow the condensation droplets to be pulled down by gravitational forces or wind movements against the tarp fabric.

So, polyester tarps require a steeper pitch, so it does not 'rain' on you in high humidity/condensation environments. It's a po-boys dyneme - my 185T Polyester Silicon treated tarp has a 5000mm hydrostatic head and needs a taut pitch to avoid the sudden wind driven whetting.

[Shug]

Condensation happens.
Can't say if it is the silpoly as I have had it on all tarps. More a weather and temp thing I think. One of camping's big mysteries.....
Shug

[WV]

All waterproof fabrics block outgoing moisture, just like incoming. The variables affecting condensation are (1) climate, and (2) you.

[dakotaross]

…Opening up the tarp, think porch mode, can help some.

Is there another way to roll?!?


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[LowTech]

Silpoly is supposed to not "absorb" as much water/moisture as SilNylon, for that reason a lot of people opt for it more often in wet/humid conditions. Hard to say without more information on the conditions but its likely that it was just a scenario of site selection and weather conditions that wouldve resulted in condensation regardless.

If you want a real deep dive, the gear nerds and backpackinglight as always have you covered - https://backpackinglight.com/forums/...rp-durability/

Not sure if I should thank or curse you for that link. Spent some there but need to go back and finish it.

"Sent w/o me knowing"

[LowTech]

So to detail the situation a bit more,
It's a desert here and we had just gotten a good days rain, not the fast "flash flood" type of rain but a slow on & off all day rain. When that happens we then get 3 nights to around a week of dew/frost before it's dry enough to end the cycle.
The first night after the rain started this questioning. The next night was even worse as it collected heavy condensation which then froze. When the sun came up it soon started raining on me under the tarp so bad I had to flip half of the tarp back onto the other side.
I was in porch - mode as that's my standard setup so that I get first sun on me and I'm not crazy about being closed in.

The next night I changed tarps to my silnylon one to see what kind of difference it made. I still got some condensation but it was thinner and more like a fine layer than the big droplets that had formed on the silpoly.

Last night I went back to the silpoly (running out of time to test unless it rains again and our previous one was back when the hurricane came up into SoCal) and again had droplets form but not as large as the time it rained inside.

So like some others have suggested I feel that the silnylon, by absorbing some degree of water cut down on how much of the water formed into droplets. Also that porch - mode didn't help and that I needed, again as was suggested, a steeper pitch to let the condensation slide down the sides and not collect over me.

Thank you everyone, I think I know what my approach will be next time even though I'm not fond of waking up walled in.IMG_20231224_104108750.jpg

"Sent w/o me knowing"