Condensation prone wall design ????

[John G]

I'm thinking of making a tarp tent that essentially looks like an old fashioned canvas wall tent.

The tarp will be pitched A-frame as high as my trekking poles go and the walls will attach to the tarp about 12-16" from the edge of the tarp so that the roof overhangs the walls like the eaves on a house.

The top 8-12" of the wall will be mesh, but the bottom 12-16" of the walls will be made out of silnylon (to cut down on wind). The ends of the tent will be a large beak style affair attached lower than the peak to form a high vent (approx 12" back from the edge of the tarp, so that the overhang protects the vent during rain).

Question: If I make the bottom 12-16" of the walls from silnylon should I expect condensation to form on them, or will being "under" the overhang from the roof likely prevent condensation on the walls ? (The edge of the roof will overhang the walls 12" inches horizontally, but still be 16" off the ground vertically).

I'm hiking in an area with high humidity, that often doesn't get any wind and will often use the tent in the spring and fall when the night time temperatures are 35-42 degrees (well below the dewpoint).

Thanks.

[Frank Deland]

Will the bottom of the walls made of silnylon be hanging straight down from the edges of the tarp?

[John G]

The walls will hang straight down, but not from the edge. The walls will attach to the tarp 12-16" inboard from the edge so that the roof sticks out past the walls about 12" horizontally. However, the edge of the overhang will be relatively high off the ground leaving about 16" of vertical wall under the "umbrella" of the roof.

The picture below gives the general idea for the roof overhang. (The slope of the roof will be alot less steep though.) Do you think the 12-16" vertical pieces of wall near the floor will get condensation, or will being under the overhang of the roof protect them ?

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Thanks.

[John G]

The picture didn't post well. It seems that all the spaces were removed…

Here's another try:

[Mike Hinsley]

Last year I ran a lot of experiments with condensation and how it was impacted by design.

A fully enclosed single-skin with a sewn in groundsheet is by far the worst for condensation.

An open-ended tarp that is pitched off the ground is by far the best.

Provided the long eges of the tarp are clear of the ground (say 2-4 inches) there will be no practical condensation – at worst a slight dampness if you touch the fabric.

Having one end closed off has minimal effect provided that the sides are clear.

Having both ends closed off (doors or vestibules) will slightly increase condensation compared with one door – providing the edges are clear of the ground.

If the edges are pinned to the ground – say for storm protection then condensation will be bad but not as bad as a fully enclosed tent.

Where you pitch also has an impact. Tarping in forests tends to be almost condensation-free in all but the highest humidity if the trees are in leaf.

Finally, if you are under a small tarp and the tarp is pitched very low the condensation will be worse than if you are under a large tarp pitched high. In practice you are the main source of condensation and this moisture will spread out over large parts of the tarp based on the airflow.

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