Peak Vents on Pyramids

Not sure how much they contribute to ventilation, but at least I didn't find them all that much extra trouble. I figured it couldn't hurt to have them.

If you don't put them in at the start, you will after the first condensation shower.

Cheers

>>If you don't put them in at the start, you will after the first condensation shower.

HA! Voice of experience me thinks.

Tell that to David at Oware Roger. Let's get his spin on this subject. From, you know, someone who sews them for a living.

I've put in vents and it doesn't make that much difference, not enough area to let through much air.

If it's not raining and you don't need privacy, leave the door open. That has enough area to help, but under some conditions you still have condensation. The door should go most of the way to the top, like have it run up to the circular reinforcement piece at the top.

I don't think peak vents on pyramid tarps do very much. They probably can't hurt, but in order to be effective, I think the vent needs to be really big – like a door being opened part-way, or a door that can be unzipped from the top.

I've had condensation in pyramid tarps with and without peak vents, and I've had condensation-free nights in both styles too. For example: I've had condensation in a GoLite SL3 (which had 3 large peak vents), and I've not had condensation many times in my MYOG 6-sided pyramid tarp with no peak vent. So from my personal experience, site location and conditions will affect your condensation, and there's not much a little peak vent can do about it.

great minds think alike : )

the other defense against condensation, is the walls are steep so condensation flows along wall and drips on edge

My vote is a big yes. Not so much for condensation, but for heat release. I find that if it is sunny and you are in a mid for any reason, it is excruciatingly hot (just like in a tent). I find that the vent lets out a lot of the heat and makes it somewhat more comfortable in there. If you are only always using the mid at night, the heat might not be an issue.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=97776&skip_to_post=831117#831117

Ben

I did not include a vent nor have I seen the need. I leave the door open whenever possible and pitch it off the ground as well. Interesting there is such divergence on this issue. Wonder if it is due to individual conditions.

I have owned and used various mids with and without vents for 7 years(Golite Hex, Oware 9×9, Solomid, and Trailstar. 2 have vents 2 don't.) and veer towards the view that peak vents are not as useful at condensation management as often claimed.

Like John Harper said. When it comes down to it, for condensation, conditions trump vents.

Heat is a different matter and vents offer an obvious escape route for hot air.

There must be a way to make bigger, more effective vents. Maybe with a small hiking umbrella at the peak over a large vent.

I can't agree with the general consensus here. I own an HMG Ultamid 2 and use it quite a bit in shoulder seasons with daytime temps of 12C dropping to around 0C at night. Its a perfect recipe for maximum condensation. On a 12 day trip, we had some condensation every night, not surprising for two guys in a tent this size. One night, however, we forgot to open the vents and the tent walls were significantly wetter the next morning – to the point of dripping. It may have been environmental variations beyond my perception that caused the notable difference that single night, but I think it was the reduced ventilation.

Similarly, on the last trip out a month ago in warmer temps, my tent mate commented as we were turning in how warm it was in the tent. We noticed the vents were closed. We opened them and instantly a draught of cool error entered – you could literally feel the tent cool. I assume the vents being opened did that.

So – based on my experience, vents matter. The do not eradicate condensation, but damn well diminish it.

Derrick

Derrick, was the tent pitched right against the ground? I wonder if having it raised a few inches off the ground would help as well?

Sounds like there may be a thermal basis for vents and condensation.

Hot air holds more moisture, so you'll get more condensation. Open the vents, drop the inside temp, and you get less moisture in the air available to condense.

To mitigate condensation you need air flow.
To create air flow in a tent you need bottom ingress and top egress.
One without the other will not work.

I asked that very question of Dave Olsen, owner of Oware and maker of many, many pyramids – hes said don't bother. He's put them in at clients' request in the past and found they don't make much difference.
My own two cents would be you have to get them pretty darn big before they will do what you want them to do, and unless you have the bottom of the mid fairly free of the ground they will not do much of anything since you need inflow to get outflow. And with the bottom high enough to make it work you get pretty good air exchange even without top vents if there is any breeze at all.

"When it comes down to it, for condensation, conditions trump vents."

+1

Ryan

Wow, well… I was hoping this thread would sort it out for me.
Now I'm more uncertain than ever, lol.

Seem to be some really compelling arguments on both sides.

@Justin

I typically pitch my tent tight to the ground with tight being about an inch or two off the ground. The higher it is off the ground and the larger the vents in the peak of course, the more airflow you enjoy. With vents open and the tent 1 or 2 inches off the ground, I do not get sufficient condensation to cause it to drip. Without them, I get condensation running down the sides and sometimes dripping. I grew in ventless tents. Awful.

I am a bit perplexed by this debate. The theoretical physics are pretty simple. While there are many variables at play, and while air conditions external to the tent are ultimately determinative of condensationdew levels, the humidity and temperature inside the tent relative to that outside is the dynamic which causes or increases condensation inside. Vents increase airflow into the tent from the outside. Air flow into tent reduces the temperature gradient, and in all but the most humid external conditions, it also decreases the humidity inside.

Experience bears it out for me.

Again, the objective is not to eliminate condensation, the goal is to manage and minimize it. Vents do this. They are not a cure, merely a mitigator.

I just can't imagine being in a tent without ventilation at the top.

Derrick

"When it comes down to it, for condensation, conditions trump vents."
+1

Top vents may make a difference in a closed tent in some winter conditions, or if you want to hang out inside in hot sunlight during the day, but for 3-season open-bottom tarps/pyramids, I have found them to be fairly ineffective. Pitching higher off the ground or an open door flap with a nod to breeze direction seem to be way more effective. Yes, any and all openings help, but no, I would not bother.

Yes. Put at least a couple vents in. Derrick and Franko have it right. No, you will never eliminate condensation. but you will help to eliminate warmer moist air from the tent as you sleep. As was said, yoi need a low vent and a high vent for maximum efficiency…one without the other doesn't work that well. Raise the bottom up 2 inches (as was said) and this works pretty well.

Door shape, position and two-way zipper pulls are all design variables. An arched top door wants a second vent right at the peak. A full fold out door just needs a bit of a stick to hold an opening. Positioning a door on a corner can be more effective than positioning on a sidewall. Putting in a double zipper pull can let you adjust both upper and lower venting.

Pyramids are natural "cones" in the sense that they concentrate heat near the top, increasing air flow at the peak vent. Don't skimp there. A 1/4oz of fabric will let you utilize this natural air flow better in the rain. Here in the NE we get LOTS of rain. The vents help.

Personally, I would make it permanently open, but sheltered from any rain. I use the vents open when it is warm, not so much at in between temps, and when it is cold. When it is above 60F, condensation is not the issue, but sending warm air out is much better than not. It is hard for me to sleep at warm temps with all the bugs. In between temps it really doesn't matter. Leave them open or close them. In cold weather (around -5C or less) any condensation will usually be as as ice. This can be annoying since any movement of the tent body will send a small snow fall onto you and your bag, and, there to melt. I open them up wide down to about -10C. This is why I say to make them permanently open. Below that they probably won't do anything since there isn't that much humidity in the air, this is perhaps the only time you wouldn't want a vent letting out the warmer air. Of course, this is assuming you make weather tight vents of fair size.

In the rain, of course, condensation will still happen on a cold surface, but heavily if you have no way of venting off at least some of the moist air inside the tent. After all, the doors will be closed. And, condensation is a two way process. At first, it simply removes moisture from the air. After the fabric is coated, though, it can also add to the humidity (by evaporation.) Soo, you breath out warm moist air, you get some from the air, you get some from the existing condensation on the tent (which also cools the fabric making it more prone to condensing) … well, with no vent, this will all be trapped inside. Want to guess what will happen in the rain storm? Yup, it will knock the condensation off in a fine mist, eventually making everything damp and wet. This may happen anyway, but at least having the vent in the tent will mitigate the multiplying effect, if not eliminate it under most conditions.

I wanted to add this tidbit-

I think everyone agrees that peak vents help combat condensation, the only disagreement is how much – very little or very much. With that said, I'm in the very little camp and if I'm buying a mid I want them in there. I'm not making it so why not.

But you're coming at this from a MYOG standpoint. Peak vents will add a fair bit of complexity to your design especially in cuben fiber. Are they worth that complexity when only 1/2 the folks think they help in a meaningful way?

Here is a link to a cuben mid I posted a while back. There may be some design info in that thread. If you do decide to go with vents, let me know if you have any questions on how to implement.

Post pics regardless!

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=94547

PS – Many people are unsure what to use for peak vent cover stiffener. Pretty sure MLD uses a cut down heavy duty zip tie which seems to work well.

Ryan

I went with the zip tie as stiffener. Design did not seem all that complex; I just made a paper triangle a couple of inches taller than the vent cutout, and wider enough that it came forward as much as I wanted. I may have played around with cutting some off the sides (making a more acute angle at the top) but overall it was fairly easy. Once I had the paper piece the size I wanted, I added seam allowances and that was that; I sewed it in, overlapping the lower portion at the bottom sides of the triangle. I left the hem of the triangle open in the middle couple of inches to insert the zip tie.

With my design, the only complexity came from the fact that I was making an asymmetrical peak (a la SMD Haven) but even then it wasn't rocket science. With a symmetrical mid, it would be quite straightforward.

d k,

Do you have a link to your cuben mid? I would be interested to see what you came up with. Obviously it's not rocket science, but more complex than ventless of course.

Ryan