Using an RV roof vent to vent a shade structure

[Papa Bear]

As mentioned elsewhere in the swamp cooler thread, I'm building a more-or-less traditional yurt (i.e. the mongolian type, not a hexayurt), cooled with one of FIGJAM's box cooler designs.

One of my remaining design decisions is how to cap/vent the roof. The rafters of the yurt all fit into a 36" outside diameter/30" inside diameter center ring. In other applications, that 30" hole at the peak would be fine for venting the yurt, and could be covered with a simple flap or even an umbrella as needed to keep out rain, but that's not going to help much with dust.

I've thought of a number of alternatives, but so far the one that seems most practical is just a plywood circle "cap" atop the ring, into which I've either built my own operable vents out of wood or mounted an RV/trailer roof vent like this: http://www.etrailer.com/Enclosed-Traile ... SP-25.html

I think the RV vent is probably plenty large enough to vent for the box cooler, but having never used an RV on the playa, I don't know what to expect from one in terms of dust reduction and durability. Obviously, I'd plan to crank it down when the yurt isn't occupied, but you never know when you'll get surprised or simply forget (in which case I'd expect the inside to get dusty; I just don't want to find the vent destroyed as well).

Can anyone who is familiar with this kind of vent offer advice about how well they do out there? My eplaya-search-fu isn't coming up with much that addresses the topic at all. (I've found a couple of notes that say roof vents are enough to vent an RV, one reference to an older vent tearing off, and one advisory to keep vents completely closed and stuffed with pillows to keep dust out).

FYI, the cap itself would not be directly attached to the yurt roof - it would just sit atop it, and be securely anchored down to the playa via its own set of guide ropes/lag screw anchors.

Thanks!

[Captain Goddammit]

They are plenty durable if in good condition and will seal dust just fine.
If you get a cheap or free one off an old trailer you can buy just the plastic cover part cheap at an RV supply place and you're good as new.

[Papa Bear]

Good to know. Thanks!

[nixiebunny]

That vent is tiny - it won't let nearly enough air through to be worthwhile.

A 30" diameter tilting plywood lid with a couple struts to hold it up at a 30 degree angle (oriented downwind) is much more likely to make you happy.

[FIGJAM]

Adjust your vent so that there is a little positive pressure in the yurt and the dust won't come through the vent.

[Papa Bear]

A 30" diameter tilting plywood lid with a couple struts to hold it up at a 30 degree angle (oriented downwind) is much more likely to make you happy.

If I were solely relying on convection, I think you'd be right on - the larger the outlet, the better the flow.

I'm not sure that that will be true with my setup, though, which will use an Endless Breeze fan in one of FIGJAM's box coolers to draw cool air into the yurt. Other than that, the yurt will be sealed up, so a larger vent probably won't help. As FIGJAM mentions, my goal is to create a slight positive pressure in the yurt to encourage dust to stay out.

Still, it might make sense to make it possible to open a larger area in the event some part of the cooler breaks down, or for future non-playa use. May not be version 1.0, though.

The yurt will have a parachute as an inner ceiling, helping to partition off the hotter air in the upper section (the cooler will be below the ceiling, obviously).

[Captain Goddammit]

They make those vents for RVs with 12 volt fans built right in, if you have power at your camp.
They also make larger vents. The 14"x14" vent is the RV industry standard vent but truck campers all have a much larger one up front, as an emergency exit as well as ventilation. Maybe you can scrounge one up. If you lived near Seattle I'd give you one of either size.
If you get a cheap/free used 14"x14" take the old plastic cover with you to the RV store (I think Wally mart even has them) because there are a few different styles of hinges and you'll wanna get the right one.
The cool thing about it if you use one of these is they crank open and closed. If your roof is too tall you can bring a pole of some sort to reach up and crank it with.

[Papa Bear]

Thanks, Captain. If I was anywhere near Seattle, I'd take you up on it. I'm not sure where I'd even begin to look to find used versions of either around here.

Since I'll have the cooler fan, I think having a fan in the vent would be unnecessary. The ability to adjust the opening via a crank, though, was one of the big reasons I was looking at RV roof vents in the first place. If the exit vents adjust in the same way, they could be a very interesting option.

I have some solar led lights for the inside of the yurt, and was considering the option of mounting the solar panels on top of the plywood cap. The major issue there would be being able to clean the dust off of them periodically, but the larger opening in an exit vent would make that easier. It would also be a help if I ever did need more venting due to an electrical failure/cooler breakdown.

[Captain Goddammit]

I don't know how close to a heavily populated area you are but check Craigslist for someone parting out or junking an old camper.

If you really wanted to get fancy, RV air conditioners all fit that standard 14"x14" hole... and are available cheap off water-rotted RVs... and are pretty powerful units...

[Papa Bear]

Ah, seems I just hadn't found the right combination of search terms on craigslist. Found a couple of listings now.

I'm about an hour north of Denver, so not terribly remote.

[Captain Goddammit]

Great! Now don't listen to me any further because I'll have you building an air conditioned, heated, fully plumbed and furnished home before you know it!

[melodiousdirge]

I use an RV vent with an endless breeze and it's plenty of ventilation for my 5x8 box trailer (using a swamp cooler at the inlet). If I wasn't using the swamp cooler though, or if I was ventilating a much larger space, I don't know if it would be enough. Even a mild breeze would produce a much stronger ventilation with a 3x3 flap or somesuch. My 24 foot dome has 2 6 foot wide slashes for windows, and unless it's windy out, they are about the right size to just let enough air circulate that it's not disgustingly hot in there.

[Papa Bear]

Good to know. I think I'm still within reasonable numbers for the box cooler, but time will tell. I need to have the yurt finished in the next couple of weeks anyway (or my wife will insist we go a simpler route), so I'll have a few weeks to experiment before heading out on Aug. 16th. My area isn't exactly the playa, but 95-100 degree days and low humidity are common enough in summer here to give me a chance to work out some bugs.

If I do get time, I'd like to experiment with an auxiliary system to give me some ventilation during big dust storms which could overwhelm the positive pressure in the main vent if I left it open.

It would be mostly borrowed from a wood shop dust collection system, consisting of a 4" port on the top with a 4" diameter hose that would run down the roof slope and vent out a little lower than the edge of the wall, terminating with a blast gate (basically a slat that can be drawn across the opening to seal it up). 4" wouldn't be enough for regular ventilation, but might help make daytime whiteouts a little more bearable, and the lower exhaust combined with positive pressure from the cooler should help prevent much dust from coming in. Might still have to install a computer fan to assist the exhaust, though.