Positioning a Roof Vent/Fan?

[Almost There]

Floor vent is mostly optional, roof vent is almost mandatory!

Heat rises, you need a way to let heat out up top hence the roof vent.

If you're planning on being in too hot of an environment but not parked on pavement, then a floor vent to let in cooler fresh air might be a good thing.

I rely on opening doors and windows to let air in and the roof vent to let hot air out.

Yes, the hardest part of installing a roof vent is cutting the hole in the might fine roof of your van.

Even *I* turned away and plugged my ears AND closed my eyes when Justin was drilling the corner holes...heck I'd just paid a whole lot of good money to have all the OTHER holes sealed in the high top and here he was making more....

 

[AbuelaLoca]

^^^ Exactly!! 

 

[Vagabound]

^^^ Exactly!! 

Speaking as someone who cut a huge hole in the side of his box truck to install a side door, ya'll are making too much of this. It's simple -- before you cut the hole, just slip a little wax paper in your butt crack. That way, when you hit Pucker Factor 9.5, your cheeks won't stick together.

Tom

 

[ArtW]

I really don't wanna do that to my van, either

 

[dr_nelson]

I recently cut my first hole ever into a vehicle, and it was for a roof vent. It was actually not too bad. In my head, it was much more dramatic, but once I actually did it, it was actually a fun job. The only advice I can give is: take your time, measure twice, and then measure again.
I started late afternoon and had to rush to finish before it got really dark.

Now I am no more afraid of cutting holes into my van. I know at least three more holes are to come.

1. Floor vent (yes HDR, with a deck lid   )
2. Floor vent for propane tank
3. Sidewall vent for battery

 

[ArtW]

OH NOEEES! MOAR HOLESSSS!

 

[AbuelaLoca]

Speaking as someone who cut a huge hole in the side of his box truck to install a side door, ya'll are making too much of this. It's simple -- before you cut the hole, just slip a little wax paper in your butt crack. That way, when you hit Pucker Factor 9.5, your cheeks won't stick together.

Tom

ROFL!! I remember reading about your door!! That does make a roof vent hole look piddly!!

 

[user 37446]

Well, those vantech roof racks for the gutter are over $200 each (per bar). They're the ones for the econoline with hightops, and I like the idea that I would not have to drill further holes into my high-top and just use the rain gutter of the van. But the price...  :-/

Try a junkyard...

 

[user 37446]

Floor vents have pro's and con's:

Pro's - 
allows cooler air in, little chance for leakage (from rain that is, duhh)
is very "discrete"
no more holes up top

Con's-
holes are now in the floor, which for unibody vans (Dodge, G20) can weaken the structure - think "swiss cheese", ha ha
if too close to exhaust lines/muffler, may allow dangerous fumes inside
are an entry point for bugs and critters unless screened

Suppliers: In addition to the way cool drain vent that was posted about, the standard is to go to a marine supplier or Amazon. Just Google search "boat ventilation" or "Marine ventilation"

Here's an Amazon link:  [font=Roboto, arial, sans-serif]https://www.amazon.com/Screw-Plate-Access-Hatch-Cover/dp/B00CJ04YUQ[/font]
and description:.  [font=Arial, sans-serif]4 inch Screw Out Deck Plate Access Hatch Cover - White by NUSET[/font]

Here's a marine supplier link: 
https://www.jamestowndistributors.c...?categoryName=Ventilation&category=674&refine


Hope this helps. Remember that Google is your friend...

 

[John61CT]

I have no spot for a fan topside, and value stealth.

I'm thinking out-going floor fans, pulling the fresh air in wherever we open windows.

This also reduces possibility of pulling in exhaust, either from engine or outside-mounted heaters.

I love the idea of seal-tight portholes, definitely need critter screening, and since the fan needs mounting outside, will need strong protection against rocks and road debris.

Any ideas or pointers welcome.

 

[WalkaboutTed]

For a 4" vent I recommend a 5" screw in deck plate glued to the floor. My floor is 2" thick and I put varmint screens on the bottom for obvious reasons. On top, when opened I put a precut screen and to hold the screen in place, I used 6" hose clamps, tightened up (on the raised lip of the deck plates) to hold the screens in place. When we move the vehicle, the screens come off and we close the deck plates. We can toss the screens if nasty.

I'm one of those "out of sight, out of mind" kind of persons, so I put the deck plates on the driver's seat to remind me to replace them for driving.

It's now almost warm here in the desert. With the constantly running overhead vent fan (with vent cover), the two 4" floor vents, the opened front windows (with rain guards) and van insulation, we do as good an job as possible in keeping the temps reasonable. We don't have much rain here in Tucson, but when it does, I don't want to worry about running to close the windows. We have a fair amount of insulation around the sides, back, top and bottom of the fridge and have a sleeping bag draped over the front. The insulation on the walls prevents the inside surface temperatures on the sunny side of the van to only be slightly above the ambient temperature.

Now, as soon as we can get the van done and the house on the market, we're up to altitude and cooler temps. This process has taken entirely too long!

 

[Vagabound]

...  On top, when opened I put a precut screen and to hold the screen in place, I  used 6" hose clamps, tightened up (on the raised lip of the deck plates) to hold the screens in place. When we move the vehicle, the screens come off and we close the deck plates. We can toss the screens if nasty.

... We don't have much rain here in Tucson, but when it does, I don't want to worry about running to close the windows. ...

WT, 

Nice post. A few questions please:

* If the bottom of your floor vent is screened, why do you also need screen on the top?

* One for you and anyone else ... I'm wondering what the benefit is of having a floor vent versus just cracking a window and letting the exhaust fan pull air in the window? You may have answered it when you described what happens when it rains. Just want to clarify.

Thanks,

Tom

 

[John61CT]

I'm one of those "out of sight, out of mind" kind of persons, so I put the deck plates on the driver's seat to remind me to replace them for driving.

If they are forward, say driver's area, can't they be left open long as it's warm weather?

 

[John61CT]

I'm wondering what the benefit is of having a floor vent versus just cracking a window and letting the exhaust fan pull air in the window?

Getting more effective air volume replacement bottom to top. Some microclimates (moist forest) air from the ground may be a bit cooler than five feet up.

Probably minor differences.

In my case no fan on top, awkward windows, desire for stealth ==> so I think no real choice.

 

[dr_nelson]

(..)
* One for you and anyone else ... I'm wondering what the benefit is of having a floor vent versus just cracking a window and letting the exhaust fan pull air in the window? You may have answered it when you described what happens when it rains. Just want to clarify.(...)

I had a window seat in physics (if this has anything to do with physics)... but it is pretty obvious to me. Tried to visualize.
[img=562x422]http://i58.photobucket.com/albums/g...e6c03fe-f23b-4651-aa57-a193bf7ebec2.jpg[/img]

I plan on installing a floor vent which can be closed for driving (deck lids). I'll share pics when I get to that step...

 

[Vagabound]

I had a window seat in physics (if this has anything to do with physics)... but it is pretty obvious to me. Tried to visualize.
[img=562x422]http://i58.photobucket.com/albums/g...e6c03fe-f23b-4651-aa57-a193bf7ebec2.jpg[/img]

I plan on installing a floor vent which can be closed for driving (deck lids). I'll share pics when I get to that step...

What you drew is what I came to intuitively.  Glad to know you agree.  However, it can be largely negated by the vehicle exhaust if not managed properly.  So, like with most things, just need to do it carefully.

Tom

 

[WalkaboutTed]

We put the vents in back, behind the bed for two reasons. One, cooler air close to the bed. When it is 115F outside, we run the roof van 24/7 and convection from the floor helps a lot. Since the two 4"vents will not provide enough air, we leave the front windows open about 2" with the rain guards. I think we're gonna do a Sternwake maneuver and put in a couple of muffin fans, though.

Between the rear vents and the front windows cracked, the entire vessel is somewhat ventilated.. Even if we put the floor vents forward, leaving them open while driving would cause a huge amount of road dust and grime

And as for the need for additional screens, we used a "varmint guard fan pipe cap with screen" from amazon
{I can't reliably put in links). The screen is only meant to keep out animals, not insects. The reason we had the limitations of 4" vents is the size of the size varmint guard is 4"

We just gotta get out of the desert, though. .
Ted

 

[WalkaboutTed]

Oh, and to those of you fearful of cutting holes into your vehicle? Go to a junk yard and buy an old hood or two and practice away. It was an amazing confidence builder when it was time to take that angle grinder to a brand new, very expensive roof and cutting holes for two windows.

 

[frater secessus]

My point is, 350CFM is a respectable amount of airflow, as long as there is an inlet cabable of replacing the air exhausted.

I wonder if leaving the vehicle's HVAC controls in open | fresh air | vent position would allow air to be drawn in through the dash.

 

[highdesertranger]

with the newer vehicles and all their computer controlled electronic gizmos the answer is no. when you shut the engine off the doors in the HVAC close. now an older vehicle with mechanical doors the answer is yes. highdesertranger