Floor vents - direct or ducted?

[BlackNBlue]

I'm ready to start cutting holes for vents in my stepvan floor. It will have two skylights that open, an extractor fan in one of them (at least), and no other dedicated ventilation. Do I install them in the middle of the floor (the walkway down the middle) to open directly to the underside, or inside cabinets off to the side with ducts to the bottom faces of the cabinets?

Direct vents have several advantages, including that they don't take up precious storage volume, and don't fix the location of cabinets (something my design has not yet finalized) as much as ducted ones would. However, I'm concerned about sound insulation. Do ducted vents significantly quiet sounds coming into or out of the vehicle? Do they flow air as well as a direct duct, if not used with a booster fan?

I'm thinking two 6"x12" (standard household vent), approximately under each skylight. Each will have a matching insert of insulation, so I can plug them up for temperature reasons, or for traveling over wet roads. Will this be enough floor ventilation?

 

[highdesertranger]

I would use marine deck plates. they seal 100% when not in use. highdesertranger

 

[BradKW]

Some other considerations I've been thinking through on my build:

1) needs to be as far from heat sources like muffler and converter as possible,
2) avoid potential intake of exhaust...seems important, yet every time I think about it I realize I have about zero facts to draw on regarding how far is far enough.
3) the further away intake is from exhaust vent, seems to me increases the area that gets ventilated. Put them opposite each other on floor/roof and it'd be a straight line.
4) Ducting could allow for some savvy venting for electronics box (inverter, CC, etc) and 'fridge compressor...perhaps even laundry bin

 

[Svenn]

I struggled with this problem for a while. Floor vents are the most stealthy, but I'm in a truck so there's no floor room for floor vents- the entire floor is taken up by bedding/mattress... plus it seems that floor vents wouldn't move all the cabin air since they point upward/downward. I eventually settled on a wall fan at the front and side of the cab and an exhaust at the back of the bed, so air would flow through the whole cabin without blowing in my face. We will see if it works or not in a few weeks!

 

[BlackNBlue]

Some other considerations I've been thinking through on my build:

1) needs to be as far from heat sources like muffler and converter as possible,
2) avoid potential intake of exhaust...seems important, yet every time I think about it I realize I have about zero facts to draw on regarding how far is far enough.
3) the further away intake is from exhaust vent, seems to me increases the area that gets ventilated. Put them opposite each other on floor/roof and it'd be a straight line.
4) Ducting could allow for some savvy venting for electronics box (inverter, CC, etc) and 'fridge compressor...perhaps even laundry bin

Regarding 1 and 2, I can just as well plug them up whenever I need to run the engine, which I expect won't be often.
Regarding 4, that's a good idea! I have not yet planned where and how to install electrics.

What are your thoughts on sound dampening with ducts vs. straight vents?

 

[BradKW]

What are your thoughts on sound dampening with ducts vs. straight vents?

I'm afraid I don't really have a guess about that, except that having the cutouts in cabinetry might help.

I figure I'll use ducted if for no other reason than it allows for putting screening/filtration in a convenient spot, and can just use blast gates for shut-offs:

 http://www.rockler.com/4-stablegate-blast-gate

Or check out this flavor if you're feeling spendy...could be wired to open when fan turns on and close when off  

http://www.rockler.com/ivac-pro-4-in-blast-gate

 

[IanC]

I'd be concerned that dust would be sucked up into the van when you're parked on dirt

 

[BradKW]

I'd be concerned that dust would be sucked up into the van when you're parked on dirt

I think that if you're in a dusty area that'll happen regardless of where the vent intake is...one of the reasons I will probably add inline filters..

 

[CottonTexas]

Had to necro this thread since it inspired my design (along with a few other helpful threads out there - many thanks to y'all), but I wanted to post & get some thoughts & opinions on this prospective setup.

Yeah, I get bored & like to play with pictures, so make fun of my potato-shop skills all you want, but be sure to include an opinion.    
Cotton

 

[deadwood]

I did my floor vent recently. With so many other things going on in the build I didn't have a lot of choices as to where to put it. I ended going with it a little in front of the rear passenger wheel well. I debated the best way to do a vent. I wanted max air flow but needed to make sure it was easy to close off as well. I ended up using a hole saw and cut a 4.5'' hole in the floor which was the perfect size to squeeze in a 4'' black pvc pipe from home depot. With the pipe in I then put a 90* elbow on the inside to direct it out of the cabinet it sits in. The cabinet will have have a false front that I can take off easily. To seal it up I just use a cap for a cleanout drain and it screws in to give an airtight seal.

On the bottom of the van I put a 45* elbow that directs to the back of the van and put wire mesh over it to keep any critters out. All I can say is that with the windows closed and my Maxfan running on a low setting blowing air out the van the vent works amazing. Better then I anticipated. Sitting on the bed you can feel a slight breeze as the air flows up and out of the van.

In the end I'm very happy with it. I'm not sure it matters where the vent is as long as you can put one in somewhere. Also important to make sure it can be easily and completely sealed off. And hopefully it goes without saying that for safety's sake to make sure to have a CO detector inside as well. You never know where you will be parked. If you are bringing fresh air in from the bottom there could always be someone idling near by or running a generator. I was reading that most of the CO deaths that happen are from near by vehicles exhaust. So no matter how careful you are setting it up you have to take in account for other vehicles that you have no control over. And none of us want to wake up dead one morning...

 

[drysailor]

I'm ready to start cutting holes for vents in my stepvan floor. It will have two skylights that open, an extractor fan in one of them (at least), and no other dedicated ventilation. Do I install them in the middle of the floor (the walkway down the middle) to open directly to the underside, or inside cabinets off to the side with ducts to the bottom faces of the cabinets?

Has anyone tried placing the intake vent(s) on the roof, & running a duct down to the floor? Could have a small fan inside, if needed.

 

[bullfrog]

There are a few builds that have 2" x 12" space between the wall and cabinet that goes almost to the top of the roof of the van less a few inches. Fans are mounted at the bottom of the cabinet blowing out into the van to circulate hot air at the roof to the floor in the winter. A floor vent next to the fan running in reverse or turned around could be used to force cool air to the top of the ceiling in summer.

 

[bullfrog]

I cannot stress enough that they need to be closed off completely when traveling on a dirt road, especially if at the rear of the vehicle. Trust me you would not believe how much dust you get just making a u turn off pavement.

 

[highdesertranger]

it needs to be 100% sealed when driving on any surface dirt or hard. highdesertranger