Vent CFM vs. Interior size

[Psyckosama]

What's a good standard to have for Vent max CFM vs. the interior volume of a van?

Right now I have an Astro (about 170-180 CF) and the vent I'm looking at pushes 100cf on full power. It's a bit loud, which makes me think I don't want to run it full tilt all the time, but at the same time, if say, 75CF is about the sweet spot for example, I see no reason to go for two.

Thinking this model vent: https://www.etrailer.com/RV-Vents-and-Fans/Ventline/VP-543SP.html
https://www.amazon.com/gp/product/B00407CK5W/

I'm going with it because I want a low profile vent that won't interfere with a solar array

 

[maki2]

You are thinking air exchage in a specific volume of space. But on a hot day you need not just an air exchange but also enough air movement to create a cooling breeze. You can make an oversized fan run slower but you can't make a tiny vent fan such as you are showing move enough air to cool you and the space down on a really hot day. Stick with a good sized fan and read up on the forum for articles where people have changed out the original speed control so there is a better range of low to high.

 

[highdesertranger]

you're leaving off a very important part.

"the vent I'm looking at pushes 100cf on full power"

100cf per what? hour, minute, second. cfh, cfm, cfs. I know the usual is cfm but not always. 100cfm ain't much.

I know it's a vent but there are going to be times you want it closed and sealed. do these do this? also bug screen?

sorry I couldn't look at the links.

highdesertranger

 

[tripper]

If you take the top vent cover off a fantastic fan it does not stick up much, you can just install over the fan, leave 2 or 3 inches gap. Use a piece of foam or custom insert on the inside to block the vent when you need it closed. A fanatic fan will move plenty of air and quiet on low speed.

 

[Psyckosama]

You are thinking air exchage in a specific volume of space. But on a hot day you need not just an air exchange but also enough air movement to create a cooling breeze. You can make an oversized fan run slower but you can't make a tiny vent fan such as you are showing move enough air to cool you and the space down on a really hot day. Stick with a good sized fan and read up on the forum for articles where people have changed out the original speed control so there is a better range of low to high.

Clearance is also an issue. I'm specifically looking at this one because it can fit under a solar array. It's why I was asking if I should go for one or two.

And I already intend to hook it up to not just speed controls but make it reversible. Independently so if I install multiple.

you're leaving off a very important part.

"the vent I'm looking at pushes 100cf on full power"

100cf per what?  hour,  minute,  second.  cfh,  cfm,  cfs.  I know the usual is cfm but not always.  100cfm ain't much. 

I know it's a vent but there are going to be times you want it closed and sealed.  do these do this?  also bug screen?

sorry I couldn't look at the links.

highdesertranger

CFM. Thought that was basically an assumed standard.

Has does have a bug screen.

And they do close.

If you take the top vent cover off a fantastic fan it does not stick up much, you can just install over the fan,  leave 2 or 3 inches gap. Use a piece of foam or custom insert on the inside to block the vent when you need it closed. A fanatic fan will move plenty of air and quiet on low speed.

Sounds sketchy and like in really bad weather it will leak.

 

[highdesertranger]

if you want one that fits under the solar I would look at stainless marine ones. again 100cfm is hardly anything. here's a bunch,

https://www.fisheriessupply.com/vents-fans-hatches-and-windows/vents

highdesertranger

 

[kygreg]

I don't know your layout but a roof fan is not the only option. My cooking exhaust doubles as my general van ventilation. On high for cooking and low for general ventilation, drawing in fresh air the full length of the van. For cooling I just have a second fan blowing directly on me, something I can move around.

 

[maki2]

I was just shopping at the sticks and bricks Fisheies Supply Store today while I was in Seattle. Quite a few items in my build have been purchased there. I even get a deep dicount coutesy of being added as authorized on my friends commercial account.

Those are nice vents but the one from E trailer has a couple of options that will make it more functional for the van. I took a look at all those types of vents when figuring out the setup for my travel trailer.

 

[bagabum]

syckosama  are you  trying to vent for prevention of   1. It's to hot in the van  2 . CO is building up constantly, feels muggy/stuffy.  I would say get what your looking at and add a variable speed "rheostat" in series with the power wire. On hot days you want to move a lot of air but on cold days and nights you want to have fresh air to breath but you will not  want  to exchange half of the air in your van every minute. It will be to cold and big time over kill.  Note: The average human consumes about 0.25 cuft of air per minute so you can safely  turn it down quite a bit. I would say build for maximum versatility and turndown while your at it so you only have to do it once. Big difference in air flow that you would desire going from hot summer day to cold winter night... my2cents  good luck!!

 

[Psyckosama]

if you want one that fits under the solar I would look at stainless marine ones.  again 100cfm is hardly anything.  here's a bunch,

https://www.fisheriessupply.com/vents-fans-hatches-and-windows/vents

highdesertranger

Most of those are much less than 100 cfm...

I don't know your layout but a roof fan is not the only option. My cooking exhaust doubles as my general van ventilation. On high for cooking and low for general ventilation, drawing in fresh air the full length of the van. For cooling I just have a second fan blowing directly on me, something I can move around.

Issue is where do I cut the hole and how large is it going to be.

I was just shopping at the sticks and bricks Fisheies Supply Store today while I was in Seattle. Quite a few items in my build have been purchased there. I even get a deep dicount coutesy of being added as authorized on my friends commercial account.

Those are nice vents but the one from E trailer has a couple of options that will make it more functional for the van. I took a look at all those types of vents when figuring out the setup for my travel trailer.

Have any links?

syckosama  are you  trying to vent for prevention of   1. It's to hot in the van  2 . CO is building up constantly, feels muggy/stuffy.  I would say get what your looking at and add a variable speed "rheostat" in series with the power wire. On hot days you want to move a lot of air but on cold days and nights you want to have fresh air to breath but you will not  want  to exchange half of the air in your van every minute. It will be to cold and big time over kill.  Note: The average human consumes about 0.25 cuft of air per minute so you can safely  turn it down quite a bit. I would say build for maximum versatility and turndown while your at it so you only have to do it once. Big difference in air flow that you would desire going from hot summer day to cold winter night... my2cents  good luck!!

That was the plan, actually. It's why I don't care that they have variable voltage build in. You can buy a potentiometer for pennies off ebay.

 

[tx2sturgis]

That was the plan, actually. It's why I don't care that they have variable voltage build in. You can buy a potentiometer for pennies off ebay.

Smoke testing, eh?

 

[bullfrog]

I have often wondered about heat build up under a solar array and if there would be any advantage of putting a lip on the bottom of the panels to allow warmer air during the day to be drawn into the van in winter. In summer reversing the fan to cool the van and panels.

 

[abnorm]

^ another link from Nataliee

 

[Psyckosama]

Smoke testing, eh?

What?

[size=medium]It can be quite problematic to keep air flowing in your RV. Honestly, on those stagnant hot summer days, it can become downright unbearable. Therefore, any RVer needs to have the best RV vent fan possible. So you can follow some information about vent fan here: https://www.rvweb.net/best-rv-vent-fans-reviewed/[/SIZE]

I'm modifying an Astro. I have limited space and clearance and I'm looking for something that won't necessitate me cutting through the part of the roof's structural support bracing to fit a vent. It's not a big van.

One of my plans to improve flow in is going to be to install one of these as a dedicated intake vent with a screened interior vent that is capable of being closed when needed.

That said, I've spotted a potentially stronger vent. Maxxair makes a van vent that moves twice the air as the ventline.