Talk to me about roof vents

JohnClimber

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Which small 12v fan roof vent would you recommend to stop condensation building up in our diesel heater toasty warm LWB campervan over night please?

On a bit of a budget now so please don't go to the range toppers.

Letting light in isn't important, what do the collective think of the 12 volt mushroom vents like this one on ebay please?
COMET 12V MUSHROOM VENT FAN GREY 7 WATT CARAVAN MOTORHOME CAMPER BOAT VAN | eBay

If not what do you recommend please? Any links would be great too.

I've had a good search on here and didn't see any threads, so thought I would ask.

Or am I just over thinking it and condensation won't be a problem?

Thanks for all of your help and advice.

John
 
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Have a look at Flettner vents. They don’t need any power other than wind power, they are roof mounted on very low friction bearings so it doesn’t take much to make the impeller rotate. Don’t know how much they cost these days but should be cheaper than an electric fan.
 
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saxonborg said:
Have a look at Flettner vents. They don’t need any power other than wind power, they are roof mounted on very low friction bearings so it doesn’t take much to make the impeller rotate. Don’t know how much they cost these days but should be cheaper than an electric fan.
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A quick google search brings them up at £72 each.
What if there is no wind? Will they still vent?
 
If you are going to cut a hole in your roof, I would be tempted to make it a standard sized hole, I.E. 400x400 mm. That way if you find the basic vent is not enough, or later on want to upgrade, it will be dead simple.

The fan I fitted is brilliant but I went for the best available after having 2 campers with NO vents!
 
Worth considering just cutting in a Fiamma roof vent and fitting a couple of
12v computer fans. £45 for vent + £12 for fans. There is a purpose made Fiamma roof vent with integral fan, but you did mention cheap.
 
JohnClimber said:
Which small 12v fan roof vent would you recommend to stop condensation building up in our diesel heater toasty warm LWB campervan over night please?

On a bit of a budget now so please don't go to the range toppers.

Letting light in isn't important, what do the collective think of the 12 volt mushroom vents like this one on ebay please?
COMET 12V MUSHROOM VENT FAN GREY 7 WATT CARAVAN MOTORHOME CAMPER BOAT VAN | eBay

If not what do you recommend please? Any links would be great too.

I've had a good search on here and didn't see any threads, so thought I would ask.

Or am I just over thinking it and condensation won't be a problem?

Thanks for all of your help and advice.

John
Click to expand...
If you have diy skills computer fans are designed to run for hours on end.

I would not want a fan that makes a lot of drumming sound, in the roof of a van it would drive me mad.

:wave:
 
Condensation comes from breathing out,so either fit the van from ebay or a similar boat one with no fan/mushroom vent.
It may also be a cold spot with poor insulation which is showing up now,you may have to look into this.
Any where that hot moist air contacts a cold front condensation will form,remember single glase windows in the last century,i used to draw on the ice inside when a child.
 
JohnClimber said:
As mentioned elsewhere, I'm still building it and due to head out in a week or two.
That's why I said "am I over thinking it"
Click to expand...

Now I understand!

My advice is fit a standard campervan roof vent, one with permanent venting. There are basically two designs to consider, those that hinge at front, or those that 'pop' up in any four directions. The front hinged type can be good in hot weather as they open very wide, the pop up ones are better in wet conditions as they can be angled against the wind and rain.
Don't underestimate how clammy it can get in a van with inadequate ventilation.
 
Cheers all.
I think I'll give the eBay one a try as no one has said anything negative about the idea so far.
 
If you are letting hot damp air out at the ceiling you are causing a vacuum at that point, cut a hole in the floor to balance pressure and you will get air flow between the two points without a fan. Hot air rises.
In the house the wood burner gets its air supply from an outside fed duct around the back of the burner, no cold draughts, now a hot draught. Upstairs the room above wood burner is heated by the hot floor ( the ceiling gets up to 38 easily) and the chimney Brest. The other bedroom is heated (no fan) from ceiling ducting from wood burner room, said air has entered via the ducting below, gone round the back of the burner, been heated and gone up to the ceiling, across the room entered ducting and made its way (4mtrs) along insulated ducting into the bedroom, which has an open vent in the window allowing free air flow utilising convection.
If you wanted to increase air flow with a fan, pressure the van with an inlet fan (a long way away from the bed to hide noise) and the excess pressure will vent out of your ceiling vent. I have plans to heat the whole house by pressurising the wood burner room and venting to all other rooms. Hot air moves very quickly you just cant see it happening unless you have thermal imaging like what I have. I find it funny that people spend so much space and money on heating when they should be insulating and compartmentalising their heating spaces. Why heat the whole van when you are in bed. install a curtain (tight roof fit) and heat that space only. Exit vent is best above bed as we make hugh amounts of moisture whilst sleeping, vented air space below mattress will stop it from stinking and getting damp. Normal movement whilst in bed will vent mattress.
 
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