Mushroom Vents, Anyone?

[Gone Galavanting]

Totally unfamiliar with mushroom vents, so looking for input from folks who have them, or have had them.

1) Are there different kinds, pros/ cons
2) Can they be left open without concerns of water (rain, melting snow, etc) leaking in?
3) Can you drive with them open?
4) Are they difficult to install?
5) How do they compare to typical vents?
6) Are they easily damaged? How well do they hold up?
7) How big are they?
8) Anything else I should know about them... I'd like to order my vents sometime in the next couple of days, need to decide between traditional vent and mushroom. The BIG factor is I need a vent that works, but doesn't shade my solar panels.

I have read some posts here about them.

I am really looking forward to replies to the post, however may be slow in answering back as am in the process of moving. Easier for me to check messages than it is to reply right now.

Thanks Everyone,
GG

 

[SternWake]

My Nicro Marine solar vent was 78$ in 2001
Requires a ~4 inch cut out in the roof.

It's fan was only 17CFM and had a 1.5v nicad battery which would run the motor for 2 days in Oregon in winter.

It is robust. The only time it leaks is if I direct a hose stream at its base at the right angle. I never worry about rain.

I've modified it my ripping ou the battery and fan motor and using computer fans to push air through it instead.

AFAIK, not many people here use them. The fantastic fan moves a LOT more air but has that pesky 14" square cutout and the maxxairs rain proof vent still sticks up far enought to be of shading concern at lower sun angles.

The shading at low sun angles is a concern, but low sun angles are much less productive anyhow.

I'd rather stuff 400 watts of solar on the roof tightly, and have them partially shaded outside those 3 hours on either side of noon, than have 300 watts farther apart so that shadowing was not a concern, or significantly less of one.

The charge rate at noon should seek to achieve 10% of the Amp hour capacity of the battery bank. This is difficult with solar.

Rolls Surrettte, who make pretty much the best flooded lead acid batteries, recommend enough solar to achieve 18% charge rate at noon, so that when one does have well depleted batteries from many days of less than ideal weather, that an ideal day has the best possible chance of returning the bank to 100%.

I vote go for as much wattage as possible on the roof space, and low sun angle shadowing, is what it is. Low sun angles are not very productive anyway.

The Mushroom vents, their installation and the attaching of computer fans can be significantly more labor and cost than just cutting a 14" square hole and putting a Fantastic fan or A Maxxair fan up there.

 

[NeedAnEscape]

My van came with a 6" round hole in the roof that was poorly patched and leaking. I put one in to fill the hole and it only leaks a tiny bit if it's raining really hard and I'm driving. Even after 30 minutes of driving in heavy rain more water came in on my shoes so I never close it unless I want to keep heat in.