To vent or not to vent

[mekanic]

I am unsure about cutting holes in the roof.
I have heard they can be a pain to seal up.
here is one i'm looking at:
12 VOLT VENTLINE NON MOTOR VENT - eBay (item 270723322796 end time Mar-27-11 13:03:20 PDT)

[Kenn]

I have used my old motor home for 20 years and I can't imagine not having vents. My new motor home will be a 20' box with 5' bed above the cab. I plan to have an airconditioner in the center and one vent above the bed over the cab and another in the bathroom above the shower witch is in the very back of the motor home. Both of the vents will be three speed with the ability to move air in or out. I have never had any leaks with my vents.

[Bob86ZZ4]

Yep, seconds on that one. I've owned 2 rv's. My old one had three roof vents similar to that ebay one, except the one in the bathroom and the one in the shower both had fans. A must I'd say. My rig now has two "Fantastic" vents. They are the best and well worth the extra money. Motorized open/close, and rain sensors. So they close and turn off if it starts raining. And you can open them and not have the fan on if you want, and they'll still close if it starts to rain. I also put the big covers over mine so you can have them open when going down the road. Which effectively makes the rain sensors not needed since the covers allow you to run the vents in the rain. The Fantastic fans are designed pretty good to make them not that likely to leak if you caulk them right. And the big covers add another level of leak prevention. For sure plan on at least a couple vents. One of mine is right above the kitchen and they didn't put a exhaust hood above the stove and it works pretty good for cooking odors and heat exhaust.

[mmmc101]

I suspect in an insulated "box", without some ventilation, that mold and mildew would become a significant problem. I wouldn't even consider building one without a vent. The standard vents require a 14" X 14" framed opening (same as the A/C) and are easy to seal. I have never had one leak on the motorhomes or trailers that I have owned. JMO
MMM

[hot rod]

Add my vote for yes. Can't be without vents for all the reasons mentioned above. Put in more than you think you need, you won't regret it. If you think you need one, put in two. My converted "toy hauler type" trailer has one in the center, one in the bathroom, plus the a/c, and I really wish I had put one directly over the bunk. Going to go back and add one more. Really nice to get a little air moving on a warm night, and to let the day's heat out. Make sure you use the covers like Bob said, MaxxAir is the common brand name, but there are a bunch of other brands that do the same job. Let you keep the vents open in the rain and while moving. Plus every trailer I had without the covers eventually had a lip blow off the vent while travelling, the MaxxAir covers cure all that. Figure $25 to $35 each depending on where you get them (every rv store has a few in stock) and 15 minute install.

The vents themselves are kind of a pain to put in depending on your roof structure as you may have to add bracing. The vent itself is easy, it's preparing the hole and bracing. The hole needs to be framed all the way around with metal or sturdy wood for the screw to fasten to, and to keep the metal on the roof rigid to maintain a seal. Use the sealer tape they have at the rv store under the flange, plus a bead of rtv silicone around the edge and on top of the screw heads and you will never have a leak to worry about. And with the covers wind and rain will never make it's way in.

Also, they have some vents with a fan, and in my experience the ones with the tiny approx 4" diameter fans are not worth wasting your money on, they are noisy and don't move much air at all. If you want a fan, bite the bullet and get the full sized fan, they are pricey but you are getting what you pay for.

[Bob86ZZ4]

Yep, the Fantastic fan/vents are great. Mine are even variable speed so if you don't want them noisy you can slow them down. But they're not too noisy even on full speed. My rig didn't have the rain covers on when I bought it. My parts place guy told me to use these special Maxxair covers for the powered ones that are pretty big. I could only fit the cover on the kitchen one. My bathroom vent is too close to the satelite dome to fit it. I looked around a bit on the net for those covers and can't find them. But I see Maxxair sells a complete powered vent fan with the rain/wind cover built in. Those look pretty nice.