Hatch Vent Question

[stollo770]

Hello,

I have a 1979 Hunter 27 and the inside of it is very, very damp. I cannot stop the moisture, and I have tried everything from an electric dehumidifier, to damp raid buckets, to those stick on wall dehumidifiers that absorb water from the air like a sponge. All them pull moisture of out the air and fill themselves with water, but moisture still exists in the boat, specifically on the roof of the cabin where excessive condensation forms visible water droplets. I'm at my wits end with this problem and I think that installing vents on my topside hatches will fix this problem. Does this sound like a good idea? The problem is at its worst when the boat is warmer on the inside than the air on the outside; so I figure that with vents I can equalize the temperature on the inside of the boat and stop the condensation. I'm also betting that the increased air flow will help decrease moisture levels. So if anyone has tried this, I would really appreciate your advice on the matter, and some good places to get hatch vents.

Thanks for your help,

 

[centerline]

there have been a couple of threads that have passed thru recently concerning this issue... here is a link to one of them....

you must make sure you get the bilge as dry as possible.. then find out if the hull, topsides, cabintop, or any hardware or fixtures are letting water inside the boat at any time.... if so, you will NEVER have a dry boat.

after you get all the leaks stoppered up, then you can proceed with the venting process to maintain a relatively dry environment inside the boat without excessive labor or costs...

read the information given in the link and you will have a better understanding of how the condensate/moisture process works, and what to do about it.

 

[stollo770]

Great post centerline, thanks for sharing it. I have only recently waterproofed my hatches and port-lights, but my bilge always has about a quarter inch of water in it at all times. I simply can't find a pump that can suck up water lower then that number; once it falls past a quarter of an inch the pump sucks up air and the water stops moving.

Thanks to your post I am totally on board with adding vents to my top side hatches to correct the moisture problem. Do you know any good places to buy said vents?

 

[centerline]

Great post centerline, thanks for sharing it. I have only recently waterproofed my hatches and port-lights, but my bilge always has about a quarter inch of water in it at all times. I simply can't find a pump that can suck up water lower then that number; once it falls past a quarter of an inch the pump sucks up air and the water stops moving.

Thanks to your post I am totally on board with adding vents to my top side hatches to correct the moisture problem. Do you know any good places to buy said vents?

if you only ever have that much water in the bilge, it will dry out after you get some ventilation going, providing it isnt continually leaking in somewhere.

I wont recommend any place for two reasons... #1, we all have a different standard for what we want and what we want to spend. #2, no matter how hard you look or where you purchase from, or how much you pay, you will probably find a place next week or next month where you could have purchased it cheaper.

what I would recommend is that you buy quality. figure out what kind you want and start searching. use the internet and dont just stick to the first few pages that the search engine offers... the best deals are hard to find and are usually many pages behind the first few you see.

and dont think the internet is always going to be your saving grace in the economics department..... by the time you pay shipping on "most" of the stuff you could purchase online, you can walk into a local store and purchase it cheaper. good luck....

and dont forget to check out the pricing from the store on this site.... call direct and possibly get an even better deal than what may be listed.

 

[Benny17441]

If you have ever camped out in a tent you will realize than your breathing in an enclosed space will create condensation on the ceiling and walls. This will also happen in a boat, our breathing expels humidity from the body. Condensation will also happen where there is a temperature and humidity imbalance between inside and outside. The secret to both is ventilation, at least allow the humidity levels to equalize while reducing the temperature difference. I have never had a problem with water in the bilge as it is kept below a floor board and lets face it on the outside the boat is surrounded by a lot of water. Water leaks in the cabin and deck will indeed create a humidity problem. So I would say fix any leaks and create an air flow. Some people are concerned about mildew which may form in unattended boats and ventilation can help with that. Her in the Gulf of Mexico we contend in the summer months with high temperatures and humidity index approaching 100%. Ventilation helps but if you want to keep mildew away you need an electric dehumidifier taking water out of the air and injecting dry hot air in return. They cost around $150 and will draw as much power as a small window A/C.

 

[stollo770]

I already have an electric dehumidifier and it is quite efficient at pulling water out of the air. In the summer months it needs to run constantly to keep up with the moisture in the boat, and even then it does little to stop condensation on the ceiling of the cabin. I am completely sold on installing some ventilation and thanks to the advice here, I ordered a solar mini vent from West Marine last night. I plan on installing it on the hatch above the v-birth, where the moisture problem is the worst, so it can pull air through the entire boat from the companion way.

Do you guys think I need two vents? I have two topside hatches, one above the main saloon and the other in v-birth. Do you think that both hatches could benefit from a mini solar vent or is the one in the v-birth enough?

 

[Benny17441]

Two provide a cross flow and better ventilation than a single one. I would also think they would not work well together with an electric dehumidifier as they will bring back in the hot humid air the unit has been trying to dry. If a problem with condensation still persists when using an electric dehumidifier then the installation of a small fan would help. But when on the hook and as cooler temperatures approach then the vents can be used exclusively. Good luck.

 

[markwbird]

I feel your pain

I have recently found the right formula for this problem on my boat after a good bit of experimenting. My solution was a solar powered vent combined with a small space heater set on low. My moisture problem was a little different that yours though. If you have water on the cabin roof particularly when the boat is warm inside then you have water getting in the boat. Nothing will fix that until you fix the leaks. Once the leaks are fixed, ventilation in the summer and ventilation + heat (very little heat) in the winter will dry out the boat.

 

[braol]

I installed a solar vent with some success. I also reversed 180* the direction of one of the two vents located at the stern rail (Hunter 27).
Remember, if you stop leaks at any of your ceiling fixtures there is STILL water leaking inside...only now it is running down your walls at the side of your headliner (and still running around the now-plugged ceiling fixture). The only real solution is to stop ALL deck leaks at the source.
Oh, also check the 90* elbow that connects your cockpit scuppers to their outlet hoses. I had one that dripped when it rained.

 

[centerline]

I already have an electric dehumidifier and it is quite efficient at pulling water out of the air. In the summer months it needs to run constantly to keep up with the moisture in the boat, and even then it does little to stop condensation on the ceiling of the cabin. I am completely sold on installing some ventilation and thanks to the advice here, I ordered a solar mini vent from West Marine last night. I plan on installing it on the hatch above the v-birth, where the moisture problem is the worst, so it can pull air through the entire boat from the companion way.

Do you guys think I need two vents? I have two topside hatches, one above the main saloon and the other in v-birth. Do you think that both hatches could benefit from a mini solar vent or is the one in the v-birth enough?

where does the dehumidifier you have dump its condensate?...
its very uncommon that with an actual mechanical dehumidifier, that the boat is still unreasonably damp inside...

with the proper dehumidifier, the boat should never need ventilation other than what is necessary to bring oxygen in to sustain life....
in fact, the air in the boat should be very much drier without ventilation, that is IF the dehumidifier is working correctly as a actual dehumidifier, which i am going to go out on a limb and say it is not..... OR you have an influx of water into the hull and the mechanical device cant keep up with the moisture... and if so, you wont see any appreciable amount of difference with ventilation.

 

[stollo770]

where does the dehumidifier you have dump its condensate?...
its very uncommon that with an actual mechanical dehumidifier, that the boat is still unreasonably damp inside...

with the proper dehumidifier, the boat should never need ventilation other than what is necessary to bring oxygen in to sustain life....
in fact, the air in the boat should be very much drier without ventilation, that is IF the dehumidifier is working correctly as a actual dehumidifier, which i am going to go out on a limb and say it is not..... OR you have an influx of water into the hull and the mechanical device cant keep up with the moisture... and if so, you wont see any appreciable amount of difference with ventilation.

My dehumidifier drains its water into my bathroom's sink. I don't have it on a dedicated drain because the unit is bing and clunky and it needs to be stowed before I can sail. I made the mistake of forgetting that once and lost a chunk of my flooring (it was not fun to fix).

My boat used to take in a ridiculous amount of water via leaky hatches and portlights, but I resolved all of those problems. The main driver of my condensation is the temperature difference between the cabin and the outside air. Though I have no idea how the water gets into my boat in the first place.

 

[braol]

I like the idea of an electrical dehumidifier on the boat...might as well let the marina pay my dehumidification bill...plus the DH acts like a mini airconditioner so it's a win/win. I have an extra unit in my basement that I think I'll bring down to the boat this spring...although I am leery of leaving an electrical device (other than the battery charger) "on" while I'm away. Well, I guess that's what insurance is for.