Ventilation vs insulation help needed

[billgewater]

Originally Posted by El Pinguino

Really? So how do you explain fog?

As I say I don't block my dorades when laying up and also... what I didn't mention is that the small hatches in my heads - one frd, one aft - stay cracked open.

We used to have a bit of a black mould on vinyl headlinings in the vicinity of the galley... sorted by wiping down the surfaces involved with a eucalyptus oil solution before leaving the boat...

We leave all lockers and cupboards open... only problem of note there has been white mould on the outside of synthetic jackets... which I don't understand... jackets are now hung in clean air in the saloon when we lay up.. problem solved.

Fog is actual precipitation, not water vapour. It is wet and what you are seeing is actual microscopic water drops. If you have fog inside you have a real problem. The temperature has to drop below the dew point for the level of relative humidity to get fog.

[Supers0nic]

I’m only familiar with the cold weather side being year round in Maine.
I don’t ventilate. The heat costs way too much to leave any thing open. I keep the boat warm and keep the air moving with a couple small fans.
It seems to me that moisture is a bit of a problem early in the heating season but less so as the boat dries out.
I always keep an eye out for any moisture and address any immediately. Either by drying, moving contents to allow air movement, or flipping cushions or mattresses to allow air flow. None of this has been a big deal.
In the spring I do find some mildew which is a part of my spring cleaning ritual. Again, no big deal.

[billgewater]

El Pinguino asked about fog. Hmm .. never seen fog in my boat. However, fog is actual water droplets that have precipitated due to the temperature falling below the dew point for that specific relative humidity - or the other way around if you wish. Fog may settle (being dense) but water vapour actually rises as its density is lower than for the two main constituent gases in air. On the atomic level a water molecule (as in the vapour form) has an molecular mass of 18 where as nitrogen has 28 and oxygen 32.
If you have fog inside your boat you have some other serious issues, particularly if it is generated inside!
The comment about condensation usually preferentially occurring on the ceilings is a manifestation of water vapour rising.
I also suspect that some surfaces may be more likely to allow condensation as when I have seen condensation it seems that some surfaces are wetter. Probably caused by the thermal conductivity and/or the specific heat capacity of the material.

[El Pinguino]

Originally Posted by billgewater

El Pinguino asked about fog. Hmm .. never seen fog in my boat. However, fog is actual water droplets that have precipitated due to the temperature falling below the dew point for that specific relative humidity - or the other way around if you wish. Fog may settle (being dense) but water vapour actually rises as its density is lower than for the two main constituent gases in air. On the atomic level a water molecule (as in the vapour form) has an molecular mass of 18 where as nitrogen has 28 and oxygen 32.
If you have fog inside your boat you have some other serious issues, particularly if it is generated inside!
The comment about condensation usually preferentially occurring on the ceilings is a manifestation of water vapour rising.
I also suspect that some surfaces may be more likely to allow condensation as when I have seen condensation it seems that some surfaces are wetter. Probably caused by the thermal conductivity and/or the specific heat capacity of the material.

Oooops..... I seem to have forgotten the on my previous post... I do have a reasonable understanding of fog and dewpoints etc.....

The major condensation point on my boat used to be the alloy window frames... which is why everything is now 'double glazed'....

[Olddan1943]

A quick question with regards to the air scoop.
I wish to create one over the galley stove.
The box on which the scoop sits, what is it called and does someone have a diagram of the inside. The box seems to have a magical way of keeping the water out.

[El Pinguino]

Originally Posted by Olddan1943

A quick question with regards to the air scoop.
I wish to create one over the galley stove.
The box on which the scoop sits, what is it called and does someone have a diagram of the inside. The box seems to have a magical way of keeping the water out.

I think you are looking for a 'dorade' https://www.diy-wood-boat.com/images...TKDhu5qG-R.jpg

Commonly seen trimmed 'on' the wind I always have mine 'off' the wind to take advantage of the venturi effect and suck air out rather than blow air in. Also less water trying to get in when off the wind. ...

[JasonDS]

Originally Posted by wrwakefield

We live on our boat in cold climates, and I have for many decades. One of the most common mistakes when heating the vessel is to close off the ventilation when it is needed the most [typically with hopes of saving heating costs while creating an unhealthy living environment and promoting dampness that permeates everything- in support of mold and fungi... False ecomnomy...]

To answer your specific questions, you need to consult psychrometric charts to understand how much insulation you will need for your intended conditions.

Practical Sailor has a good article about this, and follow-on articles that will answer your other questions.

Additionally, we have shared what we have learned over the years about living on boats in cool climates on our blog if that is of interest.

Best wishes with your projects.

Cheers! Bill

Thanks. Will check it out

[Olddan1943]

Originally Posted by El Pinguino

I think you are looking for a 'dorade' https://www.diy-wood-boat.com/images...TKDhu5qG-R.jpg

Commonly seen trimmed 'on' the wind I always have mine 'off' the wind to take advantage of the venturi effect and suck air out rather than blow air in. Also less water trying to get in when off the wind. ...

El Pinguion, thanks for the diagram, just what I needed.
The American Tug does not have hood or fan over the stove, there are no exhaust fans anywhere on the boat. I am thinking, if I install a 3 inch air scoop, (the smallest I can find) it will suck the cooking odors and grease odors out. It should go a long way to keep the cooking area clean too. The broker said, just open a window behind the stove. I want a SMALL hole.
Now, I need to find a true rheostat controlled fan, not a 3 speed. The 3-speed fans all seem to be very noisy. A small amount of air movement should solve or reduce the problem. If I cant find the fan then, I will just make the unit passive.
I am not interested in a flush mount fan. I want to add not subtract from the 'salty' look of the boat.
Thanks again.

[Terra Nova]

3" is too small for your boat.

[Olddan1943]

Originally Posted by Terra Nova

3" is too small for your boat.

It is only 34ft long. I just want a little ventilation not a hurricane.
The upper deck is getting crowded as it is. 4 diving tanks, dock box for spare lines and ditch things and an off shore emergency raft and I store the fenders up there when I am traveling. Plus 2 medium round fenders for locks and rafting.