insulation in a steel boat, to have or not to have

[NSboatman]

...and, if you're really worried about a fire risk in some areas around the foam, you can always spray coat it adfterwards with fire retardant paint. Might slow down ignition if that's the worry.


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[Lepke]

The insulation was probably removed because the hull plating was rusting behind the sheet foam. The insulation needs to fit tight to a steel hull. Otherwise moisture will collect between the insulation and the plating. Properly epoxied steel won't rust so sheet foam or fiberglass insulation should work. Normally sprayed foam works the best. Non heated spaces don't need insulation as long as they are vented.

[sy_gilana]

Must insulate, and it must be sprayed onto properly coated steel, there can be no gap. 2" is good.
You can also put double glazing in the hatches. We also use Bubble wrap in various areas.

[Rustic Charm]

Don't use any insulation that is a fire risk. You don't need to do that in this day and age. There are a number of foam's that are fire retardants and that's what you should be using now days.

[ausnp84]

Originally Posted by sy_gilana

Must insulate, and it must be sprayed onto properly coated steel, there can be no gap. 2" is good.
You can also put double glazing in the hatches. We also use Bubble wrap in various areas.

It doesn't have to be sprayed (foam panels - ie. Armaflex work just as well) BUT yes, whatever you use must fit very close with the hull. If you're going to use foam panels, you need to glue them well.

n

[Rustic Charm]

Originally Posted by ausnp84

It doesn't have to be sprayed (foam panels - ie. Armaflex work just as well) BUT yes, whatever you use must fit very close with the hull. If you're going to use foam panels, you need to glue them well.

n

You don't need to glue if you use Foilboard.

Personally i wouldnt glue at all. Creates a nightmare when needing to get it out.

[RaymondR]

My steel boat has about 1 1/4" - 1 1/2" of sprayed in urethane foam over which I sprayed a couple of coats of acrylic paint and I have never had any problem with water take up by the foam.


I have had a couple of problems where leaks in the deck allowed water to flow along and down the frames behind the foam however this would have been easily prevented had I taken care.


I think you must have insulation inside a steel boat and if it can be applied directly to well coated steel it will not cause any problems. One of the good things about steel boats is that if you want to work at it you can completely avoid any deck leaks.


One of the things I now do is rather than just drill and tap into the steel and screwing bolts into it I try to put the bolt through the steel from the inside with a nylon washer under the head then use nuts to do the fastening and cut the excess bolt off. It does not look as good but tends to stop leakage down the threads.


I also tend to use rubber gaskets bonded to the hull steel rather than just a caulking compound.

[ausnp84]

Originally Posted by Rustic Charm

You don't need to glue if you use Foilboard.

Personally i wouldnt glue at all. Creates a nightmare when needing to get it out.

I like the sound of foilboard.... will have a google now.

One other thing for the OP - stay away from a teak deck on a steel boat. It will leak eventually, it will get behind the foam or interior cabinetry, and it will turn into a nightmare. I speak from the horror of having to remove 300 black bags of wet soggy foam at the start of my boat build.....

n

[Snowpetrel]

I will say there is some truth in the possibility of the insulation causing corrosion and rust. It can trap moisture and mould if its not done right. So a boats probably better off without insulation, rather than a poor insulation job. If the boats in a mild climate and you dont live aboard not having insulation is an option. Or you could just be tough and put up with frying and freezing as Motessier and David Lewis did... But me, I am a wimp, so I will go with at least 50mm of foam.

[Patrigo]

I have owned my uninsulated steel yacht for 27yrs. I would like to ask a question. I am inquisitive about the colour of the outside of the hull.i.e.what colour are the hulls of all the boats mentioned which produce appreciable amounts of interior condensation?
My only interior condensation is on the outside of my in use beer can.

[Conall63]

Spray foam is the only way to go. Spray foam allows you to completely cover the edges of the frames and longitudinals. Any exposed steel above the water line in living space will condensate and drip when in cold climates.

I used both DYI foam kits and professional contractors to insulate my boat while I built her. The DYI kits do not produce the yield advertised due to pressure drop and temperatures. In the long run, a professional crew will be close enough to the same cost as the DYI kits, but you'll get much more material and a better looking job.

I used fire retardant foam, and I can for sure attest to the fact that this stuff does not burn. I've done welding and torch work around foam, and it will not ignite. It might smolder a bit, but once the heat source is removed, it snuffs out.

I have 2" of foam in my boat and 3" of fiberglass on top of that. If budget is an issue, one could spray in an inch or less then use fiberglass batts over that. Once the foam covers the metal and a thermal break is created, batt insulation can be used as the condensation issue has been removed. You cannot use batt insulation on bear metal without having applied foam first.

Conall

[ausnp84]

Originally Posted by Patrigo

I have owned my uninsulated steel yacht for 27yrs. I would like to ask a question. I am inquisitive about the colour of the outside of the hull.i.e.what colour are the hulls of all the boats mentioned which produce appreciable amounts of interior condensation?
My only interior condensation is on the outside of my in use beer can.

And you live in Queensland... does it ever get below 10C there???

Our topsides are a mid-blue, but we had condensation when the boat was white and light grey as well. Mind you, we were on the UK's South Coast where autumn and winter would regularly get below freezing.

n

[ausnp84]

Originally Posted by Conall63

Spray foam is the only way to go. Spray foam allows you to completely cover the edges of the frames and longitudinals. Any exposed steel above the water line in living space will condensate and drip when in cold climates.

I used both DYI foam kits and professional contractors to insulate my boat while I built her. The DYI kits do not produce the yield advertised due to pressure drop and temperatures. In the long run, a professional crew will be close enough to the same cost as the DYI kits, but you'll get much more material and a better looking job.

I used fire retardant foam, and I can for sure attest to the fact that this stuff does not burn. I've done welding and torch work around foam, and it will not ignite. It might smolder a bit, but once the heat source is removed, it snuffs out.

I have 2" of foam in my boat and 3" of fiberglass on top of that. If budget is an issue, one could spray in an inch or less then use fiberglass batts over that. Once the foam covers the metal and a thermal break is created, batt insulation can be used as the condensation issue has been removed. You cannot use batt insulation on bear metal without having applied foam first.

Conall

Conall! Haven't heard from you in ages. How's the trawler coming along now it's afloat? Did you ever hear back from Norm after he got to Mexico?

n

[norena of white]

when we first got our steel boat we had condensation problems below the waterline. To fix this problem i installed a fan that draws cool wet air from the bilge to a vent at the stern of the boat. At the bow there was a broken solar fan that i stripped the motor from to allow more air flow through the bilge. above the waterline we have insulation.

[seabreez]

I want some heat. Since condensation and inspecting the hull was a concern for the present owner for taking out the insulation (which was styrofoam ) what are we missing in this equation. Should we continue to search for another steel boat, think seriously about redoing this one or not even be concerned. Really appreciate your collective knowledge!

The insulation and the air management around a fibreglass and a steel boat.

I have sailed in both fibreglass and steel. Here is the reasoning behind insulating. From the various threads on CF, there are good comments but you do not hear the whole story. I am not to tell you what to do; I only want you to understand this phenomenon that no boat manufacturer understands completely. And if you have not experienced this fully… I learned this with experience.

In the tugboat that I operate there are four individual compartment used for storage and are painted inside with good epoxy paint. These compartments are “not” insulated and have no moisture issue. Why? It is not a liveable compartment. The paint is as the day it was done and there is absolutely no rust in those compartments. And the floor (the bottom of the hull) is painted as well and there is an elevated suspended walkway so that the paint is not scratched or damaged from walking on it. If there is a scratch the moisture will get between the paint and the hull and cause rust.

In a liveable compartment there is always moisture or condensation. The trick is to understand where it forms and to manage you space by insulating or controlling or managing you air or moisture (vapour).

A few terms “hot humid” air will rise. “cool dry” air will settle lower. “Vapour” forms on the hot side of things.

In a fibreglass boat you rarely see insulation. However you will see an outer hull and a moulded inner hull and the space between the two is an air space that will provide some insulation form the outside temperature. The vapour on the hull, will simply flow to the bilges and the bilge pump or the ventilation will take care of removing the accumulated water. If you look closely on a humid day or in the morning, you will see the condensation. If condensation accumulates under you canvass, look closely inside the hull and the moulded compartment.

Where does the moisture come from? From humans that live in a certain space, by cooking, heating, using water from showers, toilets (heads), washing dishes, dish washers, and the biggest one… breathing. This is where expression “hot air” air comes from. (just kidding). The hot humid air that is created will rise and accumulate on ceilings and windows and walls where there is less air circulating. The best example of this is frost accumulating at the lower part of the windows in the winter (in a home). The frost is on the inside. The moisture will accumulate on the hot side of where the hot and cold meet. In a house construction there is a vapour barrier ( 6 mil plastic sheeting ) on the inside just behind the finishing of gypsum or pre-finish panelling etc. The vapour barrier is on all exterior walls and ceiling. It is also in basements and now some basement floors are now done with a vapour barrier. Before the new code there was no vapour barrier in the basement and home owners would deal with the moisture, they ran a dehumidifier when the humidity is high and not comfortable. If there is good air circulation the moisture will evaporate and taken care of with your air exchanger… the exchanger will remove “hot humid air” from the inside and exchange it with outside air which is “cool dry air”. If the vapour barrier if perforated or missing, the vapour will go into the walls at that location and freeze in winter and then you insulation looses it’s “R” value and will not insulate. Furthermore the vapour in the walls will “not” dry up and eventually rot out the frame members, cause mildew etc… This same phenomenon exists also in boats.

In warm climate you do need a vapour barrier as the vapour will accumulate on the inside even if the air around the boat is warmer. In warm climate the homes have ceramic tiles all over to dry up faster and is easier on the air conditioner. You need insulation to protect you from the heat. If the moisture is too high you simply open the air space to remove the hot humid air and let the wind dry up the space or start the air conditioner to “cool” and “dry” up the space. By cool dry is only comparable with the air you have inside.

Now the problem… insulation of steel boats. The inside of the hull has to accessible all over and be painted with good epoxy paint to prevent moisture from getting between the paint and the hull. If moisture accumulates you will have blistering and there will be rust. So remove all the rust and coat the hull with good paint. The insulation has to be installed or sprayed so that NO air space is between the hull and the form. Air will create moisture and will make that spot rust and you will not be able to detect this for a long time, so do it right the first time. When the foam is spayed and cures you will see a shine on the foam. This shine the foam indicates that the foam has cured and has formed a membrane that has a good seal and this is your vapour barrier. The installer must cover all between the frame members and the framing. If the framing is not done the cold will reach the inside by conduction through the metal and will form condensation and RUST. You have to insulate all parts of the hull and ceiling all over all the way down to the waterline. By doing this you will also see a huge reduction of noise as well as the sound does not bounce off foam.

Why not insulate below the waterline? Remember the temperature inside compared to the outside… you will have very little condensation forming in the bilges as water temperature is most of the time warmer than your outside air… also you do not want to contaminate your foam with oil. Let the water go to the bilge where the pump will take care of it and you can also ventilate the bilges to remove some of this condensation. You also do not insulate too close to the engine.

If repairs are needed on the steel… you will have to locate and remove the foam from the inside and do the repairs. Immediately after… paint then insulate by using spray foam from your local hardware store.

Hope this helps... Roger

H