Condensation on Steel

[rusty69]

2 minutes ago, MtB said:

 

Same here, or so I used to think. 

 

Water used to drip sometimes from the shower room extractor fan at any time of day or night, which leads me to think there was condensation, but out of site on the steel behind the pine panelling. 

 

The inside surfaces of the slide hatches are a favourite for condensation too, as the design of the slides rarely leaves space for a layer of insulation and most are just painted. 

 

There is a sliding scale of condensation on our boat, from not much at the front (apart from a bit from the water tank), to loads in the mostly un-insulated engine room, and from the engine itself. Clothes drying, cooking and washing seem to be the biggest culprits, but thankfully I do none of those.

[magnetman]

One of my boats is remarkably free of condensation.

 

A steel trawler style craft which has 26 small polycarbonate windows mounted against adhesive foam seals in the wheelhouse which helps. One at each end opens and closes. Sea going boat which can be completely sealed (side doors and windows clamp shut on neoprene seals and there is no fixed ventilation).

 

Small cabin. Big fire. 3 CO monitors

 

Hull was lined from new with concrete for ballasting and all interior steel surfaces below the floor are greased. Rockwool insulation in huge quantities fill every single void behind lining, around pumps etc.

 

There must be some condensation somewhere but it is remarkably difficult to find it. Bilges are bone dry.

 

I live on it for about 75% of the time when not on the country estate boat. The other boat has glass windows so it does get a bit of condensation but again the fire is usually going like the clappers and door open.

 

I do keep the fire warm and windows open for through draught.

 

Edited November 23, 2022 by magnetman

[MtB]

7 minutes ago, rusty69 said:

Clothes drying, cooking and washing seem to be the biggest culprits, but thankfully I do none of those.

 

I'm the same, although I admit wash sometimes. The paintwork needs it once in a while. 

 

 

 

[Tom and Bex]

1 hour ago, Loddon said:

Mine is 1993 and sprayfoamed

 

Where as ours is 2005 and polystyrene (ex-hire boat).

[David Mack]

1 hour ago, BEngo said:

Be aware that polystyrene leaches the plasticiser out of PVC insulated cables in contact with it, and will form a groove in the polystyrene where the cable lies.

It also turns the pvc cable insulation brittle, which can mean the insulation can crack and falls off allowing bare conductors to touch where they shouldn't.

[roland elsdon]

I recal a steel narrowboat built in the 70s  and lived in with no apparent condensation problems. There ws an incident reuiring cabin repairs. T that point it was discovered the cabins structural integrity was so poor due to rust, it was an economic write off.

[The Wind Lass]

1 hour ago, BEngo said:

The proper installation of the insulation is important.  It is vital for there to be a vapour barrier between the warm, moist air and the steel if condensation is to be avoided.  For polystyrene and rockwool this will be a separate layer of plastic sheet, if it were ever installed.  Most won't  have been.  Kingspan has the vapour barrier formed in the sheets, but all the gaps need to be filled with tinned foam, or covered with aluminium foil tape.  Spray foam is inherently a vapour barrier.

 

Spray foam came in in the late 80's.  In early 1989 RW Davis were buying their own spray kit.

 

Spray foam is much the best insulation, followed by kingspan type boards, polystyrene and a long way back, Rockwool.  

 

Be aware that polystyrene leaches the plasticiser out of PVC insulated cables in contact with it, and will form a groove in the polystyrene where the cable lies.

I was wondering about a vapour barrier. I wonder if there would be an easy way to spot what insulation and/or vapour barrier is underneath (without doing damage to someone else's boat). Thank you for the information about the polystyrene interaction with PVC. 

[The Wind Lass]

Would a GRP top generate less internal condensation?

[rusty69]

2 minutes ago, The Wind Lass said:

Would a GRP top generate less internal condensation?

GRP topped, steel hulled boats have their own set of problems.

[BEngo]

55 minutes ago, David Mack said:

It also turns the pvc cable insulation brittle, which can mean the insulation can crack and falls off allowing bare conductors to touch where they shouldn't.

Yes, in theory or if you waggle it around a lot.   In practice what seems to happen is that the plasticiser digs a groove in the polystyrene which effectively holds the cable, prevents the insulation from cracking and coming off and generally stops bare conductors from occurring.   Until you disturb it when some new cable is indicated.  Fortunately most people rarely disturb cables that are hidden behind the lining, and a strip of aluminium duct tape along the cable route will  form an effective barrier between the new cable and the insulation.

 

This was all part of the early BSS nonsense where several people had their boats rewired at BW's expense following an Ombudsman ruling by Lady Ponsonby.  It, and other nonsenses, eventually led to a  review by BW's technical director which gave us advisory items and the differences between hire boat BSS and  the private boat BSS.

 

N

[Tracy D'arth]

1 hour ago, David Mack said:

It also turns the pvc cable insulation brittle, which can mean the insulation can crack and falls off allowing bare conductors to touch where they shouldn't.

This is oft quoted, I have never found it to be a problem. There was a panic about this and many boats were unnecessarily rewired in the '80s. Since than it has reared its head several times without any action being taken.

[jonathanA]

14 hours ago, The Wind Lass said:

Hello Mateys, I'm considering forking out the cash to buy a narrowboat but I have a question that keeps me up at night. These boats are primarily made of steel, steel that is often sitting in rather cold water ergo a smooth, cold surface. The inside of the boats are heated. Unless the inside is insulated spectacularly some warm air will reach the steel behind the paneling. How is there not massive condensation behind walls dripping down into the bottom of the hull, corroding the bottom of the boat beneath the floorboards? I hope I'm missing something here. Please advise. 

If worrying about condensation keeps you awake at night whatever you don't buy a boat of any sort....  (if you want to sleep at nights)

I always remind folks looking  at boats that boat stands for bring out another thousand.... 

Edited November 23, 2022 by jonathanA
Added

[MtB]

7 hours ago, jonathanA said:

If worrying about condensation keeps you awake at night whatever you don't buy a boat of any sort....

 

Seconded, I wuz thinking exactly this! ^^^

 

If you could call it 'thinking'....

 

 

 

 

[matty40s]

7 hours ago, Tracy D'arth said:

This is oft quoted, I have never found it to be a problem. There was a panic about this and many boats were unnecessarily rewired in the '80s. Since than it has reared its head several times without any action being taken.

It definitely happened on Kathy's Fernie, we had a small electrical fire in the ceiling above the electric cupboard. On investigation, not all the cabling was sheathed and the polystyrene touching cables were brittle, one section of a twin core had failed causing a short.

[MtB]

35 minutes ago, matty40s said:

It definitely happened on Kathy's Fernie, we had a small electrical fire in the ceiling above the electric cupboard. On investigation, not all the cabling was sheathed and the polystyrene touching cables were brittle, one section of a twin core had failed causing a short.

 

No fuse then?

 

 

[Dav and Pen]

In the 1980s we used a lot of polystyrene and to get a good deal we needed volume so supplied a number of local boatbuilders with fire retardant polystyrene as well as paving slabs for ballast. As far as I know they all used a vapour barrier between the insulation and the lining as we did on our own NB. 

[matty40s]

21 minutes ago, MtB said:

 

No fuse then?

 

 

Plenty of fuses, whether this wire had one I cannot recall. There were lots of strange workings on what is now a 50 year old boat(which looks like it is having another refit at present)

[Ex Brummie]

Fitting out in 1988, my shell inner was sprayed with Waxoyl, then insulated with flame resistant polystyrene. An area recently cleared for modifications shows no corrosion or evidence of condensation.