secondary double glazing.

[pquinn]

how would you go about this roger?

[blackrose]

Some forum members used a company who cut perspex to size and sold the sheets with self-adhesive magnetic strips. I didn't do it myself as I have all portholes, but those who fitted it seemed happy with the results. I can't remember the name of the company?

[Roger Gunkel]

how would you go about this roger?

Hi pqinn,

 

As I installed mine a couple of years ago, rather than go through the whole thing from scratch, here is the link to the original thread, where after the first dozen or so posts I gave full details of how I went about it. Double glazing thread

 

There are probably a number of companies that supply acrylic dg material, just google for it and if you want to try the cheap film option first, Wilkinsons, B&Q etc all sell it. I tried that before fitting the acrylic, and the result of using the film on all the boat windows was quite amazing. Huge reduction in heat loss, draughts and condensation. Because it was so successful, I wanted something reusable and removable that looked nice, hence the acrylic.

 

Roger

[pearley]

I double glazed the hatches with perspex and magnetic strip. For the portholes I had the perspex cut in circles one millimeter less than the diameter of the porthole trim, edged it with U shaped plastic trim and force fitted them in the hole. A bit of Fairy liquid helped as did leaving the perspex out in the cold so that it was at its smallest.

 

Got the trim from DIY Plastics.

[Ryeland]

I'm sort of 'developing' DG at the moment, really to stop condensation on the window frames which will ruin the wood surrounds soon. I didn't want to use the magnetic strip as it would spoil the look of the windows in the summer. I've started off using 4mm twinwall polycarbonate for extra insulation over solid sheet. This isn't transparent, but lets a lot of light through. I've fitted it only to the fixed part of the windows, so I can still see through the hopper parts and use them for ventilation. At the moment the twinwall just sits in front of the windows within the wood surrounds, with the top held by flexible plastic edging strip over the central window bar. This has been totally successful! The condensation is even improved on the top of the frame, probably due to the whole area around the windows being warmer.

 

The next version will probably use 6mm twinwall, so I can stick self adhesive foam strip on the bottom and side edges so it will sit firmly in the window surround. The edges of the sheets need sealing as well, probably with clear silicone, or a clear tape. The lack of transparency hasn't been a problem, it's increased privacy, a bit like net curtains. If needed, the sheets should then be easy to remove and replace.

 

Richard

[Rackingman]

Many years ago I looked at this problem in great detail and finally decided on fixing an Acrylic sheet in a 3/4" hard wood frame. Stained the frame to match the woodwork, stuck some double glazing seal around the outside and pushed in tight into the window recess and secured it with a brass turnbuckle on each of the four sides. Each window unit was made separately as the sizes varied slightly and then marked to suit. It worked a treat, OK we occasionally got condense between the panels and the glass but it's a simple job to simply remove the panel, dry the window with kitchen roll and replace. The improvement in warmth and general feeling of home in the boat was amazing in the winter with frost outside and in the summer the panel are simply removed and stored in my case I made a rack for then on the gunnel side. The major cost was the Acrylic and I remember cutting it to size without cracking it was a bit tricky but apart from that it was no problem.

 

The panels have now been in use for 15 years and we lived on board for 12 of those. The key is Acrylic, Perspex just goes cloudy with age, but Acrylic just cleans up like glass.

[PeterDHS]

As a failed Architect but with 40 years in the building game, I am bemused with the concept of double-glazing an NB.

The ventilation required by the Regs (for your safety) means that the heat loss by ventilation is far far greater than heat loss difference between single and double glazing.

If your problem is condensation the cure is good ventilation. Sealing yourself up in your own fug is daft and dangerous.

Lol,

Peter

[davewally]

Hi,

 

our boat is a Black Prince with Worcester Marine windows. Thos are the ones with the clips that lean the whole glasss panel inwards.

There is one mention of double glazing being available for them. Does anyone have any experience of these?

 

Thanks

 

Dave

[ditchcrawler]

As a failed Architect but with 40 years in the building game, I am bemused with the concept of double-glazing an NB.

The ventilation required by the Regs (for your safety) means that the heat loss by ventilation is far far greater than heat loss difference between single and double glazing.

If your problem is condensation the cure is good ventilation. Sealing yourself up in your own fug is daft and dangerous.

Lol,

Peter

[Roger Gunkel]

As a failed Architect but with 40 years in the building game, I am bemused with the concept of double-glazing an NB.

The ventilation required by the Regs (for your safety) means that the heat loss by ventilation is far far greater than heat loss difference between single and double glazing.

If your problem is condensation the cure is good ventilation. Sealing yourself up in your own fug is daft and dangerous.

Lol,

Peter

I would assume that as you are speaking as a failed architect, then you must be speaking as someone who has lived aboard an adequately ventilated boat, both with and without double glazing in the depths of Winter and can therefore speak with authority.

 

Having myself lived on board for 8 years with and without DG then my own experience is that that DG makes a massive difference to comfort levels, draughts, condensation and fuel use.

 

The answer to condensation is both adequate ventilation and removal of cold surfaces by the proper and effective use of insulation including DG. Good ventilation alone will certainly reduce condensation, without adequate insulation though you will also be cold or spending a fortune on heating the air outside your boat. As a builder you should be fully aware of the value of insulation and double glazing in any modern home, boat or otherwise.

 

Roger

[matty40s]

I would assume that as you are speaking as a failed architect, then you must be speaking as someone who has lived aboard an adequately ventilated boat, both with and without double glazing in the depths of Winter and can therefore speak with authority.

Having myself lived on board for 8 years with and without DG then my own experience is that that DG makes a massive difference to comfort levels, draughts, condensation and fuel use.

The answer to condensation is both adequate ventilation and removal of cold surfaces by the proper and effective use of insulation including DG. Good ventilation alone will certainly reduce condensation, without adequate insulation though you will also be cold or spending a fortune on heating the air outside your boat. As a builder you should be fully aware of the value of insulation and double glazing in any modern home, boat or otherwise.

Roger

 

which is why he failed....

DG stops condensation forming, helps keep the heat in, and doesn't affect ventilation through the mushrooms one iota.

[DandV]

 

The panels have now been in use for 15 years and we lived on board for 12 of those. The key is Acrylic, Perspex just goes cloudy with age, but Acrylic just cleans up like glass.

 

I am intrigued, my understanding is Perspex was the ICI trade name for its version of clear Acrylic sheet, generically Poly(methyl methacrylate) or simply methyl methaccrylate or PMMA.

Pexiglass I think was the DuPont name. My experience is that both UV and flexing degrades it, it losing strength and clarity with exposure

 

Don

[Roger Gunkel]

which is why he failed....

DG stops condensation forming, helps keep the heat in, and doesn't affect ventilation through the mushrooms one iota.

 

Absolutely on the nail Matty!

 

It seems to be a common misconception that ventilation is the answer to condensation, which is not necessarily so. Ventilation will certainly stop you dying from suffocation, but can also under many circumstances increase condensation if the ventilating air has a higher moisture content than the air

already in the boat. One example of that is on wet days. For those that still don't understand it, it is the temperature differential between the air mass and the surfaces that it is in contact with that cause condensation to form, together with the amount of moisture absorbed in the air.

 

Warm air will retain more moisture than cold air, so as warm moist air comes into contact with a cold surface, the air temperature will reduce allowing the dew point of the moisture to be reached and condensation forming on the cold surface. So coming back to double glazing, a single sheet of glass in direct contact with the outside air will quickly equalise it's temperature to that of the outside air. As the volume of air outside is obviously far greater than the warmer air inside, then the glass will act as a heatsink for the boat. The only way to stop it doing that is to isolate it from the inside air by double glazing it. There are specific spacings between the two sheets that give maximum thermal insulation, which I think is about 12-15mm. Above that and the air between starts convecting and transferring heat, below it and the transfer is by direct radiation. In practice, anything from about 6-50mm will give worthwhile insulation and there is some variation with different types of glazing material.

 

If anyone has any doubts as to the effectiveness of double glazing, if you already have it then try removing a sheet when you get up on a cold morning and see the instant condensation as the air touches the cold outer glass. For those that haven't, try taping a piece of cardboard tightly over a window opening then remove that in the morning.

 

It is all down to very basic physics, retain your heat, reduce your moisture production, reduce cold surfaces and keep adequate ventilation.

 

Roger

[jelunga]

Roger et al,

I read your articles on dg with interest. My problem is portholes, with nice brass heat conducting surrounds inside to outside. I am relectant to screw anything to the teak veneer panelling inside since it will spoil the appearance and screw holes do not do it for me.

Did you / do you have any solution?

Currently, and it sounds crude, we have cut sheets of bubble wrap to the size and use bluetak to fairly close fit to the cabin aides. This shows an improvement over nothing. But the condensation on the brass surround is the main problem and I can think of no simple fix for this other than replace all the brass portholes with something with a thermal break ir PV(spits in the gutter)C.

Edited February 1, 2012 by jelunga

[Naughty Cal]

Tackling the source of the condensation would be a good start. Adequate ventilation is what you need.

[jelunga]

Main source of condensation is water content of the air. At nightime when all batterned down, the water in breath causes a lot and if think I am going to stop breathing just to reduce the condensation.......think again! My sleep apnoea is bad enough already!

 

And as I think Roger mentioned in a pp, admitting new air through ventillation just brings more moisture into the boat. Of course, if the outside air is so cold that it contains very little or no moisture, then it will not bring much in. But until it warms up it will not be able to carry away the condensation either.

Edited February 1, 2012 by jelunga

[Roger Gunkel]

Main source of condensation is water content of the air. At nightime when all batterned down, the water in breath causes a lot and if think I am going to stop breathing just to reduce the condensation.......think again! My sleep apnoea is bad enough already!

 

And as I think Roger mentioned in a pp, admitting new air through ventillation just brings more moisture into the boat. Of course, if the outside air is so cold that it contains very little or no moisture, then it will not bring much in. But until it warms up it will not be able to carry away the condensation either.

My point abouted fresh air bringing in more moisture was to make the point that ventilation isn't always the answer particularly on moist days. It would be fair to say though that outside air is very frequently drier than the air inside. Of course, outside air is also cold air, and minimising moisture production as Phylis points out is always a good thing, but the problem is not actually having moisture in the air so much as stopping the forming of condensation.

 

It's a bit of a damned if you do damned if you don't situation! Cold air from outside may well often be drier, but it also lowers the internal heat reducing the amount of moisture that the air can absorb. Stopping the moisture condensing tends to make it more acceptable and less troublesome, so keeping sufficient ventilation whilst maintaining temperature becomes the priority.

 

Your brass porthole frames are a problem for you as you have pointed out, and as you reduce the cold surfaces elsewhere, they will attract even more moisture that would have previously condensed in other places.

 

You may be able to make a circular acrylic DG port that is mounted on a wooden frame to fit over tha brass surround. Perhaps make the frame round that is a tight push fit over your brass port. Thinking slightly laterally, how about a circular piece of acrylic that also covers your brass frame and is attached to the port glass with a rubber suction pad fixed to the acrylic, a bit like a driving mirror rubber cup. You could then remove it whenever you want without any visible attachment point on the wood.

 

Roger

[Ally]

My point abouted fresh air bringing in more moisture was to make the point that ventilation isn't always the answer particularly on moist days. It would be fair to say though that outside air is very frequently drier than the air inside. Of course, outside air is also cold air, and minimising moisture production as Phylis points out is always a good thing, but the problem is not actually having moisture in the air so much as stopping the forming of condensation.

 

It's a bit of a damned if you do damned if you don't situation! Cold air from outside may well often be drier, but it also lowers the internal heat reducing the amount of moisture that the air can absorb. Stopping the moisture condensing tends to make it more acceptable and less troublesome, so keeping sufficient ventilation whilst maintaining temperature becomes the priority.

 

Your brass porthole frames are a problem for you as you have pointed out, and as you reduce the cold surfaces elsewhere, they will attract even more moisture that would have previously condensed in other places.

 

You may be able to make a circular acrylic DG port that is mounted on a wooden frame to fit over tha brass surround. Perhaps make the frame round that is a tight push fit over your brass port. Thinking slightly laterally, how about a circular piece of acrylic that also covers your brass frame and is attached to the port glass with a rubber suction pad fixed to the acrylic, a bit like a driving mirror rubber cup. You could then remove it whenever you want without any visible attachment point on the wood.

 

Roger

That's a good idea, though it would need some kind of finger pull/handle or knob on the internal boat side of the disc too, or you'd never get it out. It's hard enough sometimes to open GU style ports when the seals have got hot in the sun, especially new ones, I've had to use a suction cup to grab and pull those open before now...so actually, thinking on, a suction cup/hook would get them out.

[bizzard]

Main source of condensation is water content of the air. At nightime when all batterned down, the water in breath causes a lot and if think I am going to stop breathing just to reduce the condensation.......think again! My sleep apnoea is bad enough already!

 

And as I think Roger mentioned in a pp, admitting new air through ventillation just brings more moisture into the boat. Of course, if the outside air is so cold that it contains very little or no moisture, then it will not bring much in. But until it warms up it will not be able to carry away the condensation either.

You need an breath out turbo breath heater to dispel breath water vapor,a hair dryer lashed to your cheek with the nozzle aimed at an angle to intercept the out breath.Or become a fire eater.

 

Or perhaps better still,just sit quietly with a vacuum cleaner nozzle in your mouth,but beware of severe and sudden lung collapse.

Tee pieces or spurs could be put into the vacuum pipe so as to allow everyone on board to join in,using only one machine. Result,nice clear windows.

Edited February 1, 2012 by bizzard

[bizzard]

Ah i've got it.Invest in an Eastern Hookah or Hubble bubble pipe,a communial type one with lots of tubes attached,then you can all sit around sucking and winking at each other with glee whilst all your breath condensation all ends up in the big glass jar and not on your windows.You should of course add a little stimulant to it,see the chap with the leather jacket and baseball cap that hangs about under the bridge.

[simon&jan]

Ah ,i see did wonder what he was up to !!!

[ditchcrawler]

Absolutely on the nail Matty!

 

It seems to be a common misconception that ventilation is the answer to condensation, which is not necessarily so. Ventilation will certainly stop you dying from suffocation, but can also under many circumstances increase condensation if the ventilating air has a higher moisture content than the air

already in the boat. One example of that is on wet days. For those that still don't understand it, it is the temperature differential between the air mass and the surfaces that it is in contact with that cause condensation to form, together with the amount of moisture absorbed in the air.

 

Warm air will retain more moisture than cold air, so as warm moist air comes into contact with a cold surface, the air temperature will reduce allowing the dew point of the moisture to be reached and condensation forming on the cold surface. So coming back to double glazing, a single sheet of glass in direct contact with the outside air will quickly equalise it's temperature to that of the outside air. As the volume of air outside is obviously far greater than the warmer air inside, then the glass will act as a heatsink for the boat. The only way to stop it doing that is to isolate it from the inside air by double glazing it. There are specific spacings between the two sheets that give maximum thermal insulation, which I think is about 12-15mm. Above that and the air between starts convecting and transferring heat, below it and the transfer is by direct radiation. In practice, anything from about 6-50mm will give worthwhile insulation and there is some variation with different types of glazing material.

 

If anyone has any doubts as to the effectiveness of double glazing, if you already have it then try removing a sheet when you get up on a cold morning and see the instant condensation as the air touches the cold outer glass. For those that haven't, try taping a piece of cardboard tightly over a window opening then remove that in the morning.

 

It is all down to very basic physics, retain your heat, reduce your moisture production, reduce cold surfaces and keep adequate ventilation.

 

Roger

dew point

[Roger Gunkel]

dew point

Dew point! See post 13 line 9

 

Roger

[bizzard]

dew point

Du-Pont.

[DandV]

Tackling the source of the condensation would be a good start. Adequate ventilation is what you need.

 

As a one time Heating, Ventilating and AirCond Engineer who moved on to other things, (Does this make me failed?) minimilising condensation is achieved by several things

1/ Tackling the source - do not let pots kettles etc boil unnecessarily and limit shower time and extract air close as possible to the discharge to dump the moist air immediately overboard.

If the air on board has a higher moisture content then outside air get rid of it.

As our breathing, and gas fired appliances all produce water vapour, produce nasties and deplete oxygen, sufficient continuous ventilation is required rid the moisture and replenish oxygen.

2/ Good insulation to minimilise surfaces with temperatures below the dew point of the surrounding air, Double glazing aids this.

 

Cheers Don