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Double Glazing


mark99

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We're having good results with our homebrewed sliding glass secondary DG on ports. We get best results by cracking open the outer glass, just enough to ventilate and keep gap (2.75") dry and inner glass not too cold. We do get a touch of condensation on the room side of inner glass in the bathroom in the morning after a shower.

 

Piccy shows inner glass partly open for clarity.

 

Image022.jpg

Edited by nb Innisfree
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A quick update - we fitted Ecoglaze secondary glazing to all of our 6 large windows (but not our 4 portholes). It has been extremely effective in keeping the heat in. Even when we let the fire go out overnight, we wake up to around 13 degrees (when near freezing outside) rather than around 4 degrees like we used to! The biggest difference is that when the fire gets low the boat stays warm much much longer, whereas before it would instantly get cold.

The only problem we've found is that we now get a lot of condensation, both on the perspex sheets and on the walls, where we didn't have a problem before. The condensation used to gather on the window glass where it would then drain outside the boat via the drainage channels, whereas now it gathers on the perspex and dribbles onto the floor. Hmm.

So for us it has resulted in a difficult decision -

1. keep the heat in and put up with condensation dribble marks on our lovely wooden walls and floor.

2. use a bit more fuel and have no condensation.

A difficult decision, but at the moment we're going with option 1.

 

It sounds as if you have blocked off too much ventilation.

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A quick update - we fitted Ecoglaze secondary glazing to all of our 6 large windows (but not our 4 portholes). It has been extremely effective in keeping the heat in. Even when we let the fire go out overnight, we wake up to around 13 degrees (when near freezing outside) rather than around 4 degrees like we used to! The biggest difference is that when the fire gets low the boat stays warm much much longer, whereas before it would instantly get cold.

The only problem we've found is that we now get a lot of condensation, both on the perspex sheets and on the walls, where we didn't have a problem before. The condensation used to gather on the window glass where it would then drain outside the boat via the drainage channels, whereas now it gathers on the perspex and dribbles onto the floor. Hmm.

So for us it has resulted in a difficult decision -

1. keep the heat in and put up with condensation dribble marks on our lovely wooden walls and floor.

2. use a bit more fuel and have no condensation.

A difficult decision, but at the moment we're going with option 1.

 

If you are getting condensation on the cabin side of the acrylic, then that would suggest that you have cold air from outside getting in through either the drainage holes, or around the outer windows or seals, allowing the acrylic to get much colder. If the condensation is between the panes, then there may be gaps in your seal for the acrylic, or as Idleness says, a very large space between the panes, 2" or more, allowing convection between the two.

 

We sometimes have slight condensation on the outer glass, where the hoppers are not perfectly sealed, but is easily cleared (the silica gel helps that). Our drain channels are also sealed up which reduces the chance of cold air coming into the gap. We never have condensation on the cabin side of the acrylic, even if we have a bath or dry the washing infront of the stove.

 

You could adopt Innisfree's option of allowing air into the gap from outside, it works for him, will cut down condensation between the panes, but will also increase the heat loss and promote more convection.

 

I'm a bit concerned about your condensation on the walls, as the DG shouldn't make any difference there if the space behind is properly foam insulated. The exception would normally be where a cold wood surface is not exposed to warmer ventilated air, under beds, inside cupboards etc. We have cured that on ours by putting thin cheap cord carpet on the hidden surfaces.

 

(Edited to say) We don't let our fire go out overnight, but load it right up and close it down. It keeps a slightly lower background temperature, but not enough to promote condensation. We found early on, that if we let the fire get very low or go out overnight, everything in the boat cools down considerably, requiring a lot more heat to bring back up again, virtually as much as keeping the fire reduced overnight. The other thing to bear in mind is that if the internal boat temperature drops to dew point, it may take longer to get that low, but once it does, moisture will collect on any cold surface, including double glazing. It will of course take less fuel to keep the boat warm overnight than with no double glazing.

 

Roger

Edited by Roger Gunkel
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The air-gap between the acrylic and the glass is around 2 inches or so, so there is a fairly big air gap. The condensation is not in between the panes, but on the inside of the acrylic sheets, where it soaks the curtains and the blinds. Not good.

We very rarely let the fire go out when it's cold. If we ever do it's only because we have run out of coal. As a rule it is kept in 24/7.

The condensation dribbling down the walls only happens when really cold outside (like now) and is our penance for having polystyrene insulation rather than sprayfoam. There are gaps in the insulation so the condensation inevitably forms on the inside of the steel and then dribbles down the wood. Not much we can do about it really.

Of course the problem is much worse since fitting the secondary glazing as there is not so much ventilation now, but it is so nice to be warm in the mornings that we are probably just going to have to put up with wiping away the dribbles each day. :lol:

Edited by tomandsophie
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If you are getting condensation on the cabin side of the acrylic, then that would suggest that you have cold air from outside getting in through either the drainage holes, or around the outer windows or seals, allowing the acrylic to get much colder. If the condensation is between the panes, then there may be gaps in your seal for the acrylic, or as Idleness says, a very large space between the panes, 2" or more, allowing convection between the two.

 

We sometimes have slight condensation on the outer glass, where the hoppers are not perfectly sealed, but is easily cleared (the silica gel helps that). Our drain channels are also sealed up which reduces the chance of cold air coming into the gap. We never have condensation on the cabin side of the acrylic, even if we have a bath or dry the washing infront of the stove.

 

You could adopt Innisfree's option of allowing air into the gap from outside, it works for him, will cut down condensation between the panes, but will also increase the heat loss and promote more convection.

 

I'm a bit concerned about your condensation on the walls, as the DG shouldn't make any difference there if the space behind is properly foam insulated. The exception would normally be where a cold wood surface is not exposed to warmer ventilated air, under beds, inside cupboards etc. We have cured that on ours by putting thin cheap cord carpet on the hidden surfaces.

 

(Edited to say) We don't let our fire go out overnight, but load it right up and close it down. It keeps a slightly lower background temperature, but not enough to promote condensation. We found early on, that if we let the fire get very low or go out overnight, everything in the boat cools down considerably, requiring a lot more heat to bring back up again, virtually as much as keeping the fire reduced overnight. The other thing to bear in mind is that if the internal boat temperature drops to dew point, it may take longer to get that low, but once it does, moisture will collect on any cold surface, including double glazing. It will of course take less fuel to keep the boat warm overnight than with no double glazing.

 

Roger

 

That's a really good point. Letting the fire go out at night could actually be false economy.

 

 

I would think if there is a LOT of condensation to the extent that it is dripping down and staining lining then surely there is some sort of problem with ventilation or too much moisture being generated in the cabin :lol:

 

I know its nice to have a warm boat with no draughts but in my experience a bit of ventilation does wonders for stopping condensation. it may use more fuel but I always maintained a dry boat in preference to allowing any damp, and that was with polystyrene insulation and single glazed alloy framed windows.

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The air-gap between the acrylic and the glass is around 2 inches or so, so there is a fairly big air gap. The condensation is not in between the panes, but on the inside of the acrylic sheets, where it soaks the curtains and the blinds. Not good.

We very rarely let the fire go out when it's cold. If we ever do it's only because we have run out of coal. As a rule it is kept in 24/7.

The condensation dribbling down the walls only happens when really cold outside (like now) and is our penance for having polystyrene insulation rather than sprayfoam. There are gaps in the insulation so the condensation inevitably forms on the inside of the steel and then dribbles down the wood. Not much we can do about it really.

Of course the problem is much worse since fitting the secondary glazing as there is not so much ventilation now, but it is so nice to be warm in the mornings that we are probably just going to have to put up with wiping away the dribbles each day. :lol:

 

It's possible that by double glazing you have insulated window frames from inner heat and reduced their temp thereby conducting heat from the surrounding walls. We have been very successful with our setup but it must be said I made sure that all spaces round edges of brass ports were well insulated with injected foam and, to make sure, I painted any exposed brass with anti condensation paint + brass ports don't come into contact with inner wall. DG isn't a cure all, it needs to be backed up with proper insulation. As regards ventilating versus sealing the air gap, sealing is much better from an insulation angle but the prob can be moisture trapped which has to be removed or captured, some use silica gel but at some point the gel has to be dried out so this has to be convenient. IMO if gap is ventilated then a large air gap is preferable as it gives better insulation, sealed is better with smaller gap as it reduces amount of moisture needing to be absorbed?

 

Also we have venetian blinds between the panes of glass which allows inner glass to stay warmer than it would if curtains were in front of it, as an experiment you could try leaving your curtains or blinds open somewhere and see if condensation is reduced.

 

Edited to add we never let fire go out unless of course we leave boat for several days or more. By leaving fire in the whole boat structure including actual insulation and metal hull is kept warmer so minimising temp differential which is cause of condensation

Edited by nb Innisfree
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I fitted double glazed units throughout. Wouldn't be without it. Warmer, quieter and condensation on the frames only on the coldest mornings. Even then, only wipe the bottom nearest the wood, as the rest dries before it travesl far enoiugh to do any harm.

 

Decided on a version that has the whole of the central section lifitng out - great for cleaning, escape and selling icecream to passers by in the summer!

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  • 2 weeks later...
  • 2 years later...

I have been thinking of secondary glazing and wondered about the protruding part of the top hopper. I came up with the same idea cut the protruding end off and use a file to make it neat then perhaps have the acrylic cut and put in a piano hinge so you can open the secondary glazing to get to the hopper to allow for better ventilation on warmer winter days.

Would it work ?

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I have been thinking of secondary glazing and wondered about the protruding part of the top hopper. I came up with the same idea cut the protruding end off and use a file to make it neat then perhaps have the acrylic cut and put in a piano hinge so you can open the secondary glazing to get to the hopper to allow for better ventilation on warmer winter days.

Would it work ?

 

might be as easy to just move the sdg down an inch or two on its magnetic strip.

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As others have said, reducing heat loss is great, but it doesn't deal with the problem of excessive humidity, which will cause condensation somewhere, probably where you can't see it.

 

To reduce excessive humidity, there are three main possibilities:

 

One: Light the stove. This will draw cold, relatively dry, air in from outside through whatever ventilation ports you have, and works well. The only problem is that with effective double glazing you don't need the stove so much.

 

Two: If on mains power, use a dehumidifier. These work very well, but (like generators!) are not as quiet as they are claimed to be, and of course they use power.

 

Three: Open some windows to increase ventilation. This also works well, but isn't a popular option in winter.

 

There is, of course, another option, and that is to move off the boat, because cooking, drying clothes, and breathing are the things that cause excessive humidity in the first place.

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  • 4 years later...

I have aluminium rectangle windows fortunately no curves my solution was to remove the top opening window catches and brackets i think it was refereed to as "protruding part of the top hopper" earlier, these were easily removed simply prising them off the rivets with a flat screw driver. i then sealed the top window shut and fitted some made to measure sealed units (no frame just glass) in the recess, sealing them with silicon and small non obtrusive brackets finally replacing the wooden framing, looks superb better than before in my opinion.

 

The sealed units are k glass and argon filled, boat stays so much warmer, no condensation inside however i do get condensation on the original glass, I plan to remove the sealed units on a hot summers day clean the original glass better (was short on time) refit the DG units and seal off the original windows drainage vents, the theory being that warm air will not hold moisture so once the gap is sealed the warm/dry air is trapped no more condensation.

I have left the middle two windows (kitchen area) as original as well as the Bow window and bathroom window so i can still have ventilation, interesting these windows no longer get condensation not real sure why not as they were bad before.

 

I am hoping that the K glass and argon gas will help keep the boat much cooler in summer.

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  • 1 year later...

For those using the film, do you just fit it to the inside of the wooden frames (ie several inches from the existing glass)? Probably should have got around to this earlier, but now it's gone cold there's clearly a lot of heat loss from the windows which I'd like to reduce to get a warmer boat without spending a fortune on gas and it looks like I can get supplies in local shops tomorrow (the only issue is I don't own a hairdryer so might have to buy one just to do this!) I'm thinking I'll probably go the acrylic route longer term but a quick cheap fix would be good for now.

 

Old thread I know, but I'm guessing lots of contributors or others doing this are still around.

 

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Yes, just do it on the wooden frames. If you try to do it on the aluminum window frames it will probably end up sticking to the windows.

 

I'm sure there must be cheap hairdryers on eBay or perhaps ask a friend if you can borrow one. 

Edited by blackrose
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  • 2 weeks later...

It's an old topic, but think it's worthwhile sharing my experience.  I have just fitted secondary 4mm acrylic DG using self adhesive magnetic strip 19mm. I have no association with the companies mentioned.  I bought the mag tape from https://www.first4magnets.com/tape-strip-c85/magflex-19mm-wide-flexible-magnetic-tape-premium-self-adhesive-p3526#ab_1-16|ps_2-1789 and the pre-cut acrylic from https://www.livsupplies.co.uk/product_list_poly.php?id=20. My windows are inward hoppers and as such i had to trim the stay so that it didn't protrude beyond the rectangular wooden frame. I found that the easiest way to do this was to saw through the angled bit and then heavily score the flat part. Then using two pairs of pliers the aluminium can be fatigued along the score line by bending back and forth until breakage occurred the finally smoothed with file. The next step was to fit the mag strip all round the edge of the acrylic . On the first unit I did, I mitred the corners but on subsequent units I left the joints square - easier to get a closer join. Once the mag tape had been stuck to the acrylic, I cut duplicate pieces and magnetically attached them to the strips previously stuck to the acrylic. NB the tape I used was self-mating and will only match if the tapes are in the correct polarity - if you use mitred corners, make sure it's the correct way round, if cutting square then it doesn't matter as you can simply reverse it.  

 

Now i I made my first mistake doh. I attached the pre-cut duplicates to the window frame - big mistake. The problem is that with sel-mating tape the two pieces have to match perfectly for the magnets to stick together. Even a couple of millimetres out and the magnets won't stick, as I discovered.  Luckily, I hadn't stuck the tape to the frame firmly and pulled the bottom and side strips off without losing too much of their adhesion. I then replaced the removed pieces onto the acrylic. I then positioned the sheet such that the top strips mated correctly and then simply pushed the sheet firmly round the edges into place. On subsequent units, I left the tapes on the acrylic, removed the glue protection on the top tape, positioned the sheet and pressed the top tape onto the frame and then removed the glue protection from the side and bottom tape and pushed all the perimeter firmly onto the frame. Perfect. 

 

Total cost for 6 Windows around £150. 

 

I have labelled the units so that they can go back onto the same window, although it shouldn't really matter if all the tapes have been fitted perfectly in the first place. Another point to note is to ensure your frames are clean and smooth before finally pressing the units in place.  

 

Hope me this helps others to not repeat my mistakes.

  • Greenie 1
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A good thread to revive at this time of year.  I've been considering secondary DG having seen the cost of replacing my Webster windows with DG units!  Might well try out using magnetic tape as described here.

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I'm wondering if anybody has worked out fitting perspex sheets inside the wooden frames (I saw it suggested on a similar thread)? ISTM that would be better than the magnetic mount to the outside of the wooden frames - no protrusion from the wooden frame (my curtains run between that and a metal rod and making that gap smaller wouldn't be good) and a smaller gap between the panes which should provide far better insulation properties.

 

My thoughts at the moment are to get the perspex sheets cut to a fairly close fit inside the frame and attach some sort of flexible sealing strip to the outer edges. Use some small bits of magnetic strip to attach the sheets to the metal window frames (though not trying to seal there, I reckon the seal should be between the perspex sheet and the wooden frame to avoid heat loss around the edges of the windows). Clearly I'd need to remove the hoppers, but mine are held on by screws and I could remove them from each window in a minute or two - would only add 15 minutes to the job for the boat.

 

Any thoughts on what to use to seal around the edges would be welcome.

Edited by aracer
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