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1463 posts

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  #797126 10-Apr-2013 13:05
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Yip I was aware - I was more thinking about using it as an experiement to try and identify the actual cause of why condensation was forming on the windows without introducing the cost of a commercial product.

It may be that a temporary solution might be thermal drapes with a retrofit double glaze may be a land-lord friendly way of solving the problem. But before the solution one needs to be certain of the cause I think.





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  #797128 10-Apr-2013 13:08
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stuzzo: L
Elpie: One thing nobody has mentioned - don't over-insulate old houses. It's easy to think that more insulation = more warmth however houses also need to breathe and old houses can have some serious moisture problems if their ventilation is changed. 

 



What is your reasoning behind this? Houses don't have lungs, they don't need to breathe. Old houses generally have similar basic construction to the most common modern construction.

Insulating walls will make the cladding cooler and therefore a bit wetter but as long as the correct methods are used it is fine. In NZ type climates the greatest moisture infiltration danger to walls is from the exterior anyway.


From BRANZ:
"Sources of moisture within a wall cavity may include: external water passing through a porous envelope (eg rain on brick veneer); external moisture entering around openings (eg a defective or ineffective window flashing); moisture generated within the building (eg clothes drying or cooking); or moisture rising from inadequately ventilated subfloor space where the ground is poorly drained.

Moisture transfer into and out of walls occurs in a variety of ways through the movement of liquid water and water vapour or from diffusion through building materials. The amount of water that transfers through a wall via these different mechanisms will vary with different types of construction. Moisture transfer through walls is not, in itself, a problem, but it can be problematic when drying and ventilation is inadequate to remove moisture and moisture accumulates inside walls, providing suitable conditions for fungal growth.

Potential problems with fungal growth inside walls are
  1. timber decay, which reduces the strength of framing and other wall components, and
  2. production of mycotoxins, which are deleterious/harmful to human health.
There has been a substantial amount of effort to develop robust ‘weathertight’ designs for new houses, but little guidance is available when altering existing houses. Timber treatments and drainage cavities that are usual in new houses are often not present in older houses making them more vulnerable to fungal growth and the problems that arise from this. "
http://www.dbh.govt.nz/retrofitting-insulation-guidance#aid4

I wasn't able to get a building permit for wall insulation because the local council has seen a number of older houses develop problems due to insulation. It has also been confirmed that by using very high rated ceiling insulation it changed the house's ventilation transfer. A vent had to be added under the eaves to add ventilation into the ceiling space.

 
 
 
 


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  #797152 10-Apr-2013 13:47
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Elpie:
stuzzo: L
Elpie: One thing nobody has mentioned - don't over-insulate old houses. It's easy to think that more insulation = more warmth however houses also need to breathe and old houses can have some serious moisture problems if their ventilation is changed. 

 



What is your reasoning behind this? Houses don't have lungs, they don't need to breathe. Old houses generally have similar basic construction to the most common modern construction.

Insulating walls will make the cladding cooler and therefore a bit wetter but as long as the correct methods are used it is fine. In NZ type climates the greatest moisture infiltration danger to walls is from the exterior anyway.


From BRANZ:
"Sources of moisture within a wall cavity may include: external water passing through a porous envelope (eg rain on brick veneer); external moisture entering around openings (eg a defective or ineffective window flashing); moisture generated within the building (eg clothes drying or cooking); or moisture rising from inadequately ventilated subfloor space where the ground is poorly drained.

Moisture transfer into and out of walls occurs in a variety of ways through the movement of liquid water and water vapour or from diffusion through building materials. The amount of water that transfers through a wall via these different mechanisms will vary with different types of construction. Moisture transfer through walls is not, in itself, a problem, but it can be problematic when drying and ventilation is inadequate to remove moisture and moisture accumulates inside walls, providing suitable conditions for fungal growth.

Potential problems with fungal growth inside walls are
  1. timber decay, which reduces the strength of framing and other wall components, and
  2. production of mycotoxins, which are deleterious/harmful to human health.
There has been a substantial amount of effort to develop robust ‘weathertight’ designs for new houses, but little guidance is available when altering existing houses. Timber treatments and drainage cavities that are usual in new houses are often not present in older houses making them more vulnerable to fungal growth and the problems that arise from this. "
http://www.dbh.govt.nz/retrofitting-insulation-guidance#aid4

I wasn't able to get a building permit for wall insulation because the local council has seen a number of older houses develop problems due to insulation. It has also been confirmed that by using very high rated ceiling insulation it changed the house's ventilation transfer. A vent had to be added under the eaves to add ventilation into the ceiling space.


The only circumstance where they might be likely to decline a wall insulation request would be something like brick veneer where the insulation would be likely to interfere with the drainage plain. In other cases, where you make an alteration you are generally required to bring the area up to current standards which might require adding building paper or other moisture barrier.

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  #797220 10-Apr-2013 15:55
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Can anyone attest to whether or not DIY window insulation film works for keeping the house warmer and/or reducing condensation?

http://www.energywise.govt.nz/content/diy-window-insulation-film




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  #797228 10-Apr-2013 16:17
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I've got a friend who's a master builder. I'm going to get some advice from him before I insulate our two bedrooms' outside facing walls.




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  #797252 10-Apr-2013 16:56
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lokhor: Can anyone attest to whether or not DIY window insulation film works for keeping the house warmer and/or reducing condensation?

http://www.energywise.govt.nz/content/diy-window-insulation-film


It does reduce condensation a lot, not as much as better stuff but it reduces it. Beware of pulling all the paint off your windows and not getting the glue off - I had to sand and repaint my windows afterward. I have some spare in Wellington, I mentioned it before, I have to count the boxes.

Retrofit double glazing with perspex is more effective, around $4K - $8K for an average home.

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  #797302 10-Apr-2013 18:23
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lokhor: Can anyone attest to whether or not DIY window insulation film works for keeping the house warmer and/or reducing condensation?

http://www.energywise.govt.nz/content/diy-window-insulation-film


Yes it helps.  I've made my own with Mylar film.  Only a little bit of condensation along the edge of the window glass where air leaks in.  Not perfect, but helped lots.  I'm in Auckland, in your colder climate it might not be so effective.




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  #797475 10-Apr-2013 22:28
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lokhor: Can anyone attest to whether or not DIY window insulation film works for keeping the house warmer and/or reducing condensation?

http://www.energywise.govt.nz/content/diy-window-insulation-film


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http://www.geekzone.co.nz/forums.asp?forumid=48&topicid=64936&page_no=3




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  #797577 11-Apr-2013 09:26
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lokhor: Can anyone attest to whether or not DIY window insulation film works for keeping the house warmer and/or reducing condensation?

http://www.energywise.govt.nz/content/diy-window-insulation-film


Someone at work, an architect suggested putting the insulation (in this case polystyrene sheeting) on the outside of the windows not the inside. He explained that the dew point (where the moisture vapour condenses out, should then be outside the house not inside so any condensation should occur ouside

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  #797580 11-Apr-2013 09:37
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leo0787sx:
lokhor: Can anyone attest to whether or not DIY window insulation film works for keeping the house warmer and/or reducing condensation?

http://www.energywise.govt.nz/content/diy-window-insulation-film


Someone at work, an architect suggested putting the insulation (in this case polystyrene sheeting) on the outside of the windows not the inside. He explained that the dew point (where the moisture vapour condenses out, should then be outside the house not inside so any condensation should occur ouside


The film is fragile, wind and rain will easily tear it.

Polystyrene doesn't let a lot of light through... do you mean the clear plastic sheeting? I have that on the inside of my windows, it works well.

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  #797590 11-Apr-2013 09:42
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leo0787sx:
lokhor: Can anyone attest to whether or not DIY window insulation film works for keeping the house warmer and/or reducing condensation?

http://www.energywise.govt.nz/content/diy-window-insulation-film


Someone at work, an architect suggested putting the insulation (in this case polystyrene sheeting) on the outside of the windows not the inside. He explained that the dew point (where the moisture vapour condenses out, should then be outside the house not inside so any condensation should occur ouside


From a theoretical standpoint this might be correct,

But one be issue will be durability, A glass window is much more resilient to rain and wind (and other weather conditions) A plastic sheet is much more likely to be damaged, detached etc on the outside than if it is on the inside, 

It is also likely to be noisy in winds.......

and it makes you house look like something out of some disaster movie :)

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  #797595 11-Apr-2013 09:51
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I put mine on the outside, as that is where I could get the appropriate air gap based on the shape profile of the aluminium window. The tape lasts a winter and I use thicker plastic sheeting that won't tear etc.

I'll be doing this again this year as the results are just too good to not do it. I take them down over winter. Cosmetically it's not great, but I use white PVC tape from the warehouse and have white window frames, so it's really not as bad as some would envisage.

As per the other thread on DIY secondary glazing, it will simply only work if you heat the glass to a point where condensation won't form. If you put this in a room with no heating on, the glass will never warm up and you will still get condensation. So, double glazing won't do anything to reduce condensation unless you are heating the room. Don't expect unheated spare bedrooms to be condensation free just because they have double glazing.

Also, obviously you're not removing any moisture here, just warming windows to the point where they don't cool the moisture laden air enough for condensation to form...

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  #797742 11-Apr-2013 13:07
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Jaxson: As per the other thread on DIY secondary glazing, it will simply only work if you heat the glass to a point where condensation won't form. If you put this in a room with no heating on, the glass will never warm up and you will still get condensation. So, double glazing won't do anything to reduce condensation unless you are heating the room. Don't expect unheated spare bedrooms to be condensation free just because they have double glazing.

Also, obviously you're not removing any moisture here, just warming windows to the point where they don't cool the moisture laden air enough for condensation to form...


It's not really about the internal temperature, that will only have a small effect. The temperature in a cold house will still be much above the outside temperature at the cold times.

The key thing is the air seal on the double/secondary glazing. It is denying moisture from being able to migrate into the window as condensation starts to form. There is not enough moisture in a sealed double glazed window for condensation to form but when the seal fails that's when it does.

Leo: your architect friend is off the track in the suggestion to put the secondary glazing on the outside, it doesn't change the geometry at all but exposes the outer-most surface to an even lower temperature. If you assume that the seal is not going to be good then the lower humidity might help but is likely counterbalanced by the lower surface temperature. In European houses the windows tend to be set back behind the line of with the insulation (called inners) where it is warmer as oppose to what has tended to be our standard build here (outers).

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  #797754 11-Apr-2013 13:19
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stuzzo:
It's not really about the internal temperature, that will only have a small effect. The temperature in a cold house will still be much above the outside temperature at the cold times.

The key thing is the air seal on the double/secondary glazing. It is denying moisture from being able to migrate into the window as condensation starts to form. There is not enough moisture in a sealed double glazed window for condensation to form but when the seal fails that's when it does.



Sorry mate, but that's just not the complete picture there.  Condensation will form most where you've got a cold surface and heavily moisture laden air.  The internal temperature of the room has a significant effect on the temperature of the internal most pane of glass.

Not all double glazing is filled with fully sealed air cavities, or a vacuum, or an inert gas etc.  Yes you can get condensation forming within the cavity, but the air most laden with moisture is going to be the air in the bedroom, more so than the air in the cavity.

Reducing moisture on windows specifically revolves around having the temperature of the inside pane of glass sufficiently warm enough as not to condense the moisture in the air upon contact with it.  You achieve this by heating the room, which could quite easily be 10 - 16 degrees in winter if not heated.  (For example a lot of people don't heat the room at night, but instead use an electric blanket).  In this case, you will get condensation on the windows, regardless of whether they are double glazed or not, as you have done nothing to heat the glass.

Of course, removing the moisture in the first place will also help, but my comments referred specifically to DIY double glazing.

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  #797756 11-Apr-2013 13:23
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I have retrofit double glazing. It's a sheet of 3mm thick plastic on the inside of the windows. The gap between the plastic and the window isn't fully sealed, but air movement would be slow.

I get tiny bit of condensation on the glass, and a little more on the plastic. On really cold nights, with the bedroom door closed, the interior plastic needs a light wipe with a small towel, but that's not all the time, and it's light enough it'd evaporate away especially with the DVS running during the day.

Compare that with the previous situation where you could just about path a child with the puddles on the window sills. Well, maybe not quite that much, but it fully soaked a full size bath towel wiping the windows before I had double glazing.

My point: even though it's not fully sealed, it works pretty well.

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