Retro-fitted double glazing?

[mashman]

Libra?????

I am yes...

[flyingcrocodile46]

I'm on the super absorbent pads atm... toilet is the next step

Sounds like you need to monitor the temperature and humidity in all of the rooms of your house for a few weeks to try to identify what is going on. Get yourself a dozen cheap weather stations

[mashman]

Sounds like you need to monitor the temperature and humidity in all of the rooms of your house for a few weeks to try to identify what is going on. Get yourself a dozen cheap weather stations

I did that in the last place with thermometers and there was one room that didn't retain much in the way of heat. Probably the only room that never got any sun... enough of an issue that we had a guy in with a thermal camera to give the place the once over. Nothing showed up... praps it's time to do it again with sommet that deals with humidity too. Pretty sure it's the windows though.

[flyingcrocodile46]

I did that in the last place with thermometers and there was one room that didn't retain much in the way of heat. Probably the only room that never got any sun... enough of an issue that we had a guy in with a thermal camera to give the place the once over. Nothing showed up... praps it's time to do it again with sommet that deals with humidity too. Pretty sure it's the windows though.

The windows will collect (or show) the condensation and may be contributing by way of being poorly insulated (via thermal bridging of the frames) but they do not cause the elevated moisture vapour content that is the primary problem. So, you have two problems. 1. poorly functioning/quality double glazed windows (it does happen) and 2. an excess of and/or poor management of moisture vapour.

Is your house single level, split level, or two story? What sort of roof construction is it? Do you shut the windows when you go to bed at night? which rooms/windows show the most and least amount of condensation? Is the veneer strandboard on th einside faces of all the exterior walls? What sort of ceiling lining do you have? What sort of sealer/paint/polyurethane was used on the veneer (does it breathe and allow moisture vapour to pass through?), What sort of wall wrap was used? The permeability of walls and cladding plays a really big part in moisture vapour control. You should replace your dehumidifier with one that is known to work well and leave it overnight in each room (one at a time) and monitor the condensation results. I'm thinking that maybe the walls of your house aren't breathing properly and elevated moisture vapour is the result.???

Your breathing is a big part of the condensation production process. Your breath has an RH of 95% at 35 degrees (rapidly elevating the RH of the colder surrounding air) and adds about 1 litres of water to the air for each person (when at rest) A lot more when your wife wears her strap on. Does your dehumidifier keep up with the occupants overnight moisture vapour production? Is there any capacity left over to address the production from cooking, washing, ironing, exercising etc?

To help figure out what part the windows have to play, you could find other home owners with the same joinery and see what experiences they are having? If you are all experiencing the same thing and the manufacturer installed the windows, you probably (time dependent) have a potential claim against them.

[Maki]

The windows will collect (or show) the condensation and may be contributing by way of being poorly insulated (via thermal bridging of the frames) but they do not cause the elevated moisture vapour content that is the primary problem. So, you have two problems. 1. poorly functioning/quality double glazed windows (it does happen) and 2. an excess of and/or poor management of moisture vapour.

To help figure out what part the windows have to play, you could find other home owners with the same joinery and see what experiences they are having? If you are all experiencing the same thing and the manufacturer installed the windows, you probably (time dependent) have a potential claim against them.

The primary problem, as you say is the elevated moisture vapor content. If there is a problem with the double glazed windows, then symptoms such as condensation between the panes should soon become apparent. (As long as the space between the panes is sealed the double glazed windows must be functioning correctly). If this does not appear it is unlikely that there is any problem with the windows.

[SPman]

Retrofitting d/g windows....an interesting discussion here http://forums.energymatters.com.au/a...topic2411.html
however - we also have heat exclusion considerations more to the fore over here....

[BMWST?]

if you have a moisture problem,you must find the cause of it and or ventilate.Ventilation is the only way to drive out the excess moisture that occurs from living indoors.If you have a newish house you need to ensure you do ventilate.We have an older house with single pane windows.One half of the house gets very good sun,the other half gets poor sun and is fairly close to a bank.We used to have really bad condensation in the winter.We got a DVS type system,the obe that pulls the warm air form the roof space and blows it into the house,slightly pressurizing it.The air in the house is therefore constantly changed with air form the outside,warmed in the hot roof space,pumped intot he house,where it forces the old damp air out,and drys everything because it is very dry air.Thwe installed it last year in the middle of winter.That morning the window glass was running with consednsation,the next morning there was a little the next morning NONE.We get a little condensation on the windows if the night has been quite cold.A dvs system wont work in a very new house unless there is actually a way out for the "old" air.New houses are airtight compared to a house built in the 1950-through to at least the late 90s.

[steve_t]

^ PPV - positive pressure ventilation. I'm told it's much more effective than the old extractor fan dealy. Croc?

[flyingcrocodile46]

The primary problem, as you say is the elevated moisture vapor content. If there is a problem with the double glazed windows, then symptoms such as condensation between the panes should soon become apparent. (As long as the space between the panes is sealed the double glazed windows must be functioning correctly). If this does not appear it is unlikely that there is any problem with the windows.

Is the condensation between the two panes of glass or on the inside face of glass? I just assumed it was the inside face and figured that the thermal bridging through the frame was likely causing heat loss from the glass itself (through contact with the frame) and that the condensation then formed on the cooler glass.

In any event, yes the RH of the air is most likely the bigger part of the problem. The RH in Kiwi homes is higher than the international average (climate driven) and rises to over 90% during sleeping cycles. The more I think about it the more convinced I am becoming that it is predominantly an RH problem (rather than a glazing problem)

Condensation will readily form on the windows in a well heated house following a sleep period when the RH rises to around the 90% mark. For instance a constant heat of 18 degrees with an outside temperature only 1.5 degrees less (16.5 degrees) will result in the dew point being reached with an RH of 91%. That is to say a 1.5 degree temperature difference is enough to trigger condensation when the relative humidity passes 90%

[flyingcrocodile46]

if you have a moisture problem,you must find the cause of it and or ventilate.Ventilation is the only way to drive out the excess moisture that occurs from living indoors.If you have a newish house you need to ensure you do ventilate.We have an older house with single pane windows.One half of the house gets very good sun,the other half gets poor sun and is fairly close to a bank.We used to have really bad condensation in the winter.We got a DVS type system,the obe that pulls the warm air form the roof space and blows it into the house,slightly pressurizing it.The air in the house is therefore constantly changed with air form the outside,warmed in the hot roof space,pumped intot he house,where it forces the old damp air out,and drys everything because it is very dry air.Thwe installed it last year in the middle of winter.That morning the window glass was running with consednsation,the next morning there was a little the next morning NONE.We get a little condensation on the windows if the night has been quite cold.A dvs system wont work in a very new house unless there is actually a way out for the "old" air.New houses are airtight compared to a house built in the 1950-through to at least the late 90s.

^ PPV - positive pressure ventilation. I'm told it's much more effective than the old extractor fan dealy. Croc?

Got to duck out but I will comment on this issue as it is not straight forward and yes and no answers will vary greatly depending on the project specifics but I will say this. The RH in roof spaces at different times of the day for different construction types are much higher than within the house. This means that in some instances at least part of the time you may be making things worse by using that air.

[Maki]

Is the condensation between the two panes of glass or on the inside face of glass? I just assumed it was the inside face and figured that the thermal bridging through the frame was likely causing heat loss from the glass itself (through contact with the frame) and that the condensation then formed on the cooler glass.

In any event, yes the RH of the air is most likely the bigger part of the problem. The RH in Kiwi homes is higher than the international average (climate driven) and rises to over 90% during sleeping cycles. The more I think about it the more convinced I am becoming that it is predominantly an RH problem (rather than a glazing problem)

Condensation will readily form on the windows in a well heated house following a sleep period when the RH rises to around the 90% mark. For instance a constant heat of 18 degrees with an outside temperature only 1.5 degrees less (16.5 degrees) will result in the dew point being reached with an RH of 91%. That is to say a 1.5 degree temperature difference is enough to trigger condensation when the relative humidity passes 90%

If there is condensation between the panes, the so called IGU (insulated glass unit) is defective and should be replaced, at least if it is still under manufacturer's warranty. Condensation on the inside face, not between the panes, is caused by a low surface temperature and a high dew point and as you say, the low surface temperature is often caused by thermal bridging. I have this issue in my house since the IGU's were installed in pre existing non thermally broken alu joinery and there is sometimes some condensation on the alu frames and the part of the window that is near the frame (cooled down by the frame). I am nevertheless happy with the job since it has made our house much warmer. I understood all this before the work was done and I was happy to accept this compromise to save on cost and the inconvenience of having to have our existing joinery replaced.

I am sure RH is the bigger part of the problem. RH around the 90% mark is not healthy at all and it needs to be lowered some way.

If you have IGUs outside the warranty period and start to see condensation between the panes, do not panic. All is not lost. There could be a lot of life left in the units and they may not have to be replaced for years to come. The solution is to drill small holes in the inner glass near opposite corners of the inner window pane, one near each corner (a total of two holes). This will ventilate the space between the panes and should get rid of the condensation. Of course the fact that the air between the panes is now slightly ventilated will reduce the performance of the IGU units but they will nevertheless still be far superior to single glazed windows.

Before we changed to double glazing we had the insulation in our roof upgraded. We noticed almost no difference from that but the double glazing which is admittedly MUCH more expensive has made a huge difference.

[Ocean1]

Condensation will readily form on the windows in a well heated house following a sleep period when the RH rises to around the 90% mark. For instance a constant heat of 18 degrees with an outside temperature only 1.5 degrees less (16.5 degrees) will result in the dew point being reached with an RH of 91%. That is to say a 1.5 degree temperature difference is enough to trigger condensation when the relative humidity passes 90%

Yes. Assuming you want to maintain a comfortable temperature then managing condensation means either drying the air in the house or swapping it for the drier air outside. I see the trend towards more airtight homes in an attempt to manage temperature as the single biggest driver of condensation issues. Considering that a high percentage of the water that comes into the house through your various taps ends up in the interior atmosphere it shouldn't really come as any surprise that it takes some sort of mechanism to manage it. Not saying we all need to revert to shiplapped weatherboard, but provision for detailed ventilation control should be a given for any new build.

Heat pumps are a reasonable choice in that they can control both RH and temperature OK for most applications. However, there's other problems that come with over-airtight homes that mean there's a minimum realistic through-flow required. I bought this house, which came with a hugeous fuckoff solid fuel burner and a DVS system, (two, actually) which is set to manage airflow at the minimum required to stop condensation. It works, if I turn it off we get condensation in the kitchen and bedroom at night, turn it on and set it to just above minimum flow and we get none. The roof cavity is vented, so we're essentially pulling air from outside. Given the price and capacity of the heating system I really don't care that I have to heat that small amount of fresh air.

Also, while it's not double glazed the alloy joinery is of a better quality than anything else I've seen in a domestic application, and it has particularly cute adjustable vents built into the lower rail. So if I notice any hint of condensation in a particular corner I just open that vent a tad more. So while I didn't spec' this place I'm nevertheless pleased that someone who knew their shit did.

[Ocean1]

The solution is to drill small holes in the inner glass near opposite corners of the inner window pane, one near each corner (a total of two holes). This will ventilate the space between the panes and should get rid of the condensation. Of course the fact that the air between the panes is now slightly ventilated will reduce the performance of the IGU units but they will nevertheless still be far superior to single glazed windows.

You could also take the units out of the frames, cut out most of the perimeter sealant, re-stuff the seperator with dessicant and re-seal them. It's not that difficult, but you do need to know what the original sealant was.

[Maki]

You could also take the units out of the frames, cut out most of the perimeter sealant, re-stuff the seperator with dessicant and re-seal them. It's not that difficult, but you do need to know what the original sealant was.

Not that difficult, cough cough... I have 30 IGUs in my house, some are quite large. I just don't see myself doing what you described 10 years from now...

[flyingcrocodile46]

Yes. Assuming you want to maintain a comfortable temperature then managing condensation means either drying the air in the house or swapping it for the drier air outside. I see the trend towards more airtight homes in an attempt to manage temperature as the single biggest driver of condensation issues. Considering that a high percentage of the water that comes into the house through your various taps ends up in the interior atmosphere it shouldn't really come as any surprise that it takes some sort of mechanism to manage it. Not saying we all need to revert to shiplapped weatherboard, but provision for detailed ventilation control should be a given for any new build.

Heat pumps are a reasonable choice in that they can control both RH and temperature OK for most applications. However, there's other problems that come with over-airtight homes that mean there's a minimum realistic through-flow required. I bought this house, which came with a hugeous fuckoff solid fuel burner and a DVS system, (two, actually) which is set to manage airflow at the minimum required to stop condensation. It works, if I turn it off we get condensation in the kitchen and bedroom at night, turn it on and set it to just above minimum flow and we get none. The roof cavity is vented, so we're essentially pulling air from outside. Given the price and capacity of the heating system I really don't care that I have to heat that small amount of fresh air.

Also, while it's not double glazed the alloy joinery is of a better quality than anything else I've seen in a domestic application, and it has particularly cute adjustable vents built into the lower rail. So if I notice any hint of condensation in a particular corner I just open that vent a tad more. So while I didn't spec' this place I'm nevertheless pleased that someone who knew their shit did.

Good to hear you have a good one. Yes to the window vents (they should be compulsory).


Yes it pays to know what you are doing when you build a new air tight type home. Mashman says his wall lining is strandboard or particle board with a veneer on it. If he has sealed it with a waterproof clear coat of some type, the normal (healthy) diffusion process will be prevented and the RH will be all the higher for it. A good design needs to incorporate materials and coatings that have high moisture vapour permeability to allow natural diffusion of the moisture vapour toward the cold exterior and a slightly less permeable exterior cladding/wrap. This is often not considered in new home design and will not be helping with window condensation problems. There is a company marketing wraps with different properties (for inside and outside) that act a bit like one way valves, allowing moisture vapour easy egress and restricted ingress. I am not yet convinced that it is necessary or practical to use these products as their installation requirements and the cost of the product are quite onerous.

Further on the RH contribution i just checked and see that at 18 degrees and 70% RH the glass temperature has to drop to 12.5 degrees (rather than 16.5 degrees at 91% RH) before the dew point (condensation) will be triggered.