cavity wall insulation

My house is 1964 built, and I get a lot of condensation on the windows, even with 22mm double-glazing, and on the north facing side even the walls feel damp at times. The north windows are big, about 8 by 4 feet. Would cavity wall insulation help at all, or is this condensation due mainly to the size of the windows, and perhaps the quality of the UPVC window frames? I suspect, that concrete lintels don't help either. Any advice on whether cavity wall insulation is worth it, and what type to use, would be most welcome.
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It will be worth it in your case. The small balls is the best. Make sure they inert the glue to bend them together. the gaps between the balls creates the insulation. They are also waterproof, so no getting wet.
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On 19 Oct 2003 01:12:37 -0700, snipped-for-privacy@whsmithnet.co.uk (StephenC) wrote:

That's interesting - I was always under the impression that condensation doesn't happen with double glazing. I guess that was a wrong assumption on my part.
PoP
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PoP wrote:

Double glazing is only 2-3 tmes beter than single.
However I suspect that in this case there may be eiher too much damp in the house, or not enough ventilation, or heat.

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"PoP" wrote | That's interesting - I was always under the impression that | condensation doesn't happen with double glazing. I guess that | was a wrong assumption on my part.
I've seen condensation frozen to ice on the inside of double glazing, both modern 'sealed unit' and secondary glazing. I mean on the room side, not between the layers.
Owain
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Insulation may improve things a little, but you will still be producing the moisture that is causing the condensation - and this is not going to go away just because insulation is fitted.
Facing north, with a that elevation being nearly always cooler than the rest of the house does not help either.
Condensation reduction will require you to assess the ventilation and heating of the propery and your usage patterns. There are numerous threads on this. Your description of a lot of condensation on double glazing would indicate that the use of heating in those rooms may need to be altered, and perhaps air extraction improved in other parts of the property.
Dry lining with a thermal board ( plasterboards with minimum 25mm insulation backing) would be better for individually affected rooms on the north face as this denies a cold concrete surface to the moist air..
Insulation will help retain heat, but its hard to say if this is enough on its own. If the insulation is retaining humid air, then condensation will remain.
One solution (which may not apply to you) would be to spend the money that insulation would cost on a new condensing boiler. This will allow you to heat the house more efficiently and cheaper than a traditional boiler, at little or no additional cost. This will give you a warmer house and could solve the condensation problem. This assumes that you are not currently keeping the house at a constant even temperature with your existing heating system.
dg

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It may go away as the temperature of the room rises.

Vent and heating has to be looked at.

But you will need a vapour barrier to prevent condensation occuring behind the plasterboard. Also plasterboard eliminates the thermal mass of the wall behind.

Then a vent problem as well.

First Insulation, then heating and ventilation. Suggesting a condensing boiler is bordering ludicrous in this situation. I would cavity wall insulate as it will reduce/eliminate condensation, keeping the cold outside wall away from any moisture inside, keep the house cool in summer too, and keep heating bills right down. Also look at the ventilation and heating aspects.
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If you have a heating system that you don't use constantly ( perhaps due to cost) or is not effective in keeping the property at a constant temperature, then by changing the boiler to one that is cheaper to run will mean that you do use it more often, and thus it keeps the property temperature constant.
We have many tenants/clients that still use their central heating systems for limited periods for fear of costs. If you stop start your heating, then you are allowing the moist air to condense. If you keep a constant temperature by using the heating when you are out, then this can effectively reduce/prevent condensation.
If you provide the means to heat the property constantly for little extra cost, then it is used, and this can be the only solution you need.
Insulation will not keep a room warm if the room is not heated effectively in the first place.
Thermal mass and keeping the property cool in summer are factors with little practical effect in the average domestic property.
By insulating the internal surface, you deny a cold surface for air to condense on, and you still get the thrermal qualities of the wall behind. If you insulate the cavity, then you can not be sure that the colder internal wall surface will have a sufficiently lower dew point to prevent condensation.
Again, these are options, not solutions outright.
You can not advocate that insulating the cavity will be THE solution, as there are too many possibilities of which it is merely one.
The OP would have to ask why it is that his north facing uninsulated property gets so much condensation, and similar north facing uninsulated property do not?
Condensation is a result of the occupiers USE of the property, and is not caused by the property itself.
dg

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Stephen
If your house is block inner skin and brick outer skin with a clean cavity then cavity insulation is probably the best way to improve the insulation of your house and save on fuel bills. I recommend blown mineral fibre. However this will if anything make your condensation problem worse. Condensation will always occur on the coldest surface. The most likely problems are either excessive moisture creation or poor ventilation. There is good advice on reducing condensation on a number of websites including the NHBC.
Edrich
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