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Condensation and 3G windows


Russdl

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On the last two mornings where its been pretty cold outside I've found a small amount of condensation on the insides of some of our triple glazed windows, I promised the good lady this would never happen!!

 

The house is built to passive standard, has good airtightness and MVHR. Should I be getting condensation on the insides of the windows, and if not, what is going wrong?

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2 minutes ago, IanR said:

I've not experienced condensation on the inside in 4.5 years.

 

I thought I was going to hear that ?

 

The house is currently around 20° and the humidity is around 63% (a degree/percent or two different in different rooms) 

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I got condensation these last two mornings (frosty weather) but I only have double glazing in wooden windows, I run the upstairs cooler than downstairs, I did ramp up the MVHR a bit last night but it made no difference.

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14 minutes ago, Russdl said:

The house is currently around 20° and the humidity is around 63% (a degree/percent or two different in different rooms) 

 

If those are the conditions when condensation appears, it would need the inside pane to have dropped to 12.7°C to condensate.

I can't find the reference now, but I'm sure I have something that shows the inner pane of 3G only dropping a couple of degrees when 0° outside. Hence the improved "comfort" over 2G.

 

Is the condensation at the edges, where a cold bridge through the frame may be having an effect?

Edited by IanR
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We have 1 pane that gets some condensation.  All the ones supplied fitted by Rationel have no condensation issues, but this one pane the glass unit was supplied by the local window company, and I am building up evidence to "reject" it.  When it is very cold outside (sub zero) it gets condensation near the bottom, there is also under certain circumstances evidence of marks on the inside of one of the pains.  My trouble is I have not been able to convincingly photograph the issues.  So i am hoping when the weather gets properly cold the condensation at least should show a lot more often, often enough to get their sales rep to visit and witness it.

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4 minutes ago, Russdl said:

@IanR they're timber frame, ally clad, Internorm windows. In theory the thermal breaks should be up there with the best.

 

How odd, I have the same windows, with the extra foam between cladding and timber frame.

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4 minutes ago, Russdl said:

 

Sorry, I don't understand that bit?

 

I've got the 310's with the foam under the cladding, which is what I thought you meant by "thermal breaks"

 

image.png.f446f5b771fde12ad0df35219a9324db.png

 

Looks like most of their Aluclad options now have something similar. It wasn't on all their ranges when I purchased.

 

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2 hours ago, Russdl said:

humidity is around 63% (a degree/percent or two different in different rooms)

Is that a bit high? We only have one humidity sensor (its in a weather station, so can't really vouch for accuracy), but it's usually <50% in the kitchen.   We're approaching our 4th winter and not seen any condensation yet. 

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Have to admit, I'm unsure of what the general rh is in passive houses with controlled ventilation, but to my mind, 60%+ rh sounds fairly high.

 

I only refer to my knowledge of good humidity control of the timbers I use for my work, which cover a range of some of the most valuable timber on the planet. If I see the environment getting to 60%, then I know it isnt good for it. I'd expect a range of 35%-50% in a centrally heated home.

 

Perhaps that's the issue, but as I said, I'm not up to speed on such a property.

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@Roundtuit & @Makeitstop  I’m inclined to agree, the humidity is higher than I expected it to be (based on nothing other than a SWAG) and it is seldom below 60% and normally closer to 70%. 
 

I’ve no idea what I should expect it to be and I’d be interested to hear what the humidity is in other Buildhubber’s houses for comparison, especially if they’re down here in the southwest. 

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@tonyshouse  we have the pleasure of condensation on the outside of the windows at times as we expected but we also, very definitely, have condensation on the inside. Not a huge amount but enough to pee me off. 
 

Ventilation through the summer months, and until quite recently, was MVHR and windows/doors open. Now it’s just MVHR. 

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