Attic condensation due to blown rockwool

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eamonn123456

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I got my attic pumped with rockwool to 300mm, 11 weeks ago.

I noticed that a mirror in the attic was showing signs of condensation.

I decided to wait and let things settle down.

I went up there 3 weeks ago and there is still condensation on it.

I also noticed the roof trusses felt clammy.

I checked the rafters and they feel damp, esp on the north facing side, esp up under the felt. The felt does not feel particularly damp. Some of the rafters look slightly black, unless I am being paranoid and imagining it.

I told the installers to make sure not to pump too far down the eaves in order to leave adequate ventilation.

I have timber soffits with no actual vents, but clearly there was adequate ventilation before the installation as the mirror never had condensation on it before.

The attic hatch is just a piece of MDF and was not draught proofed (but I have done this since), so, in fairness, moist air may have been getting up there, and in fairness, the attic should now be colder than before.

Questions:

1. Do I need to retrofit soffit vents?

2. Would draught proofing the attic be enough to stop the problem?

2a. Would the moisture in the attic clear itself in a reasonable time or should I use a dehumidifier? (has cleared a bit in 3 weeks but not fully).

3b. Can anyone recommend a meter to measure the humidity?

3c. What value is the limit of acceptable humidity in an attic space?

3. Should I have some kind of vents high up on the gables or high up on the tiles?

4. Should I expect the insulation people to remedy this problem, seeing I warned them to leave adequate ventilation?

I am not really in a position to clear the eaves as I would end up compressing the blown rockwool and that defeats the purpose.

Thanks for reading this far, any help would be appreciated greatly.
 
if you put in some vent tiles as high up as possible that will get rid of condensation.the reason for this is hot air is risen and when it hits a cold surface it turns into condensation,[the hot air cannot escape]get them vents in
 
No need to take off ridge tiles, you just need to replace tiles with vent tiles. Find out what kind of tiles they are and get suitable vent tiles.
 
I have the same problem in my attic since Christmas. Water is dripping off the felt and the timberwork looks very wet.
I also have some soffit vents and some ridge ventilation (all clear I hasten to add).
Personally I think it's the combination of our current cold weather and calm conditions.
I was half thinking of rigging an extractor fan like an xpelair up to one of the vented slates and seeing if would help get some air movement going.

Like you OP I'm worried about it as the timber is going black in spots.

Regards
Franm
 
Your attic is not ventilated right, when blowing in insulation they may have blew insulation down into your soffit and so clogged your vents in soffit, so the air is not circulating over your insulation, your attic should be cold and drafty especially this weather if not they are blocked, have you vents in soffit? If you have get them back to clear them.
 
OK, the latest is that the contractor finally and begrudgingly got someone out to have a look.
It was a sound guy who came out, he is going to sort out a couple of other issues related to the trap door and walkway which I didnt even ask him to.

He had a look and said the rockwool is correctly installed, and the normal amount of clearance has been left. He agreed that it could have been the root cause if it were blown too far down.

Fair enough, I just wanted that confirmed before I go and spend money on remedial work.

We both agreed that the likely cause of the issue is two fold:

the air in the attic is colder now so condensation can happen at lower humidity
and
the ventilation, while not fully blocked by the insulation, is not as good as before.

The combination of these two things means that the original ventilation provision is no longer adequate to clear any dampness out of the attic space.

My soffits do not have vents, and this was not a problem when there was completely unimpeded flow at the eaves, whatever air that came thru was enough.

Now that the situation has changed, I am going to follow this guys advice and get soffit vents retrofitted.

If that is not enough, although I think it will be, I will get vents at the apexes of the gables or vent tiles.

Hopefully that should sort it out.

I made the point that they should warn people of this unintended side effect, as it could have serious implications for the roof structure if neglected. It seems that they are now going to include that in their literature.
 
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