Condensation in loft space since cavity wall insulation

[jonnybegood]

Guys

I had cavity wall insulation (bonded bead) fitted October 2007, within a month of the install my boarded attic space was filled with polystyrene insulation which had blown out of the cavity into the loft space.
Thought nothing more of it, cleaned it up and left it.

Having not spent much time in the attic space until this week (fitting more insulation) I have noticed that the wooden rafters have some white dots on them and condensation drips in the corners of the roof (underside of felt is wet).
Before the cavity wall insulation there used to be a good draft coming up the cavity and into the attic space, but now there is still some draft but obviously the beads have prevented the same level as seen before the cavity wall install.
I have never seen condensation in the attic before, only since the cavity wall install, its a 1960s semi.

Questions.....
Do I get the firm back who install the cavity wall insulation?
The surveyor who checked it out before the job started said all will be fine.

Should this insulation be pumping into the loft space?

What other options do I have to increase the now restricted flow of air.



On a separate note regarding the cavity wall insulation, my house has never suffered excessive condensation, except when there is alot of cooking going on.
Now this time of year the windows are getting water all along the bottom of them and in one of the bedrooms condensation is gathering in the top corner of the outside wall, directly behind the cavity air brick.
Having done a little reading, could this be caused because there is no insulation where the air brick is situated making that spot on the wall colder than the rest that is insulated and attracting condensation just like the windows.

Thanks in advance for any advice

JBG

 

[JohnD]

Does this help?

//www.diynot.com/forums/viewtopic.php?p=1080717#1080717

Comments please

 

[PJ1]

JohnD's sticky is of course correct.
Having warmed up the walls with the insulation, the water vapour (created by living and breathing - so there's no stopping it!) now looks to condense on the next coldest surface - the bottom of your windows in the first instance (or behind the air brick, as you say). Then it will naturally rise through the ceilings into the loft area, where it's colder again. Hence the condensation now occurs on the underside of the sarking felt and on the timbers.

You need to consider how you live. Make sure you mechanically extract water vapour (or steam) at source and duct it to external air. Fans to kitchens and bathrooms are a must. Make sure the water vapour has cleared somewhat before turing them off. Some fans have a timed 'over-run' for this purpose.

Consider fitting 'trickle' vents to your windows to allow background air movement and natural removal of moist air (easy DIY job). They are controllable, so when it's chuffing freezing outside you can close them for a while to prevent discomfort.

Examine the ventilation provisions to the loft space. If you can't see daylight when you stand up in there without a light, there's not sufficient ventilation!
Given the age of the house I would suspect there isn't any formal provision. Look to provide cross ventilation (eg front-to-back) in the loft as per JohnD's info.
Don't delay, this problem can result in serious defects!!