Loft condensation after cavity wall insulation installed

[hellsbells1967]

Hi folks.
I am having horrendous problems with condensation in my loft after having cavity wall polystyrene bead fill installed. This is the 3rd winter in the house and prior to this year, no problems at all. Insulation was installed in July 2008.
After much complaining by myself, the installation company has been back and put a grill vent in the end wall either end of my loft cavity, but I have stuck my head up there today, as I thought it worth checking again with the temperature drop, and there are signs of condensation starting to form on the roof felt again. Last time it was so bad it was dripping everywhere. If they have installed a vent either end - are they not admitting liability and a problem with the insulation?
Anyway, I am desperate to resolve the problem as I use the loft for storage! What would you super people out there recommend?
The existing ventilation, apart from the new grills in the end walls, was eve tray type vents down both sides - I have no soffits just for reference!

Thanks and look forward to your advice - I am losing the will to live with it all.

Hellsbells1967

 

[JohnD]

Please see //www.diynot.com/forums/viewtopic.php?t=160032

If for example you drape wet washing about the house, or do not use an bathroom extractor, then your house is doomed to be wet.

 

[hellsbells1967]

Hi John.
I read this before I posted and it was really helpful. I don't do any of that though and the house has been fine for 2 winters and summers before the cavity wall insulation was done! That has been the only change, so it has to be what has caused the problem.
I think that the airflow around the cavity is what was keeping the roof ventilated and now they are filled I have lost that.
My question is - should the insulation company not have checked the existing ventilation to ensure it was adequate b4 doing the fill? And of so who is liable for the problems and costs I am now incurring!

 

[rayman_uk]

HellsBells1967, What was the outcome? I have exactly the same problem - bad sections of condensation in my loft, patches of soggy insulation and some rotten looking bits of soffit (I can see some looking dodgey around the edges from outside my hosue).

I too got Cavity wall insulation installed - 2 years ago now. Didn't notice any problems before now. I'm in a 3 bedroom 70's built semi with a wife and two young kids. Do I pickup with the cavity wall company? My local roofer had a quick look before Christmas and he talked about checking for leaks (he didn't think so), failing that he'd look at putting in some extra roof ventilation.
Keen to get this sorted ASAP as the causes me some worry!

Cheers.

 

[mointainwalker]

Thee could be an direct link, but that is the reason you had the insulation installed !

If the insulation is effective, your house is likley to be warmer. Warmer air is able to carry a greate amount of moisture and this could be why you are now experiencing condensation in the loft.

If you are getting condensation, it is because warm, moist air ( from the house) is coming into contact with the cold air in the loft, The solution is to have a vapour barrier which should be fitted between the pb and the bottom of the insulation i.e. it's on the "warm" side of the insulation.

 

[hellsbells1967]

Hi Rayman_uk.

I eventually ended up paying to have 6 univent tiles installed in the roof, which if I am honest last winter still did not filly resolve the problem. However, I would suspect that as the loft was SO wet that it would take time to dry out properly and also to get it's "balance" back. I actually moved out of the house (not because of the condensation!) in August, so have no idea what it has been like this winter.
I did however have a conversation with someone recently, due to looking at energy efficiency in my new house and was told that it has been heard of before and the cavity insulation was possibly the problem, as it sounded as if the cavities were not capped properly and had not been checked prior to the cavity wall insulation being put in.
I am in the process of going back to the company with the cost of the vents and installation of them, just on the off chance that they may have developed a conscience and will reimburse some of my costs - Yeah right!!!!

 

[rayman_uk]

Thanks for the replies guys.

So should I try and line the inside of my soffits to across the cavity (where I can see the insulation beeds) with a vapour barrier material and sit my insulation wool on top?

I’m awaiting my roofer company getting back to me. They think the roof is reasonably well ventilated but may install more roof vents.

A couple of other snippets of info –
- I have a loft conversion. The room which just acts as a storage area as a radiator in it.
- The loft conv room is boxed in and has small acess doors to allow me in to crawl around to see the eves of the roof. It’s in some eves and soffits where I can see the wet wood and soggy insulation.
- Since the CWI, cold weather always brings condensation to our upstairs bedroom Windows.

Here are some pics of what’s going on.. if anyone has the inclination or time to comment and over some help it’d be appreciated.

What kind of company specialises in troubleshooting these kind of problems? A roofing co?

 

[HarryMC]

It is essential that the loft is properly ventilated as warm moist air is finding its way into the space.
Each of the spaces between each rafter where the insulation is pushed into the eaves and the roof dampproof material (under the tiles) needs to be vented by a depth of at least 25 mm all the way around the roof.
If you stand in the loft on awindy day you should feel the fresh air flowing around you. If not you need more ventilation!