Converted attic ventilation

stella

Registered User
Messages
43
Hello,

I have a converted attic that has started developping some mould near the Velux window. I got somebody to have a look at it and he said I need to install 4 vents for a 750 euro total cost. I questioned why 4 and the answer was not so clear. Also in terms of warranty, the guy was not really specific.

Would you have a suggestion?

Thanks,
Stella
 
Is this an old conversion? Who did the work and what certification was provided in terms of compliance with building regs? The regs detail what is necessary to achieve minimum ventilation requirements.
 
Depends where and what type of mould it is. It may be a leaking outside seal or joint soaking through to the internal plasterboard. Always check out stuff your self first to have an idea of what's what.
 
Thanks for the reply. The guy that came today told me that the attic conversion was done properly and that it was really well insulated. What I need to understand if 4 vents are really necessary...anybody has a suggestion for another Roof company to have a look at it?
 
I am not a builder or anything associated with 'windows' so here goes. It means little what the guy told you about the conversion as he can not see through the roof to the installation of the Velux.

"Condensation can form on more than just glass. In some cases, the installer neglects to use roofing felt and insulation between the frame of the unit and the rough opening. This allows warm, moist air to escape from the room and come into contact with the underside of the flashing and/or cladding. The resulting condensation will drip back into the room between the frame and rough opening, giving the appearance of a leak. Having the roofer or installer add felt and insulation between the frame and rough opening should prevent this problem...." See the velux solutions site.
So it is important to look at all angles before handing over any money as there is no guarantee that it is a vent problem. Just my opinion. Is there mould anywhere else or just near the velux?
 
Stella, you need some honest advice from someone in the know. Find a local velux installer and ask them to drop out and check. If it only at the velux it would be the first thing to check. Or it could be blocked flashing on the outside with moss or leaves stopping the free flow of rain.
 
Quite likely there is an issue with the insulation around the velux resulting in cold-bridging. As a result the surfaces in the are will be colder, and more conducive to the formation of condensation. You could use a sensitive thermometer to check, an infra-red thermometer one would make it an easy job.
 
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