Tile vents - mildew HELP

[FRAN1870]

hi all,

I've noticed mildew on the eaves area of my loft conversion ... there is one tile vent in there already but no eaves ventilation that I can see.

How many tile vents are required ? Or is it trial and error ?

The space is north facing

 

[datarebal]

. Ok what is the roof covering? Slate or tile?
How much insulation do you have at ceiling level? is the loft hatch insulated too?
any pictures from outside?

 

[FRAN1870]

Its dark at the min so I've grabbed a street view to give you an idea .... the tiles are marley modern with a breathable membrane.
Ceiling insulation is that loose fill stuff you can see in the picture ( its roughly 4-5 inches deep ).

 

[FRAN1870]

sorry but no the loft hatch ( which is actually a vertical access hatch off the loft conversion landing ) is not fully insulated so its also not a vapour barrier. Its got a polystyrene insert but can't imagine its got any kind of U-value worth talking about.

This was one of my points with building control, whats the point in installing a vapour if its ok to cut a hole in it ? ( face palm city ).

 

[datarebal]

I can see the breathable underlay.
I think you should certainly upgrade insulation including hatch cover. This will lessen warm moist air upwards.
Are your bathroom extractors working? and connected to the outside?
Vent tiles are easy to fit in moderns.

 

[FRAN1870]

I'll get something to fit in the hatch and yes the extractors are working :/

How many vents do you think ? I can't find and calculations online