Mould in loft

[David]

Hi, Last year I had my loft insulation upgraded from 25mm (yep 1") to 250mm. I am now beginning to notice mould growing on suitcases and other items stored up there. The ventilation within the loft is poor, one air brick at either end of the loft. The house was built in the '70's and is a bungalow with shallow pitched roof. I was thinking of installing vents in the soffits. What sort of spacing is advised? Any other things I should consider? Do I need to get the "mould" treated first? It's not that heavy at present, mainly evident on cloth and paper based things. Am I right in thinking that lack of ventilation is the issue? And, finally, any advice of the types/stockists of vents would be greatly appreciated,

thanks in anticipation,

David

[Andrew]

Sounds like a ventilation problem now the roof space is cold. Just make sure the insulation has not been pushed down into the soffits and blocked what little ventilation you had.

[tab]

I have tiled roof on semi and have been getting must smell in loft lately.I see some houses with an odd different ridge tile among the usual rounded type.Looks like a vent,would I be right in thinking that is what they are. Ta for any info on this.

[G Cadman]

Might be the exhaust for ducted hot air heating.

[Bob Hill]

This is a classic problem with low pitched roofs that have lots of insulation and no ventilation. Because the volume of air is relatively low it soon becomes saturated with moisture and when the temperature drops beow the dew point, bingo, condensation and mould growth. I looked at a house recently in which the plywood sheathing board was black with mould and dripping wet. What you need to do is to install eaves ventilation equivalent to a 25mm continuous gap on opposite sides of the roof. to ensure cross ventilation. You must make sure that the insulation does not block the airpath into the roof. Proprietary devices are available for this and are readily installed. Try starting here

The circular soffit ventilators are the easiest to fit. They also manufacture devices to keep the insulation from blocking th eair path. Ensure the insulation goes across the wall head, otherwise cold bridging resulting in mould on walls and celings can occur.

[keith_765]

Yes, that the correct way to cure it, with a cross flow eave vent system. If you don't fancy drilling sofitt vent holes every 600 mm or 2 ft. for the inserts, Try fitting a row of vent tiles both side of the roof, one every

1.5 mtrs or 4ft.6" just above the insulation or even better still fit vent ridge 1 in 6 across the ridge. Don't forget to cut away the underlay felt or they don't work.

[David]

Thanks everyone for the advice. I've ordered a couple of hundred circulat soffit vents from Screwfix and intend to fit those. I've only two "air brick" type vents in the gables at the highest level. Will I require to fit more or will the low level vents I will be fitting be sufficient? Could you enlighten me as to what the wall head is please? Is it the area where the roof trusses bear down on the walls in the corners of the eaves, i.e. directly above the soffit?

Sorry for the questions but I want to try and get it right!

thanks,

David

[Bob Hill]

Hi David

The wall head is waht you say- the top of the wall where the wallplate for the trusses/rafters are fixed. The insulation should go over the wallhead, but not so far that it will block the ventilation route.

You don't need to fit airbricks in the gables - the eaves vent will be sufficient.

Cheers

Bob H

[David]

Thanks, Bob. Have spent most of this afternoon marking out the holes for the vents. Only managed to get a dozen fitted before the rain (and snow) started.

thankyou (and all the others) for the advice,

David