Builders Advice Please

[downwind]

As this is the "Off Topic" section, could I please ask for advice on a condensation problem that I have in my attic.
I have a lot of condensation forming on the underside of the mineral felt in my attic. My bungalow ceiling has 250mm of insulation, so very little heat loss from rooms to attic. I have 225mm square airbricks on each of the 3 gable ends. I have a "Nuaire ventilation system drawing air from the attic to provide ventilation to the living areas. (This works very well !)
Appreciate any helpful suggestions, thanks.

 

[shakey jake]

more air flow, bigger or more air bricks. if your planning big building work vapour barrier below ceiling prior to plaster board

 

[Gandy]

I’d check the vents aren’t blocked and look for a source of moist warm air such as a faulty boiler for starters.

has anything changed or has it always been present ?

 

[Tommy2bucks]

Had similar issue was a cracked tile but couldn’t see it from outside!!
also put done vents in the room to help air move freely

 

[Tommy2bucks]

Had similar issue was a cracked tile but couldn’t see it from outside!!
also put done vents in the roof to help air move freely

 

[downwind]

I’d check the vents aren’t blocked and look for a source of moist warm air such as a faulty boiler for starters.

has anything changed or has it always been present ?

The air bricks are clear but do have a fine anti-fly mesh on them.
The problem became noticeable when PVC facias and soffits were installed several years ago. I do have 75mm round soffit vents every 1.2 mtrs.

 

[Gandy]

Try and check your eves to see if the vents go through or if they are covered by the insulation.

I’d bet there lies your problem, did they overcladd over the previous eaves and if so has any ventilation in this area been compromised?

 

[downwind]

Try and check your eves to see if the vents go through or if they are covered by the insulation.

I’d bet there lies your problem, did they overcladd over the previous eaves and if so has any ventilation in this area been compromised?

Previously the rafter feet were exposed with wooden facias, with blocking between rafters. There were no eaves vents fitted before the PVC facias etc were fitted.

 

[downwind]

Had similar issue was a cracked tile but couldn’t see it from outside!!
also put done vents in the roof to help air move freely

The condensation is over the full length of the attic--not localised.
Not sure about "done vents"

 

[Gandy]

I’d just put more vent in too.

 

[downwind]

I’d just put more vent in too.

I've just sent an enquiry to Nuaire Tech support to see if they do a residential-type Attic ventilation fan.
Next move would be to remove all facias and put more vents at eaves level.

 

[Tommy2bucks]

Yeah it doesn’t matter on my roof was just one tile that was cracked and the full roof was wet on inside it then dripped onto the roof spas then onto ceiling below
It turned out to be 1 tile that was cracked !

 

[Fosbery Holster]

As this is the "Off Topic" section, could I please ask for advice on a condensation problem that I have in my attic.
I have a lot of condensation forming on the underside of the mineral felt in my attic. My bungalow ceiling has 250mm of insulation, so very little heat loss from rooms to attic. I have 225mm square airbricks on each of the 3 gable ends. I have a "Nuaire ventilation system drawing air from the attic to provide ventilation to the living areas. (This works very well !)
Appreciate any helpful suggestions, thanks.

Are you sure it’s mineral felt.....mineral felt is usually black with sand deposits, gritty to the touch.

At one time builders were using a reinforced “plastic felt”, the type l remember seeing was either green or blue with a 1” square reinforced mesh moulded into the plastic, you could walk on it when stretched out !

If its the plastic under felt that unfortunately is the problem.

 

[downwind]

Are you sure it’s mineral felt.....mineral felt is usually black with sand deposits, gritty to the touch.

At one time builders were using a reinforced “plastic felt”, the type l remember seeing was either green or blue with a 1” square reinforced mesh moulded into the plastic, you could walk on it when stretched out !

If its the plastic under felt that unfortunately is the problem.

Yes, good point. It's 40 year old under-slaters felt, not mineral felt. My bad

 

[Fosbery Holster]

Yes, good point. It's 40 year old under-slaters felt, not mineral felt. My bad

Is it actually plastic ??

Or black bituminous felt ??

 

[downwind]

Is it actually plastic ??

Or black bituminous felt ??

Deffo not plastic.

 

[Fosbery Holster]

Deffo not plastic.

Not plastic........that’s good.

For your own peace of mind get a local builder to come and have a look at the problem, and my advice would be the oldest builder you can find.......the reason being he or she could have witnessed this type of problem before in your area, good luck.

 

[J111]

Is the loft hatch well sealed? Just wondering if your nu-aire is pushing air in and the easiest route out for air is back into the loft via the loft hatch or some light fittings?
Also is your loft insulation blocking air flow from your eaves vents? i.e. have you stuffed rock wool right in to the eaves between the wall plate and the felt.

 

[Norfolk Horn]

Has this problem been since insulation was fitted and has it been more noticeable in the recent still and cold conditions we have had lately.

 

[downwind]

Is the loft hatch well sealed? Just wondering if your nu-aire is pushing air in and the easiest route out for air is back into the loft via the loft hatch or some light fittings?
Also is your loft insulation blocking air flow from your eaves vents? i.e. have you stuffed rock wool right in to the eaves between the wall plate and the felt.

I did wonder about heat loss through the loft hatch, I'll make sure that it's well insulated and sealed.
I made sure there was a good air gap between the insulation and the felt when the insulation was installed.