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Condensation in Loft

little mick said:
Hello
Had this when I first moved in property it had been unouciped for four years wasn't sure if it was just damp.hot summer followed come winter loft ringing wet off timbers and felt and stuff stored in it also, fitted vents to the soffit lots of them its a bungalow no noticeable improvement then had some tiles replaced with vented ones damp gone and not been back, the insulation is probably a couple of feet thick. My mothers bungalow is now damp in the loft although never before,we live in the south east England probably just keep an eye on hers for the mean time.
Regards
Stuart
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It's not entirely surprising that soffit vents alone didn't help much. In the US it's recommended to combine soffit vents with ridge vents so that warm (humid) air leaves via the ridge and draws colder, hopefully drier air through the soffits. I imagine your vented tiles serve a similar purpose to the ridge vents - to provide venting near the peak of the roof.

It's also looking for dirty brown patches in the insulation which could indicate warm air (higher humidity) being drawn into the attic from the living space. Sealing those leaks will save money and reduce condensation in the attic.
 
Thats interesting, thanks, I wonder though if its better to consider how air escapes, wheres it all going, just kinda in the apex I guess.
 
We have a metal roof here in Colorado. It has a continuous ridge vent and soffit vents that are sized to have the same area. Tons of airflow, zero condensation and dry as a bone up there. The loft is intended to be unconditioned space - ie pretty matches the outside temperature. The insulation on floor of the loft is where the transition from conditioned to unconditioned space occurs. If any condensation were to occur, I imagine it would be somewhere in the insulation layer as moist air from the house percolates up into the loft and reaches 100% RH. But it doesn’t seem to build up and the insulation is very dry. Damp is never an issue due to using an ERV and being at altitude, so appreciate things might be different in the UK. Still, it never seems that the extractor fans in bathrooms and kitchens in the UK are sized big enough.
 
dan m said:
We have a metal roof here in Colorado. It has a continuous ridge vent and soffit vents that are sized to have the same area. Tons of airflow, zero condensation and dry as a bone up there. The loft is intended to be unconditioned space - ie pretty matches the outside temperature. The insulation on floor of the loft is where the transition from conditioned to unconditioned space occurs. If any condensation were to occur, I imagine it would be somewhere in the insulation layer as moist air from the house percolates up into the loft and reaches 100% RH. But it doesn’t seem to build up and the insulation is very dry. Damp is never an issue due to using an ERV and being at altitude, so appreciate things might be different in the UK. Still, it never seems that the extractor fans in bathrooms and kitchens in the UK are sized big enough.
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I think a MUCH less humid climate than the UK, though. Similarly my attic in Massachusetts has always been very dry. No soffit vents (Cape style house) but gable end and ridge vents. Annual rainfall very similar to London (bit higher), but it tends to come an inch at a time with more dry days in between.
I think brick construction with a winter that is mostly above freezing, but with very high humidity and near constant showers is a much more challenging environment for attics.
 
sean99 said:
I think a MUCH less humid climate than the UK, though. Similarly my attic in Massachusetts has always been very dry. No soffit vents (Cape style house) but gable end and ridge vents. Annual rainfall very similar to London (bit higher), but it tends to come an inch at a time with more dry days in between.
I think brick construction with a winter that is mostly above freezing, but with very high humidity and near constant showers is a much more challenging environment for attics.
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I agree. Still, the fact that rafters are dripping means the transition from partially conditioned inside air to outside air is occurring in the roof. Adding ventilation will cool the attic air and reduce its moisture content via dilution (cooler outside air holds less moisture). You just need to have good insulation between the attic and living space.

(Hopefully Martin won’t come along and point out I’m off base.)
 
garyi said:
Thats interesting, thanks, I wonder though if its better to consider how air escapes, wheres it all going, just kinda in the apex I guess.
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the loft breathes-air gets in and out through any gaps large and small.


there the ones quoted above from amazon-cured my loft condensation within a week
 
Ok I have ordered some, they seem like low risk no brainer stuff. Also just had a look in the loft and nearly every eve is blocked!

Looks like I am up there this weekend. Whats happened is there seems to a specific point all along where it drips, over our bedroom there is no joist boards down its been dripping directly onto the insultation then down to our ceiling.

I feel a solution coming on this is a good feeling.
 
They cured mine and you can feel a slight breeze coming through. Absolute doddle to fit.
Place them nearer the base of the roof and try not to have them opposite each other so the breeze can't go in, through and straight out
 
Its worth checking extractor fans actually vent to the outside. So often they vent into the cavities which leads moisture up into the roof space
 
sean99 said:
These look like a great idea https://www.amazon.co.uk/dp/B01MRI51R4/?tag=pinkfishmedia-21 but I have no personal experience.
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The seller suggests every other rafter, which makes sense given it relies on gaps between tiles/slates; nice, easy, good-value suggestion.

For ventilation though an eaves soffit to empty loft, you want the equivalent of a minimum 10mm wide, continuous slot = 1000sq.mm open area, per metre run of eaves (England & wales minimum requirement) Sometimes done via circular cutouts with insect mesh, through the overhanging soffit. More is good.
 
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I think ours is just kinda open with chicken wire. We have Swifts in every year so I wouldn't want to un house them.
 
Warm, moist air hitting cold surfaces. How well is the roof space insulated? You need to stop the warm air and ventilate so the air can flow through. Soffit vents aswell as ridge vents or any high up vents would be perfect
 
spxy said:
Its worth checking extractor fans actually vent to the outside. So often they vent into the cavities which leads moisture up into the roof space
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We had this with lazy builders
They hadn't got around to putting a hose to outside so the loft became very wet
 
Finnegan said:
I refuse to watch this. I had a rat in my attic a few years ago. The pest control guy told me to stop feeding the birds- which I did. Not had any further problems (touch wood).
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Cutting to the chase, he found 24 dead rats drowned in the cold water tank to which the previous owner had been oblivious.
 
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