Black mould on underside of roof felt

I've just been up into our loft and was horrified to find what appears to b e black mould on the underside of the roof felt:
https://thumbsnap.com/Ijt6WPKP https://thumbsnap.com/w3zVIJbI
(Note: The white 'strips' are where the felt is overlapped)
I haven't been up there since last summer and I am certain it wasn't like t hat then (or at any time previously).
The house was built in 2007 and the felt appears to be of the breathable va riety (it looks like a teabag when viewed close-up) however I am assuming t hat even a breathable felt can't work miracles if there's excessive moistur e being generated in the house, particularly given how dirty the felt appea rs to be on the tile side? There appears to be no eaves ventilation (hard t o tell as it's a 2.5 storey house so the top bedroom has hipped ceilings wh ich mean the eaves aren't visible from the loft space).
We have a nearly-2yr old toddler and have also been undertaking a fair bit of building work over the last six months and so I think a combination of m ore vegetable steaming than we used to, extra loads of washing, great house occupation, reduced ventilation to 'keep the baby warm' etc have all contr ibuted to an excess of moisture and it has condensed on the cold surface in the loft over the winter months.
If the above is true then I am sure we can remove the cause through lifesty le adjustment, however I am still concerned about the mould that is already present. Should I try and clean/remove it? If so, how and what with? It lo oks like most of the black mould spray cleaners contain bleach (to kill the mould and remove the staining?) and so wondered if this might damage the f elt? Perhaps something without bleach more geared towards mould removal off fabric/furniture? If I just left it (and cured the cause) might some of it disappear anyway?
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On Sunday, 12 May 2019 11:52:42 UTC+1, Mathew Newton wrote:

be black mould on the underside of the roof felt:

that then (or at any time previously).

variety (it looks like a teabag when viewed close-up) however I am assuming that even a breathable felt can't work miracles if there's excessive moist ure being generated in the house, particularly given how dirty the felt app ears to be on the tile side? There appears to be no eaves ventilation (hard to tell as it's a 2.5 storey house so the top bedroom has hipped ceilings which mean the eaves aren't visible from the loft space).

t of building work over the last six months and so I think a combination of more vegetable steaming than we used to, extra loads of washing, great hou se occupation, reduced ventilation to 'keep the baby warm' etc have all con tributed to an excess of moisture and it has condensed on the cold surface in the loft over the winter months.

tyle adjustment, however I am still concerned about the mould that is alrea dy present. Should I try and clean/remove it? If so, how and what with? It looks like most of the black mould spray cleaners contain bleach (to kill t he mould and remove the staining?) and so wondered if this might damage the felt? Perhaps something without bleach more geared towards mould removal o ff fabric/furniture? If I just left it (and cured the cause) might some of it disappear anyway?
Bleach is the stuff to use on mould. When that's not usable I've used coppe r sulphate. Is it mould though?
NT
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On Sunday, 12 May 2019 12:17:38 UTC+1, snipped-for-privacy@gmail.com wrote:

to be black mould on the underside of the roof felt:

ke that then (or at any time previously).

e variety (it looks like a teabag when viewed close-up) however I am assumi ng that even a breathable felt can't work miracles if there's excessive moi sture being generated in the house, particularly given how dirty the felt a ppears to be on the tile side? There appears to be no eaves ventilation (ha rd to tell as it's a 2.5 storey house so the top bedroom has hipped ceiling s which mean the eaves aren't visible from the loft space).

bit of building work over the last six months and so I think a combination of more vegetable steaming than we used to, extra loads of washing, great h ouse occupation, reduced ventilation to 'keep the baby warm' etc have all c ontributed to an excess of moisture and it has condensed on the cold surfac e in the loft over the winter months.

estyle adjustment, however I am still concerned about the mould that is alr eady present. Should I try and clean/remove it? If so, how and what with? I t looks like most of the black mould spray cleaners contain bleach (to kill the mould and remove the staining?) and so wondered if this might damage t he felt? Perhaps something without bleach more geared towards mould removal off fabric/furniture? If I just left it (and cured the cause) might some o f it disappear anyway?

per sulphate.

To be honest I am just assuming it us, because it's arrived seemingly so su ddenly - I've got photos from previous jobs over the years in the loft whic h show how clean the felt has always been:
https://thumbsnap.com/7CssXGzL
(This one admittedly taken in 2011)
Whilst we don't have any issues of condensation and/or mould elsewhere in t he house I have noticed when coming home after work how humid the air has b een when my wife has been drying clothes indoors and steaming the nipper's vegetables (sound awful!). Putting two and two together I am assuming this warm moist air has risen up through less-then-perfectly-sealed upper floor ceiling and condensed on the felt.
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On Sunday, 12 May 2019 12:17:38 UTC+1, snipped-for-privacy@gmail.com wrote:

I've been reading that a solution of Hydrogen Peroxide 3% w/w can work well and is not as damaging as bleach can be?
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Yes I was wondering about that and indeed whether a bit of condensation from the causes mentioned would be enough to create it. After all it has to have come from somewhere, and I was thinking another moisture source from evaporating hot water or somesuch. Brian
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I'm starting to wonder that myself Brian. Certainly I couldn't see any 'fur' that I've seen accompanying black mould I've seen in other houses / on the web, indeed there doesn't look to be any 3D properties to what I've got as far as I can tell.
On Monday, 13 May 2019 07:23:59 UTC+1, Brian Gaff wrote:

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Forgot to add that there's no musty smell up there either and so I am really starting to have doubts now...
On Monday, May 13, 2019 at 1:50:59 PM UTC+1, Mathew Newton wrote:

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On 13/05/2019 15:33, Mathew Newton wrote:

It looks like the black lichen spots that you get on patios that are only cleaned once in a blue moon.
Do you have a combi boiler or are there tanks in the loft ?.
If the latter, are they fitted with snug-fitting lids and insulated ?.
If you have expansion/overflow tank for the heating system, is there any possibility of pumping over ?.
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On 15/05/2019 11:24, Jim K.. wrote:

Oh dear. Are you having Jeremy Kyle withdrawal symptoms ?.
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I guess there isnt enough ventilation in the roof, has someone added lots of glass fibre and blocked the vents at the eaves?
A humidity controlled fan in kitchen bathroom and laundry room will help.
[george]
On Sunday, May 12, 2019 at 11:52:42 AM UTC+1, Mathew Newton wrote:

be black mould on the underside of the roof felt:

that then (or at any time previously).

variety (it looks like a teabag when viewed close-up) however I am assuming that even a breathable felt can't work miracles if there's excessive moist ure being generated in the house, particularly given how dirty the felt app ears to be on the tile side? There appears to be no eaves ventilation (hard to tell as it's a 2.5 storey house so the top bedroom has hipped ceilings which mean the eaves aren't visible from the loft space).

t of building work over the last six months and so I think a combination of more vegetable steaming than we used to, extra loads of washing, great hou se occupation, reduced ventilation to 'keep the baby warm' etc have all con tributed to an excess of moisture and it has condensed on the cold surface in the loft over the winter months.

tyle adjustment, however I am still concerned about the mould that is alrea dy present. Should I try and clean/remove it? If so, how and what with? It looks like most of the black mould spray cleaners contain bleach (to kill t he mould and remove the staining?) and so wondered if this might damage the felt? Perhaps something without bleach more geared towards mould removal o ff fabric/furniture? If I just left it (and cured the cause) might some of it disappear anyway?
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On Sunday, 12 May 2019 12:21:24 UTC+1, George Miles wrote:

I don't think there is any eaves ventilation on these houses; certainly loo king at the soffits there's no obvious vent holes and I had always assumed that the breathable felt was the reason why (accepting it only probably wor ks in conjunction with a reasonably ventilated house below).

Funnily enough I am actually in the process of taking advantage of the buil ding work going on to install a whole-house MVHR system; having been planni ng it for ages - not for any specific problem to solve but just because I l ike the idea on how it works and stumbled across a nearly-new unit at a bar gain price.
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On 12/05/2019 12:21, George Miles wrote:

I don't think they bother these days if the roof is constructed with a breathable membrane under the tiles.
A cul-de-sac of social houses near me included a specially adapted house for a wheelchair-bound lady.
I think a lift was installed but she ended up almost bedbound.
A few years after being built I noticed that some vents had been addded to the flanks of the roof, two on each side of the ridge half way down. I guess with her living upstairs with the heating on full blast, a lot of hot moist air must have permeated into the loft space.
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On 12/05/2019 11:52, Mathew Newton wrote:

I wouldn't bother. It'll die when conditions are no longer suitable.
The bigger question is how is the damp getting into the loft. I don't suppose you have a bathroom extractor that vents into the loft instead of outside?
Andy
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On Sunday, 12 May 2019 21:51:51 UTC+1, Vir Campestris wrote:

I've found that vacuuming it makes it far less noticeable, so perhaps that might be suggesting it is not all mould (i.e. also general dirt). That or I 've just blown mould spores out from the vacuum extract!

All extractor's are properly vented, however in typical new-build fashion t he house has dot-and-dabbed plasterboard walls but in something of a 'plast erboard tent' form which almost certainly creates some airways all the way from the the ground floor upto the loft. With the ground floor currently st ripped back bare to build an open-plan extension it wouldn't surprise me if warm, moist, air is rising up behind the plasterboards all the way to the loft. I'll be foaming up around the ground floor perimeter when I get a cha nce so if that's is a contributory factor that should help.
All that said, I've just dug some loft photos out from last year and they d o show something similar so I am now thinking it might not be as 'new' as I thought, and perhaps more also not be as much mould as I thought either.
Might just keep an eye on it, and as mentioned, improve our ventilation pri or to the MVHR going in.
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Is there an open water tank feeding a heating system?
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On Monday, 13 May 2019 08:17:26 UTC+1, charles wrote:

No, we have a sealed system (and unvented cylinder for HW).
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On 13/05/2019 13:46, Mathew Newton wrote:

Which answers a question I asked.
Did the builders use foil-backed plasterboard for the upstairs ceilings (they should have).
Do you have downlighters in any of the upstairs rooms, notably the bathroom ?. These will allow warm, moist air to leak into the loft.
Ditto a badly fitted loft access hatch.
Then there is also the possibiluity that warm moist air is getting into the cavity and the water vapour molecules migrate up the cavity, into the soffitt space and then back inside your loft.
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On Tuesday, 14 May 2019 15:42:12 UTC+1, Andrew wrote:

No, just paper-backed plasterboard and a skim coat.

The only penetrations are lighting cables and an en suite extractor; all se emingly well sealed.

That too is pretty good - it's an insulated affair with a well fitting comp ressible rubber seal.

Could well be; unfortunately I can't see if the cavities have been closed a t the top due to the design of the roof.
I'll give the felt a good vacuum, and might test some hydrogren peroxide to see if that cleans it up. If I can get it back to a 'mould (or whatever it is) free' state then I can keep a proper an on it, perhaps with humidity m onitoring as George suggested along with visible observations of the felt.
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On 14/05/2019 20:07, Mathew Newton wrote:

well that is part of the problem. Water vapour molecules will migrate through the ceiling and into the loft space. The breathable membrane should cope with this but seems not to.
Modern building regs make foil-backed plasterboard mandatory for upstairs ceilings, for precisely this reason, but older re-roofed properties probably still need some normal vents even if breathable membranes are fitted.
Lofts that have 300mm of rockwool are much colder, so condensation is more of a problem.
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On 16/05/2019 16:48, Andrew wrote:

If your house was built in 2007 then it should have had foil-backed plasterboard on all the upstairs ceilings.
I wonder if NHBC or similar did the 'building control' ?. Is this a house built by one of the large national builders, or a small local outfit ?.
Look at the pdf called "Re-roofing and Plastering" at Rochdale council.
http://www.rochdale.gov.uk/planning-and-building/pages/help-with-building-regulations.aspx
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