Major condensation in loft space

[Skyedriver]

Having read through most of this - we have the same problem.
Sterlingboard roof with conc tiles above on an 80's bungalow on the Isle of Skye.
Loft space HOT in summer cold in winter. Fine layer of mould or mildew on the Sterlingboards.Any soft furnishings get mouldy too.
Some downlighters that break into the loft, 6" insulation and loads of eaves ventilation.
As I see it the ventilation is only letting in damp air all winter, asits always damp up here, also the worst area is above the bathroom and I guess the plasterboard is breathing upwards.
Often thought about a de humidifier up there but I would have to keep going up to empty it.

[Simpo Two]

Skyedriver said:

Often thought about a de humidifier up there but I would have to keep going up to empty it.

Couldn't it drain out through the wall, much like an overflow pipe?

[Deva Link]

Simpo Two said:

Skyedriver said:

Often thought about a de humidifier up there but I would have to keep going up to empty it.

Couldn't it drain out through the wall, much like an overflow pipe?

They don't work well in low temps (although you can get absorbtion models that are better - often used in garages) but it will also struggle where there's lots of ventilation.

[motco]

Sam_68 said:

motco said:

How can extractor fans - not MVHC - work in an airtight house? Air-out must be balanced by air-in.

I should explain that when airtightness is measured on a house, we temporarily seal up the background trickle vents and extract fans (basically, you then attach a bloody great fan to the front door opening, pressurise the house and measure how fast the air leaks out; the figures I gave above are in cubic metres of air leakage per hour, per square metre of floor area, with the house pressurised to 50 Pascals).

Obviously in operation, the air out from the extractor fans is balanced by the air in through the trickle vents.
Also, the Building Regulations demand that we leave a gap under the internal doors to allow air to be drawn through the dwelling.

That's why - in response to your ealier post - I said that excessive air tightness was a problem if the ventilation wasn't managed correctly; the ventilation systems should (in theory) maintain a managed amount of air flow that prevents both health and internal condensation problems.

Edited by Sam_68 on Thursday 17th December 12:53

I see, thanks. However, most of the housing stock doesn't meet those conditions, mine certainly doesn't. It was built in 1938 like so many others, has 1982 UPVC sealed double glazing (no trickle vents), and is comprehensively draught stripped around doors, etc. It weren't for the larder vent and grille in the larder door put in for the purpose by myself, I don't think the boiler would run too well being an open flue type. If the heat recovery type ventilation systems weren't such a pain to install retrospectively I'd have fitted one years ago when Wickes carried them in stock.

[M005]

Seems I'm on my own with this; Bloor aren't interested as it is 5yrs old, and NHBC aren't interested as it isn't structural.

Had a long chat with the NHBC assessor and they are sending me out a leaflet about reducing condensation in the roof space; apparently they get a lot of calls about it at this time of year.

From the discussions the main themes seem to be ventilation (increasing it - also mentioned that anything in the roof space will restrict ventilation) and restricing the moisture from the house getting up there, rather than the heat. She wouldn't be drawn on whether extra insulation, or proper insulation, was a good or bad thing.
Aparently trickle vents should be open even during the winter, washing shouldn't be dried on radiators, or on airers near radiators, etc.

One point she did stress was that the roof space isn't designed as a storage space, therefore the short answer to the issue is don't store anything up there!!

[eps]

Just out of interest, it's definitely condensation and not a leak of some sort?

Has it always been like this?

Has something changed recently which exacerbated the problem?

[M005]

Definitely condensation.

This is our 3rd winter there and it has always been as issue, getting worse each winter - I guess as more stuff is put up there.

[Sam_68]

motco said:

However, most of the housing stock doesn't meet those conditions.

Absolutely right.

But that's why I've said repeatedly on this thread that the causes of condensation in modern roof constructions are often very different (and indeed it could be argued diametrically opposite) to the causes of condensation on older properties.

[Boughton]

Jumping in on this post as we have just gone up the loft to get christmas decs and the roof felt is wet and in certain places dripping. Had this problem last year and put in roof vents thinking this would solve the problem which it obviously hasn't!! (although it does appear slightly better). The question is, is it expected that at this time of year there would be a certain amount of condensation or should there not be any? What else can we do? And is it going to cause lasting damage to the house? Very concerned and worried...any advice would be greatly appreciated.
The house is wimpey built and 13 years old.

[jules_s]

Sam_68 said:

motco said:

However, most of the housing stock doesn't meet those conditions.

Absolutely right.

But that's why I've said repeatedly on this thread that the causes of condensation in modern roof constructions are often very different (and indeed it could be argued diametrically opposite) to the causes of condensation on older properties.

Hi Sam,

I was posting in the context of a 5 year old house as depicted by the OP, not an 'old' house (and I 'think' air tightness has come about within the 5 year period?) I'm pretty certain that roof ventilation rates haven't changed since the early 90's when I started out.

I don't design houses so I'm in the other L2 bracket, however I dont think air tightness was ever considered in terms of ventilation? more so heat loss surely?

TBH I've always considered air tightness to be a (near) waste of time, we block all of the air intakes to do a test....and then hand the building over with them all open.

Anyways, having re-read the thread and your posts I pretty much agree with 99% of what you have posted.

[pstruck]

Just stumbled on this thread whilst searching for info on our own problem.

We had this issue last year and the loft has smelt a bit musty most of the summer too, although I think it mainly dried out. Now thought the underside of the felt is covered in condensation.

The linear soffit vents are all clear and there are some pre-formed polystyrene spacers under the eaves to stop the quilting from blocking the circulation. Admittedly it is very still here tonight and the temp has dipped fairly low, but the amount of condensation dripping onto the contents of the loft is worrying.

We do have our boiler flue venting at the rear of the house on the single storey kitchen extension, and although it is a number of metres away from the soffits the plume can sometimes be seen rising toward the roofline at the rear of the house in still weather. I can't help but feel that I need to re-direct the flu plume, but options are limited due to its position.

[Sam_68]

jules_s said:

I was posting in the context of a 5 year old house as depicted by the OP, not an 'old' house (and I 'think' air tightness has come about within the 5 year period?) I'm pretty certain that roof ventilation rates haven't changed since the early 90's when I started out.

Yes, you're right - air testing is quite recent, in this country and the recent massive hike in air tightness won't apply to the OP's house. His house is likely to have an air tightness figure around the 10-12 mark that we were achieving using modern construction techniques, but without really trying (most of the recent major improvements are down to attention to detail and workmanship, rather than anything fundamenal).

But even the 10-12 air test figures that are typical of 'semi-modern' housing are an order of magnitude better than many older properties. At the other extreme, for example, I'm pretty sure that my house (a Grade II listed thatched cottage with original hand-made timber windows and ledged-and-braced timber doors with half inch gaps under the bottom) wouldn't even hold enough air pressure to be testable!

But as you also say, roof ventilation rates haven't changed since the early '90's. I have discussed this with the BRE and I think you can take the fact that they haven't deemed it necessary to change the roof ventilation rates, despite the recent increases in insulation levels, is tacit admission that it wouldn't make any difference. As I've said previously, you can pretty much blow as much air as you like over the top of an 18" thick insulation quilt and it won't do much to dry out condensation that has settled to the bottom.

jules_s said:

I don't design houses so I'm in the other L2 bracket, however I dont think air tightness was ever considered in terms of ventilation? more so heat loss surely?

Approved Document F (means of ventilation) was updated in 2006, largely to take account of the enhanced 'managed' air flow that is necessary to balance the increased air tightness imposed by pressure testing under Part L and secondary standards like EcoHomes/Code.

jules_s said:

TBH I've always considered air tightness to be a (near) waste of time, we block all of the air intakes to do a test....and then hand the building over with them all open.

Yes, I kind of agree with you, since I'm basically a reactionary old bd who hates any further bureaucracy in the building industry, but I guess I have to admit that making buildings air tight then managing the airflow through properly considered and designed ventilation openings gives you more certainty than not air testing and just hoping that you will have enough air flow for a healthy, condensation-free environment but not so much that you're wasting excessive heat?

There are other problems with the current air testing regulations and methodology, but we won't go there!

Edited by Sam_68 on Friday 18th December 17:06

[motco]

BRE used to be a nice avuncular sort of place that you, even as a private individual, could phone up and find an expert on almost any aspect of buildings and chat with them for as long as you liked with no pressure from them to get off the phone. Now it has been privatised...

[iamrcb]

I've been in my loft tonight HOOVERING the water off the roofing felt. Switched the dehumidifier on, which will need to run for 4/5 days now to dry the loft out. Its absolutely soaking up there.

Over the past two years I've improved insulation, fitted 6 roof tile vents, pulled insulation back from the eaves and tried to reduce moisture in the air throughout the house BUT this problem WILL still happen in my house forever.

Usually I know when to expect it so I just switch on the dehumidifier, which prevents a mass of water forming on the roofing felt. Its been really cold recently so this is no surprise.

[motco]

It's a nonsense to have to use electricity to dry off insulation installed to save gas! World's gone crazy...

[pandrews68]

I've just been searching the web for a solution to my ("Common")problem and the postings on this topic have been very helpful in both diagnosing & flagging possible remedies. I have a 13yr old Taylor Woodrow new build detached house that I've lived in since 2006. Had no problems initially then found that last years coldspell (2008) gave rise to condensation forming on underside of felt on one half of roof only.

Common theme appears to be:-

> Bathroom & En suite both sited on this side of house + both have downlighters fitted and extractor fans
> Only a problem when temp. drops significantly.

Short Term Fix: I was going to put a Dehumidifier up there to dry it out but note that these are not good in low temperatures - Can anyone recommend some equipment thats man enough for the job ?

Permanent Solution: Did anyone find one or can anyone recommend a credible company that I can go to who are not going to try to fleece me ? (I spoke to 2 'specialist company's today who were only interested in re-insulating my loft !)but by the sound of it I just need to improve the ventilation on one side of the roof?!

[pandrews68]

M005 said:

Dave_ST220 said:

Martin Keene said:

I found this hard to believe as it had been fine for 12 years. When I sat down and though it through, I realised it started after swmbo moved in and a lot of stuff got put in the loft. Being terreced the vents where on the front and rear eves and we had the contents of the loft on a boarded section across the middle.

A damn good clear out, and rearranging what was left against the party Walls in the loft removed the condensation. We had blocked the airflow in the loft with all the st in there.

Exact same deal here, loft got so full the airflow...err...didn't!! Good clear out & all sorted.

Interesting distinction I hadn't picked up on.

All our stuff is now in the centre boarded section, whereas some had been along the edges close to the eves.

The eves are front & rear of our property as well, and I assumed that the airflow would go over the top of anything stacked in the middle?

Just spotted this posting and can relate aswell. Previous owners boarded out middle of loft and like you, I assumed that loft ventilation flow unaffected by stuff stored here ! As per my other posting, only started being a problem last year and this year also following extreme cold spells ......Did removing the items stored in the loft solve the problem for you too in the end ?

[Goochie]

pandrews68 said:

I've just been searching the web for a solution to my ("Common")problem and the postings on this topic have been very helpful in both diagnosing & flagging possible remedies. I have a 13yr old Taylor Woodrow new build detached house that I've lived in since 2006. Had no problems initially then found that last years coldspell (2008) gave rise to condensation forming on underside of felt on one half of roof only.

Common theme appears to be:-

> Bathroom & En suite both sited on this side of house + both have downlighters fitted and extractor fans
> Only a problem when temp. drops significantly.

Short Term Fix: I was going to put a Dehumidifier up there to dry it out but note that these are not good in low temperatures - Can anyone recommend some equipment thats man enough for the job ?

Permanent Solution: Did anyone find one or can anyone recommend a credible company that I can go to who are not going to try to fleece me ? (I spoke to 2 'specialist company's today who were only interested in re-insulating my loft !)but by the sound of it I just need to improve the ventilation on one side of the roof?!

Are the downlights covered with anything? Most downlights cant be covered directly with insulation which leads to people leaving gaps around them. This allows warm moist air to pass into the cold space.

I'm guiessing that if the downlights are also 13 years aold, they will just be normal open backed products and not fire rated? Some fire rated downlights also come with moisture seals to prevent warm/moist air getting into a loft.

You can get insulation support boxes which are sheet metal things about the size of a shoe box. You sit these over each downlight and then insulate over the top of the box.

You could also fabricate shomehting from plasterboard yourself.

They key thing is to allow 2 inches (5cm) clearance all around the downlight otherwise it will cook itself.

[Deva Link]

pandrews68 said:

Short Term Fix: I was going to put a Dehumidifier up there to dry it out but note that these are not good in low temperatures - Can anyone recommend some equipment thats man enough for the job ?

The issue in lofts is that its cold, and ordinary dehumidifiers don't work well in low temps.

Have a look at absorption dehumidifiers - you often see them recommended for use in garages, which are typically unheated.

Of course if the loft is well ventilated then you'd be trying to dehumidify the world, which might be a bit of a struggle!

[theboyfold]

pandrews68 said:

M005 said:

Dave_ST220 said:

Martin Keene said:

I found this hard to believe as it had been fine for 12 years. When I sat down and though it through, I realised it started after swmbo moved in and a lot of stuff got put in the loft. Being terreced the vents where on the front and rear eves and we had the contents of the loft on a boarded section across the middle.

A damn good clear out, and rearranging what was left against the party Walls in the loft removed the condensation. We had blocked the airflow in the loft with all the st in there.

Exact same deal here, loft got so full the airflow...err...didn't!! Good clear out & all sorted.

Interesting distinction I hadn't picked up on.

All our stuff is now in the centre boarded section, whereas some had been along the edges close to the eves.

The eves are front & rear of our property as well, and I assumed that the airflow would go over the top of anything stacked in the middle?

Just spotted this posting and can relate aswell. Previous owners boarded out middle of loft and like you, I assumed that loft ventilation flow unaffected by stuff stored here ! As per my other posting, only started being a problem last year and this year also following extreme cold spells ......Did removing the items stored in the loft solve the problem for you too in the end ?

Holy thread bump Batman!

I've just found this thread. Moved into a house that was built in the late 70s this summer and moved all the boxes that we used to move into the loft, I thought I was being clever when I moved them into the eaves and left the middle pretty much clutter free.

Popped up this morning and saw that the side of the house with the boxes had lots of condensation, the other side had nothing. Could it be this simple?

I've moved the boxes into the middle of the loft for now and will look to shift them soon.

The middle of the loft is boarded, the outside of the loft is not boarded and only insulated in places. There are no uplighters leaking moisture into the loft, no vents going into the loft and the loft door isn't sealed. However, you can see outside from inside the loft around the lowest part of the roof.