Condensation build-up under attic boards.

ArdDonagh

I have a 2year old house, walls insulated with ecobead and attic has up to a foot of loose fibre-type insulation. I boarded the attic out down the middle, gable end to gable end, with tongue and groove, chipboard, sheets. I have noticed in the past day that the underside of the chipboard is soaking wet (not just damp), which I am now afraid will come through in the celings. Any suggestions as how to get around this? Will I have to remove the boarding altogether (and I really do need some loft space) or can the boards be drilled into to let air circulate or even raised a couple of inches? Any suggestions would be greatly appreciated.

antoinolachtnai

It might actually be the reverse, that the water is coming from inside the house and making its way into the ceilings.

The way this could work is that the warm air containing water vapour from downstairs is somehow getting through the ceiling into the space between the ceiling and the chipboard, and then the water is condensing as it cools.

Any holes in the ceiling, downlighters or the like?

Just my opinion, but if the chipboard is the only woodwork in the attic that is wet, there is a good likelihood that this is the problem.

I am no expert though and this is something you need to sort out pretty quickly (because the dampness will lead to damage to your ceiling rafters which is much more serious than cosmetic water damage to your ceilings).

Lifting the boards would be a temporary fix, but not really getting to the heart of the problem.

Like I say, I am no expert.

yoshytoshy

Try drilling holes in your flooring to allow ventilation.

onq

ArdDonagh wrote: »

I have a 2year old house, walls insulated with ecobead and attic has up to a foot of loose fibre-type insulation. I boarded the attic out down the middle, gable end to gable end, with tongue and groove, chipboard, sheets. I have noticed in the past day that the underside of the chipboard is soaking wet (not just damp), which I am now afraid will come through in the celings. Any suggestions as how to get around this? Will I have to remove the boarding altogether (and I really do need some loft space) or can the boards be drilled into to let air circulate or even raised a couple of inches? Any suggestions would be greatly appreciated.

Hi ArdDonagh,

Your primary problem may be that the 300mm of insulation has blocked the eaves vents or prevented a clear 50mm air gap being maintained.

Diagram 6 Page 11 of TDG F Ventilation refers.

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf

Other than that your problem may have five interrelated factors causing it:

1. Water vapour in the air
2. Poor/no vapour check
3. Plenty of insulation
4. Poor ventilation
5. Cold surfaces

1. Water vapour in the air

We never see Relative Humidity of Zero.
There is always water vapour in the air in Ireland.
You get that at the poles when all the moisture is frozen out of the sub-zero air.

2. Poor/no vapour check

Downlighters and disconnected vents feeding straight into an attic increase water vapour in the air.
Not having foil backed ceiling boards or plastic sheeting means the ceiling isn't "sealed".
A normal house produces around 14litres of water vapour per day.
Unless vented or sealed, this will condense on colder surfaces.

3. Plenty of insulation

More insulation paradoxically can make matters much worse in terms of what is termed "interstitial condensation".
Warm air absorbs more water vapour then passes through insulation which cools it towards dewpoint.
Moist air hitting a cooler surface will deposit its water vapour load as moisture - "wetness".

4. Poor ventilation

Poor ventilation exacerbates the problem, but you don't suggest this occurs anywhere else.
The area under the boards has no ventilation so the moisture deposited cannot avaporate.
Perforating the board may reduce the problem, but theres still surface to condense on.

5. Cold surfaces

Part of the problem is that the board itself is a cold surface as are most surfaces in an attic with insulation at ceiling level.
Persons intending to use attic spaces in this way should really consider finishing out at roof rafter level.
Insulating between the rafters and below them allowing for a 50mm air gap.

BTW, have you insulated under or around your water tank and does it have an insulated cover?

And have you considered that the underside of every object in your attic could be getting wet?

HTH

ONQ.

ArdDonagh

Many, many thanks for those replies, and espectially for the environs.ie PDF. I am going to lift the boards first off as I had not considered that the water would also be soaking through the rafters! My roof is vented all around the the temperature in the attic is that of outside - well below freezing at the moment. The insulation is tightly packed under the boards and no doubt the hot air in the house (also with the heating being on much more than usual at the moment), is as you say meeting the cold boards and turning to water. Thanks again, I really appreciate all the help.

onq

ArdDonagh wrote: »

Many, many thanks for those replies, and espectially for the environs.ie PDF. I am going to lift the boards first off as I had not considered that the water would also be soaking through the rafters!<snip>.

I meant that if you have objects stored in the attic resting - like your boards - directly on the insulation, that the underside of them could be wet like the boards that are resting on the insulation.

And your very welcome.

ONQ.

RKQ

I agree with ONQ.
As an emergency fix, hire or buy a dehumidifier to remove moist air from your attic. Check air vents at eaves to ensure they are clear.

This severe cold spell is causing this problem as the cold frost / snow weather is very still with like or no breeze / wind - therefore very little air movement in your attic.

If you are lifting the floorsheeting, maybe consider a 50mm air gap between top of insulation & underside of relaid sheeting.

ArdDonagh

onq wrote: »

I meant that if you have objects stored in the attic resting - like your boards - directly on the insulation, that the underside of them could be wet like the boards that are resting on the insulation.

That was the first thing I looked at after your first post but luckily everything is dry (at the moment) - the water is just beginning to show through the top of the boards in specks - I had originally thought that the water was dripping down from the roof and it was only when I lifted one board that was not screwed down that I realized where the water was coming from! Thanks again.

ArdDonagh

RKQ wrote: »

I agree with ONQ.

If you are lifting the floorsheeting, maybe consider a 50mm air gap between top of insulation & underside of relaid sheeting.

Yes, I am thinking that this might be a good option. Along with getting rid of all the stuff in the attic that I have not seen in over 3 house moves!!!

antoinolachtnai

My other concern would be that if there is warm air entering the attic through the ceiling, it means there is a whole lot of heat loss going on. It might make sense to try and deal with that too. (I accept that this will not be easy or cheap.)

ArdDonagh

antoinolachtnai wrote: »

Any holes in the ceiling, downlighters or the like?

Just my opinion, but if the chipboard is the only woodwork in the attic that is wet, there is a good likelihood that this is the problem.

I am no expert though and this is something you need to sort out pretty quickly (because the dampness will lead to damage to your ceiling rafters which is much more serious than cosmetic water damage to your ceilings).

Lifting the boards would be a temporary fix, but not really getting to the heart of the problem.

We lifted the boards yesterday, and the areas where the chipboard is wet is around the opening into the loft (Stira) and just above lightfittings in the upstairs bedrooms - everywhere else is bone dry (over the stairwell, etc). So we have lifted those boards and fingers crossed!!!

powerslot

You can get a dehumidifier here

http://www.azhire.ie/equipment.hire.products.dublin.ireland.php?sectionnumber=115&number=397

Make sure you use this in as closed an area as possible. For the first few hours you will notice plenty of water being extracted, keep running this until the water flow reduces to almost nothing. Keeping the heat on will quicken this process.

ArdDonagh

powerslot wrote: »

You can get a dehumidifier here

http://www.azhire.ie/equipment.hire.products.dublin.ireland.php?sectionnumber=115&number=397

Make sure you use this in as closed an area as possible. For the first few hours you will notice plenty of water being extracted, keep running this until the water flow reduces to almost nothing. Keeping the heat on will quicken this process.

I didn't think that a dehumidifier would be of any use because the roof is vented all the way around? Plus there is no heat up there and the temperature is the same as outside.

10-10-20

In additon, the dehumidifier will have a do a huge amount of work to condence the moisture as the air will be so cold. It will freeze up before it actually gets a drop out.

ArdDonagh

10-10-20 wrote: »

In additon, the dehumidifier will have a do a huge amount of work to condence the moisture as the air will be so cold. It will freeze up before it actually gets a drop out.

Thanks for confirming that - I guessed that might be the case.

corribfitz

onq wrote: »

Hi ArdDonagh,

Your primary problem may be that the 300mm of insulation has blocked the eaves vents or prevented a clear 50mm air gap being maintained.

Diagram 6 Page 11 of TDG F Ventilation refers.

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf

Other than that your problem may have five interrelated factors causing it:

1. Water vapour in the air
2. Poor/no vapour check
3. Plenty of insulation
4. Poor ventilation
5. Cold surfaces

1. Water vapour in the air

We never see Relative Humidity of Zero.
There is always water vapour in the air in Ireland.
You get that at the poles when all the moisture is frozen out of the sub-zero air.

2. Poor/no vapour check

Downlighters and disconnected vents feeding straight into an attic increase water vapour in the air.
Not having foil backed ceiling boards or plastic sheeting means the ceiling isn't "sealed".
A normal house produces around 14litres of water vapour per day.
Unless vented or sealed, this will condense on colder surfaces.

3. Plenty of insulation

More insulation paradoxically can make matters much worse in terms of what is termed "interstitial condensation".
Warm air absorbs more water vapour then passes through insulation which cools it towards dewpoint.
Moist air hitting a cooler surface will deposit its water vapour load as moisture - "wetness".

4. Poor ventilation

Poor ventilation exacerbates the problem, but you don't suggest this occurs anywhere else.
The area under the boards has no ventilation so the moisture deposited cannot avaporate.
Perforating the board may reduce the problem, but theres still surface to condense on.

5. Cold surfaces

Part of the problem is that the board itself is a cold surface as are most surfaces in an attic with insulation at ceiling level.

Persons intending to use attic spaces in this way should really consider finishing out at roof rafter level.
Insulating between the rafters and below them allowing for a 50mm air gap.

BTW, have you insulated under or around your water tank and does it have an insulated cover?

And have you considered that the underside of every object in your attic could be getting wet?

HTH

ONQ.

great reading your answers about insulation problems and was wondering could you help me... im laying attic insulation 100m between joists 200m over them and there is no vapour barrier attached,can i lay the insulation as it is. cheers

onq

corribfitz wrote: »

great reading your answers about insulation problems and was wondering could you help me... im laying attic insulation 100m between joists 200m over them and there is no vapour barrier attached,can i lay the insulation as it is. cheers

Several threads here and over on www.askaboutmoney.com have told of difficulties with condensation in what seem to be well insulated attics this unusually cold weather.

You have to see this as a three cornered stool.

Insulation - Vapour Check - Ventilation.

More insulation without a vapour check may lead to increased condensation in the attic void because the space becomes colder while the same level of water vapour is getting into it.

Adding more insulation as you suggest will tend to block the eaves vents unless steps are taken to prevent this and preserve a 50mm air gap.

Blocking the eaves while allowing the same level of water vapour get into the attic would tend to lead to increased condensation and you are also making the attic colder by installing insulation.

You can could install the insulation while keeping the eaves vents clear and see what happens, but you should be aware of the possible consequences.

My advice would be to install a vapour check as well as ensuring that the eaves ventilation meets Part F requirements for whatever roof type you have.

Here is a link to Part F of the building regulations - section 2 refers

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf

Look at the top of the ceiling plasterboards and see if they are foil-backed - this is a form of vapour check.

If this is not installed you could paint a vapour check onto the ceiling.
http://www.wondertex.co.uk/crossproductpages/wondertex-drywall-topcoat.asp

I have no connection to this product, have not used it and do not endorse it.

All the above comments apply to a modern house using cement products.

Traditional houses using solid masonry walls and lime mortar require specialist advice and insulation techniques.

HTH

ONQ.

onq

powerslot wrote: »

You can get a dehumidifier here

http://www.azhire.ie/equipment.hire.products.dublin.ireland.php?sectionnumber=115&number=397

Make sure you use this in as closed an area as possible. For the first few hours you will notice plenty of water being extracted, keep running this until the water flow reduces to almost nothing. Keeping the heat on will quicken this process.

I was talking to a damp specialist late last year about a condensation problem and the use of a dehumidifier came up.

I was concerned that rapidly dehumifying a room might affect the timber flooring which might have had a significant rise in their moisture content due to the condensate and humidity in the air could cause problems, such as warping.

The received wisdom was to adjust the settings to 50% and let it run for a few hours and see what developed.

That was in a case of a relatively small sectioned timber floor and not the relatively large sections of timber you see in joists and rafters.

We didn't use one in the end - we amended a detail and the problem resolved itself through the building performing as intended.

ONQ.

10-10-20

Is the use of a dehumidifier considered as the treatment (full and final solution) or as a method of temporarily reducing the moisture?

I'd have concerns if this is the treatment as it's expensive to run a dehumidifier to fix what is a building defect.
Also, seeing as the attic is ventilated, you're effectively trying to boil-the ocean.

Removing the source (by treating the ceiling etc) and also lessening the humidity of the rooms below the attic (ventilation) should be seen as the priority here, instead of applying an electrical solution...

RKQ

10-10-20 wrote: »

Removing the source (by treating the ceiling etc) and also lessening the humidity of the rooms below the attic (ventilation) should be seen as the priority here,

I agree. If you have a detached house with gables then drill 100mm diameter hole in each gable, opposite each other, to increase air flow.

Condensation is usually only noticeable when the temp drops to zero or below. Especially on roof with traditional blak sarking felt. This cold weather is usually still / wind free - like the last few weeks, so there is like air movement.

This condensation is usually more visible on the cold side of the roof, where the sun doesn't shine during the day.

A dehumidifier can be considered as a temporarily treatment of reducing the moisture in the air in a house experiencing severe symtoms.