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Default roof condensation

Hi,

I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?

TIA
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On 8 Jan, 19:55, Fred wrote:
Hi,

I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?

TIA


Unless you have foil backed plasterboard or some other vapour proof
barrier moisture will migrate through the ceiling and insulation into
the loft and then condense on the cold underside of the roof.
You might limit the effect by ventilating the roof space but this will
reduce the temperature considerably and if you have loft water tanks
and pipes they may suffer!
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Fred wrote:
Hi,

I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?

TIA

Insulation (rolls)wont stop water vapour moving from of high vapour
pressure area to an area of low Vp. your easiest and probably best
solution is to make sure that your loft is adequately ventilated, also
your habitable rooms particularily bathrooms and kitchen.
Don
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On Jan 8, 8:06*pm, Donwill wrote:
Fred wrote:
Hi,


I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?


TIA


Insulation (rolls)wont stop water vapour moving from of high vapour
pressure area to an area of low Vp. your easiest and probably best
solution is to make sure that your loft is adequately ventilated, also
your habitable rooms particularily bathrooms and kitchen.
Don- Hide quoted text -

- Show quoted text -


Youve got to get rid of the vapour before it hit the cold inside of
the roof covering. This is done by venting through the highest part
of the roof. Take the dodgie ridge of and replace with a vent ridge or
a couple of vent tiles below the ridge.
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Default roof condensation

Fred wrote:
Hi,

I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?

TIA


Fred,

It's interstitial condensation - and I've got the very same problem - and in
my case, it's caused mostly by the steam from the bathroom that seems to
find its way into the well insulated attic through various nooks and
crannies [1] leaving tiny globules of frozen moisture [2] hanging on the
underside of the roofing felt.

Normally this steam is vented from the attic with the airflow through the
roof from the westerly winds that occur at this time of the year, but these
winds have changed direction or stopped for fairly long periods leaving the
moisture to collect - and because of the insulation, there is no heat in the
attic now to simply dry it.

As a matter of interest, this situation has only occurred since we had the
cavity and loft insulation installed about three years ago in a
traditionally-built house of the mid-1970's (with absolutely no loft
insulation installed at the time).

[1] I cannot persuade SWMBO to have a bath with the bathroom window
slightly open to vent the steam for the life of me - and I've tried for many
a year, but still cannot 'educate' here. Please don't show her this post or
I'll be making my own breakfast tomorrow. LOL

[2] Glitters rather fetchingly in torchlight though - but roll on the
return of the westerlies, and summer, to get rid of it!


Cash





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In article ,
Fred writes:
Hi,

I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?


There are some things to check, but it may be inevitable in this
weather.

1. You need to make sure air is not moving from the house into the
loft. Check for leaky loft hatch, oversize holes around pipes which
pass through the ceiling, recessed spot lights, and any other holes.
Check none of your extractor fans exhaust into the loft space.
A cracked lath and plaster ceiling will let moisture through too.
An ordinary plasterboard ceiling, even without vapour barrier won't
let enough moisture through, subject to 3.

2. Make sure the loft tanks have close fitting lids so they aren't
evaporating moisture into the loft. The CH expansion tank will
get warm it times, and if uncovered in a cold loft, that can
release lots of moisture. If the CH tank is pumping over, it will
get hot, and the pumping over should be fixed.

3. The loft needs to be ventilated. If it doesn't have ventilation,
eves vents can be easily fitted and will create enough air changes.

However, at this time of year, the roof surface will be colder than
even the outside air temperature at night due to heat loss by radiation,
and in this scenario, there's nothing you can do to prevent moisture
forming in a ventilated loft (well there is, reduce both the ventilation
and the insulation, but that's not realistic). This shouldn't account
for large quantities of condensation though, so I would look at the
causes above.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
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On 8 Jan, 22:36, (Andrew Gabriel) wrote:
In article ,
* * * * Fred writes:

Hi,


I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?


There are some things to check, but it may be inevitable in this
weather.

1. You need to make sure air is not moving from the house into the
* *loft. Check for leaky loft hatch, oversize holes around pipes which
* *pass through the ceiling, recessed spot lights, and any other holes.
* *Check none of your extractor fans exhaust into the loft space.
* *A cracked lath and plaster ceiling will let moisture through too.
* *An ordinary plasterboard ceiling, even without vapour barrier won't
* *let enough moisture through, subject to 3.

2. Make sure the loft tanks have close fitting lids so they aren't
* *evaporating moisture into the loft. The CH expansion tank will
* *get warm it times, and if uncovered in a cold loft, that can
* *release lots of moisture. If the CH tank is pumping over, it will
* *get hot, and the pumping over should be fixed.

3. The loft needs to be ventilated. If it doesn't have ventilation,
* *eves vents can be easily fitted and will create enough air changes..

However, at this time of year, the roof surface will be colder than
even the outside air temperature at night due to heat loss by radiation,
and in this scenario, there's nothing you can do to prevent moisture
forming in a ventilated loft (well there is, reduce both the ventilation
and the insulation, but that's not realistic). This shouldn't account
for large quantities of condensation though, so I would look at the
causes above.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]


I'm following this thread with interest, as last week (putting Xmas
decs back) I noticed with some alarm that there was moisture on the
roof felt too. However I went through a process of putting loads of
vent holes in my soffits 4 years ago, and haven't had any problem
since.

Not wanting to panic, I had a good look round, and it seemed the
moisture was concentrated ... wait for it ... on the bathroom side (we
live in big "L" shaped bungalow). Of course sods law says that this is
the part which is boarded over and used for storage as ... wait for it
again ... it's nearest the hatch !

The bathroom ceiling is well sealed .. however the hatch is not, and I
suspect this is where the vapour is rising through.

So what's the best way to seal a loft hatch ? And is it best to always
assume there will be *some* moisture in a loft, and not store
cardboard or paper goods, unless sealed with plastic ? Because (you
guessed it) most of our stuff in the loft is in cardboard boxes (with
lids ... when an old employer moved offices they over-bought on proper
document archive boxes by 20 ... they are really sturdy and easily
collapsed for storing flat)
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Jethro
wibbled on Friday 08 January 2010 22:56


The bathroom ceiling is well sealed .. however the hatch is not, and I
suspect this is where the vapour is rising through.

So what's the best way to seal a loft hatch ? And is it best to always
assume there will be *some* moisture in a loft, and not store
cardboard or paper goods, unless sealed with plastic ? Because (you
guessed it) most of our stuff in the loft is in cardboard boxes (with
lids ... when an old employer moved offices they over-bought on proper
document archive boxes by 20 ... they are really sturdy and easily
collapsed for storing flat)


Bit of rubber D profile draught strip (fiver from B&Q) might do it if the
hatch mates evenly with the frame all the way around.

--
Tim Watts

You know you need more insulation when the snow blanket on the roof makes
the house 3 degrees warmer...

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Tim W wrote:

Jethro
wibbled on Friday 08 January 2010 22:56


The bathroom ceiling is well sealed .. however the hatch is not, and I
suspect this is where the vapour is rising through.

So what's the best way to seal a loft hatch ? And is it best to always
assume there will be *some* moisture in a loft, and not store
cardboard or paper goods, unless sealed with plastic ? Because (you
guessed it) most of our stuff in the loft is in cardboard boxes (with
lids ... when an old employer moved offices they over-bought on proper
document archive boxes by 20 ... they are really sturdy and easily
collapsed for storing flat)


Bit of rubber D profile draught strip (fiver from B&Q) might do it if the
hatch mates evenly with the frame all the way around.

I use sticky tape as the hatch isn't a very good fit. I hardly ever go into
the loft - it's not used for storage.

If the loft is used for storage bear in mind that every time you open the
hatch lots of warm moist air from the house rushes into the loft and
condenses as it cools.

Edgar
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[Default] On Fri, 08 Jan 2010 19:55:51 +0000, a certain chimpanzee,
Fred , randomly hit the keyboard and
wrote:

I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?


Does your roof have breathable felt or traditional?

If breathable - these can be used without ventilation (according to
the manufacturers), provided that there is a vapour barrier underneath
and all the rooms producing moisture have adequate ventilation (i.e.,
extract fans). They say that some interstitial condensation could
occur, but that it will evapourate and be ventilated through the
membrane in summer.

If a traditional felt- this should be ventilated at the eaves along
two opposite sides. You can do this with breathable felt too. Make
sure the gaps are free and not blocked by insulation. Again, try and
reduce the moist air entering the roof space by draught-stripping the
loft hatch and using the extractor fans and trickle vents.

As others have said, insulation isn't a vapour barrier. Once the
vapour's in the roof space, you need to allow it to ventilate away.
What you don't want to do is block any ventilation path by putting
insulation between the rafters.

I have seen roofs covered with breathable membranes literally dripping
with condensation. If I had a roof like that, I wouldn't leave
anything up there that could be affected by moisture.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have I strayed"?


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On Sun, 10 Jan 2010 16:29:09 +0000, Hugo Nebula abuse@localhost
wrote:

Does your roof have breathable felt or traditional?


I don't know, how would I tell? It's a 1970's house if that helps?
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On Fri, 8 Jan 2010 22:03:20 -0000, "Cash"
wrote:

It's interstitial condensation - and I've got the very same problem


Thanks for the reassurance that it is "just" warm, moist air from the
house condensing on the unusually cold roof. Hopefully when this
unusual weather goes away, so will the problem.

my case, it's caused mostly by the steam from the bathroom


We do have a fan in the bathroom but it's a 4" connected to flexible
ducting, so it's not ideal. Sadly the window lintel got in the way and
prevented us fitting anything bigger or better.
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Fred
wibbled on Thursday 14 January 2010 21:44

On Sun, 10 Jan 2010 16:29:09 +0000, Hugo Nebula abuse@localhost
wrote:

Does your roof have breathable felt or traditional?


I don't know, how would I tell? It's a 1970's house if that helps?


Likely non breathable I would guess. If it looks black and shiny and like
it's made of sackcloth painted with black gunk, it's probably old style
sarking which is not breathable. Not sure what else they used then but
although Tyvek (breathable) has been around since the late 60's I not sure
if it was widely used then - probably very expensive.

--
Tim Watts

Icicles - nature's way of pinpointing all the leaks in your guttering...

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"cynic" wrote in message
...
On 8 Jan, 19:55, Fred wrote:
Hi,

I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?

TIA


Unless you have foil backed plasterboard or some other vapour proof
barrier moisture will migrate through the ceiling and insulation into
the loft and then condense on the cold underside of the roof.
You might limit the effect by ventilating the roof space but this will
reduce the temperature considerably and if you have loft water tanks
and pipes they may suffer!


Best seal all gaps between rooms and loft inc' ceiling roses and pipe
entries. Have a loft hatch with a seal. Then paint the loft floor with oil
based paint.This will seal enough to prevent water vapour moving from house
into the loft where it meets cold surfaces and condensates. Some paint the
ceiling with oil based paint and mat paint over. This will also keep the
house warmers as hot air is not moving out of the house -you pay for that in
energy bills.




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"Kipper at sea" wrote in message
...
On Jan 8, 8:06 pm, Donwill wrote:
Fred wrote:
Hi,


I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?


TIA


Insulation (rolls)wont stop water vapour moving from of high vapour
pressure area to an area of low Vp. your easiest and probably best
solution is to make sure that your loft is adequately ventilated, also
your habitable rooms particularily bathrooms and kitchen.
Don- Hide quoted text -

- Show quoted text -


Youve got to get rid of the vapour before it hit the cold inside of
the roof covering. This is done by venting through the highest part
of the roof.


Or stop the vapour entering the roof space, which is the best way and saves
high energy bills.

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"Cash" wrote in message
...
Fred wrote:
Hi,

I went into our loft to put the Christmas tree away and the rafters
were wet and some of the cardboard boxes up there were damp. At first
I wondered whether some of the snow had melted and leaked through an
iffy ridge tile but I've been told it is likely to be condensation.
I'm puzzled how the warm air gets up there because there's a good ten
inches or so of insulation (rolls). I've been told that once the cold
spell goes everything will return to normal. I am concerned about the
timber getting wet and all the boxes (and presumably their contents)
getting soggy. Is it likely to just be condensation and nothing worse,
and is there anything I can do to limit it? Would wedging slabs of
insulation between the rafters help?

TIA


Fred,

It's interstitial condensation - and I've got the very same problem - and
in my case, it's caused mostly by the steam from the bathroom that seems
to find its way into the well insulated attic through various nooks and
crannies [1] leaving tiny globules of frozen moisture [2] hanging on the
underside of the roofing felt.

Normally this steam is vented from the attic with the airflow through the
roof from the westerly winds that occur at this time of the year, but
these winds have changed direction or stopped for fairly long periods
leaving the moisture to collect - and because of the insulation, there is
no heat in the attic now to simply dry it.

As a matter of interest, this situation has only occurred since we had the
cavity and loft insulation installed about three years ago in a
traditionally-built house of the mid-1970's (with absolutely no loft
insulation installed at the time).

[1] I cannot persuade SWMBO to have a bath with the bathroom window
slightly open to vent the steam for the life of me - and I've tried for
many a year, but still cannot 'educate' here. Please don't show her this
post or I'll be making my own breakfast tomorrow. LOL


Seal up bathroom and paint loft floor over bathroom with oil based
paint.Then observe.

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