Wet on celotex roofside - update: problem found

[andy.budgell]

Whilst I was up in my loft last night I noticed a lot of condensation on the roof side of the celotex insulation.
So much that it had been dripping, onto the floor from where I have only partially insulated it halfway down to the eaves cupboards.

Initially I thought this was a leak, but then I thought, it hasnt rained for 4 days! After I checked all pieces, I discovered that the condensation was only
occuring on one side of the house. Which happens to be the side that a) the cold water tanks are on and b) The side that
doesnt get the sun all day (north side). There was one rafter that I hadnt insulated yet, and this was dry. It did seem wetter the closer you were
to the cold water tanks.

Is this normal? Should I make holes in the ridge board/felt before permanenly fixing the celotex?
The tanks will be removed in a few weeks when I get a combie fitted. But is this a general problem with ventilation?
My roof is ceramic tiles, battens, and felt.
Budgie

 

[Deluks]

Are your eaves vented? If you have insulated right down to the eaves then you might have restricted airflow which is the main cause of condensation. Have a look outside to see if there are any vent's in your fascia/soffits.

Covers on the water tanks are often overlooked.

 

[andy.budgell]

Are your eaves vented? If you have insulated right down to the eaves then you might have restricted airflow which is the main cause of condensation. Have a look outside to see if there are any vent's in your fascia/soffits.

Covers on the water tanks are often overlooked.

Hi Deluks!

No the insulation is not down to the eaves so I would have though there
was sufficient airflow there now. There is a cover of sorts on the cold water tank but a partial one only on the central heating one.

Its very strange indeed. Its spooked me a bit!

 

[JohnD]

fit proper covers

look and see if the vents are running into the tops of the tanks, or if they are warm

check the ventilation of your bathroom. Maybe steam is getting up through gaps.

also have a look at
//www.diynot.com/wiki/building:condensation_in_houses

 

[andy.budgell]

Realised what was going on.

If I leave the loft hatch open for a couple of hours whilst I'm working up in the loft, the warm air from the house condenses in the air gap between the felt and the celotex.

PROBLEM SOLVED. Close loft hatch whilst working!

 

[Deluks]

Problem is, this warm air may still be able to get into the loft, through the ceiling itself even. Open any trickle vents you might have or open a window upstairs slightly. If you're drying clothes on rads wjich I have been doing lots of this week, then definitely vent that room too.

 

[andy.budgell]

Yes no doubt it probably will get up into the loft. But when my cupboard are in and the insulation is platerboarded those small amounts should vent out of the velux window vents or be dispersed around.

Where I've partially celotexed it, theres a nice easy path for the air to flow up into the space between felt and celotex, which there wouldnt normally be.

I will observe the condensation levels when finished to see if its a problem. Yeah good point about the venting.

 

[JohnD]

...If you're drying clothes on rads wjich I have been doing lots of this week...

Grrrr!!!