loft insulation causing damp...

[ellie84]

Last year I installed insulation in the loft. Since then I have had damp problems. I have now realised that this is more than likely due to the fact that I done the insulation right up to the eaves and didn't leave any gaps round the edges. So, my question is, how do I rectify this? is it best to just pull the insulation back a bit around the edges, or would you cut the insulation and remove it from round the edges? Do I need to do this all the way round or just in places? And how much of a gap do I need for air flow? Also, I have disconnected the bathroom extractor (has been disconnected since we bought the house), as it makes the bathroom so drafty. I did cover over the hole with plastic and put insulation on top. Do you think this is adding to the problem with hot air getting into the loft and not enough air flow? Would I be best to reattach the extractor fan or to get the extractor fan hole plastered over? We never had a damp problem until the insulation so I am assuming this is the cause of the problem....Thanks for any help!!

 

[Burnerman]

Follow the golden rule, and have insulation on the top of your ceilings only - you must allow the roof to breathe and it does this by allowing air through the soffit area and into the loft space.
Pull your insulation back from the eaves, and make sure it doesn't touch the roof underfelt anywhere.
As for the bathroom fan, there should be minimal draught if there is a shutter at the end of its ducting which must go outside - the louvre shutters open when the extractor is on, and they flap shut when its not.
I would strongly advise recommissioning the bathroom extractor as they remove a huge amount of moisture which indeed could be part of your problem anyway.
John

 

[dhutch]

That said, i only insluated on the easy to get section, ie, not down the 10inch sloping section down to the eaves, and i now get condenstation on he inside of the rooms due to this being far colder than the rest of the room.

I would leave the insluation there and try and get the ventilation back with vents elseware, or by adding vent trays between some of the rafters.


Daniel

 

[stevethejoiner]

A cold roof space, which is what you have with insulation on top of the ceiling joists, must have air circulation so in practice you should not insulate down into the eaves space as you have done. So you must now provide adequate air flow. Ideally you would install ridge vents or tile vents high in the roof pitch as well as retrospectively installing round eaves vents. You could fit ventilation pipe from the eaves vents back through the insulation to provide a clear and direct passage through the insulation so you do not have to pull it back and compromise on the insulation.
With regard to the bathroom vent, if you can afford it, you can change it for a heat recovery ventilator. This will pull the moisture out after removing the heat and bring the warm air back into the room. I think Tool Station sell them. You can leave them on 24/7 and it helps with whole house dehumidifying.

 

[mointainwalker]

Also, I have disconnected the bathroom extractor ....it makes the bathroom so drafty. I did cover over the hole with plastic and put insulation on top. Do you think this is adding to the problem with hot air getting into the loft and not enough air flow?

So, to look at it logically, where do you think all the damp air which was previously being sucked away, is now going ?

If the extractor was draughty, then you presumably had an open pipe with no baffled shutter on the exterior wall.

 

[ellie84]

Thanks for the advice I have pulled the insulation back a bit to allow increased ventilation. When I was doing this I noticed that some of the roof felt was ripped (presumably from when the neighbours had their sofits replaced, which is what I originally thought the problem was but didn't notice the ripped felt at the time :S ) so I will have to get my dad up a ladder to fix this. It is obviously more than just the ripped felt causing the problem though, as a damp patch developed in the bedroom at the opposite side of the house and the felt in this area is fine. Hopefully this will fix the problem, otherwise I'll have to get someone else to put vents in the loft, my diy skills don't quite stretch to that!! I have reattached the extractor fan so hopefully this will help too!

 

[ellie84]

Also, I have disconnected the bathroom extractor ....it makes the bathroom so drafty. I did cover over the hole with plastic and put insulation on top. Do you think this is adding to the problem with hot air getting into the loft and not enough air flow?

So, to look at it logically, where do you think all the damp air which was previously being sucked away, is now going ?

If the extractor was draughty, then you presumably had an open pipe with no baffled shutter on the exterior wall.

I don't think this is the entire cause of the problem as the extractor fan was disconnected 7 years ago when we moved in (so we have never used it) and it is only in the last year there has been a damp problem. I assume that previously it wasn't a problem as there was no insulation in the loft so was very well ventilated up there! And no, there are no shutters on the outside of the extractor.

 

[alewis]

me and my dad did our loft insulation a few years back, we get damp in all top rooms along the outside wall alone the curve of the ceiling and wall. Looking on here i will check to see if the insulation is too close to the egde or not, but we did lag the roof and covered with thin hardboard. Was this wrong.

 

[dhutch]

me and my dad did our loft insulation a few years back, we get damp in all top rooms along the outside wall alone the curve of the ceiling and wall

I have just done the same and get the same. I assume like me you have only insulated the flat section, leaving the sloping section uninsulated (blocking this can cause damp in the attic) hence this sloping section is colder relative to the flat section and walls, which combined with reduced heating, ends i damp.

I only did mine a month ago, so done have a solution yet, but I think its going to involve find some 'ventilation trays' to keep it off the underside of the felt and stuffing some glass wool down there.
My only other thought is rigid board, either in two parts (to get it in past the joists) or posted up from the other end (sofets off, and ladders) neather of which I would look forward to! unless you about to have the roof re-done in which case you can add from the top when the felts off!

Others thoughts are welcome.

Daniel

Daniel

 

[alewis]

the slopes are insulated too, it was bear tiles so placed lagging from top to bottom and used the thin hardboard to hold it in place, so worried that the ventalation is missing and thats why the damp is showing.