Do you know the actual date of this conversion which you say was already done when you bought 6 years ago?
This conversion is more than likely requried to comply with the building regualtions.
If you put some time into it you can search these forums for information posted on attic condensation due to inadequate venting leading to interstitial condensation.
You should be aware of TGD F as this represents deemed-to-comply practice in this area.
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf
P. 11 Dia 6 Roof Type D [whichever option] refers.
In particular pay attention to the 50mm air gap detail and the need to adequately ventilate the roof at both eaves and ridge.
Your new insulation-follows-the-roof detail should contain a vapour check.
This is due to be superseded this year by an amended regulation:
http://www.environ.ie/en/Legislation/DevelopmentandHousing/BuildingStandards/FileDownLoad,21942,en.pdf
I'd be wary of assuming your attic has been properly converted as opposed to having been floored out.
Competent people who do these things for a living don't usually leave attic insulation under the flooring.
It keeps the attic colder than it should be and offers little in the way of sound insulation.
You should ask a competent engineer to cast his eye over the timber sizes that have been floored over and see if the necessary upgrade has been carried out compliantly.
Typically this can involve installing new, deeper joists with their bottom faces raised up off the existing plasterboard by say 25mm to avoid "popping" the existing ceiling plasterboard due to deflection from increased load.
You should also consider your access from the lower levels to this space and install any fire resistance that may be required.
Please bear in mind that winder stairs are frowned upon by the building regulations although not absolutely forbidden - min stairs head height is usually 2.0M clear, but some explanatory leaflets from the DOEHLG show 1.9M
There are a whole raft of issued in relation to fire safety that need to be addressed.
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1640,en.pdf
My colloquial experience suggests that a lot of conversions may have been carried out by people not competent to do so and you should ask an architect or other competent building professional or fire consultant to comment on the work to date.
While rafterloc appears to be a popular choice, you may also wish to consider products by Kingspan and Rockwool.
I have no connection to any of the people or companies producing either of these products or refterloc..
HTH
ONQ
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