Attic insulation confusion

paudie2005

Hi all I’m badly in need of some sound advice..
I am in the planning stage of reinsulating the floor of the attic of our 25 year old house. Currently there is 100mm fibreglass insulation between the ceiling joists (which are at 400mm centres). This insulation has degraded over the years and seems to have lost its thermal properties. I wish to upgrade the insulation to meet building regulations but also want to allow access to the attic space and floor the attic space with possibly 15m plywood for storage. So my dilemma is this:
If I insulate with Rockwool/fibreglass there would be approximately 250/300mm insulation which would make it impossible to floor so I was looking for other alternatives that would achieve the same uvalue’s as this depth of insulation. I came across ‘Y.B.S Super Quilt insulation’ which is about 20mm thick and ‘Actis Triso super 10’ which is also about 30mm thick. Suppliers are telling me these can be used on the flat of the ceiling floor while the company web sites only recommend them for use under the rafters.
Can anybody advise me or has anybody used any of the multi layer insulation? I’m a fairly baffled!

Thanks
P

Heatherview

Hi Paudie2005
What thickness/depth are your ceiling joists. ?
Heatherview

No6

Paudie

Multi layer insulations have not passed any agreement tests so may not be as good as you are being told!!! Why not replace the fibreglass between the joists, as much as you can fit, you don't say what size your ceiling joists are!!, put a layer of plywood down over the joists followed by a layer of thermal board or even cavity insulation fitted together with an final layer of plywood fixed through the insulation or other flooring on top. you can use 150mm fibreglass over the ceiling joists in the low and unfloored areas of the roof.

topcatcbr

Please see this
http://www.sustainability.ie/insulation.html

And for full test

http://www.foam-insulation.co.uk/building-regulations/BRE-multi-foil-insulation-measured-u-values.pdf

People are being conned into buying this as a full insulation product for Roofs. Be warned it is not. Most of the insulation is from the fact it provides a vapour/air barrier. This is required no matter what insulation is used.

This stuff was designed for conditions in space. While it is true that space is very cold it is also true that space is a vacum and as such does not conduct or convect heat. So it may be a case of what works up there may not work down here

paudie2005

Thanks for all the comments so far guys, appreciated
'Heatherview' the ceiling joists are 100mm thick.
'No6' I have since changed my train of thought to around your wave length!
If I replace the existing 100mm insulation between the joists with 100mm rockwool, then place a rigid board insulation over this (such as Knauf space board) and then place my plywood over this, this would solve the problem of being able to store items in the attic and then counter lay with 150mm rockwool where I don’t intend to put plywood.
I was talking to the builder that’s due to undertake the job and he was proposing to replace the 100mm insulation between the joists with fibreglass/rockwool and then put rigid foilbacked insulation between the rafters, I’m skeptical about this as what’s the point of heating the attic space when its just going to be used as storage.
I'm probobly making a mountain out of a moat hill here but as a recent construction graduate I don’t want to end up with egg on my face,so all opinions are appreciated!

Regards
P

paudie2005

Thanks for the links 'topcatcbr', interesting reading

m_stan

paudie what did you end up doing here? In a similar dilemna here myself now

paudie2005

m_stan wrote: »

paudie what did you end up doing here? In a similar dilemna here myself now

Hi Stan,

We ended up insulating with rockwook to a depth of over 300mm. We did not remove the old insulation but counter layed two layers on top of it.
Where we required storage space we kept the area over where there were supporting walls underneath to avoid any potential cracking of the ceiling below. To increase the space under the storage area lats we screwed to the existing ceiling joists, the space was insulated with rockwool (under the storage area the rockwool was compacted slightly which wasn't recommended but a compromise, also we did not achieve 300mm depth of insulation).
We also inserted ventilation slates to increase ventilation and ensured the soffit vents were clear.
On the attic door a sort of an 'insulated bean bag' is used to cover this area and draft seals around the attic door were added.
We received grants from the S.E.I scheme and North Tipperary County Council, I'm not sure if these are still available but definitely worth looking into.
We achieved the required insulation standards and got the relevant certs.
The house is definitely retaining the heat far better and we are not burning near as much oil or turf thankfully.
The contractor we used FPI solar - I've not connection to them but couldn't rate them any higher, they looked after everything, arrived and finished when they said they would.
Hope this helps.

Paraic