attic spaceboard insulation or need to increase height of boards between insulation?

hi. we are going to improve our attic insulation. currently we have 100 mm fiberglass and part of the attic has floor boards as we'd like to have some storage. We are thinking of putting extra 200 mm of recycled plastic insulation or fiberglass (any opinions on recycled plastic - which is better?). Regarding the part that is boarded we are going to remove the boards and add 50 mm of khauf spaceboard insulation from B&Q and also leave 100 mm remaining fiberglass there. My question is - is it a good idea or is fiberglass going to be squashed and ineffective? should we remove fiberglass from that area all together and put in 100 mm of spaceboard? - this is quite an expensive option which I'd rather avoid. Or is there a way of heightening the boards between insulation so the floor boards will lay higher and just put in another 200 mm of normal fiberwool/recycled plastic? Any advice would be much appreciated. cheers

I'm thinking of doing something similar at present. What I may do is screw something like 4" x 2" to the existing joists, thus deeping the space between them and rolling more insulation in there and then flooring the top of the joists with something like Spaceboard.

Take a look at what Leo said here..... http://www.askaboutmoney.com/showthread.php?p=999901#post999901

Compressing fibreglass insulation greatly reduces its insulating qualities. B&Q are doing good deals on insulation, at present. (2 for the price of 1 or 3 for the price of 2-not sure which).

The recommended amount of fibreglass etc. type insulation recommended in an attic is 300mm (12 inches).

I'm not sure about recycled plastic insulation but I have seen it in B&Q. However, the insulating details will be written on the wrapper.

P.S.
As far as I know, 6 inches of aeroboard insulation is about the same as 12 inches of fibreglass. And high density insulation, like that on Spaceboard, is even better.

P.P.S.
Welcome to AAM!

thanks Lex. We were in B&Q Liffey Valley this morning and discovered that they had very little out there - I think they had 2 for 1 deal over the last week or so and most stuff is gone.No 200mm insulation at all. We did see the hard boards with insulation that Leo was talking about - they seem quite dear? 8.65eur for 0.39 m2 which is over 22 eur per m2 (and it's not on 2 for 1 offer!). We are new to the whole thing so not sure if that's what it is ultimately going to cost us!? Any recommendations on any other places we can check out for insulation?

Hi again, Drunat. You should go to a builder's providers and have a look there. Their selection should be greater and they're usually cheaper than DIY stores like B&Q, Woodies, etc.

I was in Cork Builders Providers last week. I went out to the storage yard and they had an incredible selection of everything! Every type of insulation on the market. They also had the insulated attic boards but I remember thinking to myself that they were a bit dearer than I though they'd be. Not sure how they compared to Leo's ones.

If I were you, I'd get out the Golden Pages and ring around the Dublin area. You'll find them all very helpful, I'll bet.

B&Q repeat that insulation offer regularly. They might be happy to contact you the next time round, if you give them your number. They're extremely helpful in Mahon Point (my favourite store in the whole world!).

Don't worry about not being able to get 200mm rolls. You can always use 2 x 100 mm layers and it might even work out cheaper that way.

Best of luck and let us know how you get on.

Lex.

OK we went to Chadwicks in Lucan today and they have a great choice of insulating boards there. For the boarded space we are now thinking of buying 100mm Kingspan Kooltherm K7 Board (insulation-online.co.uk/kingspan-kooltherm-k7.html)
It has 4.75R value which is fairly impressive!? We are going to keep the existing 100mm fiberglass, keep mdf boards on top and then cover it all with Kooltherm Board and another layer of mdf boards. I have two questions now which I couldn't get answers to in the shop: 1) The Kooltherm boards have foil cover on both sides - is it going to cause any issues with condensation in our circumstances? 2) do we actually need to keep mdf boards between fiberglass layer and Kooltherm boards or can we just put Kooltherm boards accross so they are resting on the joist and put mdf boards on top of it all - those koolherm boards do look solid enough? cheers

I really don't know about the condensation issue but, as far as I know, you wouldn't have to put ndf under the insulation boards. Take a look at the following link. I think it applies exactly to your situation. [broken link removed]

100 mm sounds like a decent type of insulation and, given that it's so thick, there shouldn't be any need of mdf under it. Can you remember the size if the sheets and how much they are?

I just looked at it on the Kingspan site. It's phonelic (high density) board. When used externally, 70 mm of phonelic is the same as 120 mm of aeroboard type insulation. A quick calculation tells me that the one you're going to use would be the equivalant of about 170 mm of aeroboard. I might use it myself!

its 1200mm x 2400mm boards at 38 eur plus vat per board. I am going to call kingspan advisory line on Mon to check about condensation.

Thanks, Drunat. You can let us know what they say.

There are several detailed posts on Askaboutmoney in relation to attic insulation / ventilation and problems with it.

There is no point squashing fibreglass or Rockwool - the insulation properties work by trapping air between the fibres.

Increasing insulation at first floor ceiling level instead of following the line of the roof will lower temperatures in the attic space.

This can lead to problems with goods stored there and increase the risk of unlagged or poorly lagged pipes bursting in very cold weather.

Failing to following good practice guidelines in the Technical Guidance Documents can lead to a build up of moisture in the attic, and or in the building fabric.

Here are the Guidance Documents:
http://www.environ.ie/en/TGD/


The Old Part F
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,22447,en.pdf

See Diagram 6 P. 11


The New Part F
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf

See Diagram 11 P. 28 (more or less the same as in the Old Part F).

ONQ.

[broken link removed]

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Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.