insulation options

hi looking at insulation options and trying to make final decision.
Timberframe 215 sq metre house with 220mm stud walls, osb outside, 37.5mm insulated plasterboard for inside.
Roof has 60mm kingspan t7 outside the rafter and is cross battened to allow air under the slates.

1. Spray foam.
Originally i was very sold on the idea of spray foam insulation as it can double as an airtight layer, is easy to apply (by contractor) and can fill all cavities. having looked at a number of very negative posts here and on construct ireland have pretty much decided against this option as there are questions about condensation and the wood being too enclosed..
Cost in the region of 11 - 12 k
uValue: .16 in walls. .19 in roof

2. METAC rock wool.
the option provided by the TF company, it would need additional airtight membrane.
Cost: around 8-9 k (cant quite remember)
uvalue .16 in walls .19 in roof

3. Cellulose:
seemingly it would need to be sprayed into a closed frame wall because it is 220 thick.
cost 13 - 15 k
uvalue: cant find it right now, but it was not as good as some of the other insulations.

4. King span: good stuff but expensive
walls 200 mm K12 board
roof 60 mm K7 board x 3
cost: 19K
uvalue: .13 walls, .11 roof

5. Xtratherm rafterlock
have fitted 1 sample board, which fits stud sizes. although it is designed to squash and then expand into the gap it was a bit of work getting just 1 in and would leave smaller gaps unfilled..
2 x 100mm boards to walls and roof
cost: €13,891
uvalue: .14 wall, .11 roof (including external k7 board)

6. thermohemp
this also is sold in teh appropriate size for the studs. the question is; would it work with the osb and K7 outside it and the insulated plasterboard inside.
Cost 15,767
uvalue walls .19 roof ?


those are the options i can see at the moment.
price, effectiveness and suitability are the issues. i have also to take into account that i already have the k7 external insulation on the roof and the insulated plasterboard: and do these effect the potential benefits of some of the insulations, such as cellulose or hemp ( i.e. sealing them in so that their breathable properties are of no use).

any suggestions or opinions are welcome, my head is wrecked....

like a lot of us, you're suffering from TMI.

Too Much Information.

What you should look at, ihmo, is suitability, effectiveness, and then price. If price is the only arbiter, just pick Metac.

I have the Cellulose in mine, but it cost nothing like 15k in 06, at any rate...

The problem with ANY board product is quality of fit. If you have to cut any - and you will - you need to do it very well, for a very good fit, or it's hardly worth doing at all. Use - and if necessary, buy - a table saw, and work to tight, tight tolerances. The saw will pay for itself, believe me.

At the end of the day, all insulation is good - but some is better than others. Some are at a premium - if you have the cash, fine, but if not, choosing the others doesn't make yours a poor house.

Oh, and airtightness tape. Everywhere. try www.siga.ie

I am presently thinking of insulating an attic room using K7 Kingspan insulation...in a similar fashion to Fig 3b of the attached doc.
[broken link removed]

Fig 3b shows the 12.5mm plasterboard fixed directly to the rafters.
I was hoping reduce the u-value further by provided an additional thin layer of foil insulation between the rafter face & the underside of the plasterboard. The finish will be timber varnished face.

I would prefer not to use the insulated plasterboard as it would use up an extra 25mm in the attic.

Any suggestions.

you cant reduce the u value by adding a foil insulation because the insulation value of the foil is not calcuable, therefore it will be ignored in any u value calculation....

Cheers for the previous post Syd the Beat

I assume this is one product that I should not use.
[broken link removed]


Interesting test here......



Charactered Surveyor recommends it here.......page 2
[broken link removed]

Has anyone used this product & where can it be got in the ROI
[broken link removed]

According to this website using 100mm GA3100 between the rafters & the 12mm TB3012 in lieu of the proposed foil insulation as suggested in my previous thread will achieve an overall U-value of 0.24

Could you please let me have your recommendations and anyone else.