What insulation should I use?

[Padraig Clarke]

I am insulating a single brick extension as it is very cold and just looks like single brick with some plaster. I need some advice as there are loads of insulation products, but it’s not easy to choose for the novice - so what do the experts pick.

I plan to put up batons, then insultate inbetween, then T&G (nailing into the batons).

I have seen celotex boards pop up a lot, but then there is also stuff like the soft roll-out stuff: http://www.diy.com/departments/knauf-eko-roll-loft-insulation-l-7-28m-w-1-14-m-t-100mm/182146_BQ.prd

Q1: What insulation would you recommend? (Walls and ceiling)

Q2: As I want to T&G, do I nail these straight into batons, or am I meant to add in a VCL sheet, then a panel of plyboard, or drywall - finally adding the the T&G?

 

[John D v2.0]

Celotex is twice as good for the thickness, but also ten times the price. Depends on space and budget.
Celotex your can tape the joints as avcl, wool you need your own one, and to deal with any sockets etc.
You can even get celotex glued to plasterboard as a special product at extra cost.
Celotex has good compressive strength so you can omit the battens and screw straight through into the brick if it's decent enough.

 

[Padraig Clarke]

Thanks John, I have read Celotex is the best stuff

For the T&G, do I add a layer of plyboard or drywall over the Celotex, then add the layer of T&G? Or is that extra layer not needed when adding T&G?

 

[Doggit]

The cellotex website will recommend an airgap behind the cellotex, and a VCL layer across the front before you fix the T&G. In reality, foil faced cellotex that's jointed and taped with alliminium tape will stop mositure getting through to the cold wall where the moisture would then condense. Obbviously without the VLC, moisure can still go through to the wood. It's also god practice to put a DPM under the battens, or at least use tanalised timber.

 

[John D v2.0]

Extra layer isn't essential, depends if you need it for fixing. If you want to put up shelves it might be beneficial

 

[Padraig Clarke]

Thanks again! I put a graphic together to help illustrate. Does this look like the right method?

 

[Doggit]

The plasterboard isn't necessary with the T&G, and the battens will be as deep as the airgap and the cellotex. If it was to be a skimmed wall, then you could put up the battens to get the airgap, then use wide head nails to hold the cellotex in place, and then long drywall screws to fit the plasterboard. With the T&G, you've got to go direct on battens.