reinsulating timber frame concerns??

[looper]

hi,

I plan on stripping plasterboard off external walls in a timber frame house. install tyvek airguard and 50mm kinspan insulated plasterboard screw fixed to timber frame again; reskim etc. There are no vents in the house as its 25 years plus old. Could mold growth be a problem or not or should i counterbatten timber wall with 2" x 1" considering i would then loose 65mm of room. Any comments or advice appreciated.

 

[Sconhome]

looper,
I take it you are stripping the internal walls?
If this is so you should insulate the void in the timber studwork, then install your vapour barrier ensuring a tight seal around all windows and doors (on external walls).
I would recommend a 2 x 2 " counterbatten which will give you a service space for wiring, socket and switch boxes etc. without interfering with your vapour barrier. You can insulate this layer also with 50mm Rockwool or similar and simply over lay taper edged plasterboard, no need to use insulated board in this situation.
Re mould, if your vapour barrier is properly installed you should have no concerns with trapped moisture. I say should because I have no idea re the remaining structure of the house ie external skin (block, brick, render, timber cladding).
Suffice to say, in the draft Part F regulations passive vents are being frowned upon and you are encouraged to build airtight structures with no cavities and no vents. Ventilation is by active means of opening windows and allowing cross air flow for 10 minutes each day.
The fact you have had no problem with dampness in 25 years without vents would indicate a compatibility in your structure for this air tight membrane.
Good luck.

 

[looper]

Sconhome,

Its internal walls all right. When you say insulate timber frame itself would you suggest a ridgid insulation or a mineral wool as at the moment its a fibreglass insulation in the void. I agree with the services moved to the 2"x2" service void to keep structure airtight. The internal walls are Timber stud and plasterboard.