Some opinions please!

Putty Man

Hi all, long time lurker first time poster here.

I'm in the process of choosing a timber frame supplier for our house which we hope to build in the coming months. I'm getting lots of different specs and opinions, the issue of breathability seems to split the timber frame companies.

I'm concerned about damp in the frame and so have tried to stay away from specs that included vapour tight, non breathable layers (eg foil) on the inside and OSB on the outside. Is this a good idea? These specs tend to have good u values.

Anyway, I wanted to run a particular spec that caught my attention past the exceptionally knowedgable and helpful boards.ie members, so what do yis think of this...

From the outside:
Blocks/Cladding
50mm cavity
TF400 breather membrane
Panelvent
140mm cavity in the frame filled with Earthwool Frametherm
Siga airtight membrane, taped and sealed
2 inch service cavity filled with Rockwool Flexi
Insulated PIR board (bit scared of this?)
Fermacell

Apologies if the names of the products don't make sense, or if these are stupid ques.

The spec above is not particularly cheap, but apparently givse a U vlaue of 0.15 which is as good as I've been quoted.

Any advice greatly appreciated.

nulabert

Better built with concrete?

Have you given any thought to Thermal mass or heat recovery system?

Putty Man

Thermal mass - a disadvantage of TF for sure (especially as I'm thinking of UF heating), but a sacrafice I'm willing to make to keep er warm.

HRV - taken as a given, most likely going with a Vilavent, but not to concerned with that decision just yet.