Timber frame extension-insulated plasterboard on reveals...?

[Inkster]

I'm currently having a timber framed extension built at the rear of my house. It's north facing. I've gone with a flat roof. Warm roof with 150mm rigid insulation over the beams. The beams are 175mm. The ceiling will be 62.5mm insulated plasterboard below the beams. I've also got 2 large U6 Fakro triple glazed roof windows. The builder is insulating the roof kerbs with 100mm rigid insulation on the outside. The timber frame wood in the walls is 140mm x 40mm. It will be filled with 100mm rigid insulation and covered with 72.5mm plasterboard. The French door and window are triple glazed also.

Should I used 27.5mm insulated plasterboard on the French door and window reveals? The builder says that ordinary plasterboard would do because it will be attached to the wood frame, it won't touch the outer concrete block and the wood won't be a cold bridge. The frames are wide enough to take the insulated plasterboard.

Opinions anyone....?

 

[freddiemercurystwin]

Well with all that insulation I think the reveals will be feeling left out if they don't get the same treatment! Do it.

 

[cjard]

Cost of superinsulated rest of structure: £20000
Cost of adding insulation to the back of the window reveals: £200
Asking on the internet for opinions on whether you should do it: priceless