Stop batten for ventilation gap

[les_danger]

Stupid question here, but the AI response is garbled and annoying as hell.

I'm putting in rigid board insulation between the rafters of a pitched roof, and was going to put in stop battens to make sure the board doesn't go futher back and I can maintain a ventilation gap of 50mm. I only need something like 38x19mm as the boards should be a pretty tight friction fit on their own.

Shopping around for battens at the big stores - I can see 'green' pressure treated batten or kiln-dried (either sawn or par) options. These will sit outside of the thermal envelope but under the tiles and a membrane. Does that mean I should prioritise getting kiln-dried since the treated ones are mainly for outdoors?

 

[noseall]

Does that mean I should prioritise getting kiln-dried since the treated ones are mainly for outdoors?

No.

You just need to buy regular tanalised roofing (tile) batten. Either 19mm x 38mm, 25mm x 38mm or 25mm x 50mm.

It cares not whether it is indoors or out.

Is the membrane breathable?

 

[les_danger]

Thanks!

Yes the membrane is breathable, but the tiles are quite close fitting fibre cement that aren't counter battened. Hence still leaving the full 50mm. There is good ventilation from over fascia vents and ridge vents. When the wind is up i can see the membrane move like a bellows.