11mm OSB vs 12mm Medite Vent for roof sarking?

[Great_scot_selfbuild]

Which is best and why, or is there nothing in it between 11mm OSB and 12mm Medite vent panels for the roof sarking.

 

Our roof will have 350mm of warmcel between the rafters (U=0.11), with 50mm air gap above the sarking by means of battens & purlins supporting a corrugated steel roof sheeting.

 

The original scope of the timber frame had 11mm OSB listed but the designer has specified 12mm Medite vent and so I’m being asked which I would like. The price difference is £10/sheet, and we need 164 sheets, so £1,640 uplift for Medite vent.

 

Have any of you used both and what would you go for and why?

 

We’re going for quite a high spec performance build, and have prioritised the fabric of the build. If there’s a material benefit/value to be gained then we would consider this extra cost, but we can’t afford to do it just on a whim.

 

Keen to get the experienced view from this group.

 

Thanks in advance…