I have a question on the celotex/ kinspan type insulation

[notexpert]

I have a question on the celotex/ kinspan type insulation. If I use it in my loft can I put it over the beams on the floor and then put chipboard directly on top, or do I have to have ventilation between them?

 

[mointainwalker]

You don't need any ventilation above but you MUST have a vapour-barrier i.e. a continuous plastic sheet - below to prevent moist air rising through the ceiling.

 

[notexpert]

You don't need any ventilation above but you MUST have a vapour-barrier i.e. a continuous plastic sheet - below to prevent moist air rising through the ceiling.

Thanks mountainwalker

Do I need to have the vapour barrier cover the joists (i.e. along the celiing and then round each joist) or would I have the vapour barrier between the joists.

 

[mointainwalker]

Much simpler to run it in a long length and cover the joists, but don't try to pull it tight. You want it on the ceiling and then running up and over the joists.