Vapour control membrane in rafter insulation

[happyhomemaker]

Hi,

I am proposing to insulate the rafter space in a Victorian house - the loft is used for storage. I've already done the loft floor (150mm space blanket + chipboard floor). I am reluctant to increase the floor joist depth due to limited head clearance - although admit to sense of doing this .
My intention is to use 50mm celotex between the rafters, then reflective thermal foil , finnishd with plasterboard.
Would the foil be sufficient as a 'vapour barrier' or is something else required.
The rafters vary but are approx. 100/120mm deep but not regularly spaced.

Any advice most welcome.

Happy Homemaker

 

[mointainwalker]

What you are proposing is a total waste of money and effort.

You have already insulated the ceiling and so there with be little heat passing through that 150 mm.

Since your roof space should be ventilated - which will carry away whatever heat gets through - there is no point in insulating between the rafters.

And , in my opinion, forget about using reflective-foil anywhere (assuming you mean multi-foil ) as its benefits are hugely exaggerated by the producers.