Today was an important moment for the Withington Co-operative Eco-house - the first time in the 100-odd year history of the house that a piece of insulation was fitted! And here's Eddie the builder putting it in (sorry about the thing in the foreground):

We're insulating both between and below the rafters with PIR insulation (not the most eco-friendly of materials, but weight limitations preclude using anything else). This is the first layer of insulation, which goes between the rafters:

After this, there will be 2 * 75mm layers below the rafters - total thickness 175mm.

Great care is being taken to ensure a through-flow of air through the roof structure, behind the insulation. For this reason, in addition to using a breathable membrane, we've fitted vents at eaves and ridge levels, and only used 25mm PIR between the rafters: