Regulations

NHBC Regulation 2011

Insulation and control of condensation:

7.2 – D11 (a) Ventilation of main roof spaces

Pitched roofs with insulation at ceiling level should always be ventilated to the outside air to minimise the risk of ventilation.

7.2 – S14

Cross Ventilation of the roof is provided
Insulation does not block the ventilation path at eaves level
Insulation is laid over the whole loft area, including the wall plate
There are no gaps in the insulation

BS5250 Control of Condensation in buildings:

When using both LR and HR roofing underlays and on all roof pitches, “the harmful effects of condensation can be controlled by ventilation beneath the roofing underlay.”

BRE Report - Thermal Insulation - avoiding risks

2.1 (c) Provide an air path to the roof space from the eaves ventilation opening equivalent to a 50mm continuous gap.
2.3 Condensation of Thermal Bridges
2.3 (a) Carry the loft insulation over the wall plate to link with the cavity insulation.