The Hambleside Danelaw soffit and fascia product ranges provides roofspace ventilation at the lowest level of the roof line. All grille and mesh sizes are designed in accordance with the recommendations within BS5250. These vents help to avoid excessive airflow resistance and prevent the ingress of birds and large insects.Our soffit vents permit entry of air into the roofspace for most eaves details. When fitted on opposite sides of a rectangular roof structure they will satisfy the requirements of the Building Regulations. HD 7000 When introduced into existing unventilated soffit boards in refurbishment projects, the circular soffit vent will permit entry of air into the roof-space. They are easily fitted into predrilled 70mm diameter holes. Standard flyscreen conforms to regulation requirements. Properties Airflow: 2,500mm2 airflow per vent (varies according to spacing).10,000mm2 per metre at 250mm centres.Base diameter: 80mm.Hole size: 70mm.Height: 16mm.Material: polypropylene.Colour: black.