The Manthorpe Felt Lap Vent is a refurbishment product designed to increase the amount of ventilation into existing roof spaces. It helps to prevent roof condensation and moisture drops. Easy to fit, it simply slots between the felt laps and can be installed from inside the loft. The three felt clips secure the product in place even if the felt is degraded or loose. It can be fitted between 400mm and 600mm joist openings and provides 3000mm² airflow per unit. Dimensions: 275mm x 190mm. Meets building regulations.