With roof condensation becoming an increasing issue in properties, especially when the level of roof insulation is increased, it is important to ensure that the roof space has adequate ventilation. The Underlay Lap Ventilator (ULV-B) from Hambleside Danelaw can be installed inside of cold pitched roofs where condensation is a problem.
It is important to note that this product is not designed to replace conventional roof ventilation openings or recommended for use in new construction work where adequate roof space ventilation should be provided in accordance with BS 5250 Management of moisture in buildings. Code of practice.

Instead, it is designed specifically for existing properties and refurbishment, where they can create ventilation openings in areas lacking adequate roof space ventilation or where existing air pathways have been obstructed, especially in cases where loft insulation has been enhanced.
When inserted between each rafter, in the lowest underlay lap, via the two retaining tabs, the ULV-B product delivers over 5000 mm² of airflow per linear metre depending upon rafter spacing.
This video shows the speed of installation.
Contact Hambleside Danelaw
The ULV-B is available to order at Hambleside Danelaw stockists, or for more info, get in touch via the contact page.



