August 24, 2024 By Eco4 gurus

PAS ventilation requirements

Ventilation is really important when installing fabric measures as installing floor, wall or roof insulation decreases the air permeability of a building. When the ventilation is not taken into consideration and upgraded to minimum standards this may result in increased condensation, mould and an unhealthy environment for occupants.

When Fabric measures are installed a full ventilation assessment and upgrade strategy should be completed and actioned.

Below are the most common ways ventilation requirements are deemed adequate within domestic retrofit of energy efficient measures to homes. The project you are working on my require a different approach so it is important to get advice and a specification from a qualified domestic ventilation specifier.

Ventilation Requirements

To meet PAS requirements all wet rooms should have mechanical extract ventilation (MEV) and adequate background ventilation (BGV) or a PIV system as below.

When the pre-existing ventilation is deemed adequate:

1. Pre-existing MEV to all wet rooms and pre-existing background ventilation to all habitable rooms and wet rooms (air bricks or trickle vents), where there is no presence of condensation or mould.

2. Positive input ventilation ventilations with 4000mm² BGV to all wet rooms and 8000mm² BGV to all habitable rooms. And MEV’s to any wet rooms that are accessed through another room such as an en-suite or a kitchen where you have to pass through another room to get to it. MEVs may also be required in other wet rooms depending on property specific requirements

When pre-existing ventilation requires upgrading:

3. Constant flow dMEV’s to all wet rooms with BGV of 4000mm² to all habitable rooms. Where dMEVS are installed. Natural ventilation shall be removed/disabled within that room/space.

4. Intermittent MEV (IEV and cooker hoods to outside) to all wet rooms with 4000mm² BGV to all wet rooms and 8000mm² BGV to all habitable rooms.