2.2 NAT Vent Box

The key elements making up the Nat Vent Box are shown in the illustration to the left. Air is brought in through the external weather louvre 11, then through a volume control damper 10. The volume control damper can either be used to seal the building or manage/control the fl ow of air into the building. This damper can be manually operated by means of a handle or Teleflex cable. Motorised thermal dampers can be used in combination with a BMS system. A second important function of the thermal damper is to maintain the thermal line/thermal performance of the building envelope when shut.

The noise reduction across this unit is achieved through the attenuator 9. The attenuator is incorporated between the thermal damper and an internal louvre 8. The attenuator is formed by stacking W-shaped tiles which creates a honeycomb structure, restricting the passage of sound. Air however, is still allowed to fl ow through the central paths of the honeycomb body. The difference between the external noise levels and the required internal noise levels, governs the depth of the attenuator 9, the greater the difference the deeper the attenuator.

Finally, the internal louvre can be manufactured from wooden slats,  perforated metal, or a conventional internal louvre can be used.