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.

2.4 Bench Seating

Adding attenuation to the vented facade of a single storey building is comparatively easier than a multistory building, since it is often possible to extend the building envelope, accommodating the additional depth of the NAT Vent Boxes.

In the case of single storey buildings, it is common to maintain a simple vertical thermal line, by placing the thermal damper into the line of the facade 4. The acoustic attenuation in this instance is placed on the external side of the building. This design approach has been implemented by MACH Acoustics on several projects.

The NAT Vent Box has been installed under bench seating, flower boxes, play boxes, small steps in the facade and other elements. These units have all been used to hide and accommodate the additional facade depth often required when naturally ventilating a building on a particularly noisy site.

A second advantage of single storey buildings is the potential to incorporate the NAT Vent Box above or within roof lines, above corridors, over storage rooms and other areas.