Warming up a Cardiff landmark

One of the most prestigious buildings in Wales has upgraded its natural ventilation strategy in a bid to improve occupant comfort.

Built at the turn of the century, this government building in the picturesque Cardiff Bay area incorporated a number of sustainable features, including natural ventilation. This involved outside air being transported from an under croft plenum into the occupied spaces via trenches and stainless steel floor grilles.

The trenches were fitted with heat emitters and the air flow was managed by attenuators and two-stage motorised dampers.

Air change rates were managed by CO2 and temperature sensors to meet good air quality standards, but in practice occupants often complained about being too cold. This was because most of the fresh air was able to bypass the heater in the trench and enter the space at little more than outside ambient temperatures.

Occupants situated close to the floor grilles, in particular, complained of cold draughts.

On closer inspection, it was also revealed that the motorised dampers were not shutting off completely, which meant more air flowed into the space, even when the dampers were supposed to be closed.

Detailed

Following detailed study by the engineering consultants Howard Doolan Associates, it was agreed that fixed heating elements mounted directly to the motorised dampers should be used instead. This would ensure full contact between the incoming air and the heating medium and eliminate the cold blocks of air being introduced into the occupied space.

Therefore, the 21 existing motorised dampers were replaced by Vengen insulated units, manufactured by Ruskin Air Management.

The Vengen natural ventilation modules are 930 mm high, comprising a 320mm high winter section with heating coil arrangement and a 630mm high summer section with no heating provision. These double skinned, insulated dampers are very low leakage and boast excellent thermal properties. Additional changes and improvements to the existing control system were also undertaken.

In order to install the Vengen sections, which varied in length from 2,000mm to 5,650mm, the existing attenuators and motorised dampers were removed, and replaced by new Vengen motorised damper assemblies coupled to the heating coils. Finally, the existing attenuators were repositioned and fixed to the new dampers.

The heating coils were then connected to the existing low pressure hot water system and the completed installation commissioned.