As part of the monitoring activity for this project, we have undertake an extensive field experiment at the Aldwyck Housing Association Building in Luton.
This is a low energy building, designed to use natural ventilation all year to provide fresh air to the building, and there is a substantial mass of exposed concrete on each floor which provides thermal buffering of the interior from the exterior temperature fluctuations.
There is a heating system consisting of fin radiators around the perimeter of the building, but there is no mechanical cooling or ventilation. As part of the research effort, we have developed some small scale laboratory models of the building, to explore the controls on the natural ventilation flow, and we have collected temperature data every 5 minutes for over a year 2003-2004, at over 80 locations in the building.

Our modelling and monitoring have revealed the effectiveness of night cooling in summer to provide low energy cooling during hot summer days, and also the effectiveness of natural upward displacement mode ventilation in providing a well-ventilated and thermally comfortable environemnt even in deep winter, with only the provision of heating through perimeter radiators. In the design, air enters through the row of small high level windows at the top of both the ground and first floors and passes through the open plan offices into the atrium, where it rises to vent through the central stacks atop the atrium.

The atrium has five stacks for ventilation, and this can lead to multiple states, in which some of the stacks act as inflow which others act as outflow stacks, in addition to the inflow at lower levels through the windows. This multipicity in the flow regimes has been identified with some simple analogue laboratory experiments in which a heated tank of water, immersed in a larger reservoir tank, reveals the possible flow regimes and regime diagram.

The interaction of two floors venting through a common atrium is also of interest -- under some conditions the upper floor can become part of the outflow stack for the lower floor, while under other conditions both floors ventilate through the stack. Again laboratory experiment shown below reveal these two different flow regimes. In managing the building, such changes in the flow pattern are key to understand in order to develop control strategies through the opening and closing of carefully selected dampers to lead to the preferred flow pattern.