This was a project to develop a 6,000m2 Headquarters Office using a mixed mode solution. During the research for this project H&K carried out a detailed assessment of energy use, working closely with the Architect, the Michael Laird Partnership, of the following Buildings; PowerGen Headquarters (Coventry), IRO Headquarters, (Nottingham), Ionica (Cambridge), British Gas City Office (Leeds), and Cable and Wireless College (Coventry).
Arising from these findings and by use of a sophisticated multi-zone CFD model using real weather data, H&K evolved an innovative double wall comprising;
750mm naturally ventilated airspace with simple upper and lower control louvres to control airflow in summer, mid-season and winter. This space also accommodates brise-soleil walkways for shading and window cleaning. This also provides primary security when the building is ‘opened up’ during nights and weekends.
Double-glazed inner wall with opening windows for manual control by occupants during day hours with separate automated hopper windows for BMS control during nights and weekends to ‘free-cool’ the structure and fabric, for example night free cooling.
The soffit is high quality exposed concrete with integrated suspended light fittings incorporating ceiling furniture (fire alarms etc.) and an acoustic baffle.
During mild summer mid-season weather with lower wind speeds the building operates in a natural ventilation mode to ventilate the 2 x 15m deep floor zones which connect to a central atrium which also has automated opening rooflights, similar to Powergen. The building ‘freewheels’ on very low energy usage (predicted as 40% to 60% of annual operating hours).
During peak summer weather when external air temperatures rise above 22°C a supplementary ventilation system operates to supply underfloor ventilation from a variable speed AHUS (2 to 6 ACH) by means of a 450mm clear void which allows good access for IT Services, water and drainage and perimeter heating. Space provision has been made at the roof plant room to incorporate chilling and simple cooling to the supplementary ventilation supply should extra high internal heat loads arise but this is seen as a safety belt approach.
During winter and windy mid-season periods the outer wall is modified to reduce natural ventilation of the double wall. The perimeter heating system (LPHW perimeter heating in a floor trench) operates and the supplementary air supply operates at 2 ACH with tempered warm air, again all at very low energy usage.
In particular, detailed solutions to accommodate cellular offices, meeting rooms, training rooms and such like have been developed using simple supplementary spot cooling systems which allow corporate flexibility to be achieved.
This approach has been ‘challenged’ by various means and has now been accepted by the Developer and Design Team as a lower capital cost, low energy solution which will meet the needs of most Corporate Clients to provide aesthetically pleasing, light and comfortable ‘natural’ working surroundings.
