Firstly, there is a growing need for flexibility, to optimise occupancy and usage levels. Laboratories need to be adaptable spaces, in which multiple scientific disciplines can work effectively side by side and the types of activities carried out in the lab can respond to changing requirements.
Secondly, institutions with laboratory facilities need to tackle soaring utilities bills. The energy consumption of laboratories is often more than three or four times that of offices on a square metre basis. This can mean that laboratory buildings are responsible for between 50% and 80% of the total energy-related (non-residential) carbon emissions of research-intensive universities.
Government research facilities, hospitals and private sector laboratories are similarly affected, with energy consumption presenting significant financial and environmental challenges.
So how can the HVAC system designer ensure that the laboratory air management system delivers all of these benefits?
Tackling energy consumption
The higher energy costs and carbon emissions of laboratories are typically associated with the air supply and extraction requirements of fume cupboards. When sashes of fume cupboards are open, the volumes of air required to maintain a safe working environment for laboratory personnel increase significantly. For example, a 900mm wide cupboard with a maximum sash height of 500mm and face velocity of 0.5 m/s would extract approximately 225 l/s of conditioned air from the room.
So managing the supply and extraction of conditioned air effectively is key to reducing energy consumption, and variable air volume capability is crucial. Based on the example above, the minimum air volume for a variable air volume fume cupboard would only be around 55 l/s when the sash is closed, saving 170 l/s of conditioned air, whenever the sash is in the down position.
Best practice is to install a room air management system to fully integrate fume cupboard air supply and extraction with the wider air management systems to prevent wastage. Air management systems such as TROX EASYLAB make it possible for all input and extract air for the laboratory to be controlled automatically to ensure that the required ventilation strategy and levels of safety are maintained. With this design approach, the supply and extraction of the fume cupboards (or other technical air management devices) is automatically balanced and offset in line with changing requirements, reducing the total supply and extract volumes. For example, if the fume cupboards are open and extracting air, there is not the same requirement for the room system to carry out this process. By scaling down room exhaust air extraction in line with fume cupboard extraction, the room air management system is able to prevent wastage associated with over-supply of conditioned air, improving energy efficiency significantly.
Other energy saving measures to consider include reducing air change rates for the air conditioning systems (with the provision of local overrides) when the laboratories are unoccupied, for example at the weekend, or overnight. Where equipment generates significant amounts of heat, capturing it at source with a well-designed capture hood prevents the heat from entering into the room and reduces the need for additional room cooling. Or devices could be employed to automatically close fume cupboards when they are not in use.
Flexible design achieves BREEAM 'Excellence'
Room air management systems also have a role to play in increasing the flexibility of laboratory spaces. The University of Birmingham’s new Collaborative Teaching Laboratory (CTL), for example, was purposely-designed to promote interdisciplinary engagement across the different departments of the university. To achieve this, in one area of the CTL, the TROX air management system, integrated with the site’s BMS, optimises energy efficiency of 50 fume cupboards. It divides the lab into five zones, each with 10 fume cupboards, fitted with TROX EASYLAB TVLK-type fume cupboard controllers. Sash distance sensors control the volume flow rates based on the height of the sashes, and TROX BE-SEG-02 user displays, with traffic light warning systems and audible alarms, contribute to safe working procedures.
Each zone features two supply air VAV units which track the extract air, ensuring the maintenance of correct leakage flows. By matching the supply of air to the changing requirements of the space these features reduce over-supply and wastage of conditioned air, ensuring that multiple scientific disciplines can carry out teaching and research safely side-by-side, whilst achieving the optimum level of environmental and financial performance. The resulting levels of efficiency have contributed to the building’s ‘Excellent’ BREEAM rating.