Is HVAC the key to energy efficient laboratory design?
As some of the most sophisticated man made environments on the planet, laboratories are essential in a range of industries, from pharmaceuticals to food and medicine to robotics. However, as the complexity of these facilities grows, so does their energy usage. Here, John Rush, our HVAC and mechanical services SME (Subject Matter Expert), explains how to make laboratories more energy efficient.
Laboratories are energy intensive environments, consuming between four to six times more energy per square foot than standard office or commercial buildings. This is mainly due to the energy intensive heating, ventilation and air conditioning (HVAC) systems necessary to ensure correct airflow and temperature. As a result, any energy saving in HVAC can result in significant improvements in overall energy efficiency and impressive carbon emissions reduction. In fact, because the overall energy spend is so large when compared to other kinds of commercial building, even the smallest percentage saving could be valuable.
In our experience, good laboratory design can reduce energy consumption by an impressive 30 to 50 per cent. One of the key reasons for this is that more than 60 per cent of a laboratory’s energy consumption can be attributed to the HVAC system. Given that, according to a recent S-Lab audit and report1, the UKs major university laboratories consume over 730 Kwh/m2/year, the overall cost and carbon saving can be impressive.
Laboratory HVAC systems would normally use 100 per cent fresh air to replace air extracted by fume cupboard and other extract systems, might requires between 8 and 30 Air Changes per Hour (ACH), or even higher for high density fume cupboard layouts. By comparison, a typical commercial building can get away with as few as four ACH and uses substantially less energy as a result. It follows, therefore, that safely and compliantly reducing the amount of air changes per hour in a laboratory, without impinging on performance, can significantly contribute to that 30 to 50 per cent energy reduction.
So how do you make some of the most energy intensive facilities in the world more efficient?
Control contaminant sources
Designing a lab is a top down process that works hand in hand with good day to day practice to lessen contamination risks. A good design team can reduce the number of ACH if the contaminant sources can be successfully limited, which in turn reduces the amount of energy used by the HVAC system.
Small behavioural changes, such as ensuring that each fume cupboard sash is closed when not in use either by manual or automatic methods, reducing the quantities of contaminants stored in the laboratory and introducing good handling practices to minimise contaminant release - such as keeping containers sealed or removing empty containers from the lab – will significantly reduce the extraction need. This allows the designer to identify the right volumetric flow rates and create a low energy HVAC design, bringing the facility closer to the lower end of the ACH scale.
Direct digital controls
Key to making the HVAC and extract systems as energy efficient as possible is by the adoption of Direct Digital Controls (DDCs), linked to variable air volume (VAV) dampers, for supply and extraction systems. DDCs enable the systems to take advantage of diversity in use of the fume cupboards and extract systems, providing variable flow control matched to occupancy and use; this is then coupled with overall variable flow control of the air supply to the laboratory. Presence detection at fume cupboards can also reduce face velocity, further reducing supply and extract air flowrates.
Automatic occupancy controls can reduce the air change rates down to an absolute minimum at night or at weekends when labs are empty; creating further potential for HVAC related energy savings. The US standard NFPA 45, - which regulates fire protection for laboratories using chemicals, advises a minimum of four ACH per hour for unoccupied labs. However, in labs that don’t have a large number of contamination sources, organisations can safely go even lower than that.
Like any well-designed building, laboratories can make use of energy recovery technologies such as plate heat exchangers or run around coils. Extract system heat exchangers are likely to need protection against dilute chemicals in the airstream using stainless steel, vinyl coated surfaces or tinned coils as appropriate.
Low pressure loss, high efficiency heat exchanger design will ensure that the heating and cooling energy gains are not compromised by the additional fan electrical energy needed.
Extract fan energy reduction
Minimising the air charge rate and recovering energy provides the foundation for an energy efficient laboratory. Companies should then consider minimising the amount of electrical energy used by the extraction fan itself. For example, introducing a variable stack orifice or multi stack discharge, rather than fresh air make-up, means that, when the flowrate reduces, acceptable stack discharge velocity range is maintained. The traditional use of fresh air make-up, to maintain stack discharge velocity, means that extract fan energy reduction is not available.
Humidity control requirements can also be more relaxed in labs than in commercial buildings. Because of the amount of air exchange in laboratories, it is not economic or energy efficient to control relative humidity. Contrary to popular belief, humidity-control in a lab is mainly required to increase the user’s comfort and rarely serves any other critical purpose.
Apart from the technical considerations essential for lab design and planning, there are a number of operational considerations to be addressed. The designer should record the design and operational parameters in a written document so that controls and commissioning contractors, as well as laboratory users, can fully understand the design intent and how the systems will operate.
In fact, a 2009 LBNL (Lawrence Berkeley National Laboratory)2 study indicated that effective commissioning is among the most cost-effective ways to reduce energy use in high-tech facilities like laboratories.
Cooperation between the designer and the client is essential before, during and after construction. The client will usually bring a User Requirement Specification (URS) to the designer. The next step is for the Architectural designer to consider the spatial requirements and layout for each room in the facility.
Due to the unusually high level of building services in laboratories it is essential to consider plant spaces, ceiling and riser voids, with mechanical and electrical systems in mind. A good designer will not only advise on energy savings, but also work closely with the client to meet these requirements.
A good illustration of the potential further benefits of close collaboration is the reduction of over-specification in the URS. It is common to over-specify in the early stages, either because someone in the design chain believes that it will deliver improved comfort or feels that it will future-proof the application. The reality is that neither is often the case.
A designer’s job does not end with the build. Once the laboratory is up and running, the lab owner should establish energy goals, track performance and share results for continuous improvement. Just because a lab was designed with energy efficiency in mind, it doesn’t mean the efficiency rating can’t be improved further by using the insight of day to day use. It is important to keep the designer in the loop as part of this process so that best practice can be updated. Such learning can be used to develop the current facility and contribute to best practise in the design of new facilities.
Similarly, existing laboratories can be made more energy efficient. Every laboratory is different, but they all have relatively long life spans that can run over 25 years or more. A lot can change in that time, so it’s important to keep in contact with the designer and consult with them about possible improvements.
· Re-design of an active pharmaceutical ingredient manufacturing laboratory for a blue chip pharmaceutical company in Cheshire. Energy efficient measures included, replacing existing fume cupboards with VAV cupboards, adding VAV to supply and extract systems, replacing downflow booths with improved containment low energy sideflow booths, and installing controlled twin stack discharge to realise extract fan energy savings.
· Upgrade of a 2 storey research laboratory building for a large pharmaceutical company in Cambridgeshire. Measures included VAV added to supply and extract systems together with control system strategy changes to improve operation and energy efficiency of HVAC systems.
Best practice for laboratory design and usage is changing all the time, but by working with an experienced designer and builder, companies can ensure their facilities achieve high performance with lower energy usage, while still complying with all the relevant industry and building regulations.
1. Energy Consumption of University Laboratories: Detailed Results from S-Lab Audits, ©S-Lab, July 2011
2. A Golden Opportunity for Reducing Energy Costs and Greenhouse Gas Emissions, Evan Mills, Ph.D. Lawrence Berkeley National Laboratory Berkeley, CA 94720 USA. Report Prepared for: California Energy Commission Public Interest Energy Research (PIER) July 21, 2009
About the author: John Rush, Chartered Engineer (CEng) is a Member of the Chartered Institution of Building Services Engineers (MCIBSE) and a CIBSE Certification Registered Energy Assessor. He has been working at Boulting Environmental Services for over a decade and is currently Principal Engineer.