Lynette Williams, BE(Hons), MIEAust, CPEng, Umow Lai Pty Ltd
As an industry, we are constantly challenged to improve and update our design concepts to meet the objectives of energy efficiency and flexibility. Historically, laboratory design produced high energy consumption, whereas occupational health and safety were the reasons presented to ignore everything else.
For the southern states of Australia, the design conditions are summer 30°C to 35°C (93°F to 99°F) and winter 2°C to 4°C (40°F) with relative humidity of 20 to 50 percent. Consequently, air conditioning systems need to provide cooling, with minimal heating. Humidity control is not generally a consideration for our office-style spaces.
Wet laboratory spaces are moving towards open-plan layouts with associated shared small rooms as support spaces that open off the main laboratory. We are currently designing these spaces with:
For the dry laboratory or office space, either open-plan office layout with limited meeting rooms and enclosed offices or larger computer-based laboratory spaces, we use:
Active Mass Cooling utilises the structure of the building, with cooled (15°C/59°F) water pipework run in the lower section of the slab. This creates a radiant panel at about 18°C (65°F). Zoning is limited by coil piping length and pressure drop with typical sizing of 15 to 20 square meters (m²) (160 to 220 square feet [ft²]). With these criteria, this system covers the environment loads—up to 50 watts per square meter (4.65 watts per square foot)—from people, equipment, and lighting. An advantage is that it provides good thermal comfort via the radiant effect.
There are a number of items to be considered for active mass cooling. These include achieving architectural acceptance for an exposed slab, with preferably the underside being steel decking/permanent formwork, and coordinating the services reticulation so that it is atheistically pleasing. A pipework-free zone needs to be identified for penetrations for future services. In addition, a strategy for the suspension of services from the slab needs to be developed to suit the pipework.
This system is not suited to areas of high humidity as there is a risk of condensation occurring on the underside of the slab. As with any slab system, the response time is slow; however, as it is designed for internal loads, this is not an issue.
Fabric "sock" or textile diffusers provide an even-air distribution pattern and have the advantage that they run within the laboratory space yet have a lack of surfaces on which dust can collect. If the sock is contaminated it can be removed and cleaned or disposed of. With fabric diffusers, the filtration of the supply air is critical as contaminants will collect on the inside of the diffuser; however, because the air supply should be well-filtered, this is not an additional requirement. With variable volume systems, consideration should be made of the support system for the duct so that there is no noticeable collapsing of the duct under low-flow conditions.
UFAD uses a low-pressure raised floor with twirl diffusers, encouraging mixing at low level with the return air captured at high level. UFAD provides good indoor air quality as there is limited mixing and so limited capture of dust and other contaminants. UFAD also provides good flexibility, as the twirl diffusers are readily relocatable to suit layout changes. UFAD needs detailed coordination with the other services running in the raised floor zone and with the structural engineer regarding any changes in slab heights. Coordination and control by the builder is also crucial during the construction phase when services are being run in the floor void prior to the installation of the floor.
We have used these systems on a number of projects including:
Ms. Williams has worked on almost every type of building and has even dabbled in tunnel ventilation. Her particular area of expertise is in the design of laboratory and educational projects.
She is on the Victorian Committee of Chartered Institute of Building Services Engineers and has a passion for continual development and growth, for herself and others.
Ms. Williams' major laboratory project experience includes: