Over recent years, the use of cleanrooms has spread from highly specialised fields, to an increasingly diverse range of sectors including vitamins and e-liquids.
A key challenge when creating these spaces is limiting energy usage particularly within HVAC systems which must be operated at a much higher rate than in a standard room. Pre-insulated ductwork systems offer a specialist solution, reducing air-leakage throughout the system and consequently cutting fan energy demand.
ISO Definitions
ISO 14644-1:20151 separates cleanrooms into 9 classes based on the size and number of particles within a cubic metre. This allows designers to quickly identify a specification appropriate for each rooms intended purpose.
These requirements are typically met by installing High-Efficiency Particulate Air (HEPA) or Ultra-low Particulate Air (ULPA) filters within HVAC systems and operating these systems at extremely high flow rates. CIBSE recommends a ventilation rate of 10-120 air changes per hour (ACH) for non-laminar-flow rooms and 500-600 ACH for laminar-flow rooms2 . This compares with just 2 or 3 ACH for a normal building.
At these rates, it is essential that ductwork is carefully designed and installed to minimise air-leakage. Whilst this is possible to achieve with conventional sheet metal ductwork, the added detailing will often add considerably to the installation programme length and cost. Pre-insulated ductwork systems offer a simpler solution.
Advantages
Pre-insulated ductwork is typically formed from panels with an insulated core faced on both sides with aluminium foil. This eliminates the lagging stage and can significantly reduce weight when compared with galvanised metal ductwork, allowing long sections to be fabricated on or offsite and installed in a single operation.
The sealing methods and jointing systems featured on some pre-insulated ductwork can significantly cut air-leakage. In a comparative study of two identical buildings, the air-leakage from pre-insulated ductwork was shown to be 79% lower than for a sheet metal system lagged with glass mineral fibre. This means air-flow rates can be met with smaller, more efficient fans.
This enhanced airtightness is particularly beneficial for cleanrooms kept at positive pressurisation. Pre-insulated ductwork systems have been shown to support positive pressurisation of up to 1000 Pascal and their design reduces pressure fluctuations within the ductwork.
In addition, some pre-insulated systems use rigid insulation materials which are both highly thermally efficient and fibre-free. This reduces the risk of loose fibres entering the ductwork and can considerably lower energy demand in cleanrooms where air temperature must be carefully controlled as around 95% of the air is usually recirculated.
Case Study
Pre-insulated ductwork was recently used in the construction of an ISO 8 cleanroom for E-liquid manufacturer, Zeus Juice UK.
Cleanroom specialists — Monmouth Scientific Ltd — oversaw the design and construction of the rooms and specified the pre-insulated Kingspan KoolDuct System.
Monmouth Scientific operations director, David Court, discussed the installation: “We chose Kingspan KoolDuct for the air-distribution ductwork, which we designed to the pressure value of 500 Pa as. In addition to its high performance, we are able to produce a wide variety of shapes and sizes using our computer numerical control (CNC) router. This allowed us to construct complex shaped sections off-site to tight tolerances.”
Contamination Controlled
With technology developers continuing to seek smaller form factors and regulations to prevent contamination in food, supplements and other products tightening, the need for cleanroom spaces will continue to grow. Offsite construction methods offer clear benefits for these self-enclosed, high specification spaces and by utilising technologies such as pre-insulated ductwork it should be possible to create clean rooms which can be erected quickly and provide enhanced energy performance.
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