www. refrigerationandaircon. co. za RACA Journal I July 2025 31
Feature
“ Tough ambient conditions prevail in the ventilation, air conditioning and refrigeration sector as well as in mechanical engineering.”
• Condensation prevention: Design must address potential‘ duct sweating’( condensation from conditioned air reacting with outside conditions), often requiring insulation
• Optimal angles: Use 45 ° bends instead of 90 ° bends to improve airflow and reduce challenges.
• Account for air leakage: Design should accommodate potential air leakage, especially at joints, where various connection types exist to minimise it
COMMON AIR DISTRIBUTION SYSTEMS IN SA In South Africa, galvanised sheet metal and fabric duct systems are the most common. Fabric ducting, though gaining recent traction, has been commercially available for about 38 years. When evaluating projects, designers should consider the total lifetime ownership cost, customisability and future expansion potential of each solution.
Metal systems( ducts, dampers, diffusers) can lead to drafts and temperature inconsistencies due to localised air dispersion. In contrast, fabric ductwork achieves uniform air dispersion via porous fabrics, vents and nozzles, resulting in faster heating / cooling, reduced HVAC runtime and lower energy costs.
Fabric systems are versatile, suitable for open / finished ceilings, critical environments and underfloor applications, offering an innovative and aesthetic alternative. Advances in fabric technology allow for specialised applications, such as antistatic fabrics for data centres and anti-microbial treated fabrics for hygiene-sensitive areas( laboratories, food processing).
Fabric systems are much lighter than metal, impacting logistics, installation time / cost and structural load. Fabric also offers quieter air delivery without metal resonance and can absorb noise, with fabric sound attenuators available for further reduction.
A stainless steel; extract hood in a speciality kitchen.
Porous fabric systems are inherently resistant to these issues. Fabric ducts are also available in various colours, patterns and custom branding.
Metal systems require minimal upkeep like repainting and tightening over many years, enduring minor damage without functional impact. Fabric systems, however, can be commercially laundered for hygiene. RACA
“ The efficiency of a fan is the ratio of what we get out versus what we put in.”
Painted steel ducting to meet client specifications in an office building.
www. refrigerationandaircon. co. za RACA Journal I July 2025 31