In the 1990s, HVAC ducting began a transition from functional to fashionable. The reasons are easy to understand; the age of designer goods had arrived, and improved construction materials simply looked too good to hide.
Since Y2K, that trend has deepened. In the late ’80s and ’90s, air-con systems were often an added afterthought encountered in revamped clubs, bars and restaurants. In the 21st century, however, they are incorporated into building design from the outset. In addition to a contemporary feel, suspended spiral duct in new hypermarkets, warehouses and exhibition spaces is both an enormous cost saving and removes many obstacles to energy-efficient operation.
Here are just a half dozen of the key advantages of modern spiral ductwork.
If warmed, cooled and filtered air leaks from its conduits, it isn’t difficult to understand why it will be inefficient, costly to run, and prone to breakdowns. Early HVAC systems often used a variety of ducts that were difficult to machine, access and connect. Spiral duct is now almost a standard and guarantees easy installation and energy efficiency (see https://www.dustspares.co.uk/ductwork-parts/galvanised-steel-spiral-duct.html).
Health and safety
Modern ducts are lightweight and use reliable standard support fittings. There is almost nowhere you can’t safely hang ductwork.
The other main health concern with older systems was leakage of stale or contaminated air back into the building. Better fittings and easier maintenance solve that issue.
Cleaning and maintenance
Depending on the building use in different areas, it is desirable – and sometimes required – to provide facilities for regular inspections and cleaning. Some recent legislation is explained at http://www.indepthhygiene.co.uk/tr19-ductwork-cleaning-guideline-changes-2014. Duct access is facilitated by standard fittings, and curved cross-sections make cleaning straightforward.
There are two main reasons old ductwork was sometimes noisy: sharp edges and turns in rectangular or non-standard ducts cause turbulence, and pressure differentials throughout a system can set up reverberation. Spiral ducting is resistant to reverberation and minimises those sharp corners. Other sound mitigation equipment is also available.
Rectangular ducts are heavy and cumbersome, and their fittings waste three inches on all sides. Standard spirally constructed ductwork has none of these drawbacks.
Because modern systems have consistent cross-sections and airflows, the mechanical engineer can easily design the perfect system for any given building before construction ever begins. This also keeps the costs low and predictable.