Installation requirements for flexible ductwork in buildings have changed with the introduction of a new standard AS 4254.1:2021.
Consultants, certifiers, installers, and suppliers of product to the industry are advised get a copy of the new standard which has only just been published.
Formally known as ASA 4254.1 - Ductwork for air-handling systems in buildings part 1 Flexible Duct; it will address poor installation practices which lead to increased and wasteful energy consumption.
Air conditioning impacts greatly on the energy consumption of most buildings in Australia. In the new version of AS4254.1 there is a formal test method to certify R values of flex duct.
In 2012, AS 4254.1:2012 introduced a specific method for hanging flexible ductwork.
Standards Australia recognised that installers were using products such as 12mm wide blue carton strapping and 25mm wide blue tarpaulin strips. This resulted in several problems.
Narrow strapping compresses the insulation walls of flexible duct which causes cold bridging which leads to condensation. This is the reason why so many office ceilings have ceiling tiles and water stains.
It also results in the shape of the flex duct being distorted reducing airflow and the overall performance of the system. 12mm wide carton strapping can be quite abrasive, cutting through the outer jacket of the duct.
AS 4254.1:2021 now provides two options to hang flexible duct.
Option 1:- A load support strap with a minimum width of 75mm
Option 2:- A hanging strap with a minimum width of 25mm to be used in conjunction with a load support saddle a minimum width of 75mm.
Unfortunately, the industry has been slow to adapt the 2012 requirements to use a load support material when installing flex duct systems.
This is partly due to the additional product and labour costs which installers often cannot recover and partly because there has been a lack of understanding as to why a load support system is critical.
With the modifications to the 2021 version of AS 4254.1, option 1 provides the opportunity to prevent these issues with minimal impact on installation costs.
It is a win for building occupiers and the environment.