Energy-efficient HVAC systems are more likely to lead to an increase in spatial requirements.

19 December 2013 — Call it a ripple effect – when the Building Code of Australia requirements for more energy-efficient airconditioning plants kicked in, many builders, mechanical engineers and designers faced an unforeseen impasse over space. Phil Wilkinson, chief executive of the Australian Institute of Refrigeration Airconditioning and Heating, believes the way to stop everyone getting hot under the collar is to adjust design processes.

“Since 2010, [National Construction Code] BCA Section J Deemed-To-Satisfy requirements for limiting the power used by HVAC fan and pump motors has resulted in an increase to system duct and pipe sizes. At the same time, Section J has also increased minimum insulation R values and has moved to a “Material R value” basis for insulation systems, leading to increased thicknesses for traditional materials,” Wilkinson says.

“Although increasing the energy efficiency of building services systems is an essential action to control building-related energy use, the combined effect of these three changes has led to an increase in the spatial requirements of the services that need to fit into the plant rooms, shafts and ceiling spaces of BCA Deemed-To-Satisfy compliant buildings.”

Sustainability director with Waterman Group, Scott Brown, says there is a myth in the industry that energy-efficient HVAC systems are somehow smaller than standard systems.

Brown says that energy-efficient HVAC systems are more likely to lead to an increase in spatial requirements, not a decrease, because bigger ducts with more insulation need bigger shafts and deeper ceiling spaces, and more efficient chillers and boilers need bigger heat exchangers, with more plantroom access.

“A greener system configuration with air-to-air energy recovery, for instance, means more ductwork and additional heat exchangers to fit in,” Brown says.

He notes that plant rooms with an energy-efficient HVAC plant and air-to-air heat recovery can be 50 per cent or even 100 per cent bigger than they would have been had energy efficiency not been a concern.

Mark Lee, engineering manager with mechanical contractor James L Williams, says that, despite this, building designers are generally allocating the same or smaller spaces for building services as they have in the past, making access tight and future maintenance difficult.

Although new tools such as BIM software and visualisation or clash-detection tools can predict and highlight clashes between services, the practicalities around the space needed for installation is still a key pressure point on site.

“The pressures exerted by architects, designers and builders mean that on site, it becomes a race to install your services first so that the other trades have to work around you,” Lee says.

“Every project has a degree of tension between architects and engineers over spaces,” says Jason Veale, Associate Director – Building Engineering with AECOM.

“Section J is now increasing the need to coordinate and communicate about service space early.”

The core issue here is space costs money, because any increased space dedicated to plant effectively reduces the building’s Net Lettable Area (NLA).

“Developers are measuring new projects against the space ratios of the existing buildings that will compete for the same tenants,” says Peter Cass, M.AIRAH, associate – services cost management with Rider Levett Bucknall.

Apart from providing additional space for services accommodation, there are a few alternative options available. Chilled beam systems, underfloor air distribution systems, and multiple smaller systems as opposed to a large single system can all potentially deliver space-efficient solutions.

Cass also says chilled and/or heated structures (floors, walls, ceilings) are another option that is being adopted to keep ahead of the curve for building design.

An alternative modelling approach is also showing signs of providing a workable solution to the space vs services impasse. AIRAH Member Vince Aherne says JV3 modelling allows trade-offs between system components because it is the overall performance of the system that is assessed.

The alternative JV3 modelling enables a reduction in insulation requirements and therefore space requirements for pipes and ducts through a balancing act of over-complying on chillers, pumps, fans and lighting. The outcome is still energy-efficiency, without the need to battle for space to achieve it.

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