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120 PROPOSAL TO REVISE ENERGY EFFICIENCY REQUIREMENTS OF THE BUILDING CODE OF AUSTRALIA FOR COMMERCIAL BUILDINGS coils, including the additional capital cost needed, achieves a 2:1 benefit to cost ratio. The values in the Coffey report have been adjusted as the report expresses the building load in terms of the currently defined motor input power while industry has proposed changing that expression to the fan shaft input power. The table has different shaft power allowances for sensible air-conditioning loads. The sensible load (the load that causes a rise in temperature) is used as this is the load with which the fan flow rate is determined. Mechanical ventilation There has been some confusion as to what an air-conditioning system does and what a ventilation system does. Sub-clause (b) has been restructured to clarify that mechanical ventilation is about the outside air provided to met the requirements of Part F4 with (ii) for when part of an air-conditioning system and (iii) when a stand-alone system. Outside air J5.2(b)(ii) in BCA 2009 permits the minimum outside air required by AS/NZS 1668.2 to be exceeded by up to 50 per cent. This apparently generous allowance was to accommodate air-conditioning systems that serve a series of rooms with slightly different outside air requirements. Anecdotal feed back has been that 50 per cent was too generous and that the value could be significantly reduced without any additional cost in most situations. However, in some situations, such as where offices were served by the same system as a conference room, a separate system may now be needed. It is proposed to reduce the 50 per cent over supply allowance to 20 per cent. It is also proposed to amend (and relocate) the current (b)(iii)(B) for a building where the number of people per square metre is 1 or less. The sub-Clause currently requires energy reclaiming or outside air volume modulation for a Class 9b building and it is now proposed to extend this to any other building with such a high density of people. Ventilation system fans In the same report, Coffey Environments recommended changes to the fan power allowance for ventilation system fans, again on the basis of www.TheCIE.com.au
PROPOSAL TO REVISE ENERGY EFFICIENCY REQUIREMENTS OF THE BUILDING CODE OF AUSTRALIA FOR COMMERCIAL BUILDINGS 121 them being cost effective with a positive benefit to cost ratio. The value has also been reduced by 10 per cent. J5.4 Heating and cooling systems The term ‘chilling’ has been changed to ‘cooling’ to include systems that use water at slightly higher temperatures. Pump power allowance Coffey Environments also prepared a report titled ‘Section J — Review of Pump Power Provisions’, recommending that the pump power allowances also be reduced. Again, the report details the likely energy savings and the positive benefit to cost ratios for each element. All up, the package of pressure reductions for control valves, coils and piping, including the additional capital cost needed, achieves a positive benefit to cost ratio with the likely future costs of energy. Also the report used a pump efficiency of 70 per cent which is difficult to always achieve so the values have been adjusted. The recommendation for hot water pumps in the report was a single value irrespective of heating load so this has been converted into a rate based on a range of heating load. The calculations also used 80 W/m at 120 kPa and 70 per cent efficiency as the base case and after further consideration these have been adjusted to 100 W/m at 200 kPa and 50 per cent efficiency. The public and industry are invited to review and test the proposals and provide comment where they feel that the proposals are either too tough, or not tough enough. Again, at the request of industry, it is proposed to clarify that floor area measurement be ‘area of the floor of the conditioned space’ rather than the defined BCA term ‘floor area’. This is because only part of the building may be conditioned. Variable speed pumps Coffey’s proposed text did not retain the 3,500 hours a year operation for pumps to justify variable speed control. Its removal simplifies regulation as the usage is not easy to estimate and in any case, most systems would operate for sufficient time for speed control to be cost effective. www.TheCIE.com.au
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