Technical Clarification
Accounting for VRF systems in Ene-1 model
Technical Clarification Number
ENE1-T-RC1-768
Guidance
2014-02-27
1) VRF: Outdoor unit energy consumption
The energy consumption of any outdoor unit shall be determined using the ‘interpolated COP data’ as described in item (3) below and the thermal loads as derived from thermal modeling software.
2) VRF: Indoor unit energy consumption
The energy consumption of any indoor unit shall be determined using the ‘specific fan power’ as described in item (4) below and the supply air rates as described in 5) as proposed by the Project Team.
3) Interpolated COP data (outdoor units)
The interpolated COP data for the outdoor VRF units used for the calculation of the annual energy consumption of all the outdoor VRF units included in the project is to be derived from the manufacturer’s product data for –
• All outdoor unit models or types included in the project such that each outdoor unit model or type has a unique interpolated COP data set based on the manufacturer’s product data for that unit;
4) Derived Specific Fan Power (indoor units)
The derived specific fan power for the indoor VRF units used for the calculation of the annual energy consumption of all the indoor VRF units included in the project is to be derived from the manufacturer’s product data for –
• All indoor unit models or types included in the project such that each indoor unit model or type has a unique specific fan power based on the manufacturer’s product data for that unit;
5) Derivation of zone supply air rates
The derivation of zone supply air rates, to which the specific fan power, as outlined in item (4) above, is applied to determine the fan energy consumption of the indoor VRF units, must be determined through modeling the HVAC system as a Constant Volume (CV) system.
6) Treatment of sub-systems
As part-load conditions, thus part-load performance, will vary depending on each sub-system required to serve the different parts of the building that have been connected to that sub-system, it is an unacceptable methodology to aggregate the thermal loads of all zones within the thermal modeling. As each sub-system will have a different installed heating/cooling capacity and the thermal loads within each space will not be equal, each sub-system will have different part load conditions, it is required that each sub-system be post-processed using the methodology approved in item (1) above, individually to account for this. This post-processing method approved in item (1) above must clearly reference the part-load conditions derived from the peak load within the sub-system and the thermal loads of the zones within the sub-system.
Technical Clarification
Proposed methodology for modelling VRF/VRV systems (This TC supersedes ENE1-T-RC1-0097 issued on 2010/08/18)
Technical Clarification Number
ENE1-T-RC1-710
Guidance
2013-06-14
Projects that make use of modelling software which includes a simulation for variable refrigerant flow (VRF) or variable refrigerant volume (VRV) systems do not need to submit a Technical Clarification to the GBCSA prior to submittal when modelling these systems in the actual building energy model, provided that the following are met:
- The modelling package is compliant with the ‘simulation package’ requirements of the Green Star SA – Office v1 Energy Calculator and Modelling Protocol Guide.
- The modelling report clearly indicates all the inputs used within the model and demonstrates through contract documentation and product datasheets that these inputs accurately represent the system installed.
Projects using methodologies for modelling of VRV/VFR systems that are not integral to the simulation package must submit a Technical Clarification to the GBCSA prior to submittal, outlining the proposed modelling methodology for approval.
Technical Clarification
Carbon Monoxide (CO) monitoring on basement fans
Technical Clarification Number
ENE1-T-RC1-0636
Guidance
2013-02-13
Where CO monitoring is used to control the air flow of basement fans, the calculation of the required air flow rates and associated energy savings must be based strictly in accordance with a recognised best practise standard or guideline, e.g. ‘2011 ASHRAE Handbook – HVAC Applications’.
The calculation methodology must at a minimum be based on the following inputs:
• Acceptable level of contaminants in the parking facility
• Number of cars in operation at various times over a 24 hour period
• Length of travel and operation time for cars within the car-park
• CO emission rate for a typical car under various conditions
• Total volume of the parking facility
Documentation Requirements:
Within the Energy Modelling Report, the project team must;
• Clearly state the source of the calculation methodology used (recognised best practise standard or guideline).
• Describe the calculation inputs used for each of the items above.
• Provide a description of how the ‘number of cars in operation at various times over a 24 hour period’ and the ‘length of travel and operation time for cars within the car-park’ are a representative or conservative representation of the expected traffic profile for the building.
In addition, the project team must state in the Energy Modelling Report how the following issues have been taken into account within the calculations:
• Accounting for the contaminant level of outside air drawn into the basement;
• Accounting for building form and position of sensors and the effect this may have on operation of the system; and
• Providing efficient, adequate airflow throughout the structure.
The project team must demonstrate with supporting contract documentation (Design rating) or commissioning records (As Built rating) that the CO sensors are set according to the levels used within the calculations.
Note that the project team need not submit the full calculations within the Energy Modelling Report, but simply the confirmations and inputs requested above.
Technical Clarification
HVAC plant operating schedules
Technical Clarification Number
ENE1-T-RC1-0597
Guidance
2012-11-05
Should operating schedules of HVAC equipment be used as part of the energy performance or thermal comfort strategy , e.g. night flushing or early start-up of HVAC plant, the actual HVAC plant operating schedules for the related equipment as supported by tender documentation (Design) or commissioning data (As Built) may be used for the Ene-1 actual building modelling and IEQ-9 credit modelling.
Please note that if any overrides over timer based controls are included in the system (e.g. CO2 or temperature overrides) these should be accounted for accurately or assumptions conservatively justified – alternatively the HVAC plant operating schedules in the energy modelling protocol should be used.
Note that for the Ene-1 notional building, the HVAC plant operating schedules in the energy modelling protocol should be used.
Technical Clarification
Energy modelling - Calculation of total U-values of windows/glazing assemblies
Technical Clarification Number
ENE1-T-RC1-0352
Guidance
2012-07-26
For the purposes of energy modelling for the Green Star SA - Office v1 Ene-1 credit, for the actual building, where an overall window (whole glazing) U-value is not known, but the project team does have glazing U-values from the manufacturer, calculations may be performed to take account of the thermal conductance of the frame and thus ascertain the overall window U-value. Industry standard U-values for various frame materials such as those published by the CSIRO (Commonwealth Scientific and Industrial Research Organisation - Australia) may be used for this purpose. Where calculations of the overall window U-values are performed, the following must be clearly shown in the Energy Modelling Report.
• Details of composite U-value calculations.
• Individual element U-values used in the calculation and their source.
• Justification of glazing and frame areas used in the calculations.
Where the manufacturer U-value for the glazing is not known, the U-values from the table on ‘Worst-case whole glazing element performance values’ given in SANS 204:2011 should be used in the model.
Credit Interpretation Request
Intellectual property - trigeneration system design documentation
Credit Interpretation Request Number
ENE1-C-RC1-0353
Ruling
2012-07-26
The Credit Interpretation Request (CIR) seeking approval to substitute extracts of tender documentation with a statement of confirmation from the design engineers to protect the intellectual property of the tri-generation system is conditionally approved.
The CIR Review Panel notes that the Project Team is permitted to request alternative forms of documentation where they wish to protect intellectual property, however sufficient documentation must be submitted to satisfy the GBCSA of inclusion within the design. A statement of confirmation, prepared and signed by a suitably qualified professional responsible for the design of the tri-generation system, may be submitted provided the following information is confirmed:
• Estimated hourly electrical energy produced by the plant;
• Estimated electrical energy consumption of plant itself;
• Estimated hourly heat supply to the absorption chiller;
• Estimated hourly heat supply for DHW;
• Estimated hourly heat supply for tempering of fresh air;
• Size of auxiliary pumps in system and energy consumed
• Estimated amount and type of primary fuel consumed;
In addition;
• Size/capacity of major components of the system, including the generators, the absorption chillers and heat exchangers (i.e. kW).
In addition to the statement of confirmation, extracts of tender documentation must be submitted to confirm the inclusion of the tri-generation system within the design. This must be of the form of;
• Tender architectural plan drawings showing the location/space allocation of the trigeneration system;
OR
• Tender mechanical services plan drawings showing the location/space allocation of the trigeneration system.
The CIR Review Panel notes that as the project is registered for a Design certification, information contained on the statement of confirmation must be based on calculated estimates. It is not acceptable to use actual measured performance data from the tri-generation system (if operational).
Technical Clarification
Car Park Ventilation
Technical Clarification Number
ENE1-T-RC1-0118
Guidance
2010-11-23
Where car parking on basement levels which are partially below ground is to be modelled, the following guidance should be followed for the notional SANS 204 building (refer to Green Star SA – Retail Centre v1 Energy Calculator & Modelling Protocol Guide v1.1 item 6.1);
The first basement level (B1) which is partially below ground should be assumed naturally ventilated (i.e. no car park ventilation energy use). For car parking on lower basements (below B1) which are partially below ground and mechanically ventilated in the actual design (if deemed to be required under SANS 10400 parts O & T), the same flow rates as the actual peak design, with a specific fan power of 1.6 W/l/s (per SANS 204-3:2008) should be used. For car parking on lower basements which are partially below ground and naturally ventilated in the actual design (if deemed not to require mechanical ventilation under SANS 10400 parts O & T), these should be modelled as naturally ventilated (i.e. no car park ventilation energy use) in the notional SANS 204 Building.
Technical Clarification
VRF/VRV Modelling ((SUPERCEDED by TC ENE1-T-RC1-0710 issued on 2013-06-14)
Technical Clarification Number
ENE1-T-RC1-0097
Guidance
2010-08-18
Technical Clarification
Modelling software
Technical Clarification Number
ENE1-T-RC1-0096
Guidance
2010-08-18
DesignBuilder software interface for the BESTEST-certified Energy Plus modelling software is acceptable for Green Star SA purposes.
Technical Clarification
Occupied space below ground
Technical Clarification Number
ENE1-T-RC1-0090
Guidance
2010-07-07
If the actual building contains regularly occupied space below ground, the notional building must still be modelled as above-ground, with the properties laid out in the Green Star SA - Retail Centre v1 Energy Calculator and Modelling Protocol Guide (the Energy Guide). In the case that the actual building contains both occupied and parking floors below ground, the notional building must be modelled with the lowest regularly occupied floor at ground level, and the first basement parking level modelled as naturally ventilated per the Energy Guide. For example, if the actual building contains two regularly occupied floors on B1 and B2, with three levels of parking below (B3 to B5), then the notional building will have the occupied floors as ground and 1st floor, with the parking as B1 (naturally ventilated), B2 (mechanically ventilated) and B3 (mechanically ventilated).
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