Migration from Green Star model to JV3 model:
What else needs to be changed?
If you are willing to achieve compliance with the NCC energy efficiency requirements through JV3 Performance Solution, apart from the two major changes that are mentioned above, you need to change some other criteria or at least, check if they are already in place.
3- Lighting controls
Neither NCC nor Green Star modelling guidelines require Reference Project to have lighting control sensors. However, if control devices are suggested in the Proposed Project, you must look up and compare the adjustment factors within the two references. This is due to the fact that both description and adjustment factors differ from one another comparing the two references. As an example, if there is a motion detector in a toilet, NCC allows for an adjustment factor of 0.4 [NCC Vol 1.0, Section J, Part J6, Table J6.2b] but Green Star allows for not more than 0.9 [Green Star Energy Use Calculation Guide, Table 73].
Although Green Star adjustment factors for lighting control devices seems more conservative, you must always check not to allow for less than the mandated value. Note that you should only double-check if you are undertaking JV3 modelling. If you are migrating your model for JV2 modelling, you are fine!
Provisions of natural light also differ between NCC and Green Star (though NCC must be met nevertheless). Where applicable, daylight criteria and conditions for each model must be updated according to specific daylighting metrics. Find out more…
4- Air quality
last but not least, complying with the Green Star Minimum Expectation for Air Quality means that the fresh air flow rates supplied by the ventilation system must be increased compared to the industry standards for non-residential buildings:
The building must provide a 50% improvement of outdoor air required by AS 1668.2:2012 to each space in the regularly occupied areas.
[Green Star Buildings Submission Guidelines, Version 1 (Revision A), July 2021, Page 77]
Although you can keep these increased rates for the Proposed Projects of Green Star, JV2 and JV3 models, you are not allowed to have these increased outdoor flow rates for the JV3 model Reference project. The reason is explained by the NCC:
A habitable room, office, shop, factory, workroom, sanitary compartment, bathroom, shower room, laundry and any other room occupied by a person for any purpose must have—
- natural ventilation complying with F4.6; or
- a mechanical ventilation or air-conditioning system complying with AS 1668.2 and AS/NZS 3666.1.
[NCC Vol 1.0, Part F4.5]
A mechanical ventilation system, including one that is part of an air-conditioning system, except where the mechanical system serves only one sole-occupancy unit in a Class 2 building or serves only a Class 4 part of a building, must…
…not exceed the minimum outdoor air quantity required by Part F4 by more than 20%,…
[NCC Vol 1.0, Part J5.3 (B)]
According to the above, you are not allowed to increase Reference fresh air flow rates by more than 20% of what is required in Part F4 (and consequently, values of AS1668.2, Table A1). For example,10 L/s/person is the minimum outdoor airflow rate for a bar according to AS1668.2. Green Star Minimum Expectation for Air Quality requires 50% more than that (15L/s/person), whereas NCC doesn’t allow you to go more than 20% (12 L/s/person). for a large commercial building, this discrepancy between the Reference and the Proposed Project ventilation rates, may create a major gap for thermal energy compliance. A good control strategy for large commercial buildings would be the use of CO2 sensors for demand-controlled ventilation, especially in crowded spaces like restaurants or bar areas.