The National Construction Code (NCC) is an initiative of the Council of Australian Governments (COAG) developed to incorporate all on-site construction requirements into a single code. The NCC comprises the Building Code of Australia (BCA), Volume One and Two; and the Plumbing Code of Australia (PCA), as Volume Three.
Building codes operate within a broader framework of planning codes, material and product Standards and regulations for trades and professions. The Australian Building Codes Board develops model regulations that states generally adopt but not always. Pressure to standardise is increasing. Each state/territory regulates and enforces building codes. For example, NSW regulates building energy and water performance under its planning code through BASIX tool.
Recently the Building Code of Australia was integrated into the National Construction Code with plumbing (and eventually electrical) codes. BCA Energy efficiency objective is to reduce greenhouse gas emissions by improving efficiency of energy use and using low emission energy sources
Structure: There are 3 options for compliance:
- Deemed to satisfy – ‘recipes’ that comply
- Performance based approach: meets intent of BCA using approved rating tools, calculators etc
- Verification method: recognised experts consider the approach meets the intent of BCA but its innovative natures means it cannot be adequately evaluated under the other methods
Rating Tools used to assess compliance to NCC
State agencies and local government manage enforcement through private or government appointed building surveyors: for energy this is typically not done well. This raises questions of compliance with the Trades Practices Act and other consumer law. Compliance can be achieved using generally accepted rating tools.
Rating tools can be used to comply with BCA or as voluntary tools to optimise outcomes for clients. Some rating tools developed for voluntary purposes are used for regulation, or in contracts. For example, some local and state governments require minimum NABERS and Green Star ratings for some buildings.
BCA stringency is weak by international standards which requires 7‐ 9 stars required in some countries. AccuRate etc can rate to 10 stars – near zero heating and cooling energy requirement. A comparative study of comparative overseas locations showed the overall median rating is 7.5 stars, and the overall mean rating is 6.8 stars. The house designs obtained from the UK and Canada indicate that in these countries, substantial houses are built to relatively very high standards, in compliance with relatively stringent building code requirements. The current efficiency of Australian homes is well below comparative international standards in terms of energy efficiency and greenhouse gas emissions. Going forward, this can be expected to translate into a brake on the Australian economy in a world of increasing fossil fuel scarcity and rising prices.
Residential BCA Energy Requirements
- Deemed to satisfy requirements for building envelope or a 6 star rating for building envelope performance (Class 1 buildings) must be met – note some states vary from this, with lower star ratings, BASIX in NSW
- Approved rating tools – AccuRate, FirstRate 5 or BERSpro are generally accepted.
- All use the CSIRO‐developed NatHERS simulation engine
- AccuRate: comprehensive CSIRO developed tool
- FirstRate: has fewer options but a potentially ‘friendlier’ user interface
- BERSpro combines the comprehensive capability of AccuRate with more user features
- Certification requirements for users vary from state to state and are generally weak. ABSA and BDAA (industry organisations) try to improve standards
- BCA includes additional requirements beyond building envelope
- Lighting: installed lighting power density should not exceed 5 watts/square metre (4W/m2 verandahs, 3W/m2 garages)
- Hot water and space heating using heated water: must deliver hot water with a greenhouse impact of less than 100 grams of CO2 per megajoule of heat delivered under standard tests:
- Typically a 5‐star gas hot water system, good quality solar‐electric or electric heat pump will meet this requirement
- Use of fixed resistive electric heating for spaces, HW, pools etc generally does not comply
- Single bedroom dwellings and secondary HWS units in larger homes are exempt – so resistive electric HWS is OK
- Water‐efficient shower heads and taps (3‐star) must be used
- The plumbing code also sets requirements for pipe diameter, insulation, system design etc
- Minimum insulation of ducting, hydronic heating pipes etc is specified
- Thermal bridging in building fabric must be blocked
- Where some insulation is removed, compensating adjustments to rest of insulation required
- If ceiling fans are part of compliance solution, they must be permanently installed, have a speed controller and serve the whole room (up to 15m2 for 900 mm diameter fan, 25 m2 for 1200 mm fan
- Evaporative coolers must have automatic seals • Exhaust fans must have covers
Apartment Buildings (Class 2) and Residential in Non-Residential Buildings (Class 4)
Sole occupancy units must meet average 6 stars with no single unit under 5 stars using residential rating tool. Building services for individual units must comply with residential requirements. Common area lighting and central system performance are covered in Vol 1 – non‐residential buildings.
Non-Residential Buildings (Commercial)
Applies to all non‐residential buildings, not just offices. Comply with J0 (deemed to satisfy) or JV3 (use of computer simulation) approach.
BCA Section J Alternative Verification Method JV3
JV3 involves simulating a building of the proposed design that meets the DTS requirements, then simulating the proposed building to demonstrate that it achieves equivalent energy consumption performance or better under two scenarios: with defined BCA HVAC and other building services; and with proposed HVAC and building services
Modelling of actual building with BCA specified services ensures building envelope’s performance cannot be unduly compromised by use of high efficiency services technologies. For renewable energy to be factored into compliance, it must be generated on‐site. JV3 is applicable to Class 3, 5, 6, 7, 8 and 9 buildings, NOT class 2 or 4 (residential)
UnderJV3, annual energy consumption in providing all building services to specified levels is calculated using a recognised software package capable of assessing:
- contribution of building fabric, air infiltration, outside air ventilations, internal heat sources (people and appliances) and
- services such as air conditioning (both central and individual), hot water supply, vertical transport and artificial lighting
- for specific building and location.
Software must comply with the ABCB Protocol for Building Energy Analysis Software
Insulation requirements apply to internal walls etc between conditioned and unconditioned areas, not just external walls
Detailed Specifications are included in the BCA, which include accepted design solutions beyond those stated in the DTS option
Minimum Requirements for Commercial Building Façade Design
Building Code of Australia – Section J
To address the growing contribution to Australia’s greenhouse gas emissions by the commercial building sector, in 2010 minimum energy performance requirements were introduced into the Building Code of Australia (BCA) Volume One.
Section J of BCA 2010 codifies minimum glazing thermal performance measures for both façade vision glazing and roof lights. The ‘deemed-to-satisfy’ glazing regulations governed allowable glazing areas as a proportion of the floor area of sole occupancy units. Allowable glazing area limits depended on total window thermal performance: Solar Heat Gain Coefficient (SHGC) and U-value , orientation, external shading devices and climate zone (see Figure 3). A spreadsheet enabled industry to assess compliance: this was called the Method One glazing calculator. Like other areas of building regulation, the designer could either follow the prescriptive ‘deemed-to-satisfy’ measures or demonstrate compliance by using a verification method that typically involved dynamic thermal energy modelling calculations.
In order to design innovative, high-performance, BCA-compliant façade concepts, it is essential that designers grasp four key concepts:
1. passive design
2. façade area
- U-value: Coefficient of heat transfer; the rate of heat flow through a window or other building element, driven by a temperature difference across the element; measured as heat flow per unit area, per degree of temperature difference.
- Solar heat gain coefficient (SHGC): The total solar heat gain divided by exterior solar irradiance; consists of the solar direct transmittance plus the inward-flowing fraction of absorbed solar energy that is re-radiated, conducted or connected into the space.
3. P/H (sun-break ratio)
4. deemed-to-satisfy vs. performance-based modelling
Source: Horne, R E, Hayles, C, Hes, D, Jensen, C, Opray, L, Wakefield, R, and Wasiluk, K. (2005). International comparison of building energy performance standards, Centre for Design at RMIT University, Melbourne Australia.
Australian Building Code – http://abcb.gov.au/en/major‐initiatives/energy‐efficiency
NABERS – http://www.nabers.gov.au/public/WebPages/Home.aspx (includes case studies)
Green Star – http://www.gbca.org.au/green‐star/
Living Building Challenge – http://living‐future.org/lbc
Your Home – http://www.yourhome.gov.au