Energy efficiency in the NCC 2022 and beyond - Australian ...
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AUSTRALIAN
MO D E R N
BUILDING
AL LI A NCE
Safe and sustainable construction with polymers
Information Sheet 4:
Energy efficiency
in the NCC 2022 and beyond
This information sheet provides a summary of energy
efficiency performance recommendations made by
AMBA for consideration by the Australian Building
Codes Board (ABCB) in the development of the National
Construction Code (NCC) 2022 and beyond.
Towards low-energy NatHERS 7 Star thermal
buildings performance
AMBA made a submission AMBA supports the decision
following the ABCB’s invitation to increase the minimal thermal
to provide input to this scoping performance rating in the NCC
study and applauds the energy to NatHERS 7 Star and hopes
efficiency focus for the NCC that the Queensland Government
2022 – particularly in relation to will eliminate existing exemptions
domestic buildings. for climate zones 1 and 2 in the
NCC 2019.
We support a significant increase
in the integration of changes to The NatHERS insulation toolbox
the NCC that will lead to low- must be updated to reflect
energy buildings, and believe modern insulation materials
the NCC 2022 should strive and their properties – including
for NatHERS 7 Star thermal polyisocyanurate (PIR) or
performance construction. phenolic board and polyurethane
spray foam (SPF). These are
To further improve energy
manufactured in Australia and
efficiency in residential buildings:
used internationally to insulate
• there should be a greater focus low-energy buildings.
on air leakage and thermal
Although NatHERS estimates be solved before the release of
bridging (where most energy in
the potential heating and cooling the NCC 2022.
buildings is currently wasted)
energy use of a house, a recent Because of this, we strongly
• improvements and compliance CSIRO report notes that the recommend the NCC 2022
to code should be embedded current model in NatHERS for adopt prescriptive methods
in the NCC 2022. air infiltration underestimates currently used in California to
its impact on building energy reduce air infiltration (leakage)
Contemporary insulation usage.1 and building energy use (see
and prescriptive adoption of
While AMBA supports efforts to Addressing building sealing (air
international best practice is key
improve this NatHERS modelling, leakage) for more).
to achieving this.
we acknowledge it is unlikely to
1
Addressing building sealing (air leakage)
Airtight construction is the most Addressing the issue of air improves overall thermal
important pillar of an energy leakage through building performance (more closely
efficient building (thermal bridges elements/products, traditional aligning it with other developed
and moisture control being the fibrous insulation is difficult to countries) and reduces air
others).2 install without defects such as air leakage and thermal bridging
gaps,5 and as such needs to be (see Addressing thermal
A CSIRO study found that over
used with a separate air barrier bridging for more).
50 per cent of houses were
such as house wrap.
excessively leaky beyond the While the NCC 2019 contains
level of assumed airtightness By comparison, modern a new target on airtightness
in the NatHERS modelling insulation materials such as SPF (10 ACH50), AMBA recommends
software.3 and PIR board insulation are both the ABCB investigate a more
considered air barriers under stringent target of 5 ACH50.
NatHERS currently only manages
Californian prescriptive codes,
air leakages in buildings during
and don’t require the installation
the design and post-occupancy
phases. It ignores:
of a separate air barrier like This would result in
fibrous insulation. significant energy
• air leakage through building
elements/products, and
AMBA strongly recommends savings, as the energy
the ABCB consider following
demand generated by air
• gaps that need to be sealed California by adopting mandatory
during construction (variable use of exterior rigid insulation leakage is proportional
quality of workmanship and board on walls in the NCC 2022. to the reduction in the
cracks/holes that contribute to This will provide a continuous air infiltration rate.6
air leakage).4 layer of insulation external to
the frame that simultaneously
Addressing thermal bridging
Eliminating thermal bridging is a way to lower
heating and cooling demand and “improve thermal
comfort”.7 It’s also important for controlling possible
condensation problems, and can be managed by
sufficient insulation external to the building’s frame.
The NCC 2019 mandates the use of thermal breaks
on certain buildings using lightweight metal framing
to reduce thermal bridging.
While AMBA applauds this change in the NCC
2019, we recommend that the use of thermal
breaks be used on all lightweight buildings, as even
timber frames are an order of magnitude higher in
conducting heat than rigid insulation board.
If the ABCB mandates the use of exterior insulation
board in addition to insulation between wall studs
(the proven prescriptive method used by the
California Building Energy Standards), it will address
both thermal bridging and air leakage issues in our
buildings.
2
‘As built’ versus Compliance pathways
‘as designed’
While AMBA supports the NCC’s move towards a
There is a major disconnect between performance code, we do not support the downgrading
the energy efficiency of Australian of the deemed-to-satisfy compliance pathways for
homes ‘as designed’ or ‘as planned’ by the thermal comfort performance of small buildings,
software such as NatHERS and BASIX, alterations or additions.
and their true ‘as built’ energy efficiency We believe that NatHERS ‘as planned’ modelling
performance. must first demonstrate it is equal to ‘as built’ through
This can be related to elements including benchmark energy consumption of real buildings before
workmanship (excessive air leakage and we support this downgrading.
poorly installed insulation) and trade- However, we note this is unlikely to happen without a
offs on the thermal performance of one quality control system for the installation of insulation
building component against another and air barriers.
(e.g. windows versus walls).8
We therefore recommend the ABCB consider
Consequently, this performance can introducing additional deemed-to-satisfy provisions that
have a significant negative impact on the make it easier for builders to achieve an airtight, energy
NatHERS Star rating of our residential efficient envelope.
buildings.
AMBA supports efforts to quantify existing performance
For example, a study prepared for the requirements in the NCC, and mechanisms to ensure
Department of Resources, Energy all NCC compliance pathways achieve minimum
and Tourism demonstrated that the performance levels where ‘as designed’ equals
combination of uncontrolled air infiltration ‘as built’ (e.g. benchmarking planned against real
with poorly installed insulation can impact buildings).
the ‘as built’ NatHERS rating of a building
by up to 1.7 stars.9 Although AMBA understands the need to develop
‘whole-of-house’ tools to address energy efficiency
So, while NatHERS is a useful tool performance, we caution this may result in expanded
providing guidance on optimising the compliance pathways that could increase the
thermal performance of a home, it can’t complexity of the NCC.
guarantee that ‘as designed’ equates to
‘as built’ for our homes. We believe we should always first focus on reducing
the energy demand of a building by enhancing the
Reasons for this include: efficiency of its envelope before investing in renewables
• an outdated material toolbox – the German principle of ‘Energiewende’ (energy
efficiency first).10
• practical limitations to the modelling, and
The single biggest opportunity for energy saving in a
• a lack of mechanisms to address home (space conditioning) is best addressed through
variable workmanship. the use of insulation in the building envelope, rather
than offsetting with onsite renewable energy generation.
AMBA urges the ABCB to consider
improvements to the NCC 2022 to This is because the lifetime of solar panels is limited to
address workmanship in relation to the 15–25 years, and they require regular maintenance.
installation of insulation, air barriers and Comparatively, insulation continues to perform for the
vapour barriers. lifetime of the building (50+ years) without the need for
maintenance or replacement.
3More information
www.australianmodernbuildingalliance.org.au
Summary of recommendations References
For the NCC 2022, AMBA: Chen, D. and Ren, Z. (2015). Simulation of air infiltration of Australian
1
housing and its impact on energy consumption, Energy Procedia, 78,
• supports incremental changes to the 2717-2723.
NCC leading to low-energy buildings, U.S. Department of Energy (October 2000). Wall Insulation; Provide
2
and the evolution of the NCC to a moisture Control and Insulation in Wall Systems, Technology Fact
Sheet. Retrieved 11 October 2019 from https://web.ornl.gov/sci/
performance code buildings/docs/factSheets/wall%20insulation%20technology.pdf
• recommends NatHERS 7 Star level as Ambrose, M and Syme, M. (2015). House energy efficiency
3
the minimum energy efficiency measure inspections project – final report. Retrieved 1 October 2019 from
https://www.energy.gov.au/sites/default/files/house-energy-efficiency-
in residential buildings inspections-project-2015.pdf
• believes building envelope performance Chen, D. and Ren, Z. (2015). Simulation of air infiltration of Australian
4
housing and its impact on energy consumption, Energy Procedia, 78,
shouldn’t be traded off against services 2717-2723.
or onsite renewable energy generation
Edminster, A.V. (2018). Zero Net Energy Primer. Retrieved 1 October
5
2019 from http://aiacalifornia.org/wp-content/uploads/2018/04/
• does not think it is time to downgrade the ZNEprimerMar19-2018.pdf
deemed-to-satisfy compliance pathway
Munsami, K., Lockhart Smith, C. and Upadhyay, K. A. (2019).
6
to small buildings, alterations or additions RP1041: Improving the thermal performance of dwellings for carbon
positive and healthy houses. CRC for Low Carbon Living CRC,
• supports improvements to energy Sydney, Australia.
modelling software and the introduction Sustainability House (2013). Assisting NatHERS Compliance
7
of BASIX heating and cooling limits into Literature Review. Retrieved 1 October 2019 from http://www.
NatHERS nathers.gov.au/sites/prod.nathers/files/publications/Literature%20
Rev%20-%20Assisting%20NatHERS%20Compl.pdf
• advises an update of the NatHERS Munsami, K., Lockhart Smith, C. and Upadhyay, K. A. (2019).
8
toolbox to include contemporary RP1041: Improving the thermal performance of dwellings for carbon
insulation options positive and healthy houses. CRC for Low Carbon Living CRC,
Sydney, Australia.
• recommends the ABCB investigate a Sustainability House (2013). Impacts of Variable Air Infiltration Rates
9
target of 5 ACH50 for air leakage and the and Insulation Installation on Residential Energy Performance – Case
Studies using NatHERS Predictive Energy Modelling Software.
extension of thermal bridging provisions Retrieved 1 October 2019 from http://www.nathers.gov.au/sites/
to all lightweight construction prod.nathers/files/publications/Case%20Study%20-%20Impact%20
Air%20Infil%20%2B%20Insul%20Instal.pdf
• urges improvements in the NCC 2022 to 10
Murray-Leach, R. (2019). The world’s first fuel: How energy efficiency
address workmanship in relation to the is reshaping global energy systems. Energy Efficiency Council,
installation of insulation, air barriers and Melbourne, Australia.
vapour barriers
• recommends the ABCB adopt proven
prescriptive methods to reduce air
filtration, thermal bridging and energy use
– as a minimum, consider adopting the
mandatory use of exterior rigid insulation Disclaimer: This publication contains information of a general nature only,
board in the NCC 2022. is provided as an information service, and is to the best of our knowledge,
true and accurate. It is not intended to be relied upon as, or a substitute for
specific professional advice having regard to your specific circumstances.
Any recommendation or suggestions which may be made are without
warranty or guarantee, since the conditions of use and the composition of
source materials are beyond our control. It should not be construed as a
recommendation to use any product in conflict with existing patents covering
any material or its use. No responsibility can be accepted by Chemistry
Australia Ltd, AMBA (Australian Modern Building Alliance) or the authors for
loss occasioned to any person doing anything or not doing anything as a
result of any material in this publication.
4 Information Sheet 4 (Issue 2, February 2021)You can also read
