The focus of this video is the energy efficiency provisions in NCC Volume Two.
[voice over] Using the energy efficiency provisions in NCC Volume Two NCC Tutor Series
The focus of this presentation is the energy efficiency provisions in NCC Volume Two. This presentation has a practical focus and looks in detail at the specific Performance Requirements, DTS Provisions and Assessment Methods for energy efficiency that apply to Class 1 and Class 10 buildings.
This module is best viewed with a copy of the NCC on hand – to access the NCC, visit abcb.gov.au and register or log in to freely access it.
In this presentation you will learn:
Energy efficiency Performance Requirements in Volume Two
Compliance solutions for energy efficiency in Volume Two
House energy ratings, and
Assessment Methods for energy efficiency for Volume Two.
We will also explore some useful resources.
Energy efficiency in Volume Two. The first question to consider is, what is the key focus of energy efficiency in the NCC?
The focus of the energy efficiency provisions in Volume Two are:
the performance of the building fabric, or envelope, specifically how it works to reduce and allow heat flow into or out of the building, as needed to maintain a comfortable temperature in the conditioned spaces of the building, and
the efficiency of the building’s services, in this case the domestic services, which is a defined term in the NCC. This relates to the energy needed to operate the building’s services and the types of energy used.
In Volume Two, the energy efficiency Performance Requirements are found in Section 2 Performance Provisions. These are P2.6.1 Building and P2.6.2 Services. You can see how these reflect the focus of the energy efficiency provisions.
The energy efficiency DTS Provisions are located in Section 3 Acceptable Construction, Part 3.12 Energy efficiency. The DTS Provisions also reflect the key energy efficiency concerns, with the particular DTS Provisions that relate to the different factors that can affect the thermal performance of a building. This includes provisions for the construction of the building fabric, glazing, building sealing, air movement and services.
The arrows show the relationship between the individual Performance Requirements and the DTS Provisions.
Remember that the NCC is a performance-based code. You can also use Performance Solutions to meet the Performance Requirements, or a combination of Performance Solutions and DTS Solutions. Performance Solutions can be verified through the use of a Verification Method which is addressed later in this presentation.
What are the energy efficiency Performance Requirements in NCC Volume Two?
The key objective of the NCC Volume Two energy efficiency provisions is to reduce the greenhouse gas emissions that a building produces over its lifetime. An additional benefit of the provisions is that an energy efficient home can be more comfortable to live in and cheaper to operate.
The energy efficiency provisions in NCC Volume Two address 2 aspects.
The thermal performance of the building envelope – that is, the ease with which heat flows into and out of the building. It is assumed that improving the thermal performance of the building fabric will reduce the need for artificial heating and cooling. As heating and cooling are key contributors to the total energy use of a typical Australian home, improving the building’s thermal performance should reduce its energy use and therefore should reduce greenhouse gas emissions over the life of the building.
If we look at some of the key terms contained here, it helps us to understand some of the application.
Firstly, thermal performance. This is the maintenance of a comfortable temperature in conditioned spaces within a building, with an acceptable use of artificial heating and cooling.
The next is geographic location. Tthe required thermal performance depends on the NCC climate zone. There are different heating and cooling loads permitted to achieve the same star rating, in different locations.
The next is permanent features. Those with long term impacts on thermal performance, such as: mountains, existing buildings that overshadow the building or large heritage listed trees are included in the assessment.
The next is solar radiation. We want to encourage the use of passive solar design to heat the building in cooler weather and reduce the entry of unwanted heat in warmer weather.
The next is building envelope. We want to seal the building fabric between the conditioned and non-conditioned spaces to prevent unwanted entry or loss of heat.
The last is air movement. You want to design ventilation to remove excess heat during warmer weather and reduce perceived temperatures indoors.
The second is the efficiency of the domestic services – that is how much energy is used to run things like air-conditioning, heating and lighting and to heat hot water.
The source of the energy used, particularly the use of renewable energy, reclaimed energy or low greenhouse gas intensity fuels.
Let’s now look at some of the definitions here.
The first is, features that facilitate the efficient use of energy. Here, for example, we are talking about energy efficient heating and cooling systems, electrical appliances, smart meters and renewable energy sources.
The domestic service is - basic engineering systems that use energy or control the use of energy. This includes heating and air conditioning, mechanical ventilation and artificial lighting. It also includes swimming pools and spa pumps and heaters and heated water systems.
In relation to geographic location, the required performance depends on the NCC climate zone. Different levels of energy usage can be considered efficient, in different locations.
The last is renewable energy. This is onsite renewable energy generation only. This includes solar, wind, wave action and geothermal energy. Green power energy contracts don’t count as part of this provision.
Variations exist for NSW, Victoria and the Northern Territory.
In relation to variations Part 2.6 does not apply in NSW. NSW requires a BASIX sustainability rating for new homes and renovations. NSW additions in schedule 1 contain energy efficiency measures that support and complement BASIX.
In the Northern Territory Part 2.6 is replaced with BCA 2009, Part 2.6.
There are variations to both P2.6.1 and P2.6.2 in Victoria.
How can we comply with the energy efficiency performance requirements of NCC Volume Two?
On this slide, we’re going to look at the options under the DTS Provisions for achieving compliance.
Let’s look at this excerpt from Clause 3.12.0 Application of Part 3.12, in Part 3.12 Energy efficiency, from Section 3 Acceptable Construction.
This clause deals with the compliance options for P2.6.1 Building, which deals with the thermal performance of the building fabric.
The two options for complying with Part 2.6.1 (thermal performance of the building fabric) are:
Option 1 – using a house energy rating solution along with some of the elemental DTS Provisions in Part 3.12. In this solution, house energy rating software is used to assess the performance of the building fabric as a whole; and
Option 2 – using the elemental DTS Provisions on their own. In this solution, each key element of the building fabric is considered on its own.
The building sealing DTS Provisions apply to both solutions.
Remember P2.6.2 Services must also be complied with., One way to do this is using the DTS Provisions in 3.12.5 Services.
A designer or builder can choose to use a Performance Solution instead of the DTS Provisions for any aspect of the Performance Requirements. For example, they could:
comply with a different standard, such as the Passiv Haus standard, and present the Approval Authority with evidence that this meets or exceeds the thermal performance and building sealing provisions of the NCC; or
use a reference building to demonstrate that a Performance Solution will meet or exceed requirements.
Regardless of the solution used, appropriate and sufficient evidence must be provided to the Approval Authority, to allow them to assess whether the solution meets the Performance Requirements.
Building energy efficiency ratings.
As you know from the previous slide, one way of meeting Performance Requirement P2.6.1 is to do a building energy rating, which assesses the thermal performance of the building fabric, as a whole. NatHERS is the energy rating scheme that must be used. NatHERS is the Nationwide House Energy Rating Scheme.
All buildings assessed in this way must achieve a minimum 6 star rating, from a rating system that runs from zero to 10 stars. Zero stars means that the building has no energy efficiency features or savings, while 10 stars means that the building should not need additional energy to heat it or to cool it to a comfortable temperature.
There is a concession in the NCC for buildings in NCC climate zones 1 and 2, which have hot and humid weather. These concessions allow a building to rate only 5 or 5.5. stars, with certain provisos.
Buildings in most climate zones must also meet individual heating and cooling load limits that are specific to the climate zone. This applies in “mixed” climate zones where both heating and cooling are required at different times of the year.
It doesn’t apply in climates that are dominated by hot or cold weather, for example the climate zones in much of the Northern Territory and Tasmania.
Where there are specific heating and cooling load requirements, a building must meet both the heating and cooling requirements, as well as meeting the overall energy efficiency target.
So, a house in a mixed climate, for example in Canberra or Adelaide, might perform really, really well in winter – i.e. it has a very low heating load – while performing poorly in summer – i.e. having a high cooling load. When the two loads are added together the building might remain under the total required for a 6 star overall rating. However if the building exceeds either the heating or cooling load limit, it would not meet the minimum DTS requirements and would not comply with the Performance Requirement P2.6.1.
The ABCB Standard 2019:1: NatHERS heating and cooling load limits, contains separate heating and cooling load limits that apply to the design and construction of dwellings that are assessed using the NCC’s energy rating assessment pathway.
The NatHERS assessment is done by an accredited assessor using the NatHERS software.
A NatHERS rating is not sufficient on its own to comply with P2.6.1. You have to demonstrate compliance with other DTS requirements for insulation, thermal breaks, floor edge insulation and building sealing.
Remember that you also have to meet the Performance Requirement P2.6.2 Services.
Note that NSW does not apply Part 3.12 Energy efficiency. The New South Wales variations contain energy efficiency measures that apply in New South Wales to support and complement their own energy rating scheme known as the Building Sustainability Index - or BASIX for short. This too is based on different heating and cooling load limits.
Let’s have a go at interpreting the DTS Provisions. Ensure you have access to a copy of the NCC, before you attempt these questions. The answers for each question will be found in the respective Parts covered. Pause this presentation after a question and look up the relevant Part.
Question 1: Consider a ceiling area in a kitchen-family room that would usually require a minimum R-Value of 3.0 to meet the requirements of the NCC. If 2.4% of that ceiling area is uninsulated because of exhaust fans and recessed downlights, how much does the insulation R-Value in the rest of the ceiling need to increase in order to compensate for the loss?
Table 184.108.40.206h Adjustment of minimum Total R-Value for loss of ceiling insulation.
Minimum Total R-Value required to compensate for loss is 4.2, which is an increase of 1.2.
Question 2: According to Part 220.127.116.11, how are the distances P, G and H calculated, when designing shading for glazing to meet the minimum Performance Requirements of NCC Volume Two?
Table 18.104.22.168 Method of measuring P and H
P is the distance between the line of the glazing and the furthest vertical edge of the shading projection or device
G is the distance between the top of the glazing and the lower horizontal edge of the shading projection or device
H is the distance between the bottom of the glazing and the lower horizontal edge of the shading projection or device
Question 3: What DTS requirements apply to the sealing of external doors and windows?
Part 22.214.171.124 External doors and windows
An external door, internal door between a Class 1 building and an unconditioned Class 10a building, openable window or similar must be sealed when serving either a conditioned space or a habitable room in climate zones 4, 5, 6, 7 and 8
Seals to restrict air infiltration must be:
A close fitting architrave, skirting or cornice, or
A foam or rubber compressible strip, fibrous seal or similar, for the other edges of a door or the edges of an openable window
Question 4: According to Part 126.96.36.199, what is the minimum total ventilation opening area required for a habitable room in climate zone 4?
How does this change if the room has a ceiling fan or an evaporative cooler?
Table 188.8.131.52 Minimum total ventilation opening area as a percentage of the floor area for each habitable room.
The minimum total ventilation opening area for a habitable room in climate zone 4, without a ceiling fan or evaporative cooler, is 10% of the total floor area of the room.
If the room has either a ceiling fan or an evaporative cooler, the minimum total ventilation opening area reduces to 5% of the floor area.
Question 5: What referenced documents are referred to in Part 3.12.5 Services?
For thermal insulation of central heating water piping and heating and cooling ductwork, AS/NZS 4859.1 Thermal insulation materials for buildings – General criteria and technical provisions.
For sealing heating and cooling ductwork:
AS 4254.1 Ductwork for air-handling systems in buildings – Flexible duct.
AS 4254.2 Ductwork for air-handling systems in buildings – Rigid duct.
This also references Part B2 of NCC Volume Three for the design and installation of a heated water supply system, including the water heater.
Energy efficiency Assessment Methods
Whether you choose to use a DTS Solution or a Performance Solution or a combination of the two, you may need to provide some evidence that the proposed solution complies with the Performance Requirements.
The NCC recognises four valid ways of assessing possible compliance solutions, which are shown on the slide here. All four Assessment Methods can be used to demonstrate compliance with the Performance Requirements when you are using a Performance Solution.
Evidence of suitability and Expert Judgement can be used when you are using a DTS Solution.
NCC Volume Two includes two Verification Methods relating to energy efficiency, which are:
V184.108.40.206 Verification using a reference building, which can be used to demonstrate that the proposed building’s heating and/or cooling load is equal to or less than that of the compliant reference building.
V220.127.116.11 Verification of building envelope sealing, which describes the standard for compliance with the building sealing requirements in P2.6.1(f).
The next is Comparison with DTS Provisions. This is where we compare a Performance Solution with the DTS provisions in Part 3.12.
Evidence of suitability, also known as documentary evidence, can be used to support that a product, construction method or design satisfies a Performance Requirement or DTS Provision.
Examples of documentary evidence include a report from an accredited testing laboratory, a certificate from a professional engineer, product technical statements, a certificate of conformity or accreditation or a current certificate issued by a product certification body that has been accredited by the Joint Accreditation System of Australia and New Zealand or JAS-ANZ.
The last is Expert JudgementThis is where we use the expert judgement of a suitably qualified person. The expert must have demonstrated knowledge of technical issues and also peer recognition.
Let’s test our understanding of the term conditioned space.
Which of the following is a conditioned space for the purposes of NCC Volume Two?
Office space above garage with split system air-conditioning
Bathroom with under-floor heating system, or
Sunroom created by enclosing a porch with glazing.
Take a moment, pause this video and consider your answer. When you are ready to see the answers, start the video again.
• Office space above garage with split system air-conditioning: Conditioned Space – A home office is a habitable room. Since it may be used for significant periods of the day. It would normally need some form of air-conditioning.
• Bathroom with under-floor heating system: Non-conditioned Space – A bathroom is not a habitable room, and any heating is likely to have low wattage.
• Sunroom created by enclosing a porch with glazing: Non-conditioned space – if it has no mechanical heating or cooling. Conditioned space – if it has any form of mechanical heating or cooling.
Let’s practice interpreting the energy efficiency DTS Provisions. Take a moment to consider this excerpt from Clause 18.104.22.168 Heating and cooling loads. The answer to the following questions are found in this excerpt. Pause the video after the question to give yourself time to find the relevant information.
Question 1: What energy efficiency star rating is required for most buildings covered by the provisions of NCC Volume Two?
Generally six stars, derived using an approved version of house energy rating software.
Question 2: Under what circumstances can this 6 star requirement be varied?
Buildings in climate zones 1 and 2.
If they have a covered outdoor area that meets the specified requirements. For example, has a solid roof that meets the specified Total R-Value and has a permanently installed ceiling fan.
Question 3: Where can you find the required heating and cooling loads that apply in different climate zones?
In the ABCB Standard for NatHERS Heating and Cooling Load Limits. This can be found on the ABCB website.
True or False?
To meet the NCC energy efficiency Performance Requirements, all newly built Class 1 buildings in Australia must use the same amount of energy for heating, cooling & other energy requirements in order.
False, that’s right.
All newly built Class 1 buildings must achieve a similar standard of energy efficiency.
But the allowed energy use differs in different climate zones and because of other factors.
Besides the climate zone the house is in, other factors that can affect the actual heating, cooling and operational energy loads for different buildings include:
The size of the building – a bigger building naturally uses more energy than a smaller one and a house with more people living in it will also tend to have greater demands for energy. Therefore, you would not expect a 1 bedroom unit to use the same amount of energy as a 4-bedroom family home.
The other is On-site energy generation – if a building generates some of its own power, this can offset the heating and cooling loads and improve its overall energy efficiency.
What elements do the energy efficiency provisions in NCC Volume Two cover?
Pause the video to consider your answer. You may like to write them down.
• Domestic services (P2.6.2, 3.12.5)
• Air movement (P2.6.1, 3.12.4)
• External glazing (P2.6.1, 3.12.2)
• Building sealing (P2.6.1, 3.12.3)
• Building fabric (P2.6.1, 3.12.1).
True or False?
Every new Class 1 building in Australia must have a NatHERS assessment to demonstrate that it meets the NCC energy efficiency Performance Requirements.
False, yes, that’s right.
A designer or builder can demonstrate compliance against each of the elemental DTS provisions instead of doing an energy efficiency rating.
In New South Wales, BASIX ratings are used instead of NatHERS ratings.
A different rating system could also be used as part of a Performance Solution.
Let’s now explore some other useful resources.
The ABCB calculators can help with the calculations used in DTS Provisions, this includes the:
We also have the NCC Volume Two Energy Efficiency Handbook.
This is non-mandatory guidance to assist in understanding and applying NCC Volume Two energy efficiency requirements
YouTube tutorials are also available to explain the provisions and show you how to use the calculators.
These resources are not mandatory. They provide guidance and help, but nothing in them needs to be complied with in order to comply with the NCC.
Nor do the calculators act as Verification Methods. This means that you can’t present evidence from the lighting calculator, for example, to demonstrate compliance with the lighting requirements in P2.6.2.
The key points from this presentation are:
The overall aim of energy efficiency provisions in NCC Volume Two is to reduce greenhouse gas emissions from domestic building in Australia.
The second is compliance with requirements reduces energy used to maintain a comfortable temperature and operate the building.
Heating and cooling loads are key and evidence of compliance is commonly provided through energy rating – either NatHERS or BASIX in NSW.
Other elements must be met using DTS provisions or a compliant Performance Solution
This brings us to the end of the presentation.
Thank you for viewing this NCC Tutor module. Check out the other NCC Tutor modules available to build your understanding of the NCC.
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