NCC Tutor lesson - Understanding energy efficiency in the NCC

[voice over] Understanding energy efficiency in the NCC. 

NCC Tutor Series. 

The focus of this presentation is on the fundamentals of energy efficiency and how the NCC handles energy efficiency requirements across the Volumes. 

This module is best viewed with a copy of the NCC on hand – to access it, visit abcb.gov.au and register or log in to access it freely. 

Please note that this presentation does not go into details about the specific energy efficiency requirements of Volume One or Volume Two of the NCC.  

Slide 2 

In this presentation you will learn: 

• what energy efficiency means 
• why energy efficiency is important 
• key energy efficiency concepts & terminology 
• how to achieve energy efficiency 
• energy efficiency requirements in the NCC; and  
• other useful resources. 

Slide 3 

What do we mean when we talk about building energy efficiency? 

There is no exact agreed definition for energy efficiency. The most technical definition – and source of the term – relates to how much output a machine or energy service gets for the energy that is input, i.e. how much of the energy input to a machine is lost and how much is able to be used to produce an output. 

But the term is used much more broadly now in the context of reducing energy use or conserving energy. 

In a building energy is mostly used in: 

• heating and cooling of the living spaces 
• lighting 
• heating hot water, or 
• operating electronic devices. 

The NCC energy efficiency provisions are designed to ensure that a building is designed and constructed in a way that it is possible to operate the building with an appropriate minimum level of energy use, given its purpose and geographical location.  

The specific Performance Requirements differ for Class 2 to 9 buildings and Class 1 and 10 buildings, along with the way that compliance with the requirements is assessed. 

Slide 4 

Why is energy efficiency important? 

In recent years, awareness has increased about the increased level greenhouse gas (or GHG) emissions and the impact these emissions may have on the warming of global climate, including Australia’s.  

While the building sector is not the largest contributor to greenhouse gas emissions, it is one of the fastest growing sources. Energy used in buildings accounts for around 20% of all energy related greenhouse gas emissions in Australia.  

The NCC aims to contribute to reducing greenhouse gasses by increasing energy efficiency of Australia’s building stock. Energy efficient buildings and services also cost less to run and will more easily maintain a comfortable temperature in which to live and work in. 

Slide 5 

The definitions of energy efficiency terms used in the NCC are specific to the NCC. It is important to check the definition and make sure you understand it. 

Some energy efficiency terms are defined differently for NCC Volume One and NCC Volume Two. For example, the definitions of: conditioned space, building envelope or glazing. 

Slide 6 

This map is Figure 2 from Schedule 3 Definitions in any Volume of the NCC. The map, together with its associated table, defines the eight NCC climate zones for energy efficiency.   

There is a larger, expandable version of this climate zone map available at the ABCB website along with state and territory maps. 

The different climate zones are shown by the different colours. For example: Climate zone 1 is the dark orange colour in north of  Australia and Climate zone 8 is the white parts in the south east of the country. 

The eight NCC climate zones are described as: 

• Climate zone 1 - High humidity summer, warm winter  
• Climate zone 2 - Warm humid summer, mild winter  
• Climate zone 3 - Hot dry summer,warm winter  
• Climate zone 4 - Hot dry summer, cool winter  
• Climate zone 5 - Warm temperate  
• Climate zone 6 - Mild temperate  
• Climate zone 7 - Cool temperate; and 
• Climate zone 8 - Alpine. 

Appropriate design for the climate is key to achieving energy efficiency in a building. For example, in Zone 1, buildings should be designed to reduce heat gain from the sun, so you want to minimise how much sun enters windows and how much heat the windows will transmit into and out of the building. Ventilation is important for cooling the building naturally.  

In Zone 4, you want to minimise the sun in summer and ensure adequate ventilation, but in winter when it is cooler you will usually want to maximise the amount of sun you get into the building in order to warm it naturally.  

In Zone 8, where it tends to be cooler all year and very cold in winter, your main aim is to minimise the loss of warmth from inside the building. 

Slide 9 

The explanation for conditioned space on the screen issimplified a little, for space reasons, and because the purpose of this module is not to present a detailed technical analysis of energy efficiency requirements 

The definition varies between Volume One and Volume Two. You should look at the different definitions in each of the relevant Volumes before making any decisions based on the classification of a space as conditioned or non-conditioned. 

The NCC doesn’t define non-conditioned space, but it is logically the opposite of a conditioned space. Since the definition of a conditioned space varies a little between the Volumes, so does what would be considered a non-conditioned space. Check first before making any assumptions. 

This classification is important because a non-conditioned space will impact on the temperature in an adjacent conditioned space, if there is a temperature difference between them. So, for example, a warm conditioned space that has a non-conditioned space on 3 sides, will lose heat to all three of those non-conditioned spaces. If a cool conditioned space has warm non-conditioned spaces on one side (for example the western external wall of the building in summer), then the conditioned space will often “gain” heat from the non-conditioned space. This heat loss or gain continues between any spaces or surfaces with different temperatures, essentially until the 2 spaces or surfaces have the same temperature. 

Slide 10  

The envelope of a building can be thought of as identifying the boundary between a conditioned space and a non-conditioned space. 

While the building envelope is always formed from parts of the building fabric, some parts of the building fabric may not be part of the building envelope. For example, internal walls which separate conditioned spaces (i.e. rooms) from one another.  

The material used in the building fabric and the design, construction and integrity of the building envelope, may help to make the building more energy efficient. They can help to reduce the transfer of heat into and out of the building. This helps to maintain a comfortable temperature in the conditioned spaces and reduces the need to use energy to heat and or cool the building.   

Using appropriate materials in the building fabric, along with appropriate insulation, can help limit unwanted heat flow, and reduce the amount of energy needed to heat or cool the conditioned spaces in the building. 

If you identify the areas of the building that are conditioned, or can be conditioned (or for Volume One) constitute a habitable room (as defined in Volume One), which is likely to be conditioned if it becomes uncomfortable. The building envelope is made up of the walls, roof, ceilings and floors that form the boundary of these conditioned spaces – if there is a non-conditioned space on the other side. 

Slide 11 

Thermal mass is a term used to describe how well a building material stores heat. 

Materials with high thermal mass absorb heat from the environment and then release that heat slowly when the surrounding ambient temperature goes down.  

Thermal mass exposed to winter sun warms during the day, and will warm the space in it as it cools. Cool the thermal mass down overnight in summer and it will cool the space as it heats during the day. 

Effective use of thermal mass, combined with good solar orientation, can greatly reduce the need for mechanical heating and cooling. 

Slide 12 

Ventilation refers to the natural movement of air into or out of a building through an opening designed for that purpose. 

This could be a: 

• permanent opening, such as a vent 
• a part of a window that can be open, in the wall or roof, or 
• a door or other device that can be held open.  

Good ventilation can help to cool a building naturally without the use of artificial means or energy. 

Slide 13 

A building’s heating and cooling loads are calculated using approved software. 

These calculations are based on the building’s size, design, climate zone, orientation, ventilation, and the material used in the building envelope, along with a few other factors such as any shading from other buildings or significant trees and the colours used in external materials. 

Only approved software can be used to calculate heating and cooling loads, and this software is different for residential buildings versus commercial buildings, and to some extent between the different states and territories.  

A building’s heating and cooling loads are the key factor that determines a building’s star rating under the various energy efficiency rating schemes. However, only NatHERS software allocates a star rating to buildings. NatHERS is the Nation-wide House Energy Rating Scheme. Other software approved for use under Verification Method V2.6.2.2 is unlikely to allocate a star rating. 

The classification of conditioned space in a building makes a difference to the calculation of heating and cooling loads and therefore the building’s energy efficiency star rating.  

Acceptable heating and cooling loads to achieve the required star rating are different in different climate zones. This is an acknowledgement that it is easier to minimise energy use for heating and cooling in some climates than in others, particularly more extreme climates. For example, it would be difficult to design a building that had no requirements at all for mechanical heating in an alpine area. To require a building in Climate Zone 8 to have the same heating and cooling load as a similar sized building in Climate Zone 1 or 4, would not be reasonable. 

Slide 14 

Let’s test your knowledge of using the NCC climate zones. 

1. Which states or territories have Zone 8 Alpine areas? 

   Answer: New South Wales, Victoria and Tasmania.

2. Are Adelaide and Perth in the same climate zone or different ones? 
   
   Answer: Both cities are in climate zone 5, warm temperate.
3. Exmouth and Dampier in Western Australia and Mackay and Rockhampton in Queensland are not dissimilar latitudes. Are they in the same climate zone? 

Answer: No. Exmouth and Dampier – Zone 1, high humidity summer, warm winter. Mackay and Rockhampton – Zone 2, warm humid summer, mild winter

1. Complete the sentences below… 

• A building’s what represents the amount of energy required to maintain a comfortable temperature in that building.
•  
  • Heating/cooling load
• A building’s structural elements, such as the walls, roof, ceilings, glazing and floors, are referred to as the what. 
  • Building fabric
• A what in a house is a space that can be heated or cooled to maintain a comfortable temperature. 
  • Conditioned space
• A space in a house that does not have services to heat, cool or otherwise alter the temperature of the air can be described as a what.
  • Non-conditioned space.
• What term is used to describe… the parts of a building that separate a conditioned space from a non-conditioned spaces, including the outside of the building? 

The building envelope.  

The design, materials and construction of a building’s envelope help to prevent unwanted heat transfer of heat into and out of the building.  

This helps to keep the living spaces at a comfortable temperature while minimising energy use.  

The building fabric is all the structural elements and the other components used to make a building, which includes the roof, ceiling, walls, glazing and floors. The parts of the building fabric that separate conditioned from non-conditioned spaces belong to the building envelope.  

Not all parts of the building fabric will separate conditioned and non-conditioned spaces – some will separate non-conditioned spaces from each other, or they will separate conditioned spaces, for example, internal walls. 

Slide 15 

In terms of insulating properties and energy efficiency, a high R-Value is usually good, but whether you want low or high SHGC and U-Values depends on how you want the particular window to function. 

So, in a northern location, where you want to keep the sun out of the building all year round, a window system with a low SHGC and low U-Value is preferred.  

But in a southern location, where you might want to allow the sun into the building in winter, but exclude it in summer a high SHGC and moderate U-Value might work better. 

Note that the glazing energy efficiency requirements in the NCC apply to windows in the building envelope only. So, a window in an internal wall does not have to meet these Performance Requirements. For example, a window placed high on the wall between a hallway and study to let in more light. Note that this window might have to meet other Performance Requirements, such as to ensure safety and minimise noise disturbance. 

Slide 16 

Let’s now look at some terms. 

In the NCC, the term glazing includes the glass and the frame associated with it, in the building envelope. 

The term is defined slightly differently between NCC Volume One and NCC Volume Two. 

It can apply to windows and doors in walls, and some roof windows. 

Solar Heat Gain Coefficient or SHGC and Total Solar Heat Gain Coefficient: 

SHGC and Total SHGC are defined terms in the NCC. 

SHGC is a measure of the proportion of solar energy (or radiation) that passes through a glazing system (which includes the glass and the frame). In other words, it measures the solar heat gained through the glazing system. It is the measurement of the glazing’s solar transmittance. 

It is expressed as a number between 0 and 1. 

A high SHGC means that the glazing system allows in more solar energy or heat into a room. (That is, a value closer to 1.) 

A low SHGC means that the glazing system allows less solar energy or heat into a room. (That is, a value closer to 0.)

A low SHGC is good in some circumstances and a higher one is better in other circumstances, depending on how the glazing needs to function in the building. 

The definition of Total SHGC varies slightly between the NCC Volume One and NCC Volume Two. 

Like the U-Value, you will usually see SHGC values quoted for glazing and window systems. You’ll need to understand whether the value quoted is the value of the glass or the frame, or a Total SHGC for the entire window system and glazing. 

U-Value 

U-Value is a measure of how easily a material or building element transmits heat from one side to the other. It is a measure of the material’s thermal conductance. 

The higher the U-Value, the more easily the material transmits heat. 

The lower the U-Value, the better the material is at resisting the transfer of heat. That is, the better it insulates. 

A material’s U-Value is the inverse of its R-Value.   

U-Values are calculated for any type of windows, including those in walls and in roofs or ceilings.  

The NCC defines the Total System U-Value of a building component or assembly. This is a calculation of the sum of the U-Values of the individual component layers in a complete assembly or material.  The calculation includes any glazing, the frame, any insulating material in the frame, thermal breaks or air spaces between the inside and the outside, any gases used (such as argon between double glazed windows), and associated surface resistances. 

The definition of Total System U-Value varies slightly between NCC Volume One and NCC Volume Two. 

You will usually see U-Values quoted for glazing and window systems. You need to understand whether the value quoted is the value of the glass or frame, or Total U-Value for the entire window system and glazing. 

R-Value  

R-Value is a measure of how well a material or building element insulates, that is, how well it resists the transfer of heat from one side to the other. It is a measure of the buildings thermal resistance. 

R-value is a defined term in the NCC. The formal definition is the thermal resistance of a component calculated by dividing its thickness by its thermal conductivity.  

The higher the R-Value, the better the material is at insulating. That is, the less easily it transmits heat. 

The NCC also defines the Total R-Value of a building component or assembly. This is a calculation of the sum of the R-Values of the individual component layers in an composite material or assembly.  The calculation includes any building material, insulating material, air spaces between the different layers, and associated surface resistances. 

If you think of a pre-made exterior insulation and finish wall panel which could be assembled from 4 or 5 different layers (for example, a metal outer layer, a foil moisture lining, an internal frame, an insulation layer and an inner shell), each of these layers will provide some degree of thermal resistance. The Total R-Value is the sum of all of these, (plus the thermal resistance of any air gaps.) 

You might not  have to calculate an R-Value, as these values are usually included in product specifications. You will usually see R-Values quoted for the building materials typically used in walls, floors, ceilings and roofs. You might need to check whether the value quoted is a Total R-Value or just the R-Value of an element. You might also need to calculate an R-Value if you are using an unusual building material or method. 

For the purposes of calculating heating and cooling loads and therefore energy efficiency star ratings, it is generally the Total-R-Value of a roof, wall, ceiling or floor that matters. 

Slide 17  

Lets check your understanding of some key terms. 

Match the term to its explanation. 

We are going to look at Glazing , U-Value, SHGC and R-Value. 

• A transparent/translucent material and it frame in the external fabric of a building: Glazing
• A measure of how easily a building element conducts heat: U-Value
• A measure of the amount of heat transmitted through a window, glazed door or skylight: SHGC
• A measure of how well a building element resists the transfer of heat: R-Value

Slide 18 

How do we achieve energy efficiency? 

Optimal orientation is key. A building that is well positioned on the block to catch winter sunshine and reduce summer sunshine - for example in southern latitudes - will be much more comfortable to live in than one that is poorly positioned and will need far less mechanical heating and cooling. This is one of the simplest and most effective ways of obtaining good energy efficiency, although it is not enough on its own. 

The materials used in the building fabric also play a role. In warmer climates, lightweight materials that reduce thermal mass can be effective. However, in cooler climates, materials with more thermal mass are usually preferred. 

Glazing that is appropriate to the climate, orientation and position is also important. This involves considering more than just the type of glass and frame. It extends to the size of the glazing (windows) in different walls. In southern latitudes, large windows on the north that get winter sun can help to warm the building during the day and at night if there is sufficient thermal mass in the house. In the same situation, windows on the southern side of the building should ideally be kept smaller, as they act as a source of heat loss, regardless of the type of window used. 

Insulation is also key, to reduce the loss of heat in cooler weather and heat gain in warmer weather. Insulation can be in the ceiling, under the roof, under and at the sides of the floor, and in the walls. In other words, throughout the building envelope. 

Ventilation is another key consideration that is often forgotten. For example, in warmer climates and in summer in most parts of Australia, good ventilation can help clear the heat that builds up during the day and provide a comfortable temperature for sleeping at night. 

In climate zones that are warm all year round (for example in Climate Zones 1 and 2) good ventilation can make a big difference to how much heat builds up inside the building and to users perceptions of the thermal comfort in the building. 

Shading can also be a useful to consider. For example, in cooler climates positioning the building to avoid over-shadowing by neighbouring buildings in winter, and planting trees or using features such as pergolas, eaves or wing walls to reduce sun exposure and heat gain on the eastern and western sides of a building. In northern climates, where the sun can enter the building from all sides through much of the year, wider than usual eaves can help to provide shade on all sides and minimise solar heat gain. 

Energy efficient building systems and appliances also play a key role. A more efficient heating system can save significantly on the energy required to heat a building, when mechanical heating is required. The key mechanical systems that contribute to energy use are: 

• heating and cooling 
• lighting 
• heating hot water 
• pumps and other equipment related to pools and spas. 

Note that small appliances are also big users of energy – particularly as the number and size of devices in the typical home or workplace continues to increase and they tend to use more and more standby power. But as they can vary, i.e. they are not a permanent fixture within the building, they are not included in assessment of energy efficiency for the purposes of building approval. 

However, all efforts to minimise heat loss and gain are potentially wasted if the building isn’t well sealed, since all the warmth inside the building (in winter) will escape, and unwanted heat will enter the building in summer. Good building sealing means that if you use energy to heat your building, that warmth will be retained for longer inside the building and so the building won’t require so much mechanical heating. The same goes for cooling the building. 

All of these factors listed (and many others) have to be considered at the design stage, when it is cheaper and easier to ensure that the building will function well for the climate zone.  

A building is approved to be built as designed, which includes all the energy efficiency features in the approved plans. 

This then must be carried through in construction, that is the building must be built as approved and you shouldn’t be changing features that contribute to the energy efficiency of the building. For example, reducing the insulation in walls, installing ceiling insulation poorly or choosing a different material for walls or glazing, can greatly change the actual energy efficiency of the building. 

Slide 19 

Lets consider an example. This building is in Canberra – in Climate Zone 7. The building has an ideal northern orientation for living areas. 

How does the concrete floor slab contribute to energy efficiency? 

What kind of materials would you use in the building envelope? What sort of R-Value should these materials have? 

What kind of SHGC and U-Values would be best for the glazing in this building? 

What purpose do the eaves on the building serve?  

Why is the southern window designed to be smaller than the northern window? 

If you rotated this building by 90° so that the living areas faced east/west, what could be the impact on the building’s energy efficiency? 

Slide 20 

Another example. This building is located in Cairns – in Climate Zone 1. It has sun all year round from at least three directions. 

How is the design of the building different from the design of the Canberra building? 

Why is a lightweight wooden floor used in this building? 

What kind of materials could you use in the rest of the building envelope? What sort of R-Value should these materials have? 

What kind of SHGC and U-Values would you select for the glazing? 

Why are the northern and southern windows the same size in this building? 

In what different ways can the windows contribute to the building’s energy efficiency? 

Slide 21 

Building energy efficiency is largely assessed by rating likely performance of the building – as designed – against a standard. A building can demonstrate compliance with the majority of the NCC energy efficiency Performance Requirements by getting a rating against a nominated energy efficiency standard.  

These standards that can be used to rate buildings are different for commercial and non-commercial (or domestic) buildings.  

There are also some differences between the standards that are acceptable in different states or territories. 

Both Volume One and Volume Two contain Performance Requirements that focus on: 

• The performance of the building fabric, which means the extent to which the building fabric allows for heat flows in and out of the building. 
• And also The energy efficiency of the key, fixed building services, such as air-conditioning systems, lighting and hot water generation. 

Volume One also includes requirements for the energy efficiency of swimming pool or spa plant, and provisions to allow for monitoring of energy usage. 

Volume Two includes requirements for adequate sealing of the building envelope. 

These inclusions reflect the key concepts and approaches discussed earlier in this module, as making a difference to building energy efficiency. 

Some of the provisions in Volume Three also relate to energy efficiency. In particular, the Performance Requirements for heated water services require consideration of the amount of energy used to heat the water and the greenhouse gas emissions that are released.  

Slide 22 

The ABCB has developed a range of calculators to assist practitioners to develop energy efficient building solutions.  

Use of these calculators may be helpful but it is not mandatory, i.e. you do not have to use them, and they are not compliance tools or Verification Methods. For example, you can use the ABCB Glazing Calculator to identify or test glazing combinations, but you should not use the results of the calculator as the sole evidence that the glazing chosen for a building is appropriate and meets the Performance Requirements.   

There is a video on how to use most of these calculators. 

There is also a handbook that specifically applyies  energy efficiency provisions of each of Volumes One and Two. 

There are many different case studies that also cover a wide variety of topics. 

Slide 23 

True or False. The energy efficiency provisions are the same across Volume One and Volume Two of the NCC. Take a moment to consider your answer. 

False: The energy efficiency provisions are different in the two Volumes. Differences include the definitions of some energy efficiency terms, the Performance Requirements and the DTS Provisions.

Slide 24 

Which NCC Volumes contain provisions designed to improve energy efficiency? Take a moment to consider your answer. 

Answer: All three Volumes – Volumes One and Two contain provisions for ensuring minimum energy efficiency levels in different types of buildings. Volume Three contains provisions that relate to the use of energy for heating water in any type of building.

Slide 25 

The Key points from this presentation are: 

Energy efficiency provisions in the NCC aim to reduce the energy required to operate a building, and therefore the GHG produced by the buildings in Australia. 

The focus on the building envelope is to minimise the use of mechanical heating and cooling to maintain a comfortable temperature within a building 

This encourages: 

• efficient use of energy to operate a building’s services, including water services; and 
• the use of low Greenhouse gas energy sources. 

There are different requirements for buildings in different climate zones and of different building classifications. 

Slide 26  

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. 

[End of transcript]