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6 Star NatHERS Certificate

Everything You Need to Know...

About the National House Energy Rating Scheme. Find out what the requirements are to certify your project today.

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A National NatHERS Requirements Guide

Everything you need to know about the NatHERS requirements per state. 

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6 Star NatHERS reports are a pathway to compliance for Energy Efficiency under Section 3.12 in the National Construction Code. Here you will learn all you need to know about energy efficiency compliance for residential construction projects in Australia. 

 

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What is 6 Star NatHERS exactly?

 

Are you looking for a NatHERS certificate for your next project?

At Certified Energy we take pride helping our clients and their projects in reaching their full potential, ensuring maximum savings and minimum energy use, allowing for cost effective, sustainable solutions. For more information about a NatHERS certificate, read the description below, or call us at 1300 443 674.

 

What is NatHERS?

NatHERS is short for the Nationwide House Energy Rating Scheme. It uses a 10 star rating system to assess the thermal performance of dwellings across Australia. The National Construction Code (NCC) references these star ratings specifying a minimum number of star levels for all new houses built in Australia.

 

Often referred to as a NatHERS assessment, a house energy rating is required for all alterations and additions, and houses and individual units in apartments under Class 1 and 2 buildings detailed in the NCC, respectively.  This national assessment involves the thermal modelling of each individual room in a house to determine the modelled heating and cooling loads. 

 

NatHERS is the Nationwide House Energy Rating Scheme and uses a 10 star rating system to assess the thermal performance of dwellings across Australia. The National Construction Code (NCC) references these star ratings specifying a minimum number of star levels for all new houses built in Australia. BASIX supersedes the NCC in New South Wales where NatHERS approved software is used to determine the thermal comfort scores. NatHERS is the regulatory body which approves the various types of software used to assess dwellings under this scheme.

 

There are two main certification solutions that we use here at Certified Energy to achieve building compliance. These include the Deemed to Satisfy solutions as well as the Alternative Solutions.

 

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Deemed to Satisfy Solutions:

  1. House Energy Rating Scheme (HERS)
  2. Elemental Provisions (EP)

 

Alternative Solutions:

  1. Verification Using A Reference Building (VURB)
  2. State Specific Energy Protocols

 

Our team at Certified Energy will guide you through the various approval pathways to help your project achieve the necessary compliance.

 

What Is an Energy Rating?

An Energy or Thermal Efficiency star rating is an accurate indicator as to how much heating or cooling is necessary to keep your development comfortable. The energy rating generated by an accredited NatHERS assessor using licensed software indicates a dwelling’s efficiency in preserving energy. Please note, it does not indicate the dwelling’s actual consumption of energy as that depends upon appliances installed and the way in which they are used. By improving your energy rating you will require less energy to keep your dwelling comfortable and therefore provide lower energy expenses as well as a much healthier environment.

 

What do the stars represent in the NatHERS rating?

The possible 0 to 10 stars is a scale that indicates the energy efficiency of a dwelling. If a dwelling is rated 0 stars, that means it offers no insulation from the external temperature. For example, if it is 20 degrees outside it will be 30 degrees inside. A 10-star dwelling is able to maintain a comfortable internal temperature all-year-round despite external temperatures. Hence, the more stars a dwelling has, the less energy it consumes, therefore reducing energy expenses.

 

What benefits does an energy rating give me?

When simulating the thermal performance of your dwellings, we will ensure that your energy expenses are reduced and that a healthy living environment is delivered through calculated and accurate methodologies. Doing so can ultimately be cost-effective in the long-term and increase property value.

 

Who Can Perform a NatHERS Assessment?

Only assessors trained, certified and accredited by 1 of the 2 nationally operating Assessor Accrediting Organisations (AAOs) can use NatHERS second generation thermal assessment software to provide official thermal efficiency star ratings and issue relevant certificates. The two AAOs are the Australian Building Sustainability Organisation (ABSA) and the Building Designers Association Victoria (BDAV). At Certified Energy, our assessors are accredited by the Australian Building Sustainability Association (ABSA).

 

Why choose Certified Energy as your NatHERS assessors

Our years of experiences enables us to assess your project with unrivalled cost and time efficiency; whilst also maintaining the integrity of your designs. Normally, assessors provide thermal performance figures that meet the standard requirements in order to obtain compliance. However, for a small additional fee, we can optimise the use of energy saving measures so that they are placed effectively whilst still complying with the regulatory requirements. Our assessors also follow the Assessor Code of Practice and are given ongoing support so they can provide you with a high quality of service. NatHERS Universal Certificates can only be issued by NatHERS Accredited Assessors, which includes the NatHERS logo, rating and stamp.

 

What it means to be part of the Australian Building Sustainability Association (ABSA)

The ABSA is a not-for-profit industry organisation that aims to improve Australian homes and buildings by ensuring they are sustainable. This includes ensuring that Australian buildings are designed to provide comfort and efficient use of energy resources. The Association supports building professionals and assessors with membership and training.

As part of the NatHERS Protocol, the Association is also an approved Assessor Accrediting Organisation (AAO). This means NatHERS accredited assessors are able to perform simulations in order to comply with Energy Efficiency requirements of the National Construction Code and Thermal Comfort in BASIX (NSW).

 

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How are NatHERS star ratings assessed?

NatHERS is assessed through a process of thermal modelling where the proposed dwelling is modelled using NatHERS approved software. The construction type, materials, glazing, lighting and insulation are used to assess the overall annual thermal performance of the project. Climate data within the software determines the development’s total heating and cooling load throughout the year, with specific heating and cooling targets outlined by NatHERS that need to be met.

NatHERS Accredited Software is used to calculate an energy efficiency star rating and is based on expected indoor temperatures. This is assessed by assessing the project’s design, climate and household use. The tool therefore does not take electrical appliances within the dwelling into consideration, other than the air flow from the dwelling’s ceiling fans.

 

Develop a simulation model

A NatHERS accredited assessor will enter data into the software which will generate a simulation model of the dwelling. The simulation model will include: sizes and functions of the rooms, sizes and specification of openings, building materials/windows/products, type of construction, dwelling orientation and location.

 

Determining the temperature of the development

The simulation model will determine the level of heating or cooling temperature that is needed for occupants to remain comfortable within the dwelling.

 

Determining the need for heating and cooling systems

The NatHERS Accredited software model will determine the need for heating and cooling systems when internal temperatures fall outside of a comfortable range. This is based on assuming that occupants will open and close windows, blinds or awnings in an attempt to restore a comfortable temperature level prior to using the heating or cooling system.

 

Calculating a rating out of 10

Once the steps above have been completed, the total annual estimated levels of energy efficient heating and cooling are determined by a ranking out of 10 stars.

 

 

 

What is a 6 Star Rating?

 

The National Construction Code (NCC formerly known as the BCA) requires all new residential dwellings in Australia (Except NSW and NT) to achieve a minimum of a 6 Star Rating using the Nationwide House Energy Rating Scheme (NatHERS), approved software.

 

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Reference

 

This NatHERS software estimates the internal temperature in each room of a dwelling for each hour of the year based on assumptions about occupant behaviour, information about the structure and specification of the dwelling and standard weather data for the dwelling's location.

 

The internal temperature is compared against a comfortable temperature range and occupancy pattern to estimate the annual heating and cooling loads per square metre of floor area to keep the temperature within the comfort range. The loads are adjusted and converted into a star rating between 0 and 10. A 10 star home is unlikely to need any artificial cooling or heating to maintain comfortable internal conditions, whereas a 0 star home would offer virtually no protection from the external temperature.

 

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Certificate

Comfort, Energy & Water

 

How are NatHERS star ratings assessed?

NatHERS is assessed through a process of thermal modelling where the proposed dwelling is modelled using NatHERS approved software. The construction type, materials, glazing, lighting and insulation are used to assess the overall annual thermal performance of the project. Climate data within the software determines the development’s total heating and cooling load throughout the year, with specific heating and cooling targets outlined by NatHERS that need to be met.

NatHERS Accredited Software is used to calculate an energy efficiency star rating and is based on expected indoor temperatures. This is assessed by assessing the project’s design, climate and household use. The tool therefore does not take electrical appliances within the dwelling into consideration, other than the air flow from the dwelling’s ceiling fans.

 

Develop a simulation model

A NatHERS accredited assessor will enter data into the software which will generate a simulation model of the dwelling. The simulation model will include: sizes and functions of the rooms, sizes and specification of openings, building materials/windows/products, type of construction, dwelling orientation and location.

 

Determining the temperature of the development

The simulation model will determine the level of heating or cooling temperature that is needed for occupants to remain comfortable within the dwelling.

 

Determining the need for heating and cooling systems

The NatHERS Accredited software model will determine the need for heating and cooling systems when internal temperatures fall outside of a comfortable range. This is based on assuming that occupants will open and close windows, blinds or awnings in an attempt to restore a comfortable temperature level prior to using the heating or cooling system.

 

Calculating a rating out of 10

Once the steps above have been completed, the total annual estimated levels of energy efficient heating and cooling are determined by a ranking out of 10 stars.

 

What does a NatHERS assessment include?

A NatHERS assessment includes NatHERS Accredited Software that is used to determine an energy efficiency rating. This is completed by a NatHERS accredited assessor who can be verified by the NatHERS logo on the Universal Certificate. A NatHERS Universal Certificate will provide information regarding the key design features of the dwelling, the building materials, and the scope used to generate the dwelling’s star rating.

 

Energy Rating

An Energy or Thermal Efficiency star rating is an accurate indicator as to how much heating or cooling is necessary to keep your development comfortable. The energy rating generated by an accredited NatHERS assessor using licensed software indicates a dwelling’s efficiency in preserving energy. Please note, it does not indicate the dwelling’s actual consumption of energy as that depends upon appliances installed and the way in which they are used (only assessable after occupancy). By improving your energy rating you will require less energy to keep your dwelling comfortable and therefore provide lower energy expenses as well as a much healthier environment.

 

Stars

The possible 0 to 10 stars, is a scale that indicates the energy efficiency of a dwelling. If a dwelling is rated 0 stars then it offers no insulation from the outside temperature. For example, if it is 20 degrees outside it will be 30 degrees inside. Whereas a 10-star dwelling is able to maintain a comfortable inside temperature all year round no matter what the outside temperature. Hence, the more stars a dwelling has the less energy it consumes, therefore reducing energy expenses.

 

Do appliances such as, air-conditioners, etc. affect star ratings?

Generally, no as NatHERS energy ratings are based on how well designed the dwelling will be. Appliances added to the building and are likely to be changed in the future are not taken into consideration.

 

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Requirements

What do you need?

 

When is a NatHERS certificate required?

NatHERS certification is required for all new developments with multiple dwellings, however NatHERS can also be used if desired on single dwellings. It was developed in order to reduce the countries overall energy consumption along with the BASIX process. BASIX is a NSW government initiative designed to improve the environmental sustainability of residential developments. It sets out the minimum standards for compliance in the following three areas: water, thermal comfort and energy, and can be assessed at through various means such as DIY which does not require NatHERS thermal modelling. NatHERS is a national scheme that involves the thermal assessment of a development in order to generate a NatHERS energy rating, which can be used for the thermal section of the BASIX. NatHERS energy ratings are much more thorough, accurate and flexible than the BASIX thermal tool. In order to achieve the best thermal performance at the lowest cost we recommend using both BASIX and a NatHERS energy rating.

 

What are the requirements of a NatHERS certificate?

For an accredited assessor to assess a project through the NatHERS process, they require the full plans, sections and elevations for the building as well as the building materials and glazing types that are intending to be used so that the building can be simulated accurately.

Generally, appliances such as, air-conditioners, etc. do not need to be known by the assessor as they do not affect the star rating as NatHERS energy ratings are based on how well designed the dwelling will be. Appliances that are added to the building and are likely to be changed in the future are not taken into consideration.

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The  National NatHERS Requirements Guide

Everything you need to know about the NatHERS requirements per state.

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TIME

How Long does it take for NatHERS Certification?

Small projects can be NatHERS modelled in 2-3 hours, and turned around within 24 hours. Larger multi-dwelling projects can take up to 5 days to model.  

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Cost

How much does it cost?

 

What Benefits Does an Energy Rating Give Me?

Our careful consideration when simulating the thermal performance of your dwelling(s) will ensure that your energy rating delivers many benefits including:
– Accurate results
– Reduced energy expenses
– Reduced cost of complying with BASIX
– Increased property values
– Sustainable buildings
– Healthier living environments

 

The cost for NatHERS certification depends on the size and complexity of the project, depending on the amount of time that is required to fully model and assess the building. 

 

 

 

6 Design Tips for a 6 Star NatHERS Energy Rating

 

In 2010 the NCC across Australia lifted the minimum acceptable energy efficiency design standard for residential buildings from 5 to 6 stars using NatHERS approved software.

 

In 2012 a study was undertaken by the Department of Climate Change and Energy to explore how designers of residential homes in Australia are able to achieve an improved 6 star rated dwelling with the same or less construction costs over a 5 Star dwelling. The results of this study proved that if a project is designed and optimised to suit the climate and orientation for where it is built then on average the energy efficiency improvements are increased by 1 or more stars along with a decrease of 2% of the overall cost of construction.

 

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Well here’s how you can apply these locally proven methods to your project to achieve a 6 Star Rated dwelling which performs better and costs less to build.

 

Here are 6 design tips for a 6 Star NatHERS assessment:

 

1. Reduce Overall Glazing by 2-3%

Bigger is not always better, larger glazed areas produce greater heat loss in winter and can attract unwanted heat gain in summer. Up to 40% of a home’s heating energy can be lost and up to 87% of heat is gained through glazing. Reducing glazed areas by 2-3% doesn’t sound like much but the difference can have a sizeable impact on the energy efficiency of your project.

2. Glaze by Orientation

Orientation of glazing can have a considerable effect on star ratings especially in east and west facing glazing which can cause star rating problems for buildings with a high cooling load by elevating the amount of direct sunlight into a dwelling. These effects are most pronounced in daytime occupied zones which account for a large proportion of the total cooling load. In contrast, north facing windows can have a beneficial impact by facilitating passive heating intemperate and cold climates and, when teamed with adequate shading, can prevent direct sunlight in summer, in hot and in temperate climates. Similarly, in hot climates south facing windows limit direct sunlight, although in cold climates they provide no benefits from passive heating.

To make this easier to understand, refer to our ‘glazing design cheat sheet' below.

 

For a Hot Climate Zone:
  • North Windows: Less overall glazing, should use horizontal shading to prevent summer heat gain
  • South Windows: More overall glazing (natural light without passive heat gain)
  • East Windows: Less glazing to daytime zones with vertical shading
  • West Windows: Less glazing to daytime zones with vertical shading
 
For a Cooler Climate Zone:
  • North Windows: More overall glazing for passive heat gain
  • South Windows: Less overall glazing to prevent heat loss
  • East Windows: Vertical Shading to daytime zones
  • West Windows: Vertical Shading to daytime zones

 

3. Internal Room Layout and Zoning

Internal room layout – the placement of rooms within a dwelling has a significant impact on star rating, particularly when considered in conjunction with orientation. In addition to this, zone classification and whether an area is considered as a conditioned (could have mechanical heating or cooling applied) or an unconditioned zone (such as bathrooms and wet areas) in rating software can also influence star rating.

 

Here are a few practical design tips around Zoning and internal Room Layouts.

 

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HOW TO KEEP YOUR HOME COOL NEXT SUMMER

 

How do I cool down my home? Our 5 top tips to keep your home comfortable for summer

With the summer season now slowly winding up, it’s a good time to reflect on the thermal performance of your home from the past few months; 

 

  • Was my home too hot?
  • Did it take too long to cool down?
  • Were some of my rooms noticeably warmer than others?
  • Did I spend more money than I would have liked to running the air conditioner?

In the ideally designed home, you will answer ‘No’ to each of these questions, with your home remaining at a comfortable temperature year round.

Let’s take a look at 5 design elements to start thinking about now that could save you from the heat, and bill shock, of our next summer season:

 

 1. Are my windows shaded from the sun?

 

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Shading is the most effect way to reduce heat entering your home. External shading devices such as eaves, pergolas, or trees and vegetation all block direct sunlight, creating shade and reducing heating from the sun by up to 90%

You can also consider the orientation of your building to achieve maximum shading benefits 

 

  2. Are my windows the best type for my home?

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When heat gain is caused by direct sunlight access, choosing windows with a lower Solar Heat Gain Coefficient (SHGC) and lower U-Values are the smarter option.

SHGC defines the amount of solar heat directly from the sun that can pass through a window. This is expressed as a number between 0-1 and includes the type of frame used.

The U-value measures how effective a material is as an insulator and defines the amount of heat conducted through the window from the air outside to the air inside.

 Low SHGC and U-Value windows are the perfect heat fighting combination.

 

3. Did I have sufficient insulation to keep heat out?

 

A well-insulated home can keep you cool and even cut cooling bills by up to half. Take a look at your insulation levels or request the services of a professional to complete an assessment.

Climate specific insulation should be considered at the early stages of design and can significantly impact the thermal performance and cost of living of a dwelling.

 

 Picture1.pngFigure 1: How heat can be gained at different parts of the house[1] 

  

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FREE DOWNLOAD

DESIGNERS GUIDE TO INSULATION

Choosing the correct insulation applications for your project for optimal thermal comfort and reducing or removing performance glazing.

 

THE EVOLUTION OF ENVIRONMENTALLY FRIENDLY WINDOWS

Windows have developed over time from single glazing, double glazing, and more recently self-tinting (Suntuitive) glazed windows. The improvement of glass window technology since the 17th century when glass windows started has resulted in improvements around energy consumption, noise reduction, and installation costs.

 

Pre-Suntuitive Era

 If you are on a shoestring budget, having single glazed windows is the cheapest option in the market, but considering other factors such as insulation and noise reduction may not point to choosing single glazing in the end. As single glazing is significantly thin, it can leave you with a cold home even in Spring. Nowadays, single glazing is considered a thing of the past.

 On the other hand, double glazed windows provide extra security as opposed to single glazed windows as, simply put, it has an additional layer. Noise is also kept at bay due to the thickness of the panes. This can be good when a structure is close to main roads, but the extra layer also means extra insulation and could cause the space to be damp.

Modern problems caused by single glazing and double glazing only require modern solutions and that is the Suntuitive technology.

What is Suntuitive?

Residential and commercial buildings are now able to reduce their carbon footprint and maintain sufficient thermal heating levels through Suntuitive technology. This occurs from a combination of dynamic glass and polyvinyl butyl which darkens from direct sunlight. This provides a natural passive thermal heating system and can provide up to 43% saving on electricity costs which also helps reduce carbon footprint allowing natural sunlight to heat a building rather than coal-based electricity. The thermal heating will continue to operate regardless of the external temperature, so in cold climates with sunshine, the windows will function and provide the optimum room temperature in a residential or commercial setting.

The Power of Reduction                

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How Suntuitive Works

 Two things that make Suntuitive Technology stand out are noise and heat reduction. For the upcoming summer, Suntuitive’s capacity to self-tint makes it easy for people to enjoy the sun without having too much sunlight.

The additional layers of glazing reduce noise pollution levels, which makes Suntuitive good value for money. Also, the dynamic glass enables your home or building to optimise daylight and heat gain, thus less heat and glare when facing direct sunlight. Think of photochromic transition lenses worn for better vision in broad daylight, but for your home or building.

 

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Beginners Guide: Thermal Mass

 

Want to learn more about optimising the thermal comfort of your project? Read below to learn the basics regarding the Thermal Mass capabilities in certain  building materials! 

 

Thermal mass stores heat from the sun during the day and re-releases it when it is required. Heat is released usually during the night as the temperature drops

 

Thermal mass is an integral factor that influences a home’s energy rating, as it can significantly increase thermal comfort and reduce energy consumption. Appropriate use of thermal mass throughout your home can make a huge impact on its thermal energy rating. Materials such as concrete, bricks and tiles are of high density, and therefore have a high thermal mass.

 

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We measure home energy ratings through a NatHERS assessment which is calculated through a process of thermal modelling. A design's thermal mass capability is a major contributing factor in determining a NatHERS star rating.

 

The qualified team at Certified Energy can provide your project with a NatHERS assessment, and ensure your project reaches its full star potential.

 

How can thermal mass concepts be put into production to increase the energy rating of a home?

 

The Australian climate spoils us with a lot of sun in the winter. In rooms with plentiful access to the winter sun, it is useful to connect the thermal mass materials to the earth, as it has greater thermal mass due to its direct contact to the ground. An example of this is a slab on ground construction.

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Source: http://www.yourhome.gov.au/passive-design/thermal-mass

 

Masonry Walls also provide great thermal mass for a home. Using recycled bricks in masonry walls and reverse brick veneers can increase a home’s thermal rating. It is recommended to avoid finishing masonry walls with plasterboard, as this insulates the thermal mass from the interior and reduces the materials capacity to absorb or release heat.

 

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HOW TO DESIGN FOR CLIMATE:

CLIMATE SENSITIVE DESIGN

 

It is important that designers modify their designs in relation to the climate in which they are built in. In order for the occupants of a home to remain thermally comfortable, the design must work with the climate, not against it, decreasing the need to use heating and cooling systems.

 

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Climate responsive design could cut down energy used for heating and cooling to almost zero. Designing for today’s climate is important, as new homes built presently and in the future expect to see constant changes in the Australian climate. Temperatures are rising, so designers need to design homes and buildings that can remain efficient in a hotter climate.

Some key design objectives outlined by yourhome.gov give some insight into what should be considered when designing a climate sensible design. This includes:

 

1. Human thermal comfort


The main influencers of human thermal comfort include temperature, humidity, air movement (breeze or draught), exposure to radiant heat sources and exposure to cool surfaces.

The more stars a design has, the less heating and cooling energy is needed, therefore increasing human thermal comfort. Building thermal comfort can be achieved through passive design methods, and wind helps to achieve a high NatHERS energy rating.

 

2. Australian climate zones


Australia covers a large surface area, therefore resulting in a variety of climates existing in different states, cities and towns. There are eight zones defined by Your Home (2018), and each climate zone has different design and construction requirements.

The zones include:

 

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EAVES AND THERMAL COMFORT

Building for the Australian Climate

 

A building’s access to sunlight is one of the leading factors contributing to its thermal comfort, with the amount of direct sunlight that the building receives greatly influencing the passive heating and cooling factors. However, as the sun’s path varies seasonally, accounting for the required direct sunlight a building needs becomes difficult.

 

Sun Angle and Siting:

The variation between seasonal sun angles is dependent on the latitude of the site where the building is located. The difference between the sun angles greatly increases the further north or south you travel. To account for this variation eaves are a common implementation to allow direct sunlight in winter and prevent it in summer, therefore the depth of eaves varies greatly globally depending on the seasonal sun angle variation.

This difference in sun position and angle is caused by the rotation of the earth on a titled axis along with its revolution around the Sun, which changes which hemisphere of the Earth becomes closer to it. The Sydney area being in the southern hemisphere at a latitude of 34° S has a seasonal difference of 45° in solar angle (between summer and winter). In the summer solstice the sun reaches an altitude of 79° and in winter drops to 33°. Therefore, the awnings on a building need to account for the individual direct sun light requirements.

 

Climate Specific Shading:

This raises the question as to how deep awnings in the Sydney area should be. The Sydney area generally does not require deep awnings as the angle of the summer sunlight is quite large and therefore does not enter vertical windows. Also as direct sunlight is very desirable in late autumn, winter and early spring shallower eaves allow for the largest percentage of sunlight to enter the building reducing heating costs. Eave depth is also dependent on the orientation of the wall which they are on and therefore may not be equal around the entire building.

 

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PASSIVE COOLING: VENTILATION AND VEGETATION

 

One of the most influential factors to consider when studying ecologically sustainable development, is the advantageous affect that passive cooling and heating can have on the efficiency of a home. This involves the careful selection of materials appropriate to the climate in which the building is situated, the thorough consideration of the orientation of the building to allow adequate ventilation and appropriate solar heat gain and various other factors. By considering all of these aspects the efficiency of the building can increase dramatically, whilst also drastically decreasing the cost of heating and cooling the building.

 

 

Allowing for adequate ventilation relative to your climate condition can dramatically affect the thermal comfort of a living space. Air moves from a positive to a negative pressure, so understanding how to control and create this pressure differential is a key concept to allow natural ventilation. Positive pressure builds on the windward side of the building and negative on the leeward side, therefore in order to promote natural air movement a building must be oriented with windows placed in such a way to allow for this movement.

Air tends to move in straight lines and curves when it hits an obstruction. As it hits an obstruction pressure builds, and it is this pressure increase which can be used in order to promote air movement, through the use of various architectural elements and orientation as seen below.

 

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  1. Windows on the same wall facing the same direction

  • Some cross ventilation
  • Only in very small percentage of room
  1. Windows on adjacent walls facing different directions

  • Good cross ventilation
  • Half of room ventilated, positive pressure pushed on windward side, negative pressure pulled on leeward side
  1. Windows on the same wall facing the same direction at either ends of the wall

  • No cross ventilation
  • Equally positive pressure at windows preventing movement
  1. Windows on parallel walls facing opposite directions

  • Good cross ventilation
  • Cross ventilation for a percentage of the room 
  1. Windows on adjacent walls facing similar directions

  • No cross ventilation
  • Equally positive pressure at windows preventing movement
  1. Windows on the same wall facing the same direction with fin walls implemented

  • Good cross ventilation
  • Positive pressure is created at the first window from the fin wall pushing air inwards, negative pressure is then created by the second fin wall pulling air out
  1. Windows on same wall facing same direction with fins walls implemented on left side of windows

  • No cross ventilation
  • As the fin walls are positions on the same side of each window positive pressure is created at both openings preventing cross ventilation
  1. Windows on parallel walls facing opposite orientation

  • Good cross ventilation
  • Positive pressure on the windward side of the building pushes the air through, with negative pressure pulling the air out, with positive pressure greatly increased by fin wall

 

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The Basics of Passive Cooling

 

Passive cooling is the cheapest method of cooling a home, and as an added bonus is incredibly environmentally friendly. No matter the climate you live in, you'll be using passive cooling to some extent throughout the year.

 

Whether you live in an apartment or a larger home, your home can be built or modified to allow you to take advantage of passive cooling systems to help you achieve greater comfort. If you already rely on mechanical cooling systems (like air conditioners) you can reduce your energy costs by combining these with passive cooling.

 

Choosing the most appropriate passive cooling strategies for your home should be guided by the climate you live in. We've listed some of the basic strategies below to get you started!

 

Air movement

Air movement is the most basic element of passive cooling. It replaces internal air with either cool or warm air depending on the outside temperature, and increases evaporation. To make the most of natural air movement, you'll want to plan for well-designed windows, doors and vents for the air to move through.

Shading windows, walls and roofs from direct solar radiation

Shading is a simple way to keep your home from overheating in the sun. Simple ways to create shade are to plant some trees or other shade-providing plants by the areas you would like to have shaded, install an overhead shade, install screens. Depending on the shading material you use, you may be able to reflect the sun away at the same time, resulting in further efficiency benefits. A more complex option is to build or renovate your house structure so the shape of the house provides shade at certain times of day.

 

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Sample House Energy Rating Certificate

Every certified NatHERS project has a HERS certificate provided for the project. See how each of the elements of the building fabric are detailed and specified in these reports. 

 

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NEW NATHERS TECHNICAL NOTE: HOW IT AFFECTS YOU

 

The implementation of the new Nationwide Home Energy Rating Scheme (NatHERS) Technical Note legislation will result in closer building assessments with property developers, builders, assessors and designers. The question is will the new legislation support or hamper the building process?

 

Since it's inception in 1993, NatHERS has been the forefront of government legislation in regards to regulation of thermal newly built homes in Australia. Since then, NatHERS has gone through significant changes in the past 26 years, with the latest update having occurred from June 1, 2019. Some of those changes include:

 

  •  Window Opening Percentages
  •  Roof Colour Specification
  •  Glazed Verandas & Winter Gardens
  •  Ceiling Penetrations
  •  Mandatory Document Requirements
  •  Protected Trees

 

The changes being enforced are now placing more pressure on designers to pass thermal comfort targets and meets overall home rating targets. In the new NatHERS legislation a new clause under the windows section (Table 5: Provisional Window Opening Percentages) all awnings, casements and louvres must be modelled to have a 10% opening instead of 90%. This means that homes with a greater quantity of windows will suffer from reduced cooling than before the NatHERS update.

 

However, in cooler climates such as states in Victoria and Tasmania the window restrictions would also provide an increase in heating loads, particularly during winter. Despite this, the negative impact will be felt in warmer states, especially in Queensland and the Northern Territory. Builders will be struggling to meet cooling targets due to the reduction in window openings.

 

Another addition to the NatHERS Technical Note update is that builders and designers will need to specify the colour of the chosen roof as part of the floor plan. With the new clause, builders and designers will require to simulate multiple versions to highlight worst case scenarios the thermal performance of a home if the roof colour is not specified in the floor plans. Previous to the June 1 NatHERS update, all roof cases were considered.

 

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5 WAYS TO AVOID DOUBLE GLAZING ON YOUR NEXT NATHERS PROJECT

 

One of our most frequent requests from our clients is to reduce or remove the requirements of double glazing on their projects. Double Glazing can cost up to twice the amount of single glazing and on some projects it can tip the feasibility scales. Every year it seems the ever improving Energy Efficiency - Section J of the National Construction Code and the National Thermal Comfort (NatHERS) regulations are making it increasingly difficult to avoid specifying double glazing. However, at Certified Energy we have 5 tried and true tips that will go a long way to avoid specifying double glazing on your next project.

 

Ood House

 

Here are the 5 tips to avoid double glazing on your next NatHERS project:

 

1. Keep your Glass to Floor ratios down

Perhaps the only, yet most important variable that we as Thermal Comfort Assessors don't have direct control over on this list is the Glass to Floor Ratio on a project. A Glass to Floor (GtF) ratio is the total glazed area added together on a project divided by the total floor area of a project to give an overall percentage. Coming from an Architectural background I can understand that this dynamic glass to floor relationship on a project can be at the heart of the overall aesthetic appeal, but if it is not taken into account at the early design phases of a project an overly high Glass to Floor Ratio can have devastating effects to the heat loss of your project, as heat loss is generally twice as high in glazed sections of your project compared to insulated walls.

From our experience and as a general rule of thumb, here are our recommended glazing types that are required based on a projects overall % of glass to floor area (applying to the majority of climate zones).

  • 0 - 25%     Requires Single Glazed Clear Glass
  • 25 - 35%   Requires Single Low -e Glazed Clear Glass
  • 35 - 45%   Requires Double Glazed Clear Glass.
  • >45%        Requires Double Glazed with Low -e Clear Glass which generally requires improved aluminium Argon gas filled frames.

To further illustrate this point, a typical project home will have approximately 18-20% of glass to floor ratio, this can be compared to an Architecturally designed 2 story 'glass box' type house which we previously assessed that had an unusually high glass to floor ratio of over 55%.

 

Untitled design-58

 

2. Use higher performing wall insulation

Standard bulk wall insulation with reflective foil to fit within a 90mm frame for typical brick veneer construction has a highest R value of R2.5. However, it is possible to use rigid foam insulation which comes in thickness of up to 40mm which can then provide a total Rt of up to R5.6 for brick veneer construction. Providing two layers of this rigid insulation product in the 90mm brick veneer frame effectively doubles the insulation in the external walls. This method is often much more cost effective than having to specify double glazing on a project.

 

3. Lower U values on South facing windows

This is a known trick in the industry whereby you increase the insulating properties of the windows (Lower U values) of the glazing to the Southern elevations only of the project which allows for less heat loss to occur.

 

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STAR RATING: HOW TO INCREASE YOUR STAR RATING FOR FREE

The NCC sets a minimum acceptable thermal performance for residential dwellings by specifying a minimum 6 star rating for all new projects in Australia with the exception of NSW who are under the BASIX programme.

Conceptual image of white opened door. Perspective

 

13 of the largest residential builders across the country when surveyed said for an average new home it cost an average of $4000 to improve a single star rating (from 5 to 6 stars).

At Certified Energy we love helping our clients create greener buildings without it hurting the bank. So here are 4 tips to improve your star rating on your next project for no additional cost.

 

1. Add Bubbles...

By adding rigid polystyrene foam bubbles to your concrete slab when it is being poured, known as a waffle pod slab, it can increase your star rating in cooler climates by up to 0.8 stars. The actual supply and install cost of the polystyrene foam works out to be about even to the cost of the volume of concrete that is being saved. However this approach is mostly ineffective  in warmer climates as it can have the opposite effect.

Star Increase: Up to 0.8 Stars
Cost = Nil

WafflePods-DSC_6053Reference

 

2. Expose yourself...

The choice of your floor coverings can improve your project by as much as half a star rating. The two options for comparison, :-

a) exposed and uncovered polished concrete, Vinyl or Timber Floating Floors (which all perform similarly) vs. 

b) Carpet.

Both a) and b) options have their advantages depending on what climate zone you are in. For colder climates carpet performs better as it acts as an insulator to the thermal mass of your slab. For warmer climates a polished concrete / Vinyl or Timber floating floors perform better as they allow for the slab to warm during the day and release heat back into the dwelling in the evening.

Star Increase: Up to 0.5 Stars
Cost = Nil

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nick-karvounis-599740-unsplash

 

 

4 TIPS FOR CHOOSING YOUR NEXT NATHERS ASSESSOR

 

You might be in a hurry when you are looking for your NatHERS assessment. But be aware of choosing too fast and ending up with an Assessor that will take their time. We have written down 4 tips we think you should know before choosing your NatHERS Assessor.

 

  1. Check qualifications; always choose your Assessor based on their relevant building industry degree qualifications, anything from an engineering, architecture or building background should suffice.
  2. When you are on a deadline, choose for an ESD Assessor which has a minimum of 3-4 people working for them. 95% of the ESD Assessors have at least 3 consultants doing their energy assessments and will be able to respond fast.
  3. Every ESD consultant should be able to discuss certain aspects of a NatHERS assessment, ask if they collaborate together and can advise you about the best case practices when doing a NatHERS report.
  4. What about their past project experience? Can your Assessor give you a good referral?

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