Passive House Certification vs Energy Rating Scheme (NatHERS)
Passive Houses have been attracting mounting interest from architects, builders and owner-builders, as the industry pivots towards long-term sustainability and seeks to help reach the collective goal of Net Zero Carbon Emissions by 2050.
However, with the 2022 updates to the Australian National Construction Code (NCC), the NatHERS Energy Rating Scheme also needs to be considered when it comes to new residential works. So how exactly does the Passive House certification process compare to NatHERS ‘stars’ system?
Let’s take a look at the two different approaches, as well as how high-performance window and door systems like those manufactured by Thermotek can help achieve both.
What are the latest energy efficiency requirements of the NCC?
According to the 2022 update, new residential works (including apartment buildings) must meet the following guidelines:
- Thermal performance requirements must now meet 7 stars under NatHERS.
- A new Whole-of-Home Rating must be met by new homes. This applies to heating and cooling, hot water systems, lighting, swimming pool and spa pumps, windows and doors. Renewable and sustainable energy systems, such as solar panels, aren’t mandatory but can be installed to keep a home’s energy under budget.
How does Passive House certification compare to achieving 7 NatHERS stars?
The Passive House standard is based on sound design principles and has been proven to significantly reduce energy consumption and carbon emissions in buildings, by taking a ‘fabric first’ approach.
Developed in Germany in the early 1990s, it’s now overseen internationally by the Passivhaus Institut. The certification process is rigorous and requires a high level of attention to detail in the design and construction phases.
On the other hand, NatHERS is an energy rating system developed by the Australian government to measure the energy efficiency of residential buildings.
NatHERS inspectors use computer simulations to determine the energy efficiency of a building based on a range of factors, including:
1. Building orientation: This affects the amount of sunlight it receives, which can impact energy consumption.
2. Materials: The materials used in the construction of a building affect its thermal performance and energy consumption.
3. Insulation: Insulation is critical to reducing energy consumption by reducing heat loss and gain through the building envelope.
4. Glazing: The type and size of windows in a building affect the amount of sunlight and heat that enters the building.
5. Shading: Devices such as awnings, blinds, and shutters can reduce heat gain and improve energy efficiency.
6. Ventilation: Natural ventilation can help reduce energy consumption by reducing the need for mechanical cooling and ventilation systems.
NatHERS rates buildings on a scale of 0 to 10 stars, with a higher star rating indicating a more energy-efficient building. Buildings that achieve a 7-star rating or higher are eligible for government incentives such as grants and rebates.
The scheme was designed to drive innovation to make Australian homes more comfortable and keep energy costs low. Given the volatility of the energy market and the increasingly pressing issue of climate change, meeting and even exceeding NatHERS stars is imperative.
What exactly does Passive House certification involve?
Passive House certification aims to create buildings that have minimal energy requirements and can maintain comfortable indoor temperatures throughout the year without the use of conventional heating or cooling systems.
The certification process involves a set of performance criteria that buildings must meet. These criteria include:
1. Maximum space heating and cooling demand: The annual energy demand for space heating and cooling should not exceed 15 kWh/m2 per year.
2. Maximum primary energy demand: The annual primary energy demand for the building should not exceed 120 kWh/m2 per year.
3. Maximum air leakage: The building envelope should be designed to minimize air leakage, with a maximum rate of 0.6 air changes per hour at 50 Pascals.
4. Maximum thermal bridging: Thermal bridging occurs when there is a break in the insulation layer of a building, allowing heat to escape. To achieve Passive House certification, thermal bridging should be minimized.
5. Maximum window performance: The windows in a Passive House building should be designed to minimize heat loss and maximize solar gain.
6. Minimum ventilation: Passive House buildings should be equipped with a mechanical ventilation system that provides fresh air while recovering heat from the outgoing air.
What are the key differences between the two processes?
While both Passive House certification and NatHERS aim to promote energy-efficient buildings, the two schemes have several key differences.
1. Performance criteria: Passive House certification has a stricter set of performance criteria than NatHERS. It requires buildings to meet strict limits on energy consumption, air leakage, thermal bridging, and window performance, among other factors.
In contrast, NatHERS measures the energy efficiency of a building based on a range of factors, including building orientation, insulation, glazing, shading, and ventilation.
2. Certification Process: Passive House certification requires a rigorous design and construction process, with a focus on attention to detail and quality control.
The certification process involves a series of performance tests and simulations to ensure that the building meets the Passive House performance criteria. In contrast, NatHERS is a simpler, more standardized rating system that can be applied to a wide range of building types and designs. NatHERS assessors use computer simulations to calculate the energy efficiency of a building, and the rating is based on a standardized set of assumptions and inputs.
3. Cost: Passive House buildings can be more expensive to construct than conventional buildings due to the high level of detail and quality control required to meet the certification criteria.
However, Passive House buildings are designed to be highly energy-efficient and can save money on energy costs over the life of the building.
NatHERS, on the other hand, is a more cost-effective rating system that can be applied to a wide range of buildings. While NatHERS ratings may not be as stringent as Passive House certification, they can still help to promote energy-efficient building design and construction.
5. Focus: Passive House certification is primarily focused on energy efficiency and reducing carbon emissions in buildings. The certification criteria are designed to minimize energy consumption and promote the use of renewable energy sources.
In contrast, NatHERS is a broader rating system. While energy efficiency is a key focus of NatHERS, the rating system also considers other factors such as water efficiency, materials selection, and waste management.
What design principles are harnessed to meet Passive House certification?
A Certified Passive House is constructed according to five Passive House Principles, namely:
- Thermal Insulation
- Airtightness
- A Mechanical Air Ventilation System, which supplies filtered, fresh air continuously.
- Thermal Bridge Free Construction
- High-Performance Windows and Doors
To obtain Passive House Certification, the design must undergo modelling with the PHPP (Passive House Planning Package) software to ensure it meets the criteria of a passive house.
During the building process, all five principles are observed, and a ‘blower door test’ is performed to verify that the minimum standards of air tightness and exchange are met, as outlined above.
Finally, to obtain official certification status, full documentation of the entire building process and blower door tests must be provided.
How do high-performance windows and doors help achieve both Passive House Certification and a high NatHERS rating?
High-performance window and door systems like those sustainably manufactured by Thermotek can help achieve architects and builders achieve the design principles of Passive Houses, which is also likely to feed into a high NatHERS stars rating.
Thermotek Windows and doors are designed with high-performance insulation, using uPVC frames, and double or triple-pane low-emissivity glass. This helps to minimise heat loss and gain through the windows and doors, reducing the need for heating and cooling.
Our windows and door systems – such as the Boutique or Eco series – are also designed with advanced sealing systems that ensure maximum airtightness. This helps to prevent drafts and energy loss through air leakage, which is a critical aspect of passive design.
Proper placement of windows and doors is critical to achieving both passive design and a high NatHERS rating. Thermotek Windows and doors can be designed and placed to maximize solar gain in colder climates and minimize solar gain in warmer climates, as well as optimize natural ventilation and daylighting.
In warmer climates, Thermotek Windows and doors can be designed with solar control glazing or shading devices, such as external blinds or overhangs. This helps to minimize solar heat gain and prevent overheating.
By selecting Thermotek Windows and doors, architects and builders can achieve excellent energy efficiency and comfort, while reducing the overall carbon footprint of a residence.
Which path to energy efficiency should you choose?
Both Passive House certification and the NatHERS energy rating scheme in Australia aim to promote energy-efficient and sustainable building design and construction, meaning fewer greenhouse gas emissions.
Ultimately, the choice of design principles to reach a 7-star NatHERS rating depends on the project. However, Passive House design is a more calculated and documented approach to accountability, which can mean greater energy efficiency, longevity of materials and increased value for a home.
One thing is certain. Incorporating high-performance window and door systems like those sustainably manufactured by Thermotek will help you achieve both!
Contact us today to find out more about how our stylish and sustainable products can enhance your project.
