The Passive House & NCC Changes Performance Gap: Bridging the Gap Between Design & Building
The recent updates to the National Construction Code (NCC) put the focus squarely on energy efficiency. There were two key changes to residential works, including apartment buildings:
- Thermal performance requirements were raised to 7 stars under the Nationwide House Energy Rating Scheme (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.
Critics are still unhappy with the ambitions of the NCC changes, as they will do very little to bridge the performance gap of energy-efficient homes, compared to standards such as Passive House.
The Passive House – What Is ‘Passive Design’?
Originally developed in Germany in 1991 by a professor named Dr Wolfgang Fiest, the Passive House (or Passivhaus in German) is a design standard that has been adopted around the world.
It aims to create homes that are sustainable, ultra-low energy and comfortable, with great ventilation and air quality.
The house is passive in that the building envelope does most of the work to maintain the temperature, without active input. It achieves thermal comfort with minimal heating and cooling by harnessing insulation, airtight sealing, clever window and door design, ventilation, and heat recovery.
Passive House standards are performance-based, rather than having set guidelines as to materials. The Passivhaus Institut oversees a global certification scheme that assesses these performance standards.
According to the Passivhaus Institut, the definition of a Certified Passive House is:
… a building, for which thermal comfort (ISO 7730) can be achieved solely by post-heating or post-cooling of the fresh air mass, which is required to achieve sufficient indoor air quality conditions, without the need for additional recirculation of air.
Passivhaus Institut (PHI)
A Passive House is well-insulated, airtight, has high-quality windows and reliable ventilation systems with heat recovery.
The 5 Key Design Principles of a Passive House
Passive Houses have a “fabric first” philosophy, using a set of design principles to ensure energy efficiency.
1. Airtightness
Passive Houses are defined by an airtight building envelope. In effect, this means that there is a very limited number of gaps and cracks, reducing drafts and giving you control over the internal environment.
2. Thermal Insulation
Good insulation provides a sufficient layer between the heated or cooled inside environment and the outdoors. This improves comfort and reduces condensation by minimising cold surfaces.
3. Mechanical Ventilation Heat Recovery
The inclusion of a mechanical heat recovery system means you don’t need to open your windows for good air quality – although of course you still can! This kind of unit effectively salvages heated and cooled air that would otherwise be wasted while also filtering the air that’s coming into the building. This means cleaner air plus a lower risk of condensation.
4. Thermal Bridge Free Construction
‘Thermal Bridges’ are areas that cause increased heat consumption and increased condensation risk. The insulation needs to be a good thickness and continuous. This means keeping penetrations through the insulation to a minimum. If they must be made for construction, it should be done with materials that are less conductive, like timber. Alternatively, thermal breaks can be used, whereby a material that doesn’t conduct heat well separates two conductive materials (like metal).
5. Passive House (High Performance) Windows
Windows should have good levels of insulation, abandoning single glazing for low-emissivity double or triple glazing with thermally broken or non-metal frames. The size of the windows should also be consistent with the building envelope, to allow for the right amount of solar radiation in summer and winter.
Where are the Gaps in the NCC 2022?
While the update in the NCC 2022 requiring a national 7-star NatHERS rating is seemingly a very positive step, critics have pointed out that there’s a disconnect in practice.
Using the CSIRO Australian Housing Data Portal, out of 63,608 national 7-star NatHERS certificates published over the last six years, 45,932 were single glazing for Class 1 dwellings, meaning around 78% of 7-star NatHERS certificates were single-glazed. From the same data population, approximately 80% had added roof insulation below R2.0.
This data raises the question of whether 7-star NatHERS ratings are truly reaching passive design standards.
Why is Single Glazing a Problem for Passive Houses?
Single glazing is constructed using a single pane of glass, which is a thin defence against the whims of the outside environment. A standard single pane ranges between 3mm and 10mm, which isn’t adequate for insulation. It can provide up to 20 times less insulation than double glazing.
Double glazed windows have two pieces of glass, separated by a vacuum layer that acts as insulation. The glass may be UV tinted as well. Double glazing can improve thermal efficiency by up to 80%.
For homes using a heating system to warm up a house during winter, the warmth inside can be easily lost with single glazed windows. The unit is forced to work harder to maintain heat. Double glazing can reduce heat loss by half.
Thermotek Windows Optimise Thermal Performance
Thermotek windows are engineered in Germany and manufactured in Australia, crafted for outstanding thermal performance and energy efficiency.
The uPVC used has high thermal insulation properties, while the IGUs (insulated glass units) use standard Low-E glazing with argon gas.
What gives Thermotek an edge is that the frames consist of various fusion welded air chambers. These give a superior seal which increases insulation, and the dual TPE (thermoplastic elastomer) seals further enhance thermal performance.
The gap between the two panes in Thermotek windows is the main source of insulation, which slows down thermal transfer by conduction. The systems slow down air circulation to reduce the amount of heat lost in winter and gained in summer.
In winter, when cold air hits the first windowpane, it doesn’t reach the inside environment. Instead, it reaches the gas or air between the panes. By the time it hits the second pane, it is no longer freezing cold.
Thermotek systems keep your home’s temperature more stable, plus cuts down the number of times your heating/cooling system must switch on and off.
Passive Design: Smart Slide Doors from Thermotek
Thermotek’s smart-slide doors are perfect for Passive Houses, possessing outstanding capabilities for heat insulation, statics, and sealing.
They make the house airtight against air, wind, and rain, with an innovative locking mechanism and high-quality sealing with no brushes. The window-door systems also require reduced maintenance due to stable, concealed hardware.
Affordable Energy Efficiency: Thermotek Eco Series 3000
It is obviously desirable to reach energy efficiency standards while staying within the project budget. The Thermotek Eco Series 3000 windows and doors system is an affordable solution for Australian residential developments that are required to meet energy ratings.
The Thermotek Eco Series 3000 windows and doors system is produced from the global German design and engineered 3 chamber Ideal 2000 uPVC profile by aluplast.
It’s also versatile. The streamlined 60mm profile is fully insulated with a dual seal frame that caters for a wide range of opening configurations.
It is more cost-effective than thermally broken aluminium, allowing architects and builders to achieve a genuinely high NatHERS energy rating without an exorbitant price tag.
It’s also a stylish solution, with smart dual colour frames that present white internal and black or anthracite grey external.
Sustainability First – Always
Thermotek is a market leader when it comes to true passive design. We are also a low-waste manufacturer. All our products are 100% recyclable and manufactured in an ecological and responsible way.
Get in touch today to find out more about using Thermotek window and door systems in your residential project.
