Lenon & Kellie’s Home

ABCB Climate Zone 7 & NatHERS Climate Zone 66

Key Insights

  1. Heating needs reduced by up to 65%.

  2. Cooling needs reduced by up to 57%.

  3. Yearly heating and cooling costs cut by up to 68%.

  4. Overall annual energy costs reduced by 87%.

  5. Lenon and Kellie’s family will live in a resilient, comfortable, and healthy home for generations to come.

Image Source: Borland Architecture

Roger Borland, a Passive House certified architect, reached out to ARKATA to help guide and optimise this home design. It was an exciting project to undertake due to the synergy between Roger’s architectural style, a passive house principled approach and ARKATA’s philosophy for healthy, comfortable and resilient homes.

Engagement came early after the concepts were completed, where optimal energy efficiency outcomes can be implemented with ease. Pre-planning is an ideal time to explore the possibilities of energy efficiency and it is with this approach that we were able to achieve such fantastic results for Lenon and Kellie.

The Mission

Three core outcomes guided our collaboration:

  1. Recommend a balanced home specification list that achieves the highest energy efficiency outcomes within the overall budget.

  2. Provide a clear and simple way to understand each enhancement, their cost-effectiveness, and their impact on the home’s performance.

  3. Both the homeowners, Lenon and Kellie, and the architect, Roger, to have a full understanding of the energy efficiency of the home and how to implement recommendations made.

Starting Point: Energy Baseline

To provide recommendations aligned with the guiding objectives, the first task was to understand the home’s current energy efficiency levels.

As Roger is an experienced Passive House certified architect, various passive solar design features were intelligently implemented into the design of the home, with plenty of northern windows available to key living areas with little to no western windows. To aid solar access to main living areas, Roger had cleverly placed the garage and utilities on the South Eastern side of the block, enabling optimal orientation of the home where a beautiful outdoor courtyard becomes a feature on the northern side of the home.

A particular synergy between the Passive House approach and a NatHERS approach that was working from the outset was the inclusion of a heat recovery ventilation system. This meant that ceiling penetrations were kept to an absolute minimum and in most cases eliminated completely. This enables the home’s energy to be kept inside the home for longer periods of time, instead of losing heat through ceiling penetrations.

To add to this synergy between Passive House and NatHERS, we are now able to measure the influence of airtightness on the home… But more on this later!

With modest base specifications, the home’s baseline began at 4.9 Stars and required more heating than cooling throughout the year.

Key Findings & Suggestions

Through an iterative investigation of various aspects of the home’s design and construction, several opportunities were identified for enhancing the home’s energy efficiency.

  1. Insulate the slab: By disconnecting the slab from the ground, heat loss within the home is significantly reduced

  2. Darken the slab: Utilising a dark coloured slab, the slab’s thermal mass properties are enhanced

  3. Insulate the garage: Introducing thermal separation between the garage and the home yielded significant energy efficiency improvements by preventing heat loss from the living spaces

  4. Maximise insulation: Taking advantage of Passive House detailing, maximising insulation to the walls, roofs, and floors, further decreased the heating needs, fostering a more comfortable living environment

  5. Increase thermal mass: To take advantage of an optimal window to floor ratio and the high diurnal temperature range of Climate Zone 7, a strategically placed rammed earth wall to the master bedroom improved the thermal comfort of the space considerably

  6. Aligned active systems: By utilising the new NatHERS Whole of Home tool, the home’s energy efficiency performance was paired with a heating and cooling system that complemented the home’s natural energy needs.

  7. Efficient cooling: Large ceiling fans were implemented to help the high efficiency split systems to purge any heat trapped within the home at night during summer

Incorporating these upgrades increased the energy rating up to 8.4 stars and cut both heating and cooling loads by up to 60%.

In addition to this outcome, we were able to showcase to Lenon, Kellie and Roger what pursing airtightness could provide to the project. With the updated National Construction Code 2022 and NatHERS software, achieving an airtightness result of less than 3 ACH@50pa, it could be expected that the home performs in reality at 8.8 Stars.

This insight is invaluable data for a Passive House!

Figure 1: Total Heating Load Reductions (4.9 Stars to 8.4 Stars)

Human-Centred Outcomes

Combined with the above data, a temperature analysis revealed further insights regarding the home’s thermal performance. During winter, rooms with northern solar access exhibited a greater temperature disconnect from the outside than those without.

Enhancing the home’s star rating from 4.9 Stars to 8.4 Stars further amplified this disconnect, leading to a more consistent and regulated indoor temperature range with significantly less temperature fluctuations.

In summer, the home demonstrates consistent comfort, maintaining around 20°C with minimal cooling requirements. However, internal temperature spikes were observed when external temperatures exceeded 20°C.

Figure 3: Internal Temperatures During a Cold Week in Winter in The Living and Kitchen

Figure 2: Total Cooling Load Reductions (4.9 Stars to 8.4 Stars)

Figure 4: Internal Temperatures During a Hot Week in Summer in The Living and Kitchen

Given Roger's expertise as a Passive House architect and the project's focus on airtightness, the home's performance will likely exceed expectations, maintaining indoor comfort longer and reducing long-term energy costs for the Lenon and Kellie’s family.

By showcasing and combining the insights provided by the NatHERS data, we were able to suggest providing ceiling fans to manage occasional excessive warmth in the home while utilising a fireplace, located centrally, to serve as the main source of heat throughout the year.

In addition to the central fireplace, high-efficiency split systems will provide flexible cooling throughout summer and supplemental heating as needed in specific areas of the home.

Future Savings

Through this collaborative effort and the innovative use of NatHERS tools, the analysis was able to show that annual heating and cooling costs were reduced by up to a staggering 68% and overall annual energy costs cut by up to 87%!

The family not only achieved their energy efficiency goals, but also freed up budget for other aspects of their dream home by better understanding their homes performance and the effectiveness of the combination of high levels of energy efficiency and a Passive House approach to holistic construction.

Figure 5: Comparison of The Annual Cost of Heating and Cooling (4.9 Stars vs 8.4 Stars)

The Client’s Verdict

The architect couldn’t have been happier!

Truly the best energy information I have received from a consultant. So useful as we continue to develop the design for the project which will be massively improved through the recommendations offered. Very clear and well-presented allowing the client to easily understand the benefits of building better. Thank you Ben!

Roger Borland, Architect, Borland Architecture

The way forward starts here…

Ready to take the next step in making your home or project as energy efficient as possible?

1.     Fill out our contact us form for a tailored consultation: Contact Us

2.     Prefer to chat? Drop us an email at ben@arkata.au or call directly on 0431 922 265.

Let’s collaborate to enhance your project with the benefits of energy efficiency!