What Makes a New Home Energy Efficient?

An energy-efficient home starts by needing less energy in the first place.

That means getting the building itself right through orientation, shading, insulation, airtightness, glazing and ventilation. Once demand has been reduced, efficient electric systems can meet the remaining heating, cooling, hot water and cooking needs, with solar and battery storage supplying as much of that energy as practical.

A large solar system can reduce annual energy bills even when the building itself consumes a lot of energy. My preference is to reduce the demand first, then use technology to support a home that already performs well.

Start with the building

Heating and cooling can represent a significant part of household energy use, particularly in Melbourne's variable climate. How much energy is required depends heavily on the building itself.

Poorly performing windows, gaps in the building envelope and large areas of unshaded glass can create substantial heat loss in winter and heat gain in summer. Heating and cooling systems then spend more energy maintaining comfortable internal conditions.

A well-resolved building envelope creates a much better starting point. Useful winter sun can be captured where the site allows it, external shading can control summer heat gain, and continuous insulation, high-performance glazing and airtight construction can keep internal conditions considerably more stable.

In our high-performance homes, clients often notice the comfort first and the energy efficiency second. The building stays more stable, so maintaining that comfort requires comparatively little energy.

That is the relationship I am interested in: good performance improving everyday life while reducing the energy required to achieve it.

Use the opportunities the site gives you

Orientation still matters.

In Melbourne, useful northern solar access can provide valuable winter warmth while being relatively straightforward to shade during summer. East and west glazing require more care because the sun sits lower in the sky.

Orientation also affects daylight, views, privacy and the relationship between the home and garden, so the response needs to come from the actual property.

The aim is to understand where useful sun is available, where unwanted heat is likely to come from and how the architecture can respond before relying on mechanical systems to correct problems later.

We explore this in more detail in our article, Does My House Need to Face North in Melbourne?

Build an envelope that performs

Insulation, windows and airtightness work together.

Continuous insulation slows heat moving through the walls, floor and roof. High-performance windows reduce heat transfer through the parts of the envelope that are typically most vulnerable, while airtight construction limits uncontrolled air leakage.

For our high-performance homes, Borland Architecture targets an airtightness level of 0.6 air changes per hour at 50 Pascals and verifies the completed building using a blower-door test.

That target gives us something measurable to design and build towards.

Fresh air can then be provided through a properly designed mechanical ventilation system, with filtration selected according to the project. The result is much greater control over both the internal environment and the energy required to maintain it.

Our dedicated airtightness article explains this in more detail.

Design the home to be all-electric

For a new home, I would generally design for all-electric operation.

Efficient heat pumps can provide heating, cooling and domestic hot water, while induction cooking removes another requirement for gas. Lighting and appliances then operate from the same electrical energy system.

That creates a useful relationship with rooftop solar.

Electricity generated on the property can contribute to heating, cooling, hot water, cooking, lighting and appliances. Battery storage can allow some of that generation to be used later in the day.

The lower the home's underlying energy demand, the greater the proportion of its needs that on-site generation can potentially cover.

Solar works harder on an efficient home

Imagine two homes with the same roof area and identical solar systems.

One has high heating and cooling demand because the building envelope performs poorly. The other maintains comfortable internal conditions with much less energy.

The solar system on the efficient home can cover a much larger proportion of its total consumption.

This is why I see solar as part of the energy strategy rather than the starting point. Improving the building first makes every kilowatt of renewable generation more useful.

Where does battery storage fit?

Battery storage can allow electricity generated during the day to be used after the sun goes down.

The appropriate capacity depends on the home's expected energy demand, solar generation, tariff structure and the way the family uses electricity. Some systems can also provide backup power during a grid outage, which may add another layer of resilience.

Solar generation, batteries and household demand should therefore be considered together.

A well-performing home can change that calculation substantially because there is less energy demand to satisfy in the first place.

Where does Passivhaus fit?

Passivhaus provides one of the most rigorous frameworks available for designing and verifying a very low-energy building.

It brings together airtightness, insulation, thermal-bridge control, high-performance windows, ventilation and energy modelling within a measurable performance standard.

We use these building-physics principles across our high-performance work because they allow design decisions to be tested before construction begins and key aspects of performance to be verified afterwards.

Formal Passivhaus certification may be appropriate for some projects. For every high-performance home, I want to understand what the building has been designed to achieve and how we will know whether the finished result achieved it.

Model performance while the architecture can still change

Energy modelling becomes most useful during Concept Design and Design Development.

We can examine likely heating and cooling demand, assess overheating risk and compare the effect of changes to glazing, shading, insulation and building form.

If a large west-facing window creates a significant overheating problem, I want to know while we can still change the design. If a relatively modest improvement to insulation or shading produces a meaningful reduction in demand, that information should influence the architecture.

This gives us a much stronger basis for decision-making than applying an energy-efficiency label at the end of the process.

Efficient equipment still matters

Once the building's major heating and cooling demands have been reduced, the efficiency of the remaining systems becomes increasingly important.

Hot water, refrigeration, lighting, pool equipment and other appliances all contribute to overall consumption. Choosing efficient equipment and appropriately sizing it to the household can reduce that demand further.

Smart controls can help manage when some loads occur, particularly where solar generation and battery storage are involved.

I still want the home to remain straightforward to operate. High performance should make everyday life easier without requiring the occupants to become building technicians.

Energy is one part of the environmental picture

Operational energy is one part of a home's environmental impact. Construction also carries embodied carbon through materials, manufacturing, transport, replacement and eventual disposal.

Size matters too. Every additional square metre requires more structure, envelope, finishes and resources.

For a home intended to stand for at least 100 years, durability, adaptability and the amount of building we create all deserve consideration alongside operational energy.

That broader environmental question deserves its own article. For energy efficiency, the immediate objective is clear: reduce how much energy the home needs to provide the conditions its occupants want.

What should you ask about an energy-efficient home?

Before approving the design, I would want to understand:

• how heating and cooling demand has been reduced through the architecture

• how orientation, glazing and shading have been resolved

• what performance is expected from the building envelope and whether airtightness will be tested

• how fresh air will be provided when the windows remain closed

• what modelling has been used to assess energy demand and overheating

• how efficient electric systems, solar generation and battery storage relate to the expected household demand

Those answers give a much clearer picture of performance than a general claim that a home is sustainable or energy efficient.

Reduce demand first

My preferred sequence is straightforward.

Make the building perform well. Reduce the amount of energy required to keep it comfortable. Use efficient electric systems for the remaining loads, then generate and store renewable electricity where it makes sense.

The result is a home that can remain comfortable with comparatively little energy and is well positioned to take advantage of future improvements in renewable generation, storage and electrical technology.

That is what I want an energy-efficient new home to achieve.

Want to understand airtightness in more detail?

Airtightness is one of the key ways we reduce uncontrolled air movement, improve comfort and make building performance measurable.

Read our guide: What Is Airtightness and Why Does It Matter in a Home?