Renovations and additions

Key points

  • Renovations and additions can improve the energy and water efficiency of your home, at the same time as improving liveability and comfort.
  • Do your homework to find out how your home can be most cost-effectively improved. Expert assessment and advice can help you to get the best design.
  • Simple things that you can do to improve the energy and water efficiency of your home are:
    • sealing all draughts with silicone or other sealant, or with weather strips
    • installing water-efficient showerheads
    • replacing old appliances with new, more energy-efficient models.
  • More extensive changes you can make are:
    • improving insulation to ceilings, walls and floors
    • changing your windows to more efficient types (double glazing; timber, uPVC or thermally broken metal frames)
    • removing carpets and installing tiles or polished concrete to increase thermal mass.
  • Additions and extensions should be treated as if you are planning a whole building. Assess how an addition will change the energy efficiency of your home. Include insulation, thermal mass, appropriate glazing and termite proofing.
  • Many projects are likely to require local government approval before you start. A certification is provided by the relevant authority after an inspection to ensure your project complies with the conditions of approval. This depends on the scope of the work and whether changes to the exterior are included, and can vary with jurisdiction. Check with your local government.
  • You may want to do your own small changes and renovations, but you will need experts for any electrical and plumbing work, plus other larger or more specialised tasks

The process

There are 4 key stages to renovations and additions, and different experts may be involved at any stage:

  1. Assessment and design – you can design your own changes or get expert advice and services. You may get advice from an accredited energy assessor, who can audit your home and advise on the best and most cost-effective ways to improve energy efficiency. An architect or designer may also be able to give this advice, and can draw up plans for structural changes. Sometimes, your builder may be able to provide design advice or may have a designer on their staff.
  2. Approvals – if you require council approvals, you can go through the process yourself or get expert advice and services. Your designer or builder should be able to help you with the process.
  3. Building – you can do your own work, or get expert services. You will need licensed experts for some specialised changes, such as plumbing, gas, and electrical work.
  4. Certification – if you require certification, you will need a council building inspector or a registered private certifier to inspect the building works before completing the certification.


Although some minor renovations can be planned and completed by homeowners, larger changes and additions will require help from designers and tradespeople, and will most likely require development approval from your local government.

Explore Designing a home and Building a home for more information on finalising design documentation, choosing a builder, and the renovation construction process.

A tradesman works on a building site reviewing timber framing from within the structure which is a new build or renovation project.

Often experts are required when undertaking a renovation

Photo: Getty Images

Research and decision making

Before you decide on any renovations, think about how your home functions now and how it could work more effectively, both in terms of your lifestyle and your thermal comfort. In particular, this is a good time to see how well your current design suits your climate, and what you could change to make your home more energy-efficient.

Conduct a ‘SWOT’ analysis (strengths, weaknesses, opportunities, threats) of your current home to identify the most cost-effective improvements. List all:

  • strengths – current structures, spaces, uses and aspects that work well and should be retained
  • weaknesses – such as rooms that do not suit their purpose (for example, in poor condition, in the wrong place, too big or small, too hot or cold)
  • opportunities – for example, to increase solar access and reduce heat loss in winter, to reduce solar access and increase breeze capture in summer, swap room function, improve existing spaces (for example, by adding storage, or combining or dividing rooms)
  • threats – items that require maintenance or repair or are structurally unsound.

Expert services

You can get a professional to do an energy audit and give you a report on where you use the most energy and indicate the most cost-effective ways for you to save energy. Find a local accredited energy assessor through the Australian Building Sustainability Association, Design Matters National or House Energy Raters Association.

Depending on the extent of your renovations, you may wish to get other expert advice. If your renovation proposals are relatively simple, a builder who specialises in this type of work may be able to provide adequate advice and prepare simple concept plans and cost estimates. More extensive renovations might require a designer who specialises in sustainable alterations and additions.

If you are planning an addition or extension to your home, consider engaging an energy assessor to model the whole home including the addition. Building simulation using building thermal performance assessment software can identify opportunities to be pursued or weaknesses to be overcome through careful design. Once your building data are entered into the software, modelling of options can be an inexpensive way to fine-tune your design as it progresses.


Most states also require that minimum thermal performance benchmarks be met as a condition of approval for substantial additions, so the assessment process will help to ensure you meet those requirements.

Choosing a builder

For larger and more complex projects, it is a good idea to engage a licensed builder to manage construction and coordinate tradespeople. You may also need other services – this will depend on the scope of your renovation and what stage of the process you are at. For example, do you need the builder to provide design services, council approvals, engineering certification, construction certification, and survey or geotechnical reports, or do you have a designer handling these?

The processes of building a new home and renovating have much in common. However, renovations have their unique challenges so it is a good idea to choose a builder who is experienced in renovation projects.

Check the builder’s history, especially in renovations and additions. Before signing a contract, make sure you are comfortable that you can work with the builder and that they have sufficient skill and experience to build what you want, and are committed to sustainable outcomes.

Refer to Building a home for more information on choosing a builder.

Getting a price

Before planning your improvements, do your homework on the likely cost of modifications, upgrades, and additions. Obtain preliminary cost estimates for each stage of renovation or addition in your plan to allow you to schedule each stage to suit your budget and needs.

To provide a quote for renovations and additions, your builder needs to allow for many unforeseeable contingencies. Even with extensive experience, building companies usually allow for the worst-case scenario.

Builders’ preliminary cost estimates rarely come down, but they often rise. Always set some budget aside for opportunities or contingencies. It can be useful to nominate lump sums for specific areas of work, contingency allowances based on detailed materials invoices, and agreed hourly rates for unquantifiable work. Simpler projects with a trusted builder are often better managed on a cost-plus basis, with detailed weekly or fortnightly invoices.

Whichever option you choose, make sure you agree on a budget cap for each stage of the project, to be fully invoiced at each stage to avoid a massive bill at the end. Negotiate any variations or overruns as you go – do not defer them.

Protect sustainable features in the budget to make sure these are not consumed by cost overruns towards the end of the project, when they are often installed (for example, environmentally preferred finishes, solar hot water system, efficient heating and cooling, photovoltaic panels).

Rebates and other incentives

When you are calculating your costs and budget, remember that there are various incentives, including rebates, available to help you improve your energy and water efficiency and install sustainable products and technologies in your home.

You can search Australian Government and state and territory government websites for incentives to suit you. Some state-based information sites are included in References and further reading in this chapter.

You can also contact your local council and manufacturers and retailers to ask about local and product incentives.

Signing a contract

Your building contract is a legal agreement between you and your building contractor. You must have a building contract in place, regardless of the scope of your renovation, because it is a crucial document in settling any dispute.

Make sure your contract covers:

  • definite timeframes for construction
  • all expected environmental performance outcomes
  • site access, materials and waste storage requirements
  • working hours, dust, noise and access to facilities
  • site separation and safety issues
  • if and when the home needs to be vacated
  • damage to existing property (who pays)
  • insurance and warranty.

Check that all your sustainability goals are reflected in the detailed plans and specifications that are submitted to council for construction approval. These are the documents that will be tendered by builders and annexed to your building contract.

Specifying your sustainability requirements will ensure you get the features you want.

Specifying your sustainability requirements will ensure you get the features you want.

Photo: Shutterstock

Project management

Decide who will supervise the project and ensure that they understand all specified environmental performance features. For alterations and additions, this is usually you or your designer. For larger projects, you may wish to appoint a project manager.

Use checklists to ensure sustainable design outcomes and the use of specified standards, materials and practices on site. Builders often need to make quick decisions about alternative materials due to delivery times or unavailability. You or your supervisor should be in a position to make rapid, well-informed decisions.

Approvals and certification

Some renovations or additions will require approval from your local council before you proceed. Most local governments have planning policies that allow minor internal and external changes that do not alter structure or services to be made without requiring council approval, but it is always best to check first.

Different renovations may also require different types of approvals. For example, changes to services (plumbing, drainage, gas and electrical) require approval and inspection by the relevant authority, but may not require planning or building approval.

For compliance certification, choose a certifier to check that environmental objectives and other requirements have been met at each stage before signing off. This can be your local government building inspector or a registered private certifier. Your certifier should be knowledgeable about sustainable practices and committed to ensuring environmental standards are upheld.

If you rent your home, you will need to check with your landlord or agent before making any changes. Some building owners may be prepared to contribute to sustainable upgrades in the knowledge that they can increase market appeal and property values.

Do-it-yourself (DIY)

Renovating your own home can be a rewarding experience and can work well for simple improvements. Indeed, popular TV programs make home renovation look easy. However, for larger or more complex projects, inexperience may lead to unforeseen environmental and financial costs.

Critical design details such as thermal performance, and energy and water efficiency are often overlooked to achieve a quick result. Critical steps in construction might also be skipped, including termite proofing, damp proofing and adequate surface preparation before fixing finishes. This can reduce the lifespan of renovations and waste valuable resources.


If you choose the DIY path, take the time to design changes, and choose materials carefully. Also consider where you might need some expert advice or skills.

You can get a professional to advise on your design, and it is always a good idea to use professional tradespeople as required. For example, you can consider using a licensed builder to get your renovations and additions to ‘lock-up’ stage (completed structure and external building shell, so the home is waterproof and able to be locked up), and then continue additional work yourself. You must use a licensed tradesperson for any plumbing, gas or electrical work.


With careful planning, thoughtful design and a considered choice of builder, renovations can improve the liveability and sustainability of your home.

Whether your project is a simple DIY improvement or a major renovation, incorporating sustainability goals can deliver added benefits such as thermal comfort, lower energy and water bills, and improved market appeal. Even when making minor improvements such as patching up and repainting, there are small things you can do at the same time, such as draught sealing, that can deliver real benefits.


Insulation is essential for good thermal performance – it helps to keep your home warm in winter and cool in summer.

To improve your home’s thermal performance, add insulation to accessible roof, wall and floor sections. Insulation costs can be medium to high, but it is a very quick and effective way of improving the comfort of your home and lowering your energy costs.

If existing ceiling insulation has been moved or damaged, fill the gaps or replace it. Older insulation often settles or slumps and loses its insulating properties, so the best option may be to replace it all.

Replace halogen downlights with low-energy models (for example, LEDs), seal openings and replace ceiling insulation over them. For safety, there must be a clearance between halogen downlights and insulation, which creates a path for heat leakage. This can be avoided by using LED downlights that are rated for insulation contact (IC). For non-IC rated low-energy models, electrical retail outlets can supply sealed, heatproof boxes that allow you to insulate over them without fire risk.

If the underfloor crawl spaces in your home are large enough, you can install underfloor insulation in sheets or rolls. For cooler climates, consider additional bulk insulation. In colder climates, or where slab heating is used, consider insulating slab edges (though you will need to make sure that you do not create termite access). Consider placing a foam insulation layer up to 900mm wide under paths or paving around the home to prevent heat loss from the ground surface and maintain higher earth-coupled temperatures under the slab.


If roofing is being replaced, this is a good time to check and install roof insulation. If timber-framed walls are being reclad, this is a good time to fit new wall insulation under the external cladding.

Ensure all insulation is correctly installed to prevent condensation – the right technique will vary depending on your climate. For cavity brick walls, seek advice from insulation specialists about insulation solutions that do not damage the waterproofing of the cavity.

Refer to Insulation for more information on the appropriate insulation levels and installation details for your climate.

Windows and glazing

Glazing can be a major source of unwanted heat gain in summer and heat loss in winter. The size, location and design of windows, skylights and other glazing elements will have a significant effect on the thermal performance and energy efficiency of your home.

In renovations, windows are a good area to target because they are relatively simple to change. Glazing improvements can be simple and cheap, or more extensive.

Simple options include:

  • using silicone or other sealants to improve the seals around windows and doors
  • applying thermal films to windows to reduce solar heat gain and help retain winter warmth; these stick to existing glazing and are relatively easy to install yourself
  • installing acrylic panels to the inside of windows in cool and cold climates; this can bring some of the benefits of double glazing and is sometimes referred to as ‘retrofit double glazing’
  • shading problem glazing with external shades
  • installing tight-fitting insulative blinds (for example, cellular blinds) or heavy curtains with pelmets to prevent heat loss
  • planting deciduous trees or shrubs to shade the building and glazed areas in summer (use evergreen planting in tropical climates where solar gain is not required)
  • pruning or removing trees that block solar access to north-facing glass in cooler seasons.

More extensive options include:

  • replacing windows and other glazing with high-performance units appropriate for your climate (for example, double glazing; uPVC, timber or thermally broken metal frames)
  • increasing the size of north-facing windows
  • relocating or reducing the size of east- and west-facing windows

A well-fitted blind with a honeycomb design and air pockets provides good insulation for windows.

Tightly fitted cellular blinds prevent heat loss

Photo: Felicity Woodhams

A small, level courtyard with young tress and attractive landscaping features a rectractable fabric awning that can be extended in summer to help shade the area.

Install shading that can be adjusted for the time of year

Photo: © Andy Rasheed/eyefood

Ventilation and air movement

Designing your home to allow controllable natural ventilation is an important strategy for keeping your home comfortable, saving energy and contributing to a healthy indoor environment.

You can improve cross-ventilation by:

  • replacing existing windows and doors with styles that open more fully (for example, casements, louvres and bifold)
  • creating new openings in non-loadbearing walls and above doors
  • moving doors to improve breeze paths
  • designing landscaping planting, outbuildings or fences to direct breezes through the home
  • removing trees and plants that block breeze access, unless they are needed as a windbreak.

Fans can also help to move air within the home. Install ceiling fans in the stairway or hall to increase airflow through the home. Fans that ventilate the roof space in summer and can be sealed in winter can also reduce the need for cooling and heating.

The basic floor plan of a long narrow house shows windows and doors in bedrooms and living areas that are laid out in a way that maximises cool breezes in watrmer weather.

Allow cross ventilation by prevailing breezes on summer afternoons


A three dimensional, cut-through diagram shows the air flow within a house. It illustrates how fresh air is drawn in through windows and travels through the house in air currents. Hot stale air is expelled via eave or gable vents.

Whole-of-house fans should be positioned centrally (for example, in the roof, stairwell or hallways)

Source: Breezepower

Draught sealing

Small gaps around doors and windows can let cold air through in winter and warm air through in summer.

Check your home for air leaks. (Can you see light around doors or windows or feel air moving through gaps? Are curtains moving even if the window is closed? Do doors and windows rattle on windy days?)

Sealing your home against air leakage is one of the simplest upgrades you can make to save energy and improve thermal comfort.

Very simple ways to stop draughts are:

  • sealing around windows and doors and any other gaps with silicone or other commercially available sealant
  • installing a door or window seal or weather strip.

More extensive changes are:

  • fitting dampers to chimney flues or insulate if unused
  • installing non-return baffles for exhaust fans
  • replacing warped or poorly fitting doors
  • installing doors in hallways and stairwells to control winter draughts and create zones that can be separately heated or cooled (refer to Heating and cooling).

Use adhesive weather strip to seal gaps around windows and door frames

Use adhesive weather strip to seal gaps around windows and door frames

Photo: Getty Images

Thermal mass

Thermal mass is the ability of a material to absorb and store heat. Having the appropriate amount of thermal mass in your home for your climate can improve energy efficiency and thermal comfort.

Thermal mass is typically considered and included at the design and building stages. But there are some changes that can be made through renovations.

Existing brick homes often have adequate thermal mass. To improve passive heating in these homes, insulate external cavity walls, ensure that thermal mass is balanced by increased solar access, and design openings and convective flow paths to ensure that additional solar gains are distributed effectively within the home.

To improve thermal mass in any home, consider removing carpet or other insulative coverings from floor slabs and replacing with tiles or polished concrete finishes. Information from accredited energy assessors indicates that this can increase Nationwide House Energy Rating Scheme (NatHERS) ratings by up to 1 star in many climates.

Install thermal mass in rooms that have little or none and are exposed to passive heating or cooling. This can include new internal masonry walls, sealed water containers or phase-change materials.

Refer to Thermal mass for more information on how to use mass to improve the energy efficiency of your home.

Polished concrete floors store and later release the heat of sunlight

Polished concrete floors store and later release the heat of sunlight

Photo: Mike Cleaver, Clever Design

Technology and appliances

Renovations provide a great opportunity to target the replacement of old technologies in your home and upgrade to more efficient lighting, appliances, and heating, cooling, and hot water systems.

There are two energy rating labels; one for cooling gives a number of stars out of six, as well as capacity output and power input in kilowatts. The other label, for heating, gives a number of stars out of ten, and provides the same information. In both cases more stars mean a more energy efficient appliance.

Look for the energy star rating label on appliances and technology

There are 4 key areas to consider for technology upgrades:

  • Heating and cooling - heating and cooling can use up to 40% of your household energy, so it makes sense to do whatever you can to reduce your heating and cooling costs. Upgrade your heating and cooling system with one that:
    • has the highest energy star rating you can afford
    • only heats or cools rooms that are in use
    • can be expanded to include future additions.
  • Hot water - heating water for showers, baths and washing clothes can use up to 25% of your household energy. Consider installing an energy-efficient heat pump or solar hot water service.
  • Appliances and technology - new appliances such as fridges, dishwashers, and washing machines are far more efficient than older models, and can quickly pay for themselves in energy savings. The same goes for home entertainment and office equipment. Choose the highest energy star rating when replacing appliances and technologies.
  • Lighting - replace low-efficiency incandescent or halogen lights with LED lights which use around 80% less energy. Some current LED lights cannot be covered with insulation, but can be used in combination with a fire safety barrier tested and classified in compliance with Australian Standard AS/NZS 5110, Recessed lighting barrier.


A renovation provides many opportunities to reduce water use – from small upgrades to plumbing fixtures and appliances, to larger projects that might include rainwater harvesting and landscaping.

To reduce water use:

  • install flow restrictors on taps that deliver too much water (for example, hand basins, sinks)
  • install the highest WELS (Water Efficiency Labelling and Standards) star rated toilets, showers, taps and appliances available.
  • reduce lawn areas and convert parts of your garden to mulched, low-water planting beds to save work and improve privacy and air quality.
  • plant local native plants, which will reduce your water consumption because they are adapted to your climate’s rainfall, and also increase biodiversity by attracting insects, birds and reptiles.

To supplement your water source:

  • install rainwater tanks (some councils require approval over a certain size, so check first).
  • consider reusing grey water for your garden; you will need to check which systems are approved by your council, and it’s a good idea to have a soil expert explain the implications for your soil type and plants.

Shading, rainwater and greywater can help create a backyard oasis

Shading, rainwater and greywater can help create a backyard oasis

Photo: Kathie Stove

Space and amenity

Improving the space and amenity of your existing home will reduce the need for new construction with further environmental impact.


To increase your storage space:

  • experiment with more space-efficient furniture layouts to make room for additional functions and storage
  • install additional, purpose-built storage. For wardrobes and cabinets that use laminates or veneers, specify low-VOC (volatile organic compounds) products. Timber veneers should be Global GreenTag or Forest Stewardship Council (FSC) certified. Databases like that of Ecospecifier Global can help guide product selection.

Storage can be built into renovation designs

Storage can be built into renovation designs

Photo: Pixabay


If you are considering renovating your kitchen:

  • consider traffic flow and safety
  • choose energy- and water-efficient appliances
  • ensure the fridge is well ventilated and not next to the oven or other heat source
  • choose low or no VOCs materials with E0 or better finishes; use eco-product selection databases such as Ecospecifier Global.
  • consider reusing the existing joinery carcass and only installing new cupboard fronts
  • choose durable, non-dating finishes
  • include facilities for composting and recycling.

Bathrooms and laundries

If you are considering renovating your bathroom or laundry:

  • choose toilets, showers and taps with the highest WELS star rating
  • consider a 2- or 3-way bathroom design to eliminate the need for additional bathrooms
  • choose an energy- and water-efficient washing machine with a high star rating.

Floor coverings

If you are upgrading your floors, ensure timber flooring comes from sustainably managed sources with Programme for the Endorsement of Forest Certification (PEFC) or Forest Stewardship Council accreditation. Bamboo flooring can also be a good option. Ensure all hard flooring has high levels of acoustic insulation and specify low-VOC finishes.

For soft flooring, consider natural products like sisal or coir, or choose carpet using Global GreenTag or the Environmental Certification Scheme for carpets.


Choose paints with very low or zero VOC emissions, which are readily available at no extra cost. In some places, recycled paint is available, where left-over paint from other jobs is mixed to meet customer needs. Colours can be limited, but white and undercoat are often available.


Noise can be reduced by:

  • designing room layouts to buffer quiet rooms, such as bedrooms, from noisy spaces
  • adding high-performance acoustic materials to walls or ceilings
  • using laminated glass or double glazing.

Outdoor areas

To increase your living spaces, consider building or improving outdoor living spaces close to kitchen and indoor living areas, with options for summer shade, insect proofing and winter sun.

Additions and extensions

Additions and extensions can give you more space and help your home to better suit your lifestyle. Making an addition or extension can also improve the thermal performance and energy efficiency of your home. It is a good idea to see how the addition will affect the overall performance of your home, and to include energy-saving design options. These will be cheaper to include now, than to retrofit later.

  • Insulation – all new construction should be insulated as appropriate for your climate. During construction, you can also retrofit insulation to the existing building. Replace any insulation that is old or not in good condition.
  • Windows and glazing – explore your options for window size, type, placement, glass and frame. Maximise north-facing windows and minimise east- and west-facing windows. Use the right ratio of glass to thermal mass for your climate.
  • Thermal mass – include thermal mass appropriate to your climate, availability of passive heating and cooling, auxiliary heating and cooling systems, and likely occupation patterns.
  • Termite proofing – it can be easy to overlook termite proofing for additions and extensions. Make sure that any addition to your home does not provide a pathway for termites.
    • During design, allow good subfloor clearance and ventilation. Avoid slab-on-ground construction in areas with high termite risk and ensure the slab edge is exposed (min 100mm). Design for easy inspection access.
    • For construction, use a licensed, insured installer of reputable physical termite barriers to recommend, install and guarantee them. Use termite-resistant materials where practical (for example, steel, concrete, masonry, fibre cement or treated timber). Avoid all timber contact with soil and ensure all tree roots or waste timber are removed under slabs and footings. Fix leaks, waterproof wet areas, divert groundwater and stormwater. Paint existing subfloor timbers white while they are accessible, to highlight termite tubes during future inspections.
    • After construction, continue to manage moisture sources, and ensure gardens stop clear of walls.

References and additional reading

Learn more


Original author: Chris Reardon 2013

Updated: Caitlin McGee 2020