A Geelong West property that jumped from 6 stars to 10 stars over five years proves the highest-return energy improvements aren’t the ones people spend on first. Draught sealing and thermal barriers cost a fraction of solar or double glazing, yet delivered comparable bill cuts on a per-dollar basis.
The owner retrofitted the 1995-built home in stages, tracking what worked. Energy bills fell to 20-30 per cent of a typical two-person household. The hierarchy that emerged: seal air leaks first, add thermal mass second, electrify appliances third, then solar.
What delivered the biggest return per dollar
Draught proofing came out ahead. One regional energy consultant tracked a client project where sealing gaps, chimneys and exhaust fans cut annual energy costs from $3,055 to $976. That’s $2,079 saved per year, for work that cost under $500 in materials and took a weekend. The home’s rating lifted from 2.3 stars to 5.5 stars on sealing alone.
Adding a single door between a stairwell and kitchen pushed that same property to 7.1 stars. Cost: under $300 including hardware.
The Geelong West case used Magnetite window inserts instead of replacing single-pane windows with double glazing. Magnetite creates an airtight seal and can improve thermal efficiency by up to 70 per cent, at roughly one-third the cost of full window replacement. Paired with airlock blinds and pelmets, the thermal envelope tightened without a builder.
Callout: In plain English
Draught sealing stops conditioned air escaping through gaps around doors, windows, chimneys, exhaust fans and ceiling penetrations. It’s the reverse of insulation: insulation slows heat transfer through solid surfaces, sealing stops air movement. Both matter, but sealing is cheaper and often skipped.
The catch with headline improvements
Solar panels and heat pumps dominate renovation budgets, yet they optimise a leaky system. A 6kW solar array was part of the Geelong retrofit, along with gas-to-electric appliance swaps. Both reduced bills, but the biggest percentage drops came earlier in the sequence when thermal performance improved.
If you install solar on a poorly sealed home, you’re generating power to heat or cool air that escapes. The payback period stretches. Seal first, then size the solar system to actual reduced demand.
Double glazing runs $1,500-$2,500 per window. For a three-bedroom home with eight windows, that’s $12,000-$20,000. Magnetite or secondary glazing costs $400-$800 per window installed. The thermal gain isn’t identical but it’s close enough that the cost difference funds draught sealing, door seals, pelmets and blinds across the entire house.
Upgrade sequence that minimises cost per star
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Draught seal everything (cost: $200-$500 DIY, $800-$1,500 professional). Target door and window frames, ceiling penetrations, exhaust fans, chimneys, skirting boards. Expected gain: 1-3 stars depending on starting condition.
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Add thermal window treatments (cost: $100-$300 per window for airlock blinds or heavy lined curtains with pelmets). Stops radiant heat loss through glass. Expected gain: 0.5-1 star.
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Seal zones with doors (cost: $200-$500 per door). Create thermal zones so you’re not heating/cooling the whole house. Expected gain: 0.5-1.5 stars.
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Upgrade to secondary glazing if budget allows (cost: $3,000-$6,000 for a typical home). Much cheaper than full window replacement, 60-70 per cent of the thermal benefit. Expected gain: 1-2 stars.
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Electrify heating, cooling, hot water (cost: $2,000-$8,000 depending on system). Heat pumps run at 300-400 per cent efficiency versus gas at ~80 per cent. Expected gain: bill reduction rather than star rating, but positions you for solar.
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Install solar sized to your new reduced demand (cost: $4,000-$8,000 for 6-8kW). Now you’re generating for a tight, efficient home. Payback: 4-7 years in most regions.
The Geelong West property spread this over five years, tackling one or two items per year as cashflow allowed. Total outlay across the full retrofit wasn’t disclosed, but the owner described it as “modest” compared to a new build or full window replacement.
Who this works for
Owner-occupiers planning to stay 5+ years: the payback period on draught sealing is under 12 months in most cases, 2-4 years for secondary glazing, 4-7 years for solar. If you’re moving in two years, focus on items under $2,000 that improve comfort immediately.
Landlords: draught sealing and door seals are low-cost, reduce tenant complaints about cold, and support slightly higher rent in markets where energy efficiency is valued. Geelong’s rental market has tightened, making livability improvements a retention tool.
First-home buyers stretching on price: if the mortgage is tight, defer solar and big appliance upgrades. Spend $500-$1,000 on sealing and window treatments in year one, then reassess once cashflow improves.
Risks and trade-offs
Over-sealing without mechanical ventilation can create moisture and air quality issues. If you’re aiming for 8+ stars, budget for a heat recovery ventilation system ($3,000-$6,000 installed). Homes at 6-7 stars usually manage with bathroom and kitchen exhaust fans plus occasional window opening.
Electrifying before adding solar means higher grid bills in the transition period. If gas heating costs $800/year and electric heating costs $1,200/year, you’re $400 worse off until the solar goes in. Sequence matters.
Secondary glazing and Magnetite are retrofits, not replacements. They work for 10-15 years but won’t match the lifespan of factory double glazing (25+ years). For a character home you’re keeping long-term, it’s still the better cost-benefit call.
Next step
Book a thermal imaging audit ($300-$600) or a blower door test ($400-$800) to find where your home is losing conditioned air. Most people guess wrong about their worst gaps. The audit pays for itself in avoided spending on fixes that don’t matter.
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General info, not financial advice.
