It’s hard to ignore the heat right now.

Across Australia, heatwaves are becoming longer, more intense, and more frequent. Record-breaking temperatures, warm nights that never seem to cool down, and smoky air from bushfires are no longer rare events — they’re part of our new normal.

And while air conditioning can help, many households either don’t have it, can’t afford to run it, or are trying to reduce their energy use. For renters, older homes, and anyone living in poorly performing housing, staying cool in summer can quickly turn from uncomfortable to genuinely unsafe.

The good news?

Keeping your home cool isn’t a mystery — it’s the predictable outcome of good design, smart detailing, and understanding a few core principles of how heat actually behaves.

Let’s break it down.

First Things First: Keep Heat Out Before You Try to Cool Down

One of the biggest mistakes we see is focusing only on cooling the air inside the house, without addressing how heat gets in in the first place.

In summer, your home heats up mainly because of:

• Direct sun hitting windows
• Hot air leaking in through gaps
• Poor insulation and thermal bridges
• Heat stored in building materials
• Lack of controlled ventilation

Once heat is inside, it’s much harder (and more expensive) to remove.

That’s why both passive solar design and the Passive House standard start with the same core idea:

👉 Control heat at the source.

Passive Solar Design: Old Wisdom That Still Works

Passive solar design isn’t new — but when it’s done well, it’s incredibly effective in summer.

Key principles include:

1. Shade the Sun, Not the Light

In most of Australia, summer sun is high in the sky. That means:

• Well-designed eaves, awnings, pergolas or external blinds can block heat while still letting daylight in.
• External shading is far more effective than internal blinds — once the sun hits the glass, the heat is already inside.

If you’re renting or retrofitting:

• Temporary external shade cloths
• Adjustable outdoor blinds
• Even planting deciduous trees in the right location (longer-term) can make a noticeable difference.

2. Orientation Still Matters

North-facing windows are easier to shade than east or west-facing ones.

West-facing windows, in particular, are a major cause of overheating — that low afternoon sun is brutal.

Where possible:

• Minimise west-facing glazing
• Use garages, bathrooms or storage spaces as “buffer zones” on the western side of the home

Airtightness: Why Hot Air Sneaks In

Here’s something that surprises a lot of people:

The average Australian home can replace all its internal air 15–25 times per hour through uncontrolled gaps and cracks.

That means on a hot day, you’re constantly letting hot air in — and paying to cool it down again.

Improving airtightness doesn’t mean sealing yourself into a box. It means:

• Sealing gaps around doors and windows
• Draft-proofing exhaust fans and downlights
• Closing obvious air leaks

Even small DIY steps can help:

• Door snakes or draft seals
• Compression seals around doors
• Sealing unused vents

Less hot air coming in = a cooler home, with far less effort.

Ventilation: Fresh Air Without the Heat

This is where Passive House thinking becomes especially powerful.

In a high-performance home, ventilation is:

• Controlled
• Filtered
• Deliberate

Mechanical Ventilation with Heat Recovery (MVHR / HRV)

In Passive House and other high-performance homes, fresh air is supplied through a mechanical ventilation system with heat recovery.

In summer, this means:

• Stale, hot indoor air is extracted
• Fresh air is supplied in a controlled way
• Heat and moisture can be managed without opening windows at the wrong time

And critically:

• Air is filtered

During bushfire season or smoky heatwaves, this can be life-changing — allowing you to keep windows closed while still breathing clean air.

When You Don’t Have Air Conditioning (or Don’t Want to Use It)

Not everyone has air conditioning — and even if you do, there are many days when you’d rather avoid running it.

Here are some simple, low-cost ways to stay cooler:

✔ Use Fans Strategically

Fans don’t cool the air — they cool you.

• Place a bowl of ice or frozen water bottles in front of a fan for a short-term cooling boost
• Use ceiling fans together with open windows in the early morning or late evening

✔ Close Up During the Day

It sounds counterintuitive, but on very hot days:

• Close windows, blinds and curtains during the heat of the day
• Open up again once outside temperatures drop below inside temperatures

✔ Night Purge Ventilation

If nights are cooler:

• Open windows on opposite sides of the house
• Use fans to flush out built-up heat
• Close everything again early in the morning

This works best when the building fabric is insulated — another reason performance matters.

Why Passive House Homes Cope Better with Heatwaves

Passive House homes aren’t just about winter warmth or low energy bills.

They’re designed to:

• Minimise heat gain
• Avoid overheating
• Maintain stable indoor temperatures
• Protect occupants during extreme weather events

During heatwaves or power outages:

• High insulation slows heat transfer
• Airtight construction prevents hot air infiltration
• Shading and ventilation strategies are already built in

The result?

Homes that stay noticeably cooler for longer, even without active cooling.

That’s not luxury — that’s resilience.

Summer Comfort Is a Health Issue, Not a Lifestyle Choice

Heat stress affects:

• Sleep
• Mental health
• Cardiovascular health
• Respiratory conditions

For children, older people, and anyone with chronic illness, overheating isn’t just uncomfortable — it can be dangerous.

Designing (or retrofitting) homes to stay cooler naturally reduces:

• Energy bills
• Reliance on air conditioning
• Health risks during extreme heat

And that’s why we keep saying this:

Better homes aren’t about perfection.

They’re about doing the basics well.

Final Thought

As Australia heats up, staying cool can’t rely on air conditioning alone.

Whether you’re building new, renovating, or simply trying to survive another heatwave in an existing home, the same principles apply:

• Keep heat out
• Control air movement
• Ventilate intentionally
• Prioritise health and comfort

Because comfort isn’t a mystery —

it’s the predictable outcome of good building physics.