By Simone, Principal Designer at Reimagined Habitat

Last weekend, I spent an afternoon volunteering with Clean Energy Nillumbik as part of their "Ask an Expert" eco chats. It’s something I’ve done a few times over the years—people can book a chat with specialists in solar, rainwater systems, or, in my case, sustainable design. I always love these sessions because they bring together people who are genuinely curious and committed to making their homes better for the planet and their own health and comfort.

This time, something interesting happened. Out of the seven conversations I had, three people asked me the exact same question:

"We want to buy an existing home and renovate it to Passivhaus standard, or as close as we can get within our budget. What should we look out for? What would be the ideal home to start with?"

As a Passivhaus designer, this made me genuinely excited. It’s such a good sign that more and more people are not only aware of Passivhaus but actively want to renovate with this standard in mind. And because this is such a relevant topic for so many, I thought I’d share my thoughts here.

Start with the Shell: What Type of Home is Best?

When it comes to upgrading an existing home to meet Passivhaus standards, the biggest challenge is achieving airtightness and thermal continuity. You want to wrap the entire house with insulation and ensure it’s well sealed.

If you’re lucky enough to choose the type of house to start with, I highly recommend going for a home where you can easily remove the external cladding, like a weatherboard home. Once the cladding is off, you can install your airtightness layer, followed by insulation, and then finish it with a weatherproof membrane. This method is less invasive and often more cost-effective than tackling the upgrade from the inside.

In contrast, if you buy a brick veneer home or one where external access is tricky, you’ll likely need to strip all internal plasterboard. This approach also means replacing skirting boards, architraves, and often ceilings and light fittings. Essentially, you end up back at the bare bones, which is the best way to ensure performance but also significantly more expensive. If your internal plasterboard is still in good condition, it’s more budget-friendly to upgrade from the outside.

Watch Out for Mould

A high-performing home should also be a healthy home. While an HRV (heat recovery ventilation) system will manage indoor humidity and help prevent mould from forming, it can’t fix pre-existing mould issues. Mould embedded in the structure is notoriously difficult to remove. So before you commit to a property, check for signs of water damage or existing mould. A small patch might be fine, but widespread or longstanding issues can be hard—if not impossible—to fully resolve.

Minimise Layout Changes

If you’re trying to keep renovation costs under control, look for a layout that already works well. Ideally, the bedrooms, living areas, and plumbing should be in roughly the right places. Moving walls is manageable, and opening up to the north with larger windows or doors is often essential. But turning the entire floorplan upside down gets expensive very quickly.

As a rule of thumb: the more of the existing structure you can retain, the more budget-friendly your project will be.

Think North and Solar Access

Ideally, your main living areas should have access to northern sunlight. This doesn’t have to mean the back of the house faces north. Sometimes a northern side boundary works even better, as long as there’s enough space and you’re not overshadowed by fences or neighbours. That solar gain is critical for good passive solar design, which aligns beautifully with Passivhaus principles.

The Bigger Picture: Creating Healthier, More Efficient Homes

Ultimately, what we’re trying to achieve isn’t just a home that uses less energy. We’re aiming for homes that feel good to live in—that are bright, dry, quiet, and healthy all year round. Renovating to a Passivhaus standard helps you get there. And with thoughtful planning, it’s possible to do it within a reasonable budget.

At Reimagined Habitat, we naturally integrate Passivhaus principles into every home we design. Whether you’re starting from scratch or reimagining an existing home, we can help you make it healthier, more comfortable, and future-ready.

Ready to get started?

If you're thinking about buying a home to renovate or want to explore how to improve your current home’s performance, we’d love to chat. Get in touch to book a discovery call with our team today.