Wellington Passive House: a certified Passive House in Flemington, tested and proven

Anyone can draw an energy efficient house. The hard part is building one that passes an independent test at the end, and that is exactly what Wellington Passive House was built to do.

Certified on the numbers, not on a promise

Passive House certification is not a rating you can model your way into (new to the standard? Start with what Passive House actually is). Every figure below comes from the certified PHPP (the Passive House Institute's energy modelling tool), checked line by line by an independent certifier, with the airtightness figure taken from an on site blower door test.

The overheating figure is the one Melbourne buyers should look at twice. A house sealed this tightly has to be designed to stay cool in summer too, and this one sits above 25°C for less than 5% of the year, which is under the Passive House Institute's own 5% recommendation.

Forty times tighter than the average Melbourne home

CSIRO testing puts the average Melbourne home at around 19 air changes per hour at 50 pascals, which is why so many houses here feel like a glorified tent in July. Wellington Passive House tested at 0.47, roughly 40 times tighter.

That result comes from obsessing over the stuff no one sees. Every pipe, cable and duct that passes through the airtight layer is taped and sealed, every window is wrapped and taped into its opening, and the airtight layer runs unbroken around the whole house. Even the kitchen rangehood is a recirculating unit, so there is no hole punched through the roof just to vent cooking fumes.

What sits behind the plasterboard

The walls are 140 mm timber frames filled with R4.0 Knauf Earthwool, with a 45 mm service cavity on the inside holding a further R1.2 of insulation. That cavity is where the electrical and plumbing runs live, so the airtight layer behind it never gets cut for a power point. The finished wall achieves a U value of 0.228 W/m²K.

Above, the ceiling carries R7.0 Bradford batts for a U value of 0.156. Below, the 150 mm concrete slab sits on 100 mm of XPS insulation across the whole footprint, so the slab is part of the warm side of the house rather than a cold plate pulling heat into the ground.

On the outside, the house is clad in Surfmist weatherboards with Lysaght Dominion and vertical Colorbond in Basalt.

Windows that face the sun and keep the heat in

The windows are LogikHaus 68 timber frames with an aluminium outer face, fitted with PressGlass Silverstar double glazing filled with argon. More than half of the glass faces north, including a 6 metre and a 3 metre run of lift and slide doors along the kitchen, dining and living space, so the winter sun does a lot of the heating for free.

Tilt and turn windows on the other sides give secure ventilation and are what make the home's summer night purge work when the evening cools down.

Fresh air without opening a window

A Zehnder ComfoAir Q350 heat recovery ventilation system runs quietly in the background, replacing the entire volume of air in the house roughly every two and a half hours. Stale air is pulled from the kitchen, bathrooms and laundry, fresh filtered air is supplied to the bedrooms and living areas, and on the way through the unit recovers 88.8% of the heat that would otherwise be thrown away.

Because the building itself does most of the work, heating and cooling is handled by a single Daikin multi split heat pump system, and hot water comes from a heat pump with a 315 litre tank.

Inside, Hè Hè Design specified low VOC Dulux EnvirO2 paints throughout, so the fresh air coming in is not being undone by what is on the walls.

Why 7.9 stars on paper was not the finish line

At design stage, Wellington Passive House rated 7.9 stars under NatHERS, which is already comfortably above the current minimum. The catch is that a NatHERS rating is a computer model of the drawings. It assumes the insulation goes in perfectly and the house is reasonably airtight, and nobody comes back to test whether that actually happened.

Passive House certification closes that gap. The certifier reviews the as built details, the window specifications, the ventilation commissioning and the blower door result before the certificate is issued. If the house leaks, it does not get certified, which is precisely the point.

How it stacks up against our other certified homes

Wellington Passive House is our sixth certified project. Here is how it sits alongside our other certified new builds, with our Retrofit Rifle EnerPHit in Williamstown left out of the table because it is certified to the separate retrofit standard.

Every one of them is under the 0.6 airtightness limit, every one was tested, and every number above comes from a certified PHPP rather than a brochure.

The team behind it

Design and energy modelling by Maxa Design, interior design by Hè Hè Design, certification by HIP V. HYPE, and heat recovery ventilation and airtightness testing by Passive Tech. The building permit was issued in March 2025.

Our sixth certified Passive House, and one of our favourites

Wellington Passive House is our sixth certified Passive House, and it is one we will remember for all the right reasons.

It did not start smoothly. The project began with a different architect, and Maxa Design had to step in and take over the design and the Passive House modelling, picking up someone else's work and getting everyone back on the same page before anything could be locked in. We had been involved since our pre construction site investigation in 2022, so we already knew the site well when the new team came on board. That early start mattered, because Passive House is a bit like baking a cake, and if the recipe is wrong at the start, no amount of icing fixes it at the end.

We were on site for about 14 months, and like any build there were a few hiccups along the way. What made the difference was the people. We had an absolute ball on this one, and our team has said more than once that these are some of our favourite clients we have ever built for. When the owners are that engaged and that good to work with, problems get solved faster and the whole job just feels better.

If you are planning a new build or a Passive House renovation in Melbourne, book a call and we will talk you through how we would approach yours.

Frequently asked questions