What Is EnerPHit, and How Is It Different From a Passive House?

You can't always turn a hundred-year-old house into a brand-new Passive House. Anyone who promises you that is either kidding themselves or about to demolish half your home to do it. EnerPHit is the honest answer. It's the certified standard built for existing buildings, with targets set for what an old house can genuinely achieve, and it's still checked and verified properly.

EnerPHit is the certified Passive House standard for retrofits, for upgrading an existing home, not building new. It uses more forgiving targets than a new Passive House, because you can't redesign an old home from scratch, but it's still independently checked, tested and verified. Passive House performance, adapted to reality.

Carland Proof Point: Our Retrofit Rifle EnerPHit in Williamstown is certified EnerPHit Plus, taking a thirty year old home to a verified standard with airtightness of 0.43 ACH50, well inside the 1.0 EnerPHit limit.

What does EnerPHit actually mean?

It's the Passive House Institute's standard for retrofitting existing buildings, and the name is a squash of energy retrofit and Passive House. When you take an older home and upgrade it toward Passive House performance, you can't always reach the full new-build standard, so EnerPHit is the certified pathway designed for exactly that situation. Same building science, same rigour, same independent check, adapted for a house that already exists.

The key word is certified. EnerPHit isn't a loose label anyone can slap on a renovation. It's a formal standard with defined targets, and to earn it a home has to be modelled in PHPP, built to spec, tested on site, and signed off by an independent certifier. That's what separates a certified EnerPHit retrofit from a builder simply telling you he's done a deep, high performance renovation. One is verified by someone with no stake in the outcome. The other is a promise.

So EnerPHit is not a watered-down Passive House. It's the Passive House standard, rewritten for the reality of existing homes. If a renovation calls itself high performance but was never certified, who actually checked that it was?

How is EnerPHit different from a new Passive House?

The targets are a little more forgiving, and for good reason. A new Passive House is designed from a blank page, so you can orient it to the sun, get the shape right, and start the slab from scratch. An old house gives you none of that. It's already sitting the wrong way, already the shape it is, already on a slab you can't rip out. EnerPHit sets targets that account for those fixed constraints, so the standard is demanding but achievable on a real building.

The clearest example is airtightness. A new Certified Passive House has to hit 0.6 air changes an hour or better. EnerPHit allows up to 1.0, because sealing an existing structure with decades of quirks in it is harder than sealing a new one built airtight from day one. That extra allowance isn't a loophole, it's an honest acknowledgment of what you're working with. On our Retrofit Rifle EnerPHit we still landed at 0.43, comfortably inside the new-build limit, but the standard gave us the realistic target to aim at.

Everything else, the insulation, the windows, the ventilation, the moisture control, still has to perform and still gets verified. Same discipline, targets tuned to reality. Would you rather chase an impossible number on an old house, or a demanding one you can actually prove you hit?

What targets does an EnerPHit retrofit have to hit?

Real ones, across the whole building, not a single headline figure. EnerPHit checks the performance of every part of the envelope and the home as a system, then a certifier verifies the lot. On our Retrofit Rifle EnerPHit, every one of these came from the certified PHPP file.

The building envelope had to hit a U-value target for the climate, and ours came in at 0.26 W/(m²K) against a 0.5 limit, meaning the walls and roof lose heat slowly. The windows had to meet an installed U-value target of 1.25 W/(m²K), and they did. Airtightness had to be 1.0 air changes an hour or better, and we hit 0.43. The ventilation runs heat recovery, with our Zehnder unit clearing an effective 87%. And crucially, the moisture behaviour is checked, our critical surface came in at a temperature factor of 0.85 against a 0.32 minimum, which is the number that says condensation and mould won't form. Performance, measured across the board.

That's the point of EnerPHit. It doesn't verify one thing, it verifies the whole house. If a retrofit only talks about one number, what happened to all the others?

Why does EnerPHit have two different pathways?

Because no two old buildings are the same, so the standard gives you two honest ways to prove performance. The first is the component method, where each part of the envelope has to meet a set U-value target, element by element. The second is the energy demand method, where the whole house has to hit a single heating demand figure, and you have freedom in how you get there.

The component method suits a building where you're upgrading piece by piece and want a clear target for each wall, roof and window. The energy demand method suits a project where you'd rather be judged on the total result than on every individual element. Both are rigorous, both are certified, and both end in an independent check and a blower door test. Our Retrofit Rifle EnerPHit went through the component method, which is why the U-value of each part of the envelope was the number that mattered.

Two paths, same destination, a verified home. It's the standard bending to fit the building instead of forcing every old house through one rigid gate. When your retrofit gets assessed, do you even know which standard it's being held to, or whether it's being held to one at all?

Is an EnerPHit home as good as a brand-new Passive House?

Very nearly, and where it falls a little short, that's physics, not a failure. An EnerPHit retrofit usually lands with a higher heating demand than a new build, because you can't undo an old home's orientation or its existing slab. Our Retrofit Rifle EnerPHit models 31.5 kWh per square metre per year, against 9.0 for our new-build Pigeon Passive House. On paper that looks like a gap.

In the house, it doesn't feel like one. The comfort, the steady even temperature, the fresh filtered air, the dry walls, the tiny predictable bills, all of that is there, because the home is now sealed, insulated, ventilated and verified. And it's a world away from where that house started, a thirty year old home that leaked and wasted energy like every other house on the street. With solar, our EnerPHit retrofit now generates more renewable energy across the year than it uses. That's not a compromise, that's a transformation with an honest number attached.

An EnerPHit home isn't a lesser home, it's an old home made genuinely good and proven to be so. If your retrofit could perform almost like a new build and be certified for it, why would you accept a renovation that's certified for nothing?

Why does EnerPHit certification actually matter?

Because it's the difference between a home that was verified and a home you were told about. Plenty of builders will sell you a deep retrofit, an eco renovation, a high performance upgrade. Lovely words, none of them checked by anyone. EnerPHit certification forces the whole thing into the open. An independent certifier reviews the PHPP model, an independent tester runs the blower door on the finished house, and the standard gets signed off by someone with no reason to go easy on you.

This matters most on a retrofit, because so much of the work is buried in walls you'll never open again. The insulation, the airtight layer, the moisture detailing, all of it is hidden the moment the linings go on. Certification is what proves that hidden work was actually done, and done to standard, rather than trusting it was. It's the receipt for the performance you paid for.

An uncertified retrofit asks you to take the builder's word for the parts you can't see. A certified EnerPHit retrofit proves them. If the most important work in your retrofit is the work you'll never be able to check yourself, who do you want verifying it, the builder, or an independent certifier?

By Matthew Carland, certified Passive House builder and director of Carland Constructions. Five certified Passive House and EnerPHit projects in Melbourne, including a thirty year old home taken to certified EnerPHit standard.