Can you turn an old home into a passive house?
The EnerPhit standard
EnerPHit is the Passive House Institute’s certification specifically designed for retrofits and renovations. It acknowledges that existing buildings present unique challenges that make achieving full new-build Passive House standards impractical or impossible. The performance requirements are slightly relaxed to reflect these real-world constraints.
Where new passive house designs must achieve 0.6 air changes per hour at 50 Pascals pressure, EnerPHit allows up to 1.0 air changes per hour. Similarly, heating and cooling demand limits are adjusted to recognise that existing building geometry, orientation and thermal bridging can’t always be completely optimised.
Passive house designers in Australia use the same energy modelling software for EnerPHit projects as for new builds, but the software recognises the retrofit context and applies appropriate performance criteria. This means you get the same rigorous analysis and quality assurance whilst working within realistic expectations for existing buildings.
The certification provides independent verification that your retrofit meets high-performance standards even if it doesn’t quite match new construction. This matters for resale value and provides confidence that the substantial investment in upgrading has achieved genuine results.
Starting with assessment
Before committing to an EnerPHit retrofit project, thorough assessment identifies opportunities and limitations. Passive house designers in Australia typically start with energy modelling of the existing building to understand current performance. Thermal imaging reveals where heat escapes during winter and enters during summer. Blower door testing measures air leakage rates.
This assessment provides a baseline and helps prioritise improvements. Some homes are better candidates than others. Single-storey homes with simple roof forms are generally easier to retrofit than complex multi-storey buildings. Timber-framed construction often accepts modifications more readily than solid masonry, though both can be upgraded to EnerPHit standards.
The building’s orientation matters significantly. A home with poor solar access will likely not perform as well as one better positioned, regardless of how much insulation you add. However, even poorly oriented buildings can achieve substantial improvements and EnerPHit certification through comprehensive upgrades.
Addressing air leakages
Achieving airtightness represents one of the biggest challenges in retrofits. Existing buildings have gaps and penetrations accumulated over decades. Additionally, they were not built with an airtight building envelope in mind, so the physical structure can be difficult to adjust.
The EnerPHit standard recognises this by allowing slightly higher air leakage rates than new construction, while still requiring substantial improvement over typical existing building performance.Your passive house builder in Australia will focus on ceiling penetrations for lights and exhaust fans, gaps around window and door frames, service penetrations for plumbing and electrical, and junctions between walls and floors or ceilings. Special tapes, sealants and membranes designed for passive home building can dramatically reduce air leakage even in older structures.
Upgrading insulation
Adding insulation is another key step towards passive building design performance. External insulation systems work particularly well for retrofits, wrapping the entire building in a continuous thermal blanket. This approach maintains internal floor space, addresses thermal bridging at structural elements and can dramatically improve appearance with new cladding.
Or, if external work isn’t possible because of heritage considerations, site constraints or budget limitations, internal insulation is an option. But, internal insulation reduces room sizes, requires careful detailing to avoid condensation problems and doesn’t address thermal bridges as effectively.
Roof and floor insulation are typically easier to upgrade than walls. Accessing roof spaces allows substantial insulation increases with relatively modest cost. Underfloor insulation can be added from below in raised timber floors or from above when replacing floor finishes.
Replacing windows and doors
Windows and doors in a passive house in Australia typically represent the weakest points in older buildings thermally. Upgrading to high-performance units makes a big difference.
The challenge in retrofits is often integrating new windows into walls designed for different products. Proper installation requires careful detailing to maintain airtightness and thermal performance. The window should sit within the insulation layer rather than in the structural opening to minimise thermal bridging.
Sometimes existing window openings can be resized to optimise solar access. Enlarging north-facing windows improves winter solar gain. Reducing or adding shading to west-facing windows helps control summer heat. These modifications require structural considerations but can significantly improve performance and help achieve EnerPHit certification.
Installing mechanical ventilation
Why choose EnerPHit certification
While it is possible to drastically improve your older home’s energy performance and indoor comfort without certification, EnerPHit certification offers several advantages.
The rigorous quality assurance process catches problems during construction rather than after completion. Independent verification provides confidence that performance targets have been met. The certification may also increase property value and demonstrates commitment to genuine sustainability rather than superficial “green” gestures.
