What does maintenance of a passive house look like at 10 and 20 years?
One of the promises of passive house design is that the building will keep performing the way it did on day one, not just for the first few years, but for decades. While that is true, it does depend on appropriate maintenance along the way.
The good news is that maintenance on a passive house is generally simpler and less frequent than on a conventional home. The better news is that it’s predictable, which means you can plan for it rather than being surprised by it.
Here’s a realistic maintenance timeline over 20 years.
The first 10 years
In the first decade, a well-built passive house design in Australia requires very little beyond routine, low-level upkeep.
The ventilation system (a mechanical ventilation with heat recovery system, or MVHR) needs the most regular attention of any component. Filters should be checked every three to six months and replaced as needed. This is the single most important recurring maintenance task in a passive house, because dirty filters reduce airflow, increase energy consumption and can allow more dust and allergens into the home. The heat exchange core can also be cleaned around once a year, which most homeowners can do themselves with guidance from the manufacturer.
Windows and doors – particularly the multi-point locking mechanisms on tilt-and-turn units common in passive house designs in Australia – should get lubricated annually to keep them operating smoothly and maintain their seal.
Externally, the building envelope itself requires little intervention in the first decade. The airtight membrane, insulation and structural elements are not exposed and don’t require maintenance under normal circumstances. Cladding, roofing and external finishes need the same general upkeep as any home, including cleaning gutters, checking for any damage after storms and repainting timber elements if used.
Heat pump systems used for hot water and any supplementary heating generally require an annual service, similar to how a conventional reverse cycle air conditioner would be serviced, though the smaller systems used in passive house designs typically have lower service costs.
If you’ve had any work done on the building envelope, this is also a good time to ensure that documentation is being kept of what was done and how penetrations were sealed. You can read more about this in our piece on finding passive house-literate trades.
Years 10 to 20
By the second decade, a few components of the passive house systems begin to reach the point where replacement, rather than just maintenance, may become necessary.
The MVHR unit has an expected service life typically in the range of 15 to 20 years, depending on the manufacturer, usage and how well it’s been maintained. Around this point, you should consider having the unit assessed by someone familiar with passive house ventilation systems to determine whether it’s approaching its end of life or has years of service remaining. Replacing an MVHR unit is a more significant job than a filter change, but it’s a known, plannable expense rather than an emergency.
This is also a sensible point to consider redoing your blower door test – the test used to verify airtightness at certification. A test at the 10-to-15-year mark gives you a baseline of how the building’s airtightness has held up, particularly if any envelope penetrations have occurred over the first decade. Most well-built passive house designs show very little degradation at this stage, but having the data is valuable, both for peace of mind and as a reference point for any future work.
Heat pump hot water systems and any supplementary heat pumps for space heating typically have a service life of 10 to 15 years, so this period is when planning for eventual replacement should begin, even if the units are still functioning well.
External finishes like cladding, paint and sealants around windows and doors will likely need attention during this period, depending on the materials used and how exposed they are to wind, rain and sun. This is standard maintenance for any home, but in a passive house, it’s important that any work near windows or penetrations is done with the same care for airtightness as the original construction.
The passive house envelope itself – the insulation, airtight membranes and structural elements – should still be performing as designed at this stage, provided the building has been maintained appropriately and no significant envelope damage has occurred.
It has become more common for passive house designers in Australia working on retrofit
projects to use this path as it provides a financially manageable plan without sacrificing the
rigour of certified performance.
