How much does a Passive House cost to build?
Unfortunately there is no simple answer to this question but I hope the following response will shed some light on whether a Passive House is affordable for you.
In the case of Leanhaus, we aim to provide a home to the Leanhaus standard for less than a typical Architect designed home (which starts at $3300++ per sqm), BUT it will cost more than a typical custom builder’s home ($2000-$2700/sqm).
It’s worth noting that whilst typical Architect designed homes cost more than a custom builder’s home, they do not feature the critical improvements that Leanhaus offers as standard. They are built to the same standard as custom builder homes using similar materials (brick, steel and trimber). The additional cost is a result of traditional procurement practices, bespoke detailing, high end finishes and additional administration and risk costs incurred by the builder and designer. (These are some of the reasons why less than 3% of new homes have architect involvement)
To understand the cost of a Passive House, it is useful to look at a Leanhaus design for a simple family home and compare the different standards of build and costs to build in WA*.
Leanhaus - A concept floorplan for a Solar Passive 3 Bed + Study, 2 bath, 2 living area home.
154sqm internal area + 20sqm garage.
*Note: When I talk about build costs this excludes: site specific site preparation costs, external works such as landscaping, driveways and alfresco areas, Consultant and Local Government Fees. Build costs quoted would include: A custom built home, completed internally with high ceilings, including materials and finishes to a medium standard (2.4m high doors, stone countertops, timber floors)
There are four potential ways to achieve this custom homedesign.
Option 1. Typical double brick construction: Single glazed aluminium windows and ducted air conditioning. This is basically the industry standard of build and a pretty ordinary one at that. Inferior materials, poorly insulated and leaky. Refer to my blog post about brick construction here for more detail on this. Allow budget of $450k, of which the ducted a/c will cost around $20k. To offset the cost of heating and cooling you should factor in the additional cost of a large solar PV system, but this wont overcome the massive shortcomings of the build.
Option 2. Ecohaus. Timber framed with R3.0 insulation in the walls and R6.0 in the roof. Double Glazing. Ducted air conditioning. This is a significantly better option than a standard home. However, occupants should be aware that windows should be opened daily for extended periods in summer and winter to provide adequate ventilation and reduce the risk of condensation and mould. This results in higher energy costs to maintain a stable interior temperature. Allow $470k.
Option 3. Leanhaus. Same as Ecohaus plus an airtight membrane, ventilated facade and heat recovery ventilation system. Air conditioning not required. Allow a budget of $500k.
The additional costs over Ecohaus are:
High specification vapour permeable membranes externally to roof and walls, fully taped and sealed.
Fully taped and sealed airtight membrane internally. Pressure tested for leaks to at least ACH3.0.
Timber battens externally to create a ventilated facade.
Timber battens internally to create a service cavity (so that the air tight barrier is not punctured by electric and plumbing)
A heat recovery ventilation unit (HRV). Cost around $15k installed.
Airtightness barrier installation at Abbetthaus
Option 4. Certified Passive House. Same construction and detailing as our Leanhaus but certified by The Passivhaus Institute, Darmstadt, Germany. Allow a budget of $520k.
The additional costs are as follows.
tested airtight to the higher standard of <0.6 ACH50. This requires a much higher level of detail and time in construction and testing airtightness to resolve leaks.
Passive House Certifier and Thermal Bridge Calculation Costs. Approx. $6k
Passive House Designer’s additional time to complete the PHPP report and prepare all the documentation to pass certification. Approx. $4k
Builder’s additional time to document the construction and provide evidence for certification.
Abbetthaus - Certified Passive House. Image by Jody D’Arcy
In summary
It is roughly 5% additional cost for each step up in building standard. In my view, option 1 should not even be considered for a custom home. Cut back money on the finishes and appliances and upgrade the building. You can always upgrade the interior later but you cant upgrade the walls, roof and windows.
The leap from Ecohaus to Leanhaus standard will yield the greatest improvement in building comfort, operation cost and indoor environment quality. This provides airtightness plus the ventilation system ensures the building will be healthy to live in year round and future proofed against the inevitable airtightness building standard improvements to be rolled out industry wide over the next twenty years. Also, the minimal requirement for additional cooling or heating will make the home significantly more cost effective to operate over the life of the building.
Passive House Certification - Is it worth it?
The Passivhaus certification provides indisputable proof that your home is designed and built to the highest standard. At the design stage the Thermal and Passive House modelling is taken to a much more sophisticated level of detail. Thermal bridges (sources of heat loss and gain) are calculated and checked by a third party and an independent passivhaus certifier validates that the design and construction of your home meets the stringent PH1 standard. Certification places your home on a global Passive House registry and in the company of the best performing homes on the planet.
In real terms though, there may only be a marginal improvement in building performance over a Leanhaus of the same design.
There is data emerging in the Eastern States to suggest that sustainable homes achieve higher resale values and this is a consideration. Passive House is growing in awareness amongst sophisticated new home clients and it is reasonable to assume that this certification makes a home more desirable. A PH certified home is a rarity in WA, and motivated clients should take great pride in leading the industry toward a higher standard.
Passive House Plaque
