ALL over Australian websites you will find proponents of Passivhaus (confusingly usually referred to as Passive House in Australia) making unsubstantiated claims like the one above OR…

The new housing trend that could save you up to 90 per cent of your energy costs

A Passive House is designed to be energy-efficient from the very outset, integrating it into the framework of the home. The result is a home that uses 90% less energy than traditionally built houses and 75% less than the average new home built with ‘best practice’ construction techniques.

Passive house magic: How 3% higher initial costs can lower energy bills by up to 90%? On average, it is between 0-3% more expensive upfront, but you can expect that this investment will lower your monthly bills by up to 90%.

When something is described as magic and sounds a little too good to be true, your green wash radar should be flashing RED and beeping loudly. When you see these statements, please ask the claimant to provide some data. Ideally annual energy use data and the cost of the build (with date of contract).

Our approach. Light House Architecture and Science integrates

architecture that uses solar passive principles and tailors the design for the specific site and climate
theoretical building science to optimise the thermal performance during the design phase and physical building science to test the homes when constructed (with a strong focus on airtightness and insulation integrity).

We, or our clients, also collect and analyse energy use data, pre- and post-occupancy.

Because I have been talking about building science, passive solar design, thermal modelling, air leakage testing and thermal imaging since 2009, many people mistakenly assume we are Passivhaus practitioners and advocates. Read a blog I wrote six years ago, for some background on that.

Light House staff (who have been using building science and conventional ‘best practice’ Australian design and construction methods to deliver highly energy efficient and healthy homes for 13 years) are not the only ones who disagree with the bold statements above. See below.

From the Australian Government’s Your Home Guide:
The Passive House standard uses its own calculation methods, and therefore can be difficult to directly compare with other rating tools. For example, a Passive House assessment does not directly correlate to the Nationwide House Energy Rating Scheme (NatHERS) star ratings. Research undertaken by the Passivhaus Institute has shown that a Certified Passive House generally achieves a 50 to 90% reduction in energy demand compared with local minimum building-code-compliant buildings in Europe, North America and China. A similar analysis has not yet been undertaken in Australia.
From a 2017 article written by respected American building scientist Martin Halloday on the hugely successful Green Building Advisor (GBA) website:
“Longtime readers of GBA know that I get frustrated by exaggerated energy savings claims. A glaring example is the statement that “a Passive House building uses 90% less energy than a conventional building.” A variation on this claim: “A Passive House building uses 90% less energy than a code-minimum building.
”It doesn’t, of course. The oft-repeated falsehood is based on a boast made by Wolfgang Feist in the 1990s. Back then, Feist claimed that a new Passivhaus residence needed 90% less energy for space heating than a “conventional” residence in Germany. (It’s important to remember that space heating energy is just one small part of the energy-use pie.) The “conventional” residence that Feist was talking about was an average German home, not a new house meeting modern code standards. These days, Dr. Feist and the Passivhaus Institut (PHI) are usually more careful in their statements than many of their enthusiastic followers.”
(For those who read German this is a link to the original paper. The PHI found that existing homes in Germany in the late 90's - early 00's had an average heating load of 100W/m2; PHI sets a limit of 10W/m2 for PH accreditation, and this is where the broad brush generalisation that PH projects require 90% less energy arose.)
Several of the builders we routinely work with have also built Passive Houses. They snort with laughter when they hear the claim that Passivhaus projects are 0-3% more expensive. In our collective experience, Passivhaus construction costs 15-20% more than the way Light House builds. When housing costs have increased by EIGHTY percent over the last six years that equates to a LOT of money.

Light House homes (new and reno) typically use 70-80% less energy than the average Canberra house, when comparing actual total energy use (from energy bills post-occupancy) with data from the highly regarded energy specialists Paul Ryan and Alan Pears and their excellent article Unravelling home energy use across Australia or to their own pre-Light House data (if the same clients lived there before).

We also already know from the CSIRO developed Nationwide House Energy Rating Scheme modelling that our 8 star projects are predicted to require 30-50% less energy for heating and cooling than a 6-7 star home design the same size. Note: energy ratings are per square meter. Typically new homes are not space efficiently designed to minimise their carbon footprint and are considerably larger in floor area than a Light House. A 6 star home requires twice as much energy per square metre to maintain at comfy temps -> if it is twice the size of the 8 star Light House it will require four times the total heating/cooling energy being required for the home. In actual fact, the typical 6 star home is much leakier than the EER software assumes, while Light Houses are much better sealed than the software assumes. As a result once built and lived in, Light Houses usually require 80% less energy for heating and cooling across a year compared to other Canberra homes.

We look forward to Passivhaus proponents sharing actual total energy use for their projects post-occupancy. An easy thing to do would be to compare results with the data provided by Ryan and Pears.

We also look forward to Passivhaus proponents sharing cost to build data for their projects. Noting that the date of the construction cost data is critical because things have changed dramatically in the last few years.

Light House goes out to tender 2-3 times per month to multiple builders so we have our finger on the pulse in relation to construction costs in Canberra, unlike many architecture firms who only do a few homes per year and often very different homes.

The sad fact is that just seven years ago our projects, which are usually between 130 and 170 m2 (plus carports and decks), typically had a fully inclusive cost of around $3,000 per square metre of internal living space. They are now over $5,000 per square metre of internal living space [Noting that this per square metre cost includes the cost of driveways, carports, decks, pergolas, water tanks, pumps, clothesline… all of the external stuff too. We are not sneaky - we do not divide the comprehensive tender prices by the area of the decks and carports as well to give the impression that the square meter rate is cheaper].

Passivhaus construction is more complex and requires more material and more labour. The result is significantly more cost. It is ridiculous to suggest that Passivhaus only costs 0-3% more.

We provide cost to build and cost to run data with every award application we do. Check total energy use data from the reno/extension of a 1980s home in Giralang here (21:30 mark of the webinar), a new build in Watson here, and reno extension of a 1960s home in Weston Creek here and a new build in Wright here. Jenny will be publishing more on our website next year when she has more time.

A really important point. Check out the graph below from the excellent article I referred to earlier and note just how much energy use varies across Australia because our climate varies so much. It should come as no surprise to anyone that Tasmania, Victoria and the ACT have by far the highest energy use for “space conditioning” and the vast majority of this is for heating.

It begs the question: why on earth are people investing in Passivhaus accreditation outside of these colder areas? The bang for buck is extremely low. Reducing heating costs by 90% when heating makes up less than 25% of your total energy bill in those warmer climates is not that impressive. You may also have heard… our climate is getting warmer. This does not mean I am not a fan of airtightness and thorough insulation in warmer climates — that good basic building sience makes sense everywhere. The return on investment (bang for buck) of exceeding basic levels of airtightness and insulation integrity achievable with NCC-compliant construction, diminishes significantly even in the colder climates and the return drops off massively in mild climates.

Before anyone gets cranky at us — we know all about condensation management, heat recovery ventilation and air quality. We also have experience with well over 100 Light Houses being exposed to intense bushfire smoke during the summergeddon of 2019/2020. We are not luddites. We are just very focused on bang for buck and creating positive change in the mainstream market. Affordability is a critical part of the discussion. If you don’t get that given current economic conditions then I doubt you ever will. [Note from Jenny - I have three adult chidlren and mutiple talented staff who are facing living in crappy rentals and having no housing security for a long time or potentially the rest of their lives. Lets get serious about housing and stop being distracted by this stuff.

Light House, Building Science, Passive Solar, Passivhaus, Passive House & Green Wash