It’s not uncommon for those in the Passivhaus world to get into heated discussions around the detailed concepts covered by the standard, whether it can be applied the world over or whether it works at all.
Discussion abounds over how it delivers real comfort and real savings, alongside real benefits for health and well-being. But many discussions start on less than equal footing, with many misconceptions about the standard. Here are a few great ones:
Passivhaus is an energy standard
Right out of the box, this is one of the biggest misconceptions of the standard; that it was created purely for saving energy. Not true! The fundamental basis of Passivhaus is the international thermal comfort standard ISO 7730 Ergonomics of the Thermal Environment, or thermal comfort. What are buildings for again? Oh, that’s right - people!
Passivhaus is just another tool; throw it in the basket with the rest of them
Passivhaus isn’t a system or a tool “invented” by anyone – in fact, the Passivhaus principle was discovered. Passivhaus has evolved from the study of existing buildings and great practices used across many hundreds of years when complex systems for comfort just weren’t available. Centuries of experience - can’t beat that.
The stated 120kWh/m2 per annum is a huge amount for an energy allowance! Particularly when, on a domestic scale, you compare to NatHERS.
Yes, it is! I have two points here though:
- This is the total energy use for the WHOLE building, not just HVAC – computers, lights, heater, ventilation system, TV, kettle, phone charger, fridge and so on.
- The calculation for energy use in Passivhaus is primary energy. This means it takes into account the amount of energy back at the source (i.e. primary), which is what the 120 refers to. For Victoria, this is brown coal, for Tassie it’s hydro or diesel generators or Victoria’s brown coal (or whatever the balance is at time of writing.) Plus, it includes all the inefficiencies and losses to produce and transport that energy to the point of use. Generally, the accepted calculation is to divide by 2.6 (the primary energy factor) meaning that the energy allowance at the building is more like 46kWh/m2 per annum. This figure is tougher to achieve!
The primary energy factor used in past versions of the PHPP calculation has been directly transplanted from Europe and this generally works in our favour, particularly in areas where we burn coal as our primary source. With the release of the new PHPP version 9 and Passivhaus certifications – Plus and Premium – projects now need to get the regional primary energy factor approved before certification. In this way, the calculation is more accurate, and the Passivhaus standard is more locally relevant. Additionally, the standard seeks advancement in the decarbonisation of the local electricity grid. An aspirational objective.
15kWh/m2 per annum is a lot for heating or cooling
The standard is targeted at a ‘sweet spot’ for energy efficiency versus increased capital investment. This is the point at which you can begin to make drastic changes to the size and type of HVAC systems you put in but any further would require complex technological fixes or extreme building envelopes. The standard of 15kWh/m2 equates to roughly 8 Star NatHERS in Melbourne, and how many dwellings achieve this, in modeling or (more importantly) in practice? Passivhaus is an as-built standard which is a key selling point.
Passivhaus costs more - lots more
This one is a grey area, but suffice it to say, it shouldn’t cost considerably more. While it is anticipated that building to the standard might cost more for early adopters, it’s tricky to say how much.
Locally, leading projects have been at the bespoke or luxury end of the market, and so the figures could be skewed anyway. And you could argue that, in Australia, we are starting from a low base with which to compare. Windows are generally the biggest additional cost element, along with added “risk factor” from builders and their view that this is going to be a significant undertaking.
Long-term data from Europe shows that Passivhaus can be achieved for around three to eight per cent more than standard building practices. But as the minimum compliance standard increases and the market adjusts, it can be cost neutral and often cheaper to build Passsivhaus. That’s right – cheaper! Why? Because you can reduce the size of necessary HVAC systems (plant and ducting) and potentially also give plant space back as occupiable area. Passivhaus should appeal most to those who retain interest in a building long-term, with ongoing savings adding directly to the bottom line. And that’s not even considering the lower vacancy rates and potentially higher rents due to more desirable space.
And the local tide is turning. There are now a number of projects in Australia targeting Passivhaus at no additional cost, including those on large scale (multi-unit residential) and single dwellings.
Passivhaus hasn’t evolved with the times
Recent criticism leveled at the standard took a jab at the fact that the metrics to achieve Passivhaus haven’t moved since its inception. Far from being a static tool, the calculation tool behind Passivhaus, the PHPP, is now up to version 9, and there is now a SketchUp plugin that enables users to work from 3D models with PHPP interoperability.
The PHPP also provides peak heating and cooling loads for sizing mechanical systems and, while most modeling protocols suffer a sizeable performance gap (up to 250 per cent), the PHPP has remained one of the most accurate tools for predicting actual in-use energy consumption on the planet (within 0.5 per cent.)
The standard also evolved to better suit retrofit projects with EnerPHit, and there are now Passivhaus Plus and Premium certifications to reward on-site energy production and net positive energy buildings. The standard has now also been successfully implemented across a huge range of building typologies and construction systems. The key criteria remain largely unchanged because they are indeed simple building directives, with a large degree of flexibility in how to achieve them. This is a key strength of the standard.
It isn’t suitable for hot climates
“American molecules and atoms are different to those in the rest of the world.” A stinging barb from Bronwyn Barry, co-chair of the North American Passive House Network, when highlighting how this same argument plays out in the USA.
The Passivhaus standard is based on building physics, and there’s nothing more universal than heat transfer. The Passivhaus standard did originate in the cold climes of Germany, but its evolution was on a global scale. The founders, Bo Adamson in particular, travelled the globe and researched the effects of different building strategies and practices across the ages in many climates, including Scandinavia, the Middle East and China.
Hot climates were common themes, and the absence of cooling even in these climates was just a necessity due to available technology; thus, strategies excluding heat dominated.
There are now a number of Passivhaus dwellings in operation in Australia, including in climates where it gets quite hot, such as Castlemaine, Canberra and Adelaide. While early data is limited, anecdotal feedback from occupants is very positive.
So what’s great about Passivhaus?
It simplifies the design. Being a fabric-first approach, the standard short-circuits the usual approach of taking a poorly designed building and throwing technology at it to make it work. The systems required to keep a Passivhaus building comfortable are simpler and less energy-intensive to run, and are often cheaper due to the reduction in air-conditioning loads and associated reticulation.
What’s not to love? Feel free to feed the discussion!