Passive House is a building design system that appears to have stirred passionate support and equally passionate concerns, especially the latter from those in hotter more humid areas of the country. But are these concerns warranted?
Isn’t the argument for PH, established by German building physicists decades ago, airtight (to borrow a pun), with super comfortable interiors that can be opened to the elements on-demand with no maximum window or door sizes as long as the building can pass the air blower test when shut?
Is lightweight construction and passive solar better in Australia’s climate and what of PH’s claims that passive solar is a fundamental starting point for PH?
Tackling these issues in this extended and lightly edited format for the debate are well known Queensland-based architects Kerry and Lindsay Clare supported by work from equally well-known engineer Ché Wall of Flux, arguing against PH. Supporting PH is the team from the Australian Passive House Association, led by Chris Nunn, chair of the association, supported by various members of PHA including building physicists and engineers.
The arguments are organised in columns, currently three. We can add a fourth later if readers would like to contribute.
Note: the Clares have called for independent scientific assessment but reject this if it comes from members of PH or someone aligned with the standard. This is a view dismissed by APHA, which urges understanding of PH to properly assess its implementation and benefits.
|Passive design and Passive House – a comparison Concerns about Passive House. Prepared by Lindsay + Kerry Clare, Clare Design, visiting professors, Abedian School of Architecture, Bond University||Response: Chris Nunn, chair of the Australian Passive House Association and head of sustainability at AMP Capital Real Estate has collated input from members of Passive House Association, including from building engineers and building and physicists.||Further responses from Kerry and Lindsay Clare and Che Wall.|
Additional feedback (in a fourth column) may be added later, depending on reader responses. However, the APHA declined to make further responses at this time.
|Lindsay Clare: I grew up on the northern outskirts of Brisbane in the ’50s and ’60s. The family home was an old Queensland house. It was a four roomed Queenslander with verandahs on two sides. I slept on the verandah, on the north-east corner which was semi enclosed with adjustable timber louvres and rollaway timber shutters. I learned very early how to trim the louvres and shutters to capture a summer breeze or the winter sun. I also had the all-essential mosquito net tucked around my bed during the summer months.||This nostalgic view of an era before airconditioning, before houses used insulation materials, before building science, technology innovations and certainly before climate change, of a rustic ideal of the Australian lifestyle is anachronistic. A lot has changed in the last 70 years. The Australian climate is less benign now and getting ever more ferocious. Bushfire smoke and air pollution are an annual reality. Most people in Australia now expect a higher level of comfort and indoor air quality than outdoor conditions can freely provide.||These comments were for background. They do not say that the way things were done in the past are how they should be done today. They are however outlining that there are lessons from traditional methods that are still highly relevant, and we draw from that experience. Also – responses to climate (albeit changing) are still relevant in passive solar design.|
|My family spent summers with my grandparents who lived on Bribie Island. My grandmother would row us out into the Bribie Passage and give instructions on how and where to fish. They lived in two army-type Nissen huts with hinged plywood flaps that you propped open for light and air. The flaps formed hoods over the openings, providing sunshading or encourage cooling air movement during humid summer rain.||It is unrealistic to simply tell people to open a window and enjoy the cross breeze. Housing affordability pressures have inevitably squeezed us all closer together, with less open space where breezes can travel uninterrupted. The surface roughness of the urban environment means most urban and suburban dwellers don’t have the luxury of an unimpeded reliable daily sea breeze. A key difference between Passive Solar and Passive House Certification is that Passive Solar designs rely and depend on the combination of favourable outside conditions, and active user behaviour to work, whereas Passive House Certified buildings always work – even in bad weather, and even if the building user isn’t home or doesn’t notice when a breeze is blowing through. In a Certified Passive House, the user can choose to open windows and enjoy a fine day just like in a Passive Solar design.||Poor housing design is a big concern for us all. As we have demonstrated in our projects – simply opening a window (even in density) is possible. We have lived (in comfort) for some time in high density medium/high-rise in Redfern in Sydney and did not have airconditioning. The building was well designed on P solar principles (AJC architect). Passive House was not necessary. Passive House works “even in bad weather” – so does Passive Solar Design. We agreed in our paper that you can build both but we do not think both are necessary. We don’t agree that passive solar design needs to rely on someone being there to operate the house. Many of the passive systems (sunshading, weather protection etc) don’t need adjustment if designed correctly. Even with PH, you need someone to open and close windows. It is the same for passive solar design.|
|I was also lucky enough to spend time surfing on the Gold Coast and the Sunshine Coast from about age 14, learning to predict where the surf would be good by observing the winds, tides and swells. In the early ’70s, when I was an architecture student at QUT and working at Mooloolaba for Gabriel Poole I realised these experiences gave me an innate understanding of how to respond to environmental conditions.|
|Poole was always exploring innovative ways to occupy space to optimise enjoyment of climate and landscape. He pursued a mix of approaches that brought together traditional Queensland methods and modernist ideas – always modifying and manipulating his designs in plan, section and detail, placing openings to admit breezes and balance light – always with an economy of means.|
|Kerry (my wife and partner for more than 40 years) had similar experiences growing up in Sydney’s northern suburbs, camping at The Basin most Christmases and fishing with her grandfather around Pittwater. Her parents had built two family homes in Sydney both carefully placed to optimise summer breezes and winter sun. The second house was influenced by the Pettit and Sevitt display homes designed by Ken Woolley and Michael Dysart, and later by Harry Seidler, Russell Jack and Neil Clerehan.|
|In the early 70s Kerry’s family moved to the Northern Territory for three years where they lived in a standard 60s Darwin house which relied on a thin plan (long walls facing north and south), louvred internal walls that stopped short of the ceiling and louvred external walls to optimise total cross ventilation.||The vernacular architectural responses were all methods to “make-do” in the prevailing environmental conditions. They were a good way to cope, but they are no longer best practice or state of the art. In those days, there was no computer energy performance simulation or computational fluid dynamic modelling to verify if natural ventilation strategies would actually work. Many times, they didn’t. Often, the well-behaved blue arrows on architectural drawings denoting a cooling cross breeze didn’t correspond to reality. Conditions are less favourable now, and the building science and technology that designers and builders have at our disposal is vastly more advanced.||We are not referring to a vernacular. We are referring to passive solar design that works. Many of the well designed/built houses in Darwin in the past were far more sophisticated than “make-do” and maintain comfort for large parts of the day or year without the need to close up. Airconditioning can be added for extremes, ie mixed mode design. Bad design is the basis of most issues with comfort.|
|Airconditioned houses were not the norm at that time. The louvred walls allowed the house to open completely from one side to the other capturing the prevailing morning and afternoon breezes – air movement across the skin being the most effective way to provide thermal comfort in the tropics. After leaving Darwin Kerry’s parents settled on a farm on the Sunshine Coast Blackall Range. Her arrival in Gabriel’s office in the mid 70s was fortuitous, and we have collaborated on many and varied projects since that time.||Whether you like it or not, airconditioned houses are now the norm in Australia. In 2011 the ABS reported that “Three out of every four of Australian households now have a refrigerated air conditioner or an evaporative cooler, which is almost double the rate of ownership back in the late 1990s.” 4602.0.55.001 – Environmental Issues: Energy Use and Conservation, Mar 2014 (abs.gov.au) and in forecasts by the Australian Energy Market Operator in 2019, it assumed that 95 per cent of dwellings built up to 2006 have airconditioning, and 100 per cent of Queensland dwellings built since 2007 have airconditioning. Whatever the actual percentage of households with airconditioning in Australia, it is clearly an overwhelming majority of dwellings, and it is the way the vast majority of people want to live. Expecting people to just cope with indoor conditions that are little different from outside isn’t going to be a sensible or even survivable strategy for many Australians.||We were not referring to the number of airconditioned houses today, or for what periods people use them. Our comment is that you can design housing for comfort without airconditioning. This is still the case, even in Queensland and NT.|
|We believe that architecture should provide a strong sense of both physical and psychological connection to place, and therefore a building needs to be tailored to work specifically with the local conditions of its site and context. Optimising passive solar design can, in many parts of Australia, provide comfortable conditions in and around the building for most of the year. Any added technology (heating and cooling) then only needs to be used to temper extremes.||Passive House Certification uses the Passive House Planning Package, a sophisticated computer simulation using local climate data, to ensure the design of a Certified Passive House is tailored to work specifically in the local climate. It embeds all the thinking and design principles of Passive Solar design, and takes out the guess work. In a Certified Passive House, the insulation, high performance glazing and solar shading do the majority of the work of keeping the building cool in summer and warm in winter, meaning that active heating systems are not required. Body heat, electrical appliance waste heat and carefully controlled solar gains do the work of heating in a Certified Passive House. Air conditioning may not be essential to achieve Passive House Certification, small AC units are often specified to ensure that in a heat wave, the occupants can take the edge off summer extremes, and stay comfortable and healthy when outdoor conditions are unfavourable.||Please clarify “sophisticated”. Our understanding is that it is a simple steady-state calculation Excel spreadsheet and that the climate data is limited to monthly average temperatures, solar exposure, etc. Can you provide more information about the computer simulations as they are not evident on the website? Both passive solar design and PH can have airconditioning added – this has not been disputed.|
|In the mid 90s Dr Richard Hyde from the University of Queensland asked if he and his PhD students could access one of our projects to look at the effects of different construction systems.|
|Measurements of the internal temperatures over a period of time in summer and in winter was used to analyse their performance. They tested and compared four houses by various architects, one being a recently built house of cement earth aggregate construction (CEAC, or commonly known as rammed earth) on the Sunshine Coast.|
|They also tested our Buderim house, a single dwelling that we had recently built as a project home on the northern slopes of Buderim (which we liked so much that it became our family home for seven years first).|
|The Buderim project home, which was lightweight construction (no thermal mass) demonstrated better than expected performance in winter compared to theory – due to its passive solar design, consideration of orientation, openings, insulation and shading. In summer the effective use of roof insulation (designed to reduce heat gain) and effective natural ventilation (use of prevailing sea breeze for cross and stack ventilation for calm conditions) fostered internal temperatures within the comfort zone.1.||It would be interesting to see the results of this monitoring and compare it to data from Certified Passive House buildings. I feel confident that the Certified Passive House buildings would maintain better thermal comfort, better indoor air quality, with lower energy consumption per square metre.||The interesting point is that we achieved comfort with windows open in summer, and comfort in winter due to orientation and normal levels of insulation and glazing without the need to shut the house down to a level where you need to use mechanical ventilation. The house was also a low-cost build. Please let us know where we can get independent verification of better thermal comfort, better indoor air quality, with lower energy consumption a sq m.|
|Further studies and analysis of the Buderim house pointed to the importance of the way the design engaged with the external environmental conditions to create favourable external comfort conditions.|
|Notable also were the influences of topographical and natural features of the site. 2. The biophysical engagement of this project has also been noted as an integral part of the overall architectural concept.3.||The use of district or neighbourhood planning strategies referred to here is equally possible with Passive House Certified buildings, but unlike with Passive Solar design, it is not essential. It is possible to build Passive House Certified buildings in dense conditions, without the benefit of a prevailing breeze, in noisy or polluted urban environments, and the occupants of the Certified Passive House building will enjoy stable, comfortable conditions, year round, and breathe clean, filtered fresh air continuously, without the nuisance of traffic or aircraft noise. This is not possible with Passive Solar design.||PH is not essential in dense conditions. Neighbourhood planning is not essential to workable passive solar design. It obviously makes P Solar and PH both have to do less work. Passive solar design is essential for achieving comfort and low energy use. We agree that some filtering of air will remove some outdoor air pollutants, but understand the PH standard for certification does not require a level of filtration that eliminates small particle outdoor pollutants. Also, a key issue of occupant amenity is dilution of indoor pollutants, where increased ventilation correlates to improved air quality.|
|At that time the NatHERS program (“Nationwide House Energy Rating Scheme is a star rating system … that rates the energy efficiency of a home, based on its design”4) was just being brought into building regulation and, had our house been subjected to this analysis would have achieved only one star due to the inability of the program to holistically model the passive solar design attributes that made it so comfortable and energy efficient; specifically air movement achieved by cross ventilation and stack effect.||NatHERS has its problems, and it does not sufficiently recognise the attributes and performance outcomes of a Certified Passive House, but even with its shortcomings I doubt any Certified Passive House buildings would achieve as low as a 1 Star rating.||The point here is that the house was highly comfortable in summer and winter, and independent on-site as-built testing by PhD students from UQ verified that, and NatHERS could not predict the actual performance. So achieving NatHERS stars in the early 1990s did not necessarily correlate with good passive solar design and comfort. NatHERS could not model stack effect, amongst other techniques and had to be revised.|
|In a subsequent project, Hyde tested our Cotton Tree Housing project (a mix of public and private housing built in 1994). The Cotton Tree Housing project became a model for reduced heat island effect in medium density housing (RAIA Environmental Design Guide Case 21).5.|
|Conclusions point out that the environmental masterplanning of the Cotton Tree Housing demonstrates how the typology developed in the Buderim house could be transformed to a precinct scale. Notable features are the permeability of the layout consistent with principles of helio thermal planning allowing airflow through to all the dwellings.|
|Variations in the massing of the development to create breezeways, connect courtyards and retain trees creates thermal comfort through natural ventilation and solar heating.6||These master planning techniques are equally possible with Passive House developments, and as described above, favourable outside conditions are essential to make Passive Solar design strategies work, but in a Certified Passive House, you can enjoy good weather, open the windows, feel the breeze when it’s nice outside, but when it’s baking hot or miserably cold, you can breathe easy in your Certified Passive House building and remain perfectly comfortable. This is the advantage of Passive House, it is methodically designed to maintain comfort and air quality in all conditions, all year round, not just when the prevailing conditions are favourable.||Favourable outside conditions are not essential to make P solar design strategies work. P solar design moderates the outside conditions. Our understanding is that PH does not require (or reward) access to breezes or the enjoyment of the weather for its certification. To close down or open up windows needs that same actions from the occupant whether it is PH or P solar.|
|Around the mid 1990s Peter Stutchbury introduced us to an environmental engineer,|
|Ché Wall, then director of Advanced Environmental Concepts (now FLUX). We have engaged Ché at concept design stage since then to provide input through sophisticated modelling to optimise performance of our public and housing projects. Architects can develop a relatively good understanding of building performance, however, detailed building science is highly specialised and with new products and methods constantly introduced into the building industry, we believe that specialist, up-to-date advice is essential.||The Passive House Certification methodology is the state of the art building design technology. Through constant refinement by a German building physics research institute, Passive House has a track record of design simulation that closely correlates to actual performance. This is not true of much of the building energy performance simulation techniques used in the Australian building industry today. Often the design stage energy performance simulation is out by 30 per cent or more versus the built reality. This does not happen with the Passive House Planning Package building performance simulation tool. What gets designed performs as it was intended, because the Passive House methodology has an independent certification process, that checks the built form matches the design details entered into the design stage building performance simulation. This rigorous method, and quality assurance process is another strength of Passive House Certification, which sets it apart from other design and construction techniques, and it means that Passive House Certified buildings work.||We have not seen evidence of the track record and the actual performance for Australian PH dwellings. What energy performance simulations are being referred to here? We agree that many simulations are not reliable. We clearly state that sophisticated (verified) simulations are required. Rigorous certification methods and QA don’t necessarily mean that certified buildings work.|
|Kerry Clare: There is a plethora of building environmental performance software, rating tools, analyses and certifications (LEED, BREEAM, BASIX, WELL, NatHERS, Greenstar, Passive House, to name a few) as well as new construction systems, materials and codes that are currently facing architects.|
|The objectives of each are different and is reflected in the level of attention or otherwise given to the impacts of design for energy and comfort. Passive House (originated in Germany in the’80s), has been promoted as “a building design, construction, and operation methodology to provide for high levels of occupant thermal comfort at low levels of energy consumption” 7.|
|It came to our attention decades ago and was promoted as a sealed building solution to reduce energy use.|
|Passive House certification does not preclude constructing a house that can work passively, however, the core idea is that when closed up, the dwelling has a highly controlled amount of air changes via ventilation fans in order to reduce the amount of heating or cooling energy that is lost.|
|It is a sealed building system that eliminates the usual leaks that occur in standard Australian building practice. However, if you have a Passive House and you also want it to work well passively, we consider that you are unnecessarily mixing two different types.||Passive House Certification builds on and incorporates the knowledge of Passive Solar design principles, and extends that knowledge into a verifiable performance-based system that works every time, all year round, not just on a fine day. The owners and occupants of Certified Passive House buildings enjoy the outdoors, a gentle breeze, and warm sunshine just as much as anyone. But in addition, when it’s brutally hot or uncomfortably cold, their Passive House will consistently be delightfully comfortable and well ventilated.||We don’t know where to find independent verification that PH “is consistently delightfully comfortable and well ventilated”. This independent verification is the work that needs to be done in our opinion.|
|Over several decades and more than one hundred built projects we have experienced firsthand the benefits of passive design methods utilising good planning and orientation and appropriate use of shading and insulation.||Passive House Certification has a proven track record around the world, including in warm climates. There are more than 60,000 Passive House Certified buildings around the world. Over 30 years of monitoring and verification of thousands of those buildings, has demonstrated that the Passive House Certification methodology works. There is a database of Passive House Certified projects here: http://www.passivhausprojekte.de/projekte.php?lang=en You can filter the results to see the Australian projects. Passive House buildings are becoming more common in Australia, with a growing variety of residential and institutional buildings, with exponential growth in some markets. As members of an international building standard, Australian designers, builders and policy makers have access to a global pool of experience and expertise in relation to all building types. Passive House is tried and true.||Where do we find independent verification of this? We would be interested in the ones that perform in similar climates to Australia as described in our paper. The link is to a PH promotion website with construction and PHPP details only. We could not see any independent verification of IAQ, thermal comfort, etc. However, if they are not independent assessments they are not the verification that we seek. A certification does not make something “tried and true” or confirm that the Certified Passive House solution was the optimum achievement in energy efficiency, occupant comfort in that country or that it was the most economically rational solution to those challenges.|
|Therefore, we find it hard to reconcile a strategy that would encourage one to be sealed off from our benign climate that is so easy to live in. The human body is also highly capable of adaptation to seasonal changes and we can enjoy indoor outdoor living at most times with season-appropriate clothing.||Firstly, the Australian climate is not benign. The oft repeated myth that conditions are so mild in Australia that we can basically live outside, then rug up in winter and splash at the beach in summer is just not true. Not everyone survives that strategy. The elderly, sick, or vulnerable in our society and many average Australians swelter in summer and freeze in winter in their own homes. And these conditions and those attitudes actually kill people. More people die of cold in Australia than Sweden, largely because of our inadequate standards of insulation. And it doesn’t have to be. Our summer heatwaves are becoming hotter and longer. State of the Climate 2020: Bureau of Meteorology (bom.gov.au) In Australia, heatwaves have claimed more lives in the last century than any other natural hazard (Steffen et al., 2014) with nearly 500 registered deaths for the 2009 eastern Australian heatwave alone (Nairn and Fawcett, 2013). The climate is not benign. Our building stock is generally not fit for purpose to keep Australians comfortable and safe. Most residential buildings in Australia are neither comfortable nor healthy, and leave many people vulnerable, sick, in “energy poverty” and sometimes even dead. That is the sad reality. We should acknowledge and face into this. At APHA, we believe that Certified Passive House buildings are a genuine, robust, scalable solution to these problems. Denial of the problem just perpetuates it. Second, this belief that the climate is mild and that we can just adapt, is based on an assumption of a rugged, healthy, mobile and able adult who can adapt to any outside conditions. It is not reflective of the diversity of people in our society. We need to design and build buildings that cater to and protect the most vulnerable, not buildings that only work for the most able and robust. Human comfort depends on a range of factors, but it is well established that people are most comfortable in a temperature range of 20-25 degrees C. Outside that range, people start getting uncomfortable, and well outside that range, vulnerable people can die. People may have physical or medical health conditions that make them more likely to be affected by heat or cold, eg if they are overweight, underweight, have a respiratory illness, if they are taking medication, drugs or alcohol. Thermal comfort can be affected by a worker’s age, fitness level and gender. For example: a fit body regulates its temperature more efficiently, and aging can make it harder for people to keep warm or to stay cool due to hormone changes. Women tend to feel the cold more than men because of different body mass and different “clothing factor” – the layers of clothing worn. Tense or stressed people can feel colder. Always Cold: Symptoms, Causes, Diagnosis, and Treatments (healthline.com) So there are a lot of human variables. We can’t assume that people will be fine if indoor temperatures are 15 deg C or 32 deg C, it’s a nuisance for almost everyone, and it can be a real health problem for some people. A Passive House Certified building maintains internal temperatures within a comfortable range – no more than 10 per cent of the hours in any given year are allowed to exceed 25°C. Surfaces (like window frames) don’t get too hot or cold, so everything in a Passive House Certified building is a pleasant temperature. External walls, roofs must not be more than 1°C below the indoor air temperature, window surfaces must be less than 3.5°C below. Internal air speeds are low, because there are no large temperature differences between internal surfaces, so there are no draughts. The result of these strict performance criteria is that Certified Passive House buildings perform as expected, providing exceptional comfort, consistently excellent air quality, and outstanding energy efficiency, while also avoiding building health and durability issues caused by condensation and mould. Passive House Certification uses building science to create environments that keep people safe and comfortable, with a minimum of energy.||A lot of Australia’s climate is benign. Housing can be built in most of Australian climate zones that are comfortably occupied by people using passive solar design principles with no need for PH. This is describing poorly designed housing outcomes that are already constructed. Are you suggesting that they should all be converted to PH and no other? We suggest that some more easily added passive solar techniques, insulation, etc can be used to upgrade existing housing stock. Because current building stock may be poorly designed and poorly built this does not mean the PH is the answer. Our argument is that there are other ways to achieve comfort and reduce energy use and have healthy homes. Human adaptive comfort is accepted in research and standard around the world. This includes the work of Dr Richard de Dear from Sydney Uni, which formed that basis of the ASHRAE standard https://www.sydney.edu.au/architecture/documents/staff/richard_de_dear/RP884_Final_Report.pdf. Humans are not adapted for homogeneous indoor environments as extensively demonstrated in research and summaries in Nic Baker’s essay “we are all outdoor animals”. 10 per cent of hours in the year for “no overheating” is equivalent to the entire summer of daytime hours.|
|The Australian Passive House Association (APHA) writes that, “We are often being asked whether in a Passive House one can still enjoy the Australian indoor-outdoor lifestyle. Absolutely yes. If the weather is right, a Passive House like any other building should be opened up to provide the connection to the outdoors and make use of natural ventilation.|
|“But even in warm and hot climates, there are times when it is just too hot or too humid to keep windows and doors open. That is the time when Passive House buildings stay comfortably cool with significantly reduced reliance on active systems”.|
|However, the association then goes on to clarify, “One more thing worth mentioning is that there is one exception to the aforementioned Passive House benchmarks. In humid climates, the cooling demand allowance significantly increases due to the energy demand associated with active dehumidification.” 8|
|This is an interesting declaration which we feel glosses over a number of issues. Our own projects have demonstrated that thermal comfort can be achieved for most of the year with good passive solar design and natural ventilation.||The statement doesn’t gloss over anything. It transparently recognises that in more humid climates, additional thought is required to keep people comfortable. The cooling demand allowance is increased to allow for dehumidification energy use as simple HVAC modelling shows that well recognised comfort ranges (the combination of both temperature and humidity) can’t be met for an acceptable proportion of the year. Allowance also implies that should you have a scientifically robust approach for achieving comfort without additional energy use this is also fine||It is our opinion that this note on the PH website does not explain the implications of the amount of additional energy that is needed. So, we consider that the information on the website “touches lightly” on the energy efficiency in humid climates (which PH acknowledges is a key first step in delivering good buildings). We are keen to understand independently verified results. In humid climates good passive solar design can achieve comfort without PH.|
|The vast majority of our work has been in regions that experience heat and humidity, from Sydney to Rockhampton, and more recently in Darwin. APHA notes that their system requires fundamental adjustment to benchmarks and fundamental value proposition in humid climates, and therefore will require more energy use. So why is there a keenness to introduce it throughout Australia?||Passive House Certification is appropriate for warm and humid climates. There is a recently certified exemplar Passive House in Brisbane, Vanquish, recently covered by The Fifth Estate. The Passive House standard remains entirely voluntary, and is one of many approaches available for application in any climate. Reports from users and clients from hot and humid climates tell us that, generally, most people in these climates both have airconditioning and use it regularly. We are not claiming that all homes must be Passive House, but it is a robust method to deliver comfort to those who demand it. It is true that many people can and do live without airconditioning but its uptake is increasing, and to reduce the impact of this demand, peak loads, infrastructure impacts and GHG emissions, fundamental efficiency approaches must be applied. Indeed, in Darwin it is well accepted that many people turn on airconditioning for months at a time. The Passivhaus approach recognises that energy efficiency is a key first step in delivering good buildings.||Independent information on performance would be interesting to see. There are many passive solar exemplars in Queensland. It would be interesting to compare costs and performance. (Independently). Reports from users and clients could be considered anecdotal? (NOTE: Vanquish is being assessed independently and we will report the results if permitted – TFE) We agree that not all homes must be PH.|
|Passive House is gaining traction within the architectural fraternity and the building industry. With a few easy steps it could be assimilated into building regulation.|
|Concerningly, if embraced by the industry the inadvertent outcome could be that the air-tightness regulation lays a pathway for reduced operable windows and cross ventilation (a construction cost efficiency at the expense of liveability). Many states in Australia sadly have no regulation for cross ventilation. We discussed these issues and other questions with experts Richard Hyde and Ché Wall and asked what are the real facts behind all the hype and information? To assist us they investigated the science that supports Passive House to uncover its benefits (or otherwise) for Australia.||Passive House Certification does not lay a pathway for reduced operable windows or cross ventilation. That is simply false. A Certified Passive House is required to have operable windows in every habitable room, and can have extensive openable areas of windows and doors, and just as effectively provide for natural cross ventilation strategies as a Passive Solar design. However, in addition, a Certified Passive House can operate effectively when outside conditions are not favourable, providing continuous filtered fresh air and stable comfortable indoor conditions even when it’s hot or cold outside. Passive Solar design is far less able to maintain comfort and effective ventilation in adverse weather conditions. What happens in a Passive Solar design when it’s too cold? You shut the windows and doors, and now you have no ventilation. So, you can either be warm, or have fresh air, but you can’t have both. Likewise in Passive Solar design, if it’s too hot or humid outside, you shut the building and turn the AC on. So you can be cool, but you have no fresh air. That doesn’t happen in a Passive House. The Passive House standard requires that the ventilation system provide 30 cubic metres of fresh air, every hour, for every person in the building. So there’s always a feeling of freshness and good ventilation, with no risk of stale or stuffy interiors. A heat recovery ventilation system ensures a supply of fresh, filtered and clean air all year round. A Passive House-certified ventilation system delivers the air silently without drafts to every occupied space, and exhausts stale air where moisture or odors exist.||OK – we did not express this well and have updated it in column A. This is not saying that PH has to have reduced operable windows or cross ventilation. To clarify – this point is about regulation and the application of regulation. The Apartment Design Guide has described many good passive solar design strategies and they are linked to policy. Developers who are less interested in quality and comfort than pre-sales and profit can already provide the minimum amount of ventilation to meet NCC. This does not meet comfort in the vast majority of cases. The ADG has been able to rectify this to some extent however it is only adopted in NSW. If strict “sealed building” codes are being considered we believe they need to be independently verified for suitability and value. Developers love fixed glazing, no sunshades, etc. A close-to-sealed building system on top of this could be very dangerous. If PH does not reward P solar techniques – what might be the outcomes? 30 m²/hr, is 8.3 l/s/person, which is minimum fresh air, is not a generous amount and not an amount to promote better well-being. We also question how fan noise is silenced – what acoustic criteria is required under PH?|
|The Australian Passive House Association website lists the Passive House Criteria as follows.|
|Indoor Air Quality|
|The absolute indoor air humidity levels do not exceed 12 g/kg for more than 20 per cent of the occupied time. Dehumidification allowance if no cooling plant is proposed|
|Airtightness is set at = 0.6 ACH (+/- 50 Pascals). Alternatively, air permeability is set at = 0.6m3/hr.m2 (+/- 50 Pascals) for larger buildings. This is a minimum requirement for all Passive Houses, and represents an extremely air tight building with only minimal gaps in the envelope. An air tight building allows more closely controlled environments, with significantly improved thermal comfort (no more draughts!).|
|The air temperature must not exceed 25°C for more than 10 per cent of the occupied time to ensure that comfortable temperatures are achieved during the hot summer months.|
|Annual Space Cooling/Dehumidification Demand / Load|
|Annual space cooling/dehumidification demand is set at = 15kWh/a square metre a year. Alternatively, space cooling load is set at 10W a sq m. This represents the demand on the cooling system to maintain a consistent comfortable temperature throughout the year. It is a function of the building fabric thermal performance, the air permeability and the outside air ventilation required for maintaining indoor air quality. It is also independent of the proposed mechanical plant efficiencies.|
|Annual space heating demand/load|
|Annual space heating demand is set at = 15kWh a sq m a year. Alternatively space heating load is set at 10W a sq m. This represents the demand on the heating system to maintain a consistent comfortable temperature throughout the year. It is a function of the building fabric thermal performance, the air permeability and the outside air ventilation required for maintaining indoor air quality. It is independent of the proposed mechanical plant efficiencies,|
|Annual Primary Energy Demand|
|Annual primary energy demand is set at = 120kWh a sq m a year . Alternatively with renewables, it is set at = 60kWh a sq m a year. This is the predicted total energy demand of the building, including heating, cooling, hot water generation, ventilation, lighting and equipment loads. It takes into consideration the efficiencies of mechanical plant and any renewable generation (if proposed).9|
|So, what do all these parameters really mean, how do they contribute to thermal comfort and how are they accurately measured? We asked our experts, and the modelling and research undertaken by Wall and Hyde 10 reveal the following.|
|Indoor Air Quality|
|The ventilation rate required to be supplied for Passive House certification is less than the minimum required by the NCC. As a dwelling would have openable windows the NCC wouldn’t necessarily mandate any increase in capacity to match the requirement of AS 1668.2, which established the minimum for natural ventilation.||Passive House ventilation rates do have some differences to the current NCC (National Construction Code) 2019 and also to AS1668.2, however both can be applied successfully for dual compliance. They originate from a European EN standard which has far more rigorously researched outcomes than the Australian documents mentioned. It is unfortunately a reality that the NCC still lags European, Canadian, and a large proportion of US building code in many areas, however, there is significant work being done locally to close this gap which is receiving good support from the Australian Building Codes Board (ABCB). The NCC also provides a simple to follow baseline standard for construction but provides (and encourages the use of) Performance Solution pathways to allow for solutions that provide equal or better performance.||This confirms that the European specified minimum ventilation requirement is not adequate for Australia and therefore quantities have to be lifted to meet local regulation? Is PHAA suggesting that the Australian standard for minimum ventilation should be reduced? Please provide detail of how the EN standard is far more rigorously researched.|
|Either way, there is a significant difference between providing a minimum amount of ventilation and providing ventilation for excellent indoor air quality. . . .In all considerations of air quality, healthiness and wellbeing, increased ventilation above the minimum prescription is required.||Mechanical ventilation has been shown in countless studies to provide a reliably higher minimum level of indoor air quality versus natural ventilation in all types of buildings. |
Like increasing insulation thickness there are diminishing returns for increasing ventilation rates above a certain point, and overventilation carries with it a risk (predominantly in cooler lower humidity climates such as the southern parts of Australia) of excessive dehumidification, that can result in occupant discomfort.
|Please provide details of the studies referenced. Were these mechanical systems supplying only minimum fresh air rates? Were the naturally ventilated buildings well designed?|
|The claim that Passive House provides excellent air quality is therefore completely at odds to their technical requirement to minimise ventilation as far as possible.||The Passive House standard does not require that ventilation is minimised as far as possible. Rather it applies a ventilation rate that delivers well documented outcomes of high indoor air quality, while having low energy use, and minimising equipment sizing and cost.|
A critical improvement in indoor air quality via mechanical systems (that is not available when relying on natural ventilation), is the filtration of fine particles that are known to cause respiratory issues. Given the increasing density of development in cities this one of reasons most cited by owners wanting mechanical ventilation.
|Information that we have indicates that the rates of air change in PH can be reduced to very low. We have already established that the mechanical ventilation rates need to be lifted to meet the minimum code in Australia. We understand that this affects the Indoor Air Quality. PH’s website talks about humidity under the Indoor Air Quality heading – not pollutants. We refer to off gassing, pets, and number of occupants. Does PH have an override that increases the air changes when the quality of the air is sub-optimal?|
|Passive House presents air leakage rates at conditions about 20 times worse than the real-world conditions that are relevant to a home owner. This has falsely promoted the idea that Australian homes are too leaky. Ché Wall notes that the real-world infiltration performance of the average Sydney house, “is not too bad considering air tightness is not regulated in Australia. Importantly, some infiltration is relied upon to prevent pollutant and moisture build-up in dwellings.||Australian homes are leaky. The reason that this leakiness is currently accepted as a “good” thing is because our ventilation strategies are, overall, inadequate and result in more unhealthy and dangerous outcomes Higher pressures (50Pa) are used to test the leaks in a building as a way of accurately measuring leakiness and finding the holes in the building envelope which cause draughts, undermine the effectiveness of heating and cooling systems, and which can cause condensation and mould, and building durability problems when moisture gets into building assemblies. The ABCB has accepted the science showing building fabric air leakage is detrimental to building performance. This has been reflected in air tightness provisions introduced into NCC2019 Vol1, and is this is expected to be further expanded in the upcoming NCC2022 revision.||We have been advised that infiltration performance of the average Sydney house is not too bad and the point being made is that the Air Change rates quoted in the advocacy of Passive House present a picture of leaky homes that is not relevant to real-world conditions. https://www.thefifthestate.com.au/columns/spinifex/tighten-up-the-regulation-to-tighten-up-our-homes/. An objective discussion on the merits of air tightness should not be abstracted to the consideration of performance-only test pressures. To get to the facts there is need for independent research. Independent review of ABCB “accepted science” should be sought.|
|“An existing house in Sydney will have a typical air change rate of 0.25-1 air changes per hour, which for 75 sq m dwelling results in 14-28 litres of fresh air per second, which is the minimum ventilation required to meet acceptable amenity for occupation by one to three people. PH requires 0.6 air changes per hour at a test condition of 50P which, due to real-world conditions in Sydney, will produce less than one litre per second of fresh air ventilation in a household.||The authors have confused building fabric air tightness with ventilation rates. Relying on air leaking into your home for breathing is akin to relying on water leaking through your roof for drinking. As stated above, the Passive House standard requires that the ventilation system provide 30 cubic metres of fresh air, every hour, for every person in the building. That’s 30,000 litres of air per hour, or 500 litres per minute, or 8.3 litres per second PER PERSON.|
Not 1 litre per second for a household. More than 8 litres per second per person.
Passive House requires a continuous supply of filtered fresh air. There’s always a feeling of freshness and good ventilation, with no risk of stale or stuffy interiors.
A heat recovery ventilation system ensures a supply of fresh, filtered and clean air all year round. A Passive House-certified ventilation system delivers the air silently without drafts to every occupied space, and exhausts stale air where moisture or odours exist. This cannot be said of naturally ventilated buildings.
|We disagree with this analogy and the inference that infiltration is to be relied upon as the sole means of ventilation. We believe generous natural ventilation is critical and disagree that mechanical ventilation is a necessity to provide minimum levels of air quality. Minimum outdoor air is regulated to prevent the build-up of indoor pollutants. It makes no difference whether this ventilation arrives through windows, though a fan or through infiltration. If you get adequate ventilation for dilution through windows or infiltration, a mechanical system is not needed. We understand that infiltration has a significant energy cost in Europe. We question whether the same value proposition exists in much of Australia.|
|“This does not meet minimum ventilation requirements and causes an absolute reliance on mechanical ventilation to remove moisture and pollutant build-up acceptable for human occupation.”||Many studies have shown building fabric infiltration to be a highly unreliable way of maintaining indoor air quality, and in fact carries with it a risk of introducing contaminate laden air as the incoming air path is unknown. It also has inadequate moisture removal.||Could you please cite the studies? Our information is that infiltration is generally OK in Australian dwelling construction – and not the big issue for achieving indoor air quality and comfort. We also note ASHRAE 62.2 Ventilation and Acceptable Indoor Air Quality in Residential Buildings, (which is the very well researched US standard) allows you to reduce the rate of mechanical ventilation for minimum fresh air by the amount of passive air infiltration that is calculated for a dwelling. Please provide more detail of why the same volume of air from a natural source has inadequate moisture removal compared to a mechanical system.|
|To add to these discrepancies a simple energy balance shows that in a Sydney winter the amount of energy that one will need to run the mechanical ventilation will exceed that of any energy saved from reduced heat loss, confirming that PH air tightness “carries an energy penalty in warm temperate climates”.||This is incorrect and can be demonstrated with basic HVAC knowledge. The typical Mechanical Ventilation with Heat Recovery system in an average sized house uses approximately 40 watts. If for a rough approximation we take the average daily winter temp in Sydney to be 14 deg C and desired indoor temp 21 deg C, a high efficiency HRV system will avoid in excess of 300W in heat energy needed to maintain a stable 21 deg C. If we assume this comes from an efficient split system AC with a COP of 3.5 then the saved electrical power is 300W/3.5 or 85W. This is slightly more than double the required HRV operating power. As the indoor and outdoor temperature differences increase, this saving increases, and conversely as it decreases the savings decrease. As a side note specifically for humid climates, mechanical ventilation with an enthalpy exchanger can also reduce the impact of high summer outdoor humidity. These can provide substantial saving in cooling and dehumidification energy use, that is not apparent based on observation of temperatures alone. This is a tiny energy cost for a continuous supply of filtered fresh air. Air tightness saves energy by ensuring that when it’s cold outside the supply of fresh air comes through the mechanical ventilation system which uses heat recovery to temper the cold incoming air by passing it by the warm outgoing air. The air streams don’t mix, but they pass by each other in fine tubes, so that the heat from the outgoing indoor air is passed to the cold air as it comes in. This heat exchange process reduces the energy needed to warm the inside air in winter. Combined with the improved insulation, high quality windows, and minimisation of thermal bridges, these things keep a passive house warm with no energy input other than people’s body heat and other heat loads from within the building, like appliances and controlled solar gains. This is the most efficient way to heat a building. In contrast a “leaky” conventional naturally ventilated building is constantly admitting cold winter air into the building via cracks, and heat is constantly flowing out of the building through thermal bridges, which together increase the heating energy required to stay warm, and causes uncomfortable draughts. The energy cost to heat a leaky building is therefore vastly higher than to heat a passive house. This video explains how air infiltration up an internal wall can suck heat out of an older home, but can be solved by making the top of the wall air tight to stop the cold draught. https://ecoevo.com.au/sucking-the-comfort-out-of-your-home-via-internal-walls/. We should all be able to intuitively understand this – when you have a cold draught coming in under a door, you might put a draught strip there, or a ‘draught snake’ to stop the cold air coming in. That makes it easier to stay warm. It’s a simple air tightness improvement that demonstrates the point. Uncontrolled air pathways allow cold air in, and warm air to escape, making it harder and more expensive to stay warm. More videos here: https://ecoevo.com.au/||The energy balance we referred to was for the whole year, not just winter. The need for heating and cooling, IAQ and comfort can be met efficiently with good P solar design and added technology for extremes. PH is not essential to meeting these criteria. PH may be one way of achieving these criteria however independent verification is required for PH IAQ and comfort performance.|
|Heating and cooling load targets|
|PH targets are actually worse than the heating and cooling load caps required by BASIX in the Sydney metropolitan region. . . it is unclear why Passive House continues to promote such an explicit emphasis on improved thermal insulation, including triple glazing and an exacting focus on thermal bridging.||If it’s unclear to the authors why Passive House promotes improved thermal insulation, better glazing and the removal of thermal bridging, then the authors have a lot to learn about keeping buildings comfortable while making buildings efficient. Insulation, double and triple glazing and the removal of thermal bridges are well understood as good things that all sensible sustainability advisors should be arguing in support of. BASIX now recognises the Passive House Standard as a pathway to meeting the thermal comfort requirements of the NSW State Environmental Planning Policy (BASIX) is a sustainable planning measures and has been required in NSW since 2004. It requires all projects to meet requirements for energy, thermal comfort and water with the aim of encouraging sustainable residential development.|
The thermal comfort section of BASIX aims to: ensure thermal comfort for a dwelling’s occupants, appropriate to the climate and seasonreduce greenhouse gas emissions from artificial cooling and heating through good building design and use of appropriate construction materialsreduce the demand for new, or upgraded, energy infrastructure by managing peak demand for energy required for cooling and heating. On average the passivhaus single dwellings modelled outperformed the BASIX caps by 60 per cent for heating and 51 per cent for cooling. The worst performing for heating was a 26 per improvement over the BASIX caps, the best performing was an 85 per cent improvement. The worst performing for cooling was a 21 per cent improvement over the BASIX caps, the best performing was a 67 per cent improvement. An apartment building was also modelled, it significantly outperformed the BASIX caps in all modelled climate zones. The heating performance improvements ranged from 39-95 per cent over the BASIX caps. For cooling the range was 40-75 per cent.
|We note that PH has an explicit emphasis on improved (increased?) thermal insulation and including triple glazing however our argument is that these measures are not essential to achieving comfort, IAQ and low energy use. The modelling that is referred to for a PH single dwelling is measured by what software? And the apartment building is measured by what software? We are interested to know the basis of the argument so that there can be discussion about its merits.|
|We presume that the requirements remain so stringent not for thermal and energy efficiency reasons but are instead necessary to prevent the increased mould growth risk that Passive House introduces through all but eliminating passive infiltration of air through dwellings.”||The requirements are entirely about improving occupant comfort, air quality, and energy efficiency, and they achieve this superbly, as tens of thousands of built examples around the world, including in warm and humid climates have demonstrated time and again. The authors seem unaware of this huge evidence base. We refer them to this excellent publication which provides case studies on more than 25 Certified Passive House buildings in Australia, which are working beautifully, keeping people comfortable, and providing them with filtered fresh air and dramatically reducing the energy needed for heating and cooling. The book also explains the basics of Passive House. If you’d like to know more, the Australian Passive House Association also runs introductory courses, as well as training to become a Certified Passive House Designer or Tradesperson.||A reference to a publication by PH is not what we are seeking. We are interested in independent analysis of performance in the Australian climate. We are very interested in providing comfort, good IAQ and low energy solutions. This has always underpinned all of our work for decades – using P solar and additional technology only for extremes.|
|How do the Passive House methods of calculation compare?|
|NatHERS (and through association BASIX) requires hourly weather data for a region and dynamic thermal modelling of performance at each hour of the year (AccuRate developed by CSIRO).|
|By comparison PH uses a simplified steady-state calculation of a single average condition to determine energy demands for each month.||Complex dynamic simulation forms the basis of all inputs and algorithms in the PHPP. The PHPP was established and is constantly updated based on both theoretical dynamic simulation, and real-world monitoring and experimentation. In a real-world study of 17 leading global dynamic simulation software by an independent European body, testing the ability of the software to reflect a real-world building, the PHPP and its feed-in software, Dynbil, were established as leaders in accuracy and predicted conditions.||Could you please be clear with respect to the PHPP used to certify – is it based only on steady state calculations and average monthly climate variables? We would expect considerable thought went into the design of PHPP but would like to understand the limitation of the tool that is in the hands of users.|
|Our researchers note that this oversimplification, “inherently bounds the capacity to calculate complex dynamic interaction between solar gain, thermal response of materials and natural ventilation, all of which are fundamental to passive design…the proper dynamic thermal simulation adopted by AccuRate (hourly weather data to simulate each hour of the month) over one month would involve at least 5040 climatic variables compared to eight of Passive House.”||Passive House buildings are typically modelled with PHPP, a steady-state and almost defacto approach globally. The calculations within PHPP are based on the methods outlined in ISO 13790: 2008: Energy performance in buildings. They are also tested in accordance with ASHRAE 140: Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs. This is the same testing method as AccuRate and its supporting simulation Chenath. Unlike the Chenath engine, PHPP has also been tested against the PHI’s Dynbil software and empirical data from a large number of completed projects since it was first released in 1998. When used alongside verified high performance construction, it is the only known software solution that produces better results (total heating and cooling demand) than in operation. Therefore, if anything, PHPP can be described as a fully validated and tested software that is based on monthly data by virtue of 23 years of validation.||We are not disputing that the least sophisticated of the methods described in ISO13790 is not valid for some situations. We are simply highlighting that more sophisticated methods allow testing of dynamic impacts, and dynamic simulation is the normal expectation for certification of energy performance. This contrasts to the monthly method of ISO13790, which is applied in PHPP. Using this method provides only one single calculation of heat balance per month. This can only be done with significant simplification of climate impacts.|
|This means that PH calculations do not require knowledge of the path of the sun and resulting radiation dependent on cloud cover. They do not require knowledge of the shading or heat throughout the day and overnight dissipation of heat through air infiltration and re- radiation to the night sky.||The PHPP includes consideration of radiation from all directions, as well as diffuse radiation, for the simulation of heat and comfort conditions. Additionally, the daily temperature swing is calculated, confirming whether the home will remain comfortable across the course of a day in peak conditions.||Please clarify the extent of daily calculations in PHPP. We understand the calculation to be based on a single monthly condition. Please confirm the calculation of daily diurnal temperature. Is this a single range for all days and seasons? How is this applied if hourly (or daily) calculation are not needed in PHPP?|
|Our researchers note that, “The inability of Passive House to properly calculate the process necessary to optimise passive design is a fundamental limitation that should preclude its consideration in any regulatory or policy context.”||This is incorrect.|
Passive House Certification incorporates the principles of Passive Solar design and extends them into a proven method for delivering comfortable, efficient buildings.
|The comment was based on lack on calculations other than mean monthly performance. Clarification of the above will be useful to further understanding.|
|These facts and clarifications were very concerning for us and, in discussion, we asked some further questions of Wall and Hyde:|
|Does Passive House remove pollutants like smoke?|
|“Only partially. The filter specification required for Passive House certification only removes about 50 per cent of the smallest smoke particles from bushfires. These are the ultra-fine particles that penetrate directly into the bloodstream through the lungs and provide the biggest risk to health.||The authors are promoting Passive Solar design relying on natural ventilation, which freely admits bushfire smoke. There is no filtration against outdoor pollutants in a naturally ventilated building. In contrast the Mechanical Ventilation systems used in Certified Passive House buildings include high grade filters which do remove outdoor pollutants. In several Certified Passive House buildings under construction in Australia HEPA filters are being installed to provide extra protection against fine particles. This is higher grade filtration than most premium commercial office towers provide.||We have noted that the second stage of infiltration is required by PH if smoke particles are to be removed. PH has confirmed that each dwelling can have a HEPA filter on hand for instances such as bushfire. However, our enquiry has been into what the PH certification requires. We agree that general construction will allow infiltration of smoke. We consider that holistic passive measures are an imperative to solving this problem rather than all new building stock having to be meet the airtightness levels of 50Pa.|
|“If you want protection from the health risk of bushfires you would need to add a second stage of filtration to the PH specified particle filtration and this would increase the fan’s energy beyond the PH budget.”||So, if you really want to stop PM1s entering a building, you do need an airtight building with a mechanical ventilation system, plus a HEPA filter.|
Passive House Certified buildings are well placed to protect occupants from bushfire smoke. The solution we’ve developed is to add a HEPA filter that can be inserted during a bushfire, and removed when the smoke clears. This minimises fan energy during the year, and accepts there will be a small energy penalty to screen out fine particulates during an emergency like a bushfire or severe pollution incident.
|Does Passive House pose potential health issues if the building occupants rely entirely on the mechanical system without opening the windows?|
|Yes, but is also dependant on the outdoor environmental quality. “The reliance on mechanical heat recovery ventilators was associated with health issues in Europe where supplementary natural ventilation was not adequate. Problems were found due to poor installation, poor performance arising from maintenance and increased internal pollutant loads due to more occupants or the presence of pets.”||Firstly, no. With windows closed, the ventilation system would maintain a constant supply of filtered fresh air, which would be a far more consistent and reliable source of fresh air and maintain higher indoor air quality, and therefore be far healthier than a conventional naturally ventilated building.|
Secondly, it’s unrealistic to assume anyone living in a Certified Passive House in Australia wouldn’t open the window. Of course they’ll be opening windows and doors just like everyone else. In colder climates like Europe, maybe this is more of a problem, where due to the cold weather, people are more reluctant to open windows. But in Australia, when the weather is fine, of course occupants of a Passive House building will open the windows. So, this is a non-issue. Also, even in that European example, compare the situation of a Certified Passive House with a user who wants to keep all the windows closed, to a naturally ventilated building that remains closed up. The occupant behaviour is the same, but the Passive House at least has a reliable ventilation system continuously providing fresh air. A comparable Passive Solar design that remains closed up, will create far worse indoor air quality issues.
|First point, please direct us to independent verification that this is achieved. Second point, we do not assume that many people won’t open windows. However, over occupation of a dwelling or with windows closed due to outdoor temperatures there is potential to create poor IAQ if a house is highly sealed. A closed house that is designed with good passive solar design principles should be made to meet performance requirements for IAQ and achieve low energy usage. Regulation and good building techniques are required. Our point is that PH is not essential to achieving these parameters and that independent verification is required to demonstrate if PH does achieve these parameters.|
|Can a German climate-based system apply to Australian Cities?|
|“The analysis of heating degree days (HDD) and cooling degree days (CDD) outside normal internal comfort ranges shows a clear difference between German cities and Australian cities. The German cities are all quite similar and heating dominated with no significant need to consider cooling.|
|By comparison, Australian cities show a diverse range of climates with none being as heat dominated as the German cohort. CDD indicated that outside air is warmer than inside air for a greater proportion of the year in all the Australian cites, even Canberra and Hobart.|
|An analysis of the climate shows that the energy recovered in Sydney from the high efficiency heat recovery device (mandated by PH for the mechanical ventilation) is about 25 per cent of that which would be recovered in a typical German city.|
|It also shows that the energy cost of running the fan exceeds the energy recovered, resulting in a net energy penalty when the mechanical ventilation is used over the year. Given a net expense, the mechanical ventilation would never recover its initial capital investment in Sydney. This compares to a typical German city which could expect a payback period of less than 10 years.”||This is not correct.|
The fan energy is not more than the energy saved. There is an energy payback, and there is a huge health benefit.
Also, given that the MVHR fan power is less than a single 40W incandescent light bulb, this really isn’t an issue.
Yes, the climate of Germany and Australia is different. That is well understood. What the authors have missed is that Passive House responds to local climate, and the starting point of the Passive House Planning Package software calculations is the local climate.
|Please let us know where we can find independent verification of the net energy penalty. Passive solar design specifically responds to local climate.|
|While the environmental penalty of a net energy cost for heat recovery ventilation in warm temperate climates can be offset through investment in renewable energy, a fundamental concern remains with the requirement to invest capital into equipment of arguable environmental benefit to meet a cold climate standard when the investment could be better deployed when responding to the local climate.||Passive House is not a cold climate standard. It has been applied in a huge variety of climate zones around the world. Here is a map of the Passive House Certified buildings around the world:|
Yes, there are a lot in Europe and the colder parts of North America and Asia. However, there are also a very significant number of Certified Passive House buildings in hot and humid climates including Thailand, Southern China, Southern USA and Mexico, Brazil, Turkey, Saudi Arabia, the UAE, and of course Australia and NZ. The following articles go into how Passive House Certified buildings work in warm climates: https://www.phius.org/NAPHC2014/white-lisa-Hot&Humid.pdf https://blog.passivehouse-international.org/summer-comfort-passive-house/ https://elrondburrell.com/blog/passivhaus-different-climates/
|The number and position of PH certified buildings is not the discussion as one could argue that the number of passive solar design buildings that work would be extensive. We are interested in independent verification and comparison to other methods.|
|What role do shading and sun access play in Passive House?|
|“The most stark difference between traditional Australian integration of passive solar design and Passive House is the attention given to sunshine and shade. The use of shading to selectively screen the harsh summer sun but allow in warming winter sun is fundamental to the Australian approach but is noticeably absent in the Passive House primary requirements.||This is not correct.|
There is no stark difference between passive solar design and Passive House regarding the use of external shading. Solar shading is integral to the Passive House Certification process in Australia. It is absolutely not “noticeably absent”. In Passive House design, shading remains a core strategy to reducing unwanted solar gains, just like it is in Passive Solar design. This is one of the many ways Passive House integrates the Passive Solar design approach and extends and improves upon it.
|Is PH interested in providing the software for independent review and comparison?|
|“An analysis of the solar heat from direct sun each hour of the year in Australian and German cities shows differences in climate that are more pronounced than even the differences in temperature.|
|“A seasonal comparison shows that whilst peak levels are not significantly dissimilar, these are only experienced for a small proportion of the year in the German cities, whereas Australian cities experience a high level of direct solar radiation for a much greater period. . . High levels of direct sun will increase the benefits of proper solar shading in summer to prevent overheating and harnessing sun in winter to offset heating requirements. . .simple mapping shows that direct solar radiation is not a significant design consideration for passive design in most German cities due to low amounts of sunshine.||The authors clearly do not understand that Passive House Certification uses local climate data. It is a global design system, applicable in all climate zones. Use of solar shading is equally relevant for a Passive House as it is in Passive Solar design.||We understand that solar radiation data in PHPP is strictly limited to the average radiation per month in each of the cardinal directions and the horizontal plane. We question whether this is adequate to optimise the performance of solar shading in a climate where sunshine is an important driver for P solar design. Is PH interested in providing the software for independent review and comparison?|
|“By comparison, the only Australian city that suggests passive solar management is not of major importance, is Hobart. Most cities benefit from proper passive solar design considerations, which require shading to minimise solar heat in summer and maximising capture of solar heat in winter.|
|“On the basis of this simple climatic comparison alone, the Passive House standard appears to have significant deficiencies when applied in Australia.”||The discrepancies are in the authors’ understanding of Passive House, not in the Passive House Certification methodology.||Is PH interested in providing the software for independent review and comparison?|
|What are the unintended consequences of using Passive House in the milder climates of Australia?|
|There is an increasing number of studies pointing to occurrence of overheating in the PH type of low energy housing in climates where there is both a cooling and heating demand.|
|“…temperate climate buildings designed to reduce heat gains for winter will overheat in summer. This is particularly notable in new houses.11 Mitigation is by natural ventilation or airconditioning.||The cited article relates to overheating in buildings without airconditioning in Europe and the UK, where the primary concern is with staying warm in winter, and “virtually no consideration is given to summertime heat gains”. The article also notes the influence of user behaviour in overheating in the UK which included leaving heaters during summer, defective trickle ventilation systems, and window opening restrictors in high rise flats limiting openable window area, and window opening being curtailed in many homes due to security or noise concerns. Overheating will be less of an issue in a Certified Passive House with its vastly improved insulation (which also works to keep heat out), and high-performance glazing, than in conventional buildings in Australia. A passive solar design will arguably experience similar or worse overheating than a Passive House Certified building. In passive solar design, thermal bridges are common, and single glazing with low quality metal frames is still often used. These are significant sources of heat into a building. Passive House Certified buildings eliminate these problems and are therefore less prone to overheating.|
These are some of the good reasons why people in cities end up not opening windows, and why the natural ventilation strategies relied on in Passive Solar design often fail in reality.
In a study of homes in California, (Reference: Ventilation Behaviour and Household Characteristics in New California Houses, Phillip N Price and Max H Sherman, Indoor Environment Department, Lawrence Berkeley Laboratory, University of California, February 2006) it was found that many occupants do not get substantial ventilation through window opening, with windows providing much less than 0.3ACH for most homes in winter, and less than 0.35 ACH in about half of homes in fall and spring. The main reasons people close windows or keep them closed are Not home 91 per centSecurity & safety 83 per centSave energy 79 per centKeeping dust insects, pollen and adverse weather out So the assumption in Passive Solar design of active users constantly monitoring the weather, and taking advantage of cross breezes doesn’t turn out to work because often, people aren’t home, or they close windows for security, or they have the AC running and they want to save energy, or the weather outside isn’t favourable. For these reasons, natural ventilation strategies often fail. In contrast Passive House Certified buildings maintain adequate ventilation at all times with an MVHR. In a monitoring study of Passive House Certified and conventional houses in Australia the data showed that typical naturally ventilated houses have CO2 levels that regularly exceed 1500ppm and up to 3000ppm overnight. These are dangerously high levels. CO2 is a direct IAQ indicator and a strong proxy for good IAQ generally. Whereas in a Passive House with mechanical ventilation CO2 was well below 1000 at all times. The study shows that in Australia, natural ventilation strategies do not maintain good IAQ, but MVHR does. (Reference: Passive House Conference 2020, Day 4 – Stream 8 – Cameron Munro)
|Please refer us to independent verification that a Certificate Passive House will overheat less than a “conventional building”. Please also refer us to independent verification that a Certified Passive House will perform better than a well design P solar house in relation to heat gain. This seems to support ASHRAE 62.2 Ventilation and Acceptable Indoor Air Quality in Residential Buildings which allows you to reduce the rate of mechanical ventilation for minimum fresh air by the amount of passive air infiltration that is calculated for a dwelling.|
|“Current guidance from the Chartered Institution of Building Services Engineers (CIBSE) defines overheating as when operative temperatures exceed 28°C for more than 1 per cent of occupied hours, based on simulations using weather files from a design summer year (DSY).12.|
|“Empirical definitions of overheating, based on adaptive thinking and occupant behaviour, can support the use of natural ventilation to better connect buildings to the external environment and reduce dissatisfaction.13|
|“A further study from the UK reports ‘This standard (Passive House) aims to improve occupant comfort and energy efficiency, potentially changing the ways in which homes operate and how occupants interact with them. With increasing construction of low energy dwellings, there is an emerging gap in knowledge in relation to occupant health and wellbeing, thermal comfort, and indoor air quality (IAQ)’”.14|
|Wall and Hyde conclude that, “Cursory analysis suggests that Passive House is a poor fit for Australia. The claimed benefits do not appear to have been substantiated in the Australian context and practitioners and regulators should apply caution before promoting the use of Passive House.||The analysis is cursory. A proper analysis using monitored data shows that Passive House Certified buildings in Australia outperform naturally ventilated passive solar designs in terms of comfort, indoor air quality and energy efficiency.|
Contrary to the authors’ conclusions, regulators, policy makers, designers, builders, developers and occupants can have full confidence in promoting Passive House Certified buildings in Australia, because there are many built examples in all Australian cities performing superbly. APHA’s recent book includes many of the best examples:
|Can this analysis be made available for review? Does it include temperature, humidity, IAQ? We are interested in independent analysis rather than a book published by PH.|
|“The need to improve the energy efficiency, healthiness and resilience of Australia residential building stock needs careful consideration to ensure that effort and capital are directed towards improving outcomes, delivers the improvements necessary and does not result in expensive sub-optimal thermal outcomes, degraded amenity and reducing resilience.||The implication that Passive House Certified buildings deliver poor thermal outcomes, degraded amenity and reduced resilience is not correct.||The comment is a blanket comment about the future of housing in Australia and that effort needs to be put into getting good outcomes, and this can only be done with the knowledge of independently verified outcomes.|
|“Our brief analysis of Passive House suggests that outcomes in each of these areas in Australia are substantially different to the promise, and that robust local testing is essential to back up the current claims”.10||The Passive House methodology delivers very close alignment between predicted and actual outcomes, due to the rigor and accuracy of the Passive House Planning Package software, and the certification checks performed as part of Passive House Certification. It is incorrect to say that the promise of Passive House is not delivered in the built reality of Passive House Certified buildings. Quite the opposite. Passive House buildings perform exactly as designed, because they are based on over 30 years of building physics research, informed by feedback from monitored data in thousands of Certified Passive House buildings in all climate zones around the world, including in Australia. They are designed using a proven method that is underpinned by sophisticated software modelling, they are tested and certified during construction to verify that the built form matches the design, and that it why they work.||We would be pleased to be able to review the actual software. Is there independently verified information that PH buildings perform exactly as designed? We would be pleased to review it. We are happy to look at the sophisticated software modelling.|
|Looking into Passive House promotion you will find it has a commercial aspect with direct representations for German insulation and vapour barrier products, distributors for European window and door products, specific air-tightness products, mechanical ventilation and heat-energy products (MVHR) and blower door testing. These promotions have a clear commercial interest and do not represent independent environmental performance advice.||The Australian Passive House Association (APHA) is not-for-profit national association that aims to lead change by educating, promoting, and supporting the delivery of Certified Passive House buildings in Australia. It is our vision that all Australians live and work in healthy, comfortable, low energy, resilient buildings. We do not promote Passive House for the commercial benefit of our members, any more than advocates of passive solar design promote it for commercial gain. We promote it because we have good reasons to. Because it works. Because it’s a proven globally successful way to deliver comfortable, healthy, low energy buildings that perform in reality exactly the way they were designed to. APHA and our members reject the assertion we are not objective. APHA has nearly 400 members (390 as of Feb 2021) in Australia who understand Passive House Certification. Like all Passive House accredited professionals around the world, they study an intensive technical course and a pass stringent exam to become a Passive House Accredited Designer or Tradesperson. We promote Passive House Certification because it is scientific, it is rigorous, and it works. The standard adaptable and climate specific and works brilliantly in Australia, just as it does everywhere else, because it delivers measurable performance outcomes. As the Australian and international market for Certified Passive House products develops, APHA members will promote these in addition to currently available products from Europe. The Australian market is growing, for example this Passive House Certified wall and roof panel system was designed and is manufactured in Australia, specifically for the Australian market:. The Chinese market is now also producing a full range of certified Passive House products can be found here||We understand that PH strives for healthy, comfortable, low energy, resilient buildings. We are saying that independent review and advice is not what PH can do. It has to be done by others. We are not aware of any objective review. The assumption of APHA’s mandate was taken from APHA’s website: The Australian Passive House Association (APHA) is an independent, not-for-profit organisation which aims to lead change by educating, promoting, and supporting the delivery of Certified Passive House buildings in Australia. If this is so, would PH be happy for the scientific basis for certification to be objectively reviewed by others? Further Comments |
A mechanical system is needed to deal with increasing polluted outdoor air Air quality measurements generally show outdoor air pollution levels are reducing. The reductions are due to improved regulation for emissions from cars and industrial sources. An extreme example is the pea-soupers they used to get in London, which led to the Clean Air Act. More relevant examples are the measured reduction in outdoor air pollution in Sydney in recent years. This trend of improving air quality will continue with the closure of coal-fired power stations, the move to the electrification of vehicles and buildings and the continued tightening of regulation governing industrial emissions. There are two exceptions to the continued reduction in outdoor air pollution. Smoke from bush fires will increase with climate, and atmospheric CO2 levels will continue to rise. Che Wall expects that the latter issue will become more visible soon as all the minimum ventilation codes (EU, Aus, US, etc) are based on the amount of outdoor air required to reduce indoor CO2 concentrations (emitted by occupants). To maintain indoor CO2, with higher levels of CO2 outdoors, requires increased volumes of air to increase dilution. The current standard is based on an atmospheric CO2 level. For example, the EU standard EN13779 is based on 600ppm above ambient. Therefor to hit a 1000ppm threshold, an ambient of 400pm is assumed. The northern hemisphere crossed this threshold in 2012 and the southern hemisphere in 2016. Global average atmospheric CO2 levels continue to trend steeply upwards with an increase of 15ppm in the last 15 years. The expectation is that minimum fresh air rates will need to increase for Climate adaption. This is also without considering the elevation of CO2 in urban environments, which is caused by trapping CO2 in street canyons (CO2 is heavier than air so it needs continuous breezes to remove it from cities). An elevation of +60ppm can be expected in urban localities. This is also about a baseline minimum ventilation rate to maintain acceptable conditions for human habitation. Increasing ventilation rates beyond the minimum improves health, wellbeing and productivity. The above makes us very concerned about defending any system that, by design, provides only the lowest air ventilation rates currently allowed. To suggest this approach will provide “perfect” indoor air is not credible. There will be increasing prevalence for the bush fire smoke, but Passive House’s requirement does not have the level of filtration needed to filter out the respirable particles. Of course, you can upgrade, but then it’s not Passive House; it’s something different. You can also buy HEPA filters than recirculate the air in the space. You don’t “need” a Passive House to address bush fire smoke. The price to pay for being able to swap out your filter for a HEPA filter in a bush fire event is the burden of minimum rates of fresh air and associated running cost for the rest of the year. The year-round limitation is a high price to pay, and it is expected that a portable indoor filter would provide a better-balanced solution. Also, important but absent in the Passive House discussion are the indoor pollutants, which is why we have minimum regulation for ventilation. Pets, cooking, visitors and deliveries from Amazon all introduce additional pollutant loads. Overheating risk in Australia There is a lot of evidence that overheating has been an issue in certified Passive Houses in Europe. These include houses in Scotland where the bedroom routinely exceeds 30 degrees and overheating occurs even in winter. This cannot be dismissed as a non-issue in Australia, “as we are used to designing for the conditions, or you can always open the windows”. It also contradicts the whole premise of Passive House, that we have been mis-designing buildings, and the prescriptions in Passive House are a universally optimum outcome. When people design to achieve a certificate, they focus on the items that contribute to achieving that certificate. If the certification does not give appropriate weight to an important initiative, it is a fundamental problem. In the case of passive solar protection and summer conditions, the PHPP tool is fundamentally flawed. A paper from ESRU, University of Glasgow observed that PHPP follows the quasi-steady monthly method included in the European Standard EN ISO 13790:2008 for the calculation of energy use for space heating and cooling in buildings (Passive House Institute 2012). Therefore, PHPP is focused on estimating annual energy performance, but it does not account for variation in the indoor environmental conditions in different parts of the house at different times. The inherent limitations baked into the PHPP tool will always make application problematic in Australia, where solar heat is of paramount importance. Even the DesignPH extension, which allows you to model shading geometry in 3D and map temporal performance, translates the result to a simple shade factor for use in PHPP, where it used to adjust average monthly energy for the whole home. This simple process cannot address overheating risk in the sunny parts of Australia. For natural ventilation, PHPP can again only consider the effect of windows on the house’s entire air volume. This may be an acceptable approximation for energy loss or gain (although still questionable) but is irrelevant to natural ventilation for comfort, which is inherently grounded by air changes within rooms and relative to heat sources. Put simply, PHPP places the greatest attention to the wrong details. The elements which are essential to passive design in Australia are over-simplified to a level where value cannot be assessed. Of course, you can always apply different tools to design solar shading and natural ventilation to fill this gap, but this is not what Passive House certifies. It is, therefore, not part of the Passive House value proposition. The PHPP tool and its simplifications represent a significant step backwards from the tools developed to assess the passive performance of buildings over the last 25 years. There may be a benefit in a standard calculation procedure for certification, but representing PHPP equivalent to proper dynamic thermal modelling for passive design in Australia is a significant overreach. On the two issues alone, we think objective discourse is warranted to temper some of the messaging and zeal that accompanies Passive House.
|The Australian Passive House Association is an independent not-for-profit organisation however its clear mandate is promotion of PH for the benefit of its members and it is not expected to contribute objective appraisal.|
|We are sure that there are a lot more conversations to be had about increasing the performance of housing in Australia, however, these conversations need to be based on fact and science to provide a more clear understanding of the broad requirements of ‘human comfort’ and how to deliver the best outcomes in a sustainable way.||The authors have used personal anecdotes, nostalgia and crude calculations that misunderstand Passive House, and mis-construed references to articles as the basis for their argument, not facts and science. In contrast to this article, Passive House Certification actually is based on facts and science, and a rigorous methodology that has been proven to work both here and around the world over the last 30 years.||We also have used fact and science. An objective review would be the best way forward to get some independent answers and credibility to all the questions.|
|Architects need data, information and proven facts at their fingertips while they balance the solutions for quality of life in our cities and our country for all of its wide and varied population. If anything, 2020 has taught us the imperatives of resilience, heeding science-based advice and caring for people and planet.||The Authors would be well advised to engage with and better understand Passive House Certification. We can recommend the following upcoming courses to improve their knowledge: Certified Passive House Designer/Consultant Course, including PHPP e-learning moduleCertified Passive House Designer/Consultant Exam PreparationCertified Passive House Designer/Consultant ExamCertified Passive House Tradesperson CourseCertified Passive House Tradesperson Exam||We would welcome more information about your calculations, analysis, outcomes. Please let us know if you wish to engage further in order to find some answers.|
|Hyde, R A, ‘Thermal Performance of Innovative Lightweight Construction Systems: Building Response in the Queensland Climate’ in the proceedings, Ecological Perspectives and Teaching Architectural Science, ANZAScA Conference, Canberra, Australia, July 1995 pp. 171-179.|
|Hyde, R A, 2000, Climate Responsive Design, Earthscan, London 2000|
|Beck, H + Cooper, J 2015, UME Clare Design – Works 1980-2015, ORO Editions, California, USA, pp.1-271|
|Hyde, R A, Nov 2000, Cotton Tree Project, Environmental Design Guide, Case Study 21.|
|Hyde, R A, Ed, Bioclimatic Housing – Innovative Designs for Warm Climates, James and James, UK. The specific reference is Case Study 7.3. Cotton Tree Housing, pp. 257-267. 2008|
|The Australian Institute of Refrigeration, Air Conditioning and Heating, 05-19-Eco-technical-paper, AIRAH website, https://www.airah.org.au/Content_Files/EcoLibrium/2019/05-19-Eco-technical-paper.pdf|
|Passive House in Warm Hot Climates, APHA website, https://passivehouseaustralia.org/APHA/|
|Passive House Criteria, APHA website, https://passivehouseaustralia.org/APHA/What_is_Passive_House/Criteria/|
|Wall, C and Hyde, R A, Passive House (Passiv Haus): The value proposition for Australia, forthcoming 2021|
|Kevin J. Lomas & Stephen M. Porritt (2017) Overheating in buildings: lessons from research, Building Research & Information, 45:1-2, 1-18, DOI: 10.1080/09613218.2017.1256136, http://dx.doi.org/10.1080/09613218.2017.1256136|
|CIBSE Guide A Environmental design (7th ed.), Chartered Institution of Building Services Engineers (2006) ISBN 978190387668|
|Nicol , FJ, J Hacker, J., Brian Spires, B. and Davies, H (2009),’ Suggestion for new approach to overheating diagnostics’, Building Research & Information, 37:4, 348-357, DOI: 10.1080/09613210902904981|
|Foster, J., Sharpe, T., Poston, A., Morgan, C., Musau, F., 2016, ’Scottish Passive House: Insights into Environmental Conditions in Monitored Passive Houses,’ SUSTAINABILITY, Volume: 8, Issue 5, 412|
|Lindsay and Kerry Clare established their practice, Clare Design, in 1979. Both are Visiting Professors, at Abedian School of Architecture, Bond University. Kerry and Lindsay were jointly awarded the Australian Institute of Architects Gold Medal in 2010.|
|Ché Wall led Australia’s first professional practice dedicated to sustainable design – Advanced Environmental Concepts (Lincoln Scott, 1996). He was the founding Chairman of the World Green Building Council from 2002 to 2007. In 2004 he was named the Prime Minister’s Environmentalist of the Year, Banksia Environmental Foundation and in 2007 named in Architectural Record (American Institute of Architects), as one of the 6 most influential living engineers in the world. In 2009, Ché’s work developing a carbon trading scheme for the built environment was drafted into legislation and was the subject of a Senate enquiry in 2010. He was member of the advisory board the Clinton Climate Initiative Climate Positive Development Program for precincts from 2009-2010.|