HPH025 : The Myths of Passivhaus (Passive House) – with Elrond Burrell from Architype
Elrond Burrell from Architype helps bust some of the common myths that surround the Passivhaus standard.
Interview with Elrond Burrell
Elrond is originally from New Zealand, which is also where he trained as an architect, but in 1998 he moved to the UK. After working on various sustainable projects he then joined Architype in 2006 and became more aware of the Passivhaus standard.
The Passivhaus Standard was Developed to Close the Performance Gap
Passivhaus is a performance standard for a building that is not specific to the type of building. It was developed over 20 years ago by professors Bo Adamson and Wolfgang Feist, who were looking into why buildings didn't perform as well as they were predicted to do. By carrying out lots of careful analysis they established that in order for a building to be comfortable and energy efficient, it needs to be airtight, well insulated and have good ventilation.
Understanding Passivhaus with Coffee!
Elrond gives an example of two ways that you could keep your coffee warm. In the first situation there is a hotplate, where energy is continually put in so that it keeps bubbling and at temperature. In the second scenario the hot coffee is poured into a thermos flask and kept warm by screwing the lid on. Passivhaus works in the same way. Some warmth must be provided initially, be it through solar energy from the sun, occupancy heating (movement) or cooking, etc. But, by having the building built correctly and well insulated that heat is kept in so that you are not losing it.
Mechanical Ventilation with Heat Recovery Provides Fresh Air Without Losing the Warmth
Instead of throwing out all the warm air and bringing in fresh cold air which then has to be heated, mechanical ventilation with heat recovery allows fresh air to be brought into the house and the old air to be expelled but importantly the heat is retained.
The Myths of Passivhaus
This episode is slightly different from any that we've done in the past. We put out a message on Twitter asking Passivhaus builders and designers to tell us what common misconceptions they hear. Now we discuss the items that cropped up the most.
A Passivhaus Heats Itself – MYTH
This is not factually correct, because nothing heats itself. A Passivhaus needs to get the heat from somewhere, but a Passivhaus building retains the heat (as discussed above).
You Can't Open the Windows in a Passivhaus – MYTH
This may be easy to buy into but in a Passivhaus there is nothing to stop you from opening the windows. Elrond says that it really depends on the time of the year and what you want as to whether you open the windows. In summer (UK) it is likely that the mechanical ventilation would not be running anyway, so natural ventilation would be important and that means opening the windows. In winter there's probably no need to open the windows because there's enough fresh air and it doesn’t feel stale or stuffy. In a traditional buildings that's why people tend to open the windows in winter because it's stuffy, which is essentially the CO2 levels getting a bit high, whereas in a Passivhaus there's constant ventilation in the background and there just would not be the need.
The Aesthetics of a Passivhaus are Not Good – MYTH
Elrond suggests that many of the first buildings to meet the Passivhaus standard were located in Germany and Austria, and so had a continental aesthetic. As these buildings attracted a lot of publicity it is no great surprise that there is the perception that a Passivhaus will look a particular way. Also, many of the initial attempts at doing Passivhaus may have mimicked these buildings as designers were grappling with a new challenge. However, as time goes on, Elrond believes we are seeing more buildings in the local vernacular styles.
Having worked on three certified Passivhaus schools, Elrond is proud that Architype achieved a similar aesthetic to their non-Passivhaus schools.
A Passivhaus Must be Built with Sustainable Materials – MYTH
Elrond finds this one interesting because he hears the other argument, that Passivhaus doesn’t put enough emphasis on encouraging use of natural materials. At Architype they have always had an interest in using healthy materials that don't emit noxious fumes, so that there is no knock-on impact with occupants suffering from conditions such as asthma.
The choice of which materials to use in a Passivhaus will normally be determined by the designer or client's preference. When it comes to insulation there are also complexities in balancing how much carbon might be involved in the materials, for example using polystyrene, and how much carbon is being saved due to the energy saving attributed to a good insulating material.
Building a Passivhaus is Too Expensive – IT DEPENDS
Elrond says there’s quite a lot of published data which shows that Passivhaus buildings can cost more than non Passivhaus buildings. However, when designing a Passivhaus building it’s a quality assurance standard, so what gets built has to match what gets designed and it has to meet the appropriate standard of workmanship on site with the finishes, etc. Thus, comparing that with a building that only reaches standard building regulations (in the UK), there’s very little quality assurance that a finished building matches what was designed at the outset. This means there is an issue of comparing like for like, because if that building was constructed exactly as it was designed it would probably cost slightly more than it did.
Another factor that increases cost is when existing plans are adapted to go down the Passivhaus route, which of course will add extra cost. The best way to approach Passivhaus is to have it as an objective from the very beginning. Take the budget and prioritise how the money will be spent. For example, in order to meet the standard there will need to be triple glazed windows, etc. This way, once the essentials have been priced up, there will be an amount of money with which to work. The building may need to take on a simple but elegant form but it will allow the overall budget to be balanced.
The Air is Too Dry in a Passivhaus – IT DEPENDS
Elrond says that this issue is more complex than it might seem on the surface. For an in-depth answer he suggests reading a paper on Passivhaus ventilation that Mark Siddall wrote for the AECB. However, most occupants are used to living in buildings that don't perform very well and perhaps have more moisture than would be ideal (which may lead to environments that encourage mould growth and in turn can cause occupant respiratory difficulties such as asthma). In buildings which are built right – high levels of insulation, airtight, well ventilated, etc. – the humidity will definitely be lower in certain circumstances than traditionally constructed buildings. That’s not necessarily a bad thing because a drier building will tend to be a healthier building. If things are not balanced properly or something is not quite right, then it may feel slightly drier than is comfortable.
MVHR is Too Noisy – IT DEPENDS
Careful design and installation should mean that noise from MVHR is not an issue. In a Passivhaus building the MVHR should be in a separate area (like plant room or cupboard) but it can even be outside the building (providing good acoustic separation).
The Passivhaus standard also requires that background noise from MVHR should not be greater than the World Health Organisation‘s recommended noise levels for people to sleep comfortably. It's also worth noting that the fans are running at an incredibly low speed so there should be very little noise coming from them.
Where there might be the possibility of sound travelling through the ducts from one room to another, there needs to be acoustic attenuation built in, which will eliminate the problem.
MVHR Costs More to Run Than the Energy it Saves – MYTH
Clearly when you move from a house without MVHR to one that does have MVHR, there is a new cost to pay. However, as discussed earlier, it is often difficult to compare like for like between a Passivhaus and a non Passivhaus.
But, so long as the airtightness of the building reaches a certain level (approximately 1.5 air changes per hour), it's been proven that the amount of energy saved and the cost of that energy saving is much greater than the cost of running the MVHR.
Mechanical Ventilation Has to be Running All the Time in a Passivhaus – MYTH
Elrond quickly shoots this one down by saying that at Architype they design their buildings to use natural ventilation in the summer and MVHR just for the winter months.
It should be easy to tell when to switch off the MVHR. When opening the window, if it feels dramatically colder outside than indoors then a lot of heat energy is being lost and there's also a cold draught coming in. This would be when you would want the MVHR to be on. Alternatively, when opening the window if the fresh air coming in feels comfortable and there's no cold draught, then probably you don’t need to have the MVHR running.
Mechanical Ventilation is Too Complicated to Use – MYTH
Elrond argues that this is a myth because the controls are simple to understand with a small amount of training. Most people can operate a boiler, switching off the heating for the summer, for example. Mechanical ventilation is no more taxing.
You Can't Have a Woodburner in a Passivhaus – MYTH
This is more a case of there's no need to have a woodburner in a Passivhaus. People often desire them for emotive reasons because it’s nice to sit around a fire or to feel heat emanating from something.
Having a woodburner in a Passivhaus is generally discouraged for a couple of reasons:
- It would only be used for a very short time of the year
- A lot of heat will be generated and that heat will be retained
Passivhaus Will Only Work on a Sunny Site – IT DEPENDS
Passivhaus does optimise the solar gain so as to make the most useful benefit of the heat from the sun. With a small building on a site that gets little sunlight it would be more of a challenge and would really have to be addressed on a specific case by case basis as to whether it was viable or not. As a building gets bigger the parameters change slightly. Elrond uses Architype's schools as an example. Having more people in a building means there's more heat energy being generated and so there's less of a need for using heat from the sun.
Passivhaus is Best Suited to a Domestic Market – MYTH
Elrond wonders whether there might be some confusion in the word Passivhaus (or passive house). One of the reasons the German word is the preferred form is that the literal translation of ‘haus' means building. In other words a Passivhaus can be any type of building.
Elrond is All Over Twitter!
Follow Elrond Burrell on Twitter
Download a transcript of the interview with Elrond Burrell.
UK Passivhaus Awards
Ben shares the exciting news that his production company, Regen Media, is producing video inserts for the UK Passivhaus Awards. This means that very soon you'll be able to find out why the following projects have made it to the shortlist:
Private Housing (sponsored by Ecology Building Society)
• Crossway, Hawkes Architecture Ltd.
• Plummerswood, Gaia Architects
• Totnes Passivhaus, Passivhaus Homes Ltd.
Social Housing (sponsored by Kingspan Insulation Ltd)
• Ditchingham Passivhaus, Parsons & Whittley
• Lancaster Cohousing Project, Eco Arc Architects
• Racecourse Passivhaus Bungalows, Gentoo
Non-domestic (sponsored by Munster Joinery)
• Green Base, Simmonds Mills Architects
• Canolfan Hyddgen, JPW Construction
• Interserve Office, Interserve
ArchiHaus Granted Planning Approval to Build 150 Passivhaus Homes
Ben also has more good news. In episode 24 he interviewed Jonathan Hines about ArchiHaus and Architype‘s proposal to build 150 houses in Kingstone. Well, not long after the episode was published they received the go-ahead!
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