Passivhaus

Part two of my lesson on standards was about Passivhaus.




I've written about Passivhaus before, and the video is based on this lesson: https://minuszeroeco.blogspot.com/2018/01/talking-about-passive-house-lesson-14.html

One advantage with teaching online has been more flexibility in time.

Classroom lessons are fixed at 90 minutes, which is great if you have one bit of content that takes 60 minutes to get through and another related bit that takes 30 minutes.

If you have two bits of 60-minute content, they aren't going to fit in one lesson in class.

They will fit online though. Sorry students! I'll make it up to you with some weeks with less content, and remember you can proceed at your own pace.

Visit Matsumoto Passive House

"International Passive House Open Days" is an annual opportunity to visit Passivhaus and low energy buildings around the world. This year it is held between 9th and 11th November. 

You can find a building near you from Passivhaus international's database here.




If you're in Japan, click here for information from Passive House Japan about buildings that are open.
 

If you're interested in visiting a non-certified Passivhaus in Matsumoto 9th or 10th November, please fill in this form.

'A masterpiece': Norwich council houses win Stirling architecture prize

From the guardian: https://www.theguardian.com/artanddesign/2019/oct/08/stirling-prize-architecture-goldsmith-street-norwich-council-houses

It looks like the windows are slightly tilted from the vertical to increase solar gain. 

47 views of scaffolding

I started off taking pictures of our house as they were building it. Then the scaffolding came to obscure my view.

In this pictues, you can see where they added an airtightness sheet around the upstairs floor, which becomes very difficult to make airtight after the walls have gone in, if your airtight layer is inside the structure.  

Then they started covering the scaffolding with sheets.

This happened all around the house.

Other, greater buildings are blighted with scaffolding. Here is an old building in Athens which I believe Victorian engineers tried very hard to "repair" by straightening all the lines on the structure. It turns out it had been carefully designed with non-straight lines so that it would look right.

I remember visiting Tokyo Disneyland and seeing the centrepiece, Cinderella Castle, surrounded with scaffolding, which had been carefully covered with sheets depicting the castle. I wasn't sure whether this made the building seem more real or more fake.

Here is another view of our house.

Squaring the Circle for Traditional Buildings

It often seems that there is a battle going on between traditional building techniques and high-insulation high-airtightness approaches such as Passive House. Advocates and practitioners of traditional buildings have a strong case that years of experience will show how and when buildings fail, and how they can be built to last. They claim natural materials can absorb and release moisture and are free from dangerous chemicals, so they are better for the building and more healthy for the inhabitants.

But traditional buildings do not use a lot of insulation and are not airtight, so here are two questions: 

How do you keep a traditional Japanese building warm in the winter? 

How does ventilation work in traditional Japanese buildings to ensure good air quality?

I'll get to the answers soon.

High airtightness is sometimes achieved with synthetic membranes, but concrete, plaster on stone or brick, and oriented strand board (OSB) can also play a part in a building's airtight layer. Insulation materials are often polymer-based, especially where a high performance is needed. To get the same insulation as ten centimetres of top-grade foam, you need over 30 centimetres of thatch, over 80 centimetres of wood, a similar thickness of clay mixed with straw, or over two metres of rammed earth. Cellulose fibre insulation is better than all those traditional alternatives, but you would still need over twice the thickness to match foam.

It is interesting to note that a mixture of clay and straw has a similar insulation level to wood, which means that a structure of wooden posts and pillars filled with traditional walls may have an even layer of insulation, avoiding cold spots. But a typical passive house wall has something like ten times higher insulation than a traditionally-built house, so for those walls to perform in the same way, they would need to be ten times thicker.

So how do you keep a traditional Japanese building warm in the winter?
Short answer: You don't. 

When it's cold outside, it gets cold inside. The walls are porous so moisture does not tend to build up. If you want the house to be warm you have to start burning stuff. Today that stuff is usually fossil fuel, either directly, or indirectly with electricity generated from fossil fuels. So you certainly can build with traditional, natural materials, but the inhabitants are only going to be comfortable with a steady flow of un-traditional, unnatural fossil fuels. 

Traditional Japanese heating is with wood burnt in an irori open fire or charcoal smouldering under a kotatsu table heater. Irori are open fireplaces in the middle of the room. Traditional Japanese buildings don't have chimneys, so the smoke finds its way up though the house, killing any bugs on the way, and then out through the ample gaps in the structure.

Traditonal kotatsu burn charcoal in a small irori pit, with a table over the top covered in quilts and blankets. The kotatsu just provides a warm space to sit in rather than warming the whole building, which in some ways is a very efficient use of fuel. This 1820 woodblock by Eisen Keisai also hints at other ways couples kept warm on long winter nights. 

Today people do not want open fires because of the risk of the house burning down, and the increased soot and extra cleaning. Charcoal-burning kotatsu are also a carbon monoxide risk so modern kotatsu use electric heating elements. They are still occasionally fatal because of the heat shock when elderly people get in or out of them. Many people in Japan love their kotatsu, but if they start living in an insulated house, they do not miss them!

Most Japanese homes do not have any central heating system, often relying on kerosene fan heaters, electric carpets, or air conditioners in heating mode. Some houses have underfloor heating, but there are frequent stories of people who use it for one year, see the electricity bill, then never switch it on again. None of these heating techniques is traditional or natural. 

Wood burning stoves may be a more natural method, and cast iron stoves from New England or the west coast of Ireland do look very nice in Japanese houses. The rituals of preparing wood and the cleaning and maintenance may not suit everyone's lifestyle, the smoke may not please the neighbours, and unless the house is in the middle of a forest the source of wood may not be sustainable. An increase in wood-burning stoves has been blamed for poor air quality in London, and since London is not a major producer of wood, you also have to wonder about the carbon footprint of transporting the fuel. 

Wood pellets are much more efficient than burning wood directly, which not only means less wood, but also less ash to clear from the stove and less pollution going through the chimney. The first wood pellets were made from sawdust waste from timber mills. However, as demand increases, and efficiency leads to less waste, trees need to be specially cut and grown for wood pellets. Economically speaking, pellets may have started off being made from a waste product with zero cost, but as and demand increases, the price may go up. The impact is not zero and while burning wood pellets may be better than burning fossil fuels, they do not provide a solution to the world's energy problems, and whatever you are burning, it's still better to burn less. Ideally some of the trees in our dwindling forests will be left as habitat, and end up falling to the ground and emerging in a few millennia as a carbon source for future inhabitants of the planet. But I may be digressing from the topic of traditional buildings. On the other hand, preservation of the environment may be exactly what advocates of traditional building want. 

If I may return to more urgent matters of survival, when a building is airtight, it must be ventilated. The solution used in most passive houses is a mechanical ventilation system with heat recovery. Advocates of traditional building techniques often have a visceral reaction to the idea of mechanical ventilation as it is clearly not a traditional way to ventilate buildings. It uses electricity, so how could that ever be natural?

It is not natural. But what exactly does "natural" mean? When people call for natural materials, what are they asking for? Asbestos occurs naturally in the ground, but I'm guessing you wouldn't want that in your natural building! Polyethylene and polypropylene are completely synthetic and harmless to taste and touch.

If you really want nature, you should go and live outside. Buildings are not natural. Rather than asking a binary question whether specific materials or techniques are natural or not, we need to look at health, comfort and energy use, over the lifetime of the building and make the least bad decisions to get the best health and most comfort for the least energy use and lowest environmental impact.

So how do you ventilate a traditional building? 

I'm temped to say that you don't, but of course traditional buildings are ventilated—just not in a very systematic way. If there is a fire in the building then it is also working as a ventilation system by sending hot air up and out of the building while drawing air in through those thoughtfully provided gaps and porous surfaces. When there is no fire, air must find its way in and out through open windows and doors. The amount of natural ventilation then depends greatly on the outside temperature, wind speed and direction. So if a house is designed to always have fresh air, it will usually have too much ventilation. This will lead to uncomfortable drafts and a steady loss of heat. If it is designed to minimise drafts and heat loss, then there won't be enough ventilation for good air quality and control of moisture. 

The traditional builders will usually choose too much ventilation because that is the only way to guarantee there will be no moisture build up. So the house should not be airtight. If the builders do make the house airtight, they need to put in mechanical ventilation. They could ensure ventilation by providing a fire for you to keep stoked, but if they do that, they need to make sure there is no risk of carbon monoxide poisoning, which again will probably mean avoiding airtightness.

Mechanical ventilation does use electricity, but it provides fresh air, takes excess humidity out of the house, and keeps you warm very cheaply by recovering the heat from the expelled air. Heat recovery ventilation will only work if a building is airtight, making sure that air is coming in and out through the heat exchanger. Also, the insulation will only work effectively and without risk of condensation within the walls if the building is airtight. And if the building is airtight, active ventilation is needed because natural ventilation is unreliable.

Without active ventilation and airtightness, extra insulation is a risk as air leaking out of the house in winter drops in temperature and hits the dew point, producing condensation.

So the traditional builders are going to hand you a choice: 

Pay a lot for heating, or be cold. 

On the other hand, a traditional structure can be wrapped in an airtight insulating layer, and include a ventilation system. This will protect the structure and make it last longer, and will make it nice for the inhabitants, who probably do not want to live a traditional life that is not as comfortable and not as long.

In the fight for survival of traditional building, insulation, airtightness and active ventilation are not the enemy. They may be the saviour! 

References:

Pollutionwatch: wood burning worsening UK air quality, Guardian (2018, February 1st)

Steven Goodhew and Richard Griffiths (2004) Sustainable earth walls to meet the building

regulations

Emissions from Wood:

Roger Drouin (2015) Wood Pellets: Green Energy or New Source of CO2 Emissions?

Talking about Passive House. Lesson 14

This low energy building course is really just propaganda in disguise. The whole course has been framing the question, and the answer is Passivhaus. I also like to talk about differences in building culture, and mention my own experience trying to build a low energy house in Japan. I can, with honesty and some innocence, present my discovery Passivhaus as an epiphany on my road to building a house.

As usual term starts running out with too many lessons left over. In week 13 of 15 I had to get them into groups for their final presentations, and then give them some guidelines of what to do, and what not to do, when designing and delivering their own presentations. I could spend a whole lesson talking about preparing presentations. In this class I probably should, focusing on presentation construction as a piece of architecture.

They had put their own presentation ideas into a forum on the online part of the course, and then chosen their top three choices in an online quiz, so I had most of the data needed to make the groups, but of course a few students had not actually added their top choices for a presentation topic, a few others missed the lesson, and as usual a small number of the topics were very popular and they did not fit neatly into seven topics that were the first choices of exactly four students. In the end over half the lesson was taken up discussing their presentations, and I could only get through half of my beautifully prepared full lesson, with its narrative from building cultural differences between the isles on the East and the West of the Eurasian continent, to my own journey into house building, and discovery and application of the Passivhaus standard.

Energy balance for a Passivhaus

Descriptions of standards can be dry, and there's a maximum of ten minutes I can talk to any class in English before they lose attention, so tasks are needed. I like setting them problems to solve, and also want them to practice real-world calculations where possible.

First I had them brainstorm heat gains and losses in a house. They got most of these, but needed a bit of a hint to remember ventilation.

The next task was to get from the definition of Passivhaus in English to the numerical heating load. This is a fairly straightforward calculation from the floor area per person, the volume of air needed per person, the maximum temperature air can be heated to before it burns, and the heat capacity of air.

Next, I wanted them to work out what U value they would need for the walls of a Passivhaus in Matsumoto. This involves several steps, and I made the mistake of giving them too many of the steps to work out in one go. I don't think the calculation itself is particularly difficult, but I guess I'll find out because I've set that for their homework!

The first step, to make the calculation easier, is to assume that the heating load is equal to the loss of heat through the walls. Remembering the energy balance of a building, you can get to this by assuming that solar gains through windows roughly equal heat losses through windows and internal heat gains roughly equal heat losses through roof, ground, and ventilation.

The next step is to work out the wall area of the house. I gave them the volume, told them it was two-story, and assumed they'd just be able to work out the wall area from that. Half of them are studying
architecture so I think I can be forgiven for my assumption. It turned out to be wrong though. Perhaps there were too many assumptions for them to make: the height of the walls, the squareness of the building footprint, the use of square root to get from an area to one of it's sides, the number of sides on the square... Perhaps they were worried about other things: did they need to subtract the windows and doors? What shape was the roof going to be? Perhaps they were distracted from this question because they were expecting thermodynamics rather than geometry. Anyway, I think have learnt my lesson, and will chop the problem into bite-size chunks for them next time.

I should probably have realised this sooner, and modified the task, but while preparing the lesson I had been more impressed by the result of the calculation: 0.162 W/m2K. This number may not mean a lot to you, but as I scrolled down the slides to the introduction to my own house, I noticed that in fact the U value of my walls is 0.162 W/m2K. Perhaps just a coincidence, but it does show you
the power of rough estimates!

Unfortunately I didn't have time to share this bit of synchronicity with my students as the lesson had somewhat dissolved into scratching heads, spurious scribbling and many over-precise, under-accurate sums. The bell was going to go before I got to the happy ending that is Matsumoto Passive House.

Passive House in Canada

While Passive House remains a mystery to most, and a misnomer to many in the building trade, here is some news of steps in Canada. And why wouldn't you?

Tree hugger reports here on a Canadian charity building social housing to Passive House standard.

CBC News​ reports here ​h​ow Canadians are constructing North America's biggest green buildings​.​ And perhaps the greenest big buildings too.

​And here's an article from High Performance Building Supply about why smart cities need passive house buildings, which is not really about Canada​, but they do mention a project in Toronto.

Passive House News

​There's another Passive House blog​ here:​
http://www.notey.com/blogs/passive-house

​And news of an affordable Passivhaus ​development in the UK here: https://inhabitat.com/groundbreaking-passivhaus-development-features-ultra-green-homes-that-you-can-actually-afford/ ​

And a great story here about Fridtjof Nanse, possible creator of the first Passivehouse, which floated, and went to both the Arctic and Antarctic over a hundred years ago. While the mess on Scott's ship was underneath the ponies they were taking to Antarctica, Amundsen was staying in comfort on the Fram, with high insulation and airtightness. It also had a windmill generating electricity for the lights inside.
https://www.treehugger.com/green-architecture/happy-birthday-fridtjof-nansen-pioneer-passive-house.html

What is Passive House? Probably not what you think

Here's my short answer:

Passive House is an excel spreadsheet.

There are loads of other definitions and mis-definitions out there. The term is frequently used loosely for any superinsulated building, and often mistakenly for passive solar buildings.

Passive House is not a way of using natural energy. It's true that Passive Houses will take natural energy into consideration, for example considering heat from the sun, but just pointing big windows south will not make a Passive House.

A Passive House is not a building without a heating system. Passive houses invariably have heating systems, but the amount of heating needed is very small. In fact the best definition of a Passive House is one where all heating and cooling needs can be met by heating or cooling the air coming in through the ventilation system.

There are many other things that Passive House is not, and in his excellent blog, Elrond Burrell gives a longer list.

My definition may put you off. I think excel spreadsheets put a lot of people off, including many architects. This is one barrier to the standard's popularity. If Passive House was a simple product you could buy to stick on your house, then lots of people would no doubt buy it. If it was a simple step you could add to the design process, designers would probably take it.

Passive house will help you to reduce your energy bill, and probably help reduce your environmental footprint. But if you want to save the planet, you need to do some sums. Laying a bit of turf on top will not make it green.

And now that we are firmly in the computer age, we can get a spreadsheet to do the sums for us. As with all good spreadsheets, you put various bits of information into the Passive House software, and you get out a simple and accurate picture of what is happening. In this case all the information going in relates to the building size, shape, location, materials and systems.

It is not difficult to find most of the information that you need to put in. But you do need to find it. You need to know the dimensions of the walls and the thicknesses and relative proportions of the various materials going into them.  The spreadsheet needs to know the insulation performance of each material, but most of them are already in there. You can also choose the hot water and ventilation systems, and their efficiencies. You need to know the size of the windows, and also their U values, and the psi values for the thermal bridges. The supplier of the windows should be able to supply these, and if not they may not be the right windows for a low-energy house. You need to know which direction each wall is pointing in. You need to know your local climate, or at least choose your location so that it finds your local climate.

The only piece of information you need to get up from your desk to find is the results of an airtightness test. If you're building an airtight house, then you probably should run an airtightness test anyway, and if you're building a house that is not airtight, start thinking about it.

​
W​hen​ all the information is in there, you know whether you have met the standard or not. More specifically it will tell you how much energy you need for heating over the year, how much total energy you need, and how often the house will go over 25 degrees centigrade. Even if you are not interested in meeting the standard, the software will give you a very accurate estimate of how much energy you are going to need to run your house.

Could Passivhaus be cheaper?

Passivhaus, Herefordshire, 2016 

I don't just mean cheaper than it is now, but could Passive House be cheaper than a regular building. And I don't mean cheaper in the long term, but cheaper to build.

Low energy buildings, Pennyland, 1979

When we were building, we found in most cases the extra demands of passive house provided extra opportunities for builders and contractors to charge us more money. I think this was partly our fault for not finding people who were interested in changing the way they work, so rather than seeing our house as an opportunity to learn how to build better houses in the future, they saw it as a diversion from their usual practice. Where we did work with people who were used to working to rigorous energy specifications, I got a strong sense that they were able to charge more because they thought nobody else could do what they were doing, or because they were aiming for rich customers who just judged value by the price tag.

The theory behind Passivhaus is that increasing insulation means massively reducing the heating system, so extra costs insulating are balanced by lower costs installing a heating system. Since Passivhaus also required a ventilation system, and rather than removing the heating system it just scales it down, this seems like a challenge. The cost of extra insulation, structural changes to accommodate and support the insulation, airtightness barriers, increased window specs and ventilation system all need to add up to less than a fraction of the heating system. 

State of the art building, Lavenham Wool Hall, UK, 1464 

According to this report from the Passive House Trust, sponsored be AECOM, passive houses cost 3-8% more in Germany, where many are built to the standard. In the UK they typically cost 15-20% extra, although the extra costs are less for large projects, terraces, north-south oriented buildings, and projects where the design can change after tender.

But some people are saying that Passivhaus can, and will cost no more, for example Passivehouse Plus in Ireland give the builder's view on why passive house doesn't cost extra.

And Nick Grant says here that if you think Passivahus will cost more, it will!

Low cost, zero maintenance house, Japan
Twentieth century

And there is a best practices document developed in collaboration with EEBA, and Proud Green Building that asks this question: Can you build a high performance home without additional cost?

And they answer: YES!

Bird Table, Huddersfield,
Turn of millenium

You can Download your copy today! Which will tell you about putting a value on high performance, how to shift costs where they matter most, opportunities in green remodeling, builders' perspectives on achieving high performance, high performance home ratings and certifications, case studies and financial considerations.

Odds and ends

In 1962 Bob Dylan was worried that the world would be engulfed in nuclear holocaust and he would not have time to write all the songs he had ideas for. So he put them together into one song: A hard rain's gonna fall. Fifty four years later he won the Nobel prize for literature, and Patti Smith sang that song in Stockholm. 

I'm not too worried about nuclear holocaust, and would be even more speechless than Dylan to receive a Nobel Prize, but I do have over 700 emails in my drafts box, of which over 100 are nascent blog posts. So here are some of the bits, all thrown into one mass of mildly interesting information.

Design

Interesting piece here from January 2008 by Dr Andrew J Marsh saying the biggest energy savings can be made in the first couple of weeks of the design process. If you read nothing else about low energy building, read this!
http://naturalfrequency.com/articles/efficientbuildings

Should cups be made out of plastic or paper, or neither? That old chestnut!
http://carbon-clear.com/files/Reuseable_vs_Disposable_Cups_2012.pdf

Buildings

A Passive House building in Sweden using thermal mass

http://www.rehva.eu/publications-and-resources/hvac-journal/2012/012012/energy-efficient-passive-house-using-thermal-mass-to-achieve-high-thermal-comfort/

A passive house retrofit of a block of flats in the UK
http://europhit.eu/cs14-wilmcote-multifamily-house-portsmouth

A passive house in Ireland
http://passivebuild.blogspot.jp/2012/05/getting-passive-house-passivhaus.html

A Japanese company providing dome houses
https://www.bess.jp/products/

A guy who built a house in about six weeks.

http://themetapicture.com/this-guy-started-with-nothing-after-6-weeks-he-built-something-awesome/

A very cool-looking shed
http://www.mnn.com/your-home/remodeling-design/blogs/tetra-shed-for-all-of-your-home-office-and-adult-time-out-needs

Increasingly random but not necessarily any more interesting

Solar powered airships
http://www.solarship.com/

How to market green building features to home buyers

http://www.proudgreenhome.com/blog/12769/How-to-market-green-building-features-to-home-buyers

A nice design for a desk light

http://www.earthtechling.com/2011/05/led-desk-lamp-made-from-recycled-e-waste/

A recipe for white concrete

http://www.concreteconstruction.net/concrete-articles/some-notes-on-white-concrete-mix-design.aspx 

Primary energy factors - how much energy was used to get the energy to your house

http://www.slideshare.net/sustenergy/webinar-primary-energy-factors-for-electricity-in-buildings

Pros and cons of induction heating
http://theinductionsite.com/proandcon.shtml

A paper on Phase Change materials for thermal energy storage by Alvaro de Graciaa, Luisa F. Cabezab (Energy and Buildings, 103, 15 September, 2015)
http://www.sciencedirect.com/science/article/pii/S0378778815004338

And if you're still thinking about building an igloo, but wondering what the U value will be, here is a forumla for the thermal conductivity of snow depending on its density ρ (in g/cm³):

k_eff = 0.138 - 1.01ρ + 3.233ρ² {0.156 ≤ ρ ≤ 0.6}

This puts compressed snow at around 0.2 W/mK, which is slightly worse than wood. 

https://www.researchgate.net/publication/252860601_The_thermal_conductivity_of_snow

UK Passivhaus case studies in Architects Data File

Architects Data file "Building Envelope" contains case studies of five recently completed UK Passivhaus projects. This includes The biggest UK Passivhaus building at Leicester University; Wilkinson Primary School in Bilston, West Midlands; a house at Landsdowne Drive, East London; Cre8 Barn at Stirley Community Farm in Honley, West Yorkshire and a terrace at Burnham Overy Staithe, Norfolk.

Passive House open days in Japan November 11th to 13th

Look inside passive houses around Japan, and around the world, between November 11th and 13th. They will be warm inside, but probably won't have turned the heating on yet!

国際パッシブハウス・オープンデー2016 • PASSIVE HOUSE JAPAN

You can search internationally here: passivhausprojekte.de.

Certified Passivhaus Consultant

Passive House Institute sent me a letter saying I passed the exam, and can now call myself a Certified Passive House Consultant. 

Passive House (or Passivhaus) is a standard that ensures buildings provide a comfortable environment, all year, with a very low energy cost. The Passivhaus Institute is based in Darmstadt, Germany. 

There are over a thousand certified Passivhaus consultants and designers in Germany, hundreds in the UK, over a hundred in South Korea, and three of us in Japan.

This qualification means:

• I can advise house builders and architects on Passive House building, and low-energy building in general. 
• I can work with builders and architects to calculate the energy performance of a building.
• I can determine whether a building meets the standard and help apply for Passive House certification.
• I can calculate the impact of changes in construction details, and estimate the longer-term energy costs. 
• I should be writing here more regularly!

Here's some free advice: if you are going to make a low-energy building, that should be one of the first decisions you make. Adding low-energy features is a bit like starting to make a boat, and only deciding later that you're going to be using it in water.

Note:

Above it says Passivhaus Berater. I think this is the German word for "consultant" although I am always happy to berate people who build to waste energy!

Lesson 11, Part III: Passivhaus

Passivhaus is a voluntary standard based on super insulation, high levels of airtightness, a heat exchange ventilation system. The windows must be of good quality, and mostly on the south of the building to consider solar gain. The standard is largely based on comfort, so the whole house is warm, there are no drafts, no cold surfaces, no overheating, and the air is always fresh. 

The standard came out of collaboration between German Wolfgang Feist and Swedish Bo Adamson in 1988, leading to the Passivhaus being built in Darmstadt, Germany in 1991. The Passivhaus institute was founded in 1996 and between 1998 and 2001 the CEPHEUS project--Cost Effective Passive Houses as European Standard--monitored several building from the top of Finland to the bottom of Spain to ensure their calculations of building performance were working. And they are working, which puts the Passivhaus standard into stark contrast with other building standards that typically only deliver half of the promised energy savings.  

By 2010 there were 15,000 Passivhaus buildings in Europe, and the first certified Passivhaus in Japan was built in 2011, the same year as my house, which meets the standard, but is not certified.

The big idea behind Passivhaus is that if you increase insulation, at some point a central heating system becomes unnecessary, and heat can be delivered by small scale heaters or by adding a bit of heat to the ventilation system. This reduces the building cost, especially in Europe where central heating is standard. In fact you can calculate how much heat can comfortably be delivered through the ventilation system, taking into consideration a volume of 30 cubic metres of air per person per hour, floor space of 30 square metres, a maximum air temperature of 51°C to avoid burning smells in the air, or on your skin or hair. As everyone knows, the heat capacity of air is 0.33 Watt hours per cubic metre kelvin, giving us about 10 Watts of heating per square metre of floor space. 

This is a fixed standard, unlike many other standards that keep changing in attempts to become more stringent and lower energy. Passivhaus is based on comfort and the human physiology that we inherited from the savanna and have taken to the four corners of the world, which we now know to be round. The extent that the standard changes is that the modelling and simulation become more accurate, and applicable to more climates and situations. The heating load is not arbitrary, but at some kind of optimum where any more will require a heating system and increase costs, and any less will probably put the extra insulation costs beyond the potential gains from reduced heating bills.

15 quid a year Passive House in Wirral wins award

On the BBC here.

And more details from architects John McCall here.

It's similar to our house in many ways:

• Roof integrated solar panels, although I think we about have twice as many
• Atmospheric heat pump, so electricity is the only energy source
• Underfloor heating
• The same foundation structure
• Similar annual heating load where we are and the Wirral 

The construction is completely different. Ours is wood but theirs is concrete block. It looks to have better insulation and better windows, and is more airtight.

They say they use about six times less total energy than the Passive house standard. I'm not sure how they calculate this. We use around 15% less than the standard. From the copy of their electricity bill, it looks like their house uses a little over half the electricity of ours. They don't give the area of the house but judging by the total cost and cost per square metre it looks to be 180 square metres. When the energy usage is worked out per floor area, I would expect them to be 40% of the standard. I calculated our primary energy use to be 2.7 times the electricity we used, and I think the UK has a similar energy profile to Japan, so every unit of electricity consumed in the home has taken 2.7 units of primary energy to produce and get it there. Some of their electricity is coming from solar panels, so they may choose a different value, and perhaps I should too! If they take the electricity as primary energy they get to 6 times less than the passive house requirement.

Whether it's 40% of the Passive house requirement, or six times less, it's still very impressive. 

Affordable housing project wins Passive House Institute Awards

Another advantage of these low energy buildings is a reduction in fuel poverty. I was recently corrected by Green Party Energy Spokesperson Andrew Cooper that it's not fuel poverty, it's just poverty. Good, old fashioned poverty. If people don't have to pay expensive fuel bills, they will be less poor.

Usually the people renting houses are paying fuel bills, while the house owners are responsible for upkeep and maintenance of the building, such as increasing the levels of insulation, or the efficiency of the heating equipment. If it's your own house, and your own fuel bills, there's a strong incentive to put in better insulation. If it's not, then there is less incentive. It's not always true, but generally speaking people who are poor do not own homes.

Proud Green Home reported recently on affordable housing in the US that recently received an award.

Exeter council in the UK has also built over forty council homes to Passive House standards. It has been found that tenants in low energy houses are less likely to miss rent. In a conventional high-energy house, tenants have to pay rent and heating bills. If money gets tight, they have to choose which one they can pay. Don't pay rent and you may be evicted. Don't pay heating and you may get sick and end up in hospital. Neither is a good choice. If the landlord is the council, then obviously tenants not paying rent is bad news, but tenants ending up in hospital is also bad news. Passive houses reduce the heating bills to a trivial amount, so both tenants and councils are less likely to get to that difficult situation.

The extra costs involved in building Passive Houses, if there are any, are much less than these long-term social costs. Since Passive Houses generally last better and need less maintenance, there are long term savings there too. There are several critics of the Thatcherite Right to Buy, but even if the councils intend to sell off their houses, and will have to do so at a discount of the market value, this may help them since Passive Houses have higher resale value. 

Passive House Days - November 13th, 14th and 15th

Our house will be open to visitors for the international 2015 Passive House Days.

I signed up to this before, but this time, we're listed on the Japan Passive House site, so some people are coming.  

Find a passive house to visit near you in the international Passive House database. 

Visits to our house by reservation only. 

The timelessness of the Passive House standard

I was lucky enough to participate for a few days of a training course for Passive house designers and consultants led by Nick Grant in Herefordshire. I learnt many things, as well as reinforcing the knowledge I had, and brushing the rust off some maths skills. A couple of things really struck me. 

One was that the Passivhaus standard is timeless and objective. Many standards are somewhat arbitrary, and most standards are revised and changed from time to time. Passivhaus is based mostly on objective criteria that will not change, and most of those criteria are based on human comfort. Passivhaus guarantees that room temperature and humidity will stay around what we are physiologically suited to. The standard should guarantee good air quality, and prevent moulds and bacteria from building up.

The energy part of the standard is set to a low enough energy demand that the house can be kept at a comfortable temperature just by adding heat to the incoming air. This doesn't mean that the house has to be heated by the incoming air, but it does mean the heating demand will be very small. So whatever the heat source is, it's not going to use very much energy, and the house would not be too uncomfortable if it stopped working.

Although the standard is fixed, Passivhaus is not standing still. Where the changes and innovations are being made is in how to better estimate the performance of a building from its plans. This has been going on for at least thirty years and means that the Passivhaus estimation of a building's performance is within a few percent. Other energy estimations are often out by a factor of two.

In implementation there are always new technologies and techniques that can meet the standard at lower cost, and there are still locations and types of building that have yet to be made to the Passivhaus standard.

Passivhaus is neutral on a lot of things. In the goal to reduce energy use, most significant is perhaps embodied carbon. The Passivhaus standard is just looking at the building in its lifetime. Other standards are needed to reduce the carbon footprint while it is being made, and of course many people involved in Passivhaus are also looking for building materials and techniques that will reduce carbon from cradle to grave. Such buildings should still be trying for the Passivhaus standard so that energy use during the lifetime is kept low.

Also the standard is neutral on renewable energy. You can use wood pellets for a boiler, or burn fossil fuels. Whatever heat source you use, you will need less of it. If you're aiming for zero-carbon or plus-energy, starting with a Passivhaus makes it much easier when you stick some solar panels on the roof.

Great Passive House blog!

Check out Elrond Burrel's blog: Passivhaus in Plain English

Elrond is a New-Zealand born, UK-based architect, who builds some very nice passive houses. 

I especially liked Elrond's "Ten things I hate about passivhaus" which includes gems such as: not being able to just check boxes to deliver sustainable buildings, not being able to hide poor details, and arguing with building services engineers. Read it here.