Why are Japan's building energy standards low and lax compared to Northern Europe?

Just looking back over some homework. After a lesson last year on building standards, including comparisons between standards in Japan and Europe, I asked my students this question: Why do you think Japan's building energy standards are low and lax compared to Northern Europe?


(The letters afterwards correspond to the nationality of students. See below for a key.)

Some of them commented on the climate, for example:

The Japanese Archipelago extends from north to south, and Japanese climate has more variety than Northern Europe. Japan region has its shape long from the North to the South, (not like Denmark, UK), It has a really cold winter like in Hokkaido, but most of the population is located in the warmer place like Tokyo, Osaka. (K, J1, V)
Northern Europe has a higher latitude than Japan. That means the winter is colder so for the very survival of the people they need to be concerned about building houses which will lose less heat. There comes the idea of low energy building. The example is same as Australia and Sweden when we compare the death rate from cold. (B)
Because, the climate change of Japan is more irregular than Northern Europe. When every season changes, temperature of Japan is changeable. (K)
There's a lot of earthquakes and typhoons in Japan. Rather than focusing on energy saving, Japanese focus more on preventing their house from getting blown away by typhoon or getting crushed by earthquake. (M)
There's a rumour in Malaysia that Japanese tend to build cheaper and simple house, so that when natural disaster comes, they won't have much loss even when their house is crushed, and they could have their house rebuilt in a shorter period. (fast, easy, and cheap) (M)

Old building ways focus on summer (even though low energy building would help them in summer too) (P)

Typical 1960's Japanese house (!)

They also commented about building industry:
The Japanese tend to treasure their own traditional buildings and they are not flexible to accept new standards. (J2)

Often demolishing old houses and building new ones instead (not enough time for payback of a more expensive to build low-energy house) (P)

And they made comments about Japanese culture:

I think that there is cultural differences. Japanese have table known as kotatsu and they love it, They usually prepare to stay in kotatsu rather than keeping the whole house warm. Therefore they aren't paying any attention towards the overall warmth of the building. (M)
Culture of shouganai [there's nothing we can do about it] and 'living with nature' (P)
They are patient to changes of season because Japanese island has basically the four seasons and it means they don't need to employ efficient standards because of their acquired patience. (J2)

They also mentioned population and technology.
Northern European specially Scandinavian countries have way less population than Japan. When you have more people, the matters you need to worry about increase by number. Also it takes time to solve them. I think that is another reason of having a less standard. (B)
Japan try to reduce a consumption of primary energy by installing housing equipment. (J3)

(B: Bangladesh; J: Japan; K: South Korea; P: Poland; V: Vietnam)

This year I just asked a multiple choice question. Fifteen students gave answers. The number of responses is in brackets.

"In your opinion, what is the biggest reason for Japan's lax low-energy building standards? (There is no correct answer. I'm just interested what you think!)"

Scandinavian countries have a similar climate, but Japan is an archipelago going from very hot places to cold places. (4)
Creating low-energy electrical appliances and products is more important for Japan's economy. (3)
Northern European buildings are built for the cold winters, but Japanese buildings are built for the hot summers. (3)
Japanese builders like traditional buildings, and they do not want to change. (1)
All of these reasons are equally important. (1)
Some other reason. (Please tell me next lesson!) (1)
Because of earthquakes and other natural disasters, Japanese people do not want to spend a lot on buildings. (0)
I don't know. (2)

Some of these answers are interrelated, so the question doesn't really lend itself to the multiple choice format. Looking back on it, the most commonly selected answer doesn't clearly answer the question. I guess the implication is that Japan's varied climate makes it difficult to set single standards. I'll have to try again next year! Perhaps they should be able to give ratings to several different reasons.

Is that factoid true?

I came across this comment as I was preparing a lesson on cooling: 

"US uses more electricity on cooling than Africa does on everything."

As often happens, the factoid gets divorced from its source, and just stays there, overly confident in its truth. But is it true? And how do I find out? As Churchill said, "A lie gets halfway around the world before the truth has a chance to get its pants on." He said this long before the internet was invented and the term "social media" was coined, but some things do not change. Or perhaps, and somewhat more scarily the world today is similar to the 1920s, and we are heading towards a repeat of the 1930s. 

According to this article in Mother Jones (July, 2015), the US spends 11 billion dollars on air conditioning, and in the process emits 100 million tons of CO2.

According to the Carbon Dioxide Information Analysis Centre (2008) Africa's carbon emissions 311 metric tonnes. But that's all emissions, not just electricity. 

Wait a minute, was the Mother Jones statistic metric tonnes, long tons or short tons? The latter are 10% more or less the former. Also, the factoid said "electricity" and Africa presumably has other carbon emissions than electricity. So it may be true.

According to accountants KPMG, Africa's electric generation capacity was 680 billion kWh in 2012. The US average 12 cents per kWh. So, I can work back from the 11 billion dollars to get 90 billion kWh. Now we're even further out and Africa is using over seven times more energy for everything than the US does for cooling.

US Energy Information Administration's website gives around 2 pounds CO2 per kWh of electricity. If a short (US) ton is 2000 pounds, that's 1000 kWh per ton of CO2. So 100 billion kWh on air conditioning in the US.

Interestingly, if the above emission figures are correct, Africa's energy generation is at least twice as clean as the US. This is possible if Africa has a higher proportion of hydroelectricity, and a lot of the plant is newer and more efficient. 

Or perhaps this factoid was just talking about domestic air conditioning, rather than commercial or industrial.

This is neither US nor Africa, but may have some air conditioning

Or maybe the article was just wrong. This US Department of Energy site claims $29 billion were spent by homeowners on air conditioning, emitting 117 million metric tonnes of CO2. 

But where did I actually get that factoid from in the first place? It probably came from this July 2012 article on Yale Environment 360 by Stan Cox. It was probably true at some point, since the US has a long history of air conditioning, and Africa is still rapidly developing as an electricity consumer. 

Oh for that world of long ago, when all good things were true...

I thought I was wrong once, but I was mistaken

For the past couple of years I've been looking at the windows at work and thinking how thick they are.

Not so much as a question, but more as an exclamation. Last year I wanted to estimate their thermal performance as an activity for a lesson on windows, so I measured the thickness of the glass, and it came to 8 mm. This was the thickness for two panes, plus glass, which leaves precious little air between, and it is the air between that is important since it is around fifty times better at insulation than the glass is. I guessed the 8 mm was made up of 2 mm panes with a 4 mm air gap, although usually glass is 3 mm, which would leave a 2 mm air gap. 

A year later, I was still in disbelief at either a 2 mm air gap, or 2 mm panes of glass, and I was still wondering how I could actually measure the thickness of panes and air gap when I remembered that glass was transparent, and its surfaces reflect light. I have no idea why I didn't think of that before. Using a spoon on a sunny day, I got these pictures, and it looks like the ratio of air thickness to glass thickness is around two to one.

I used a smartphone to take these pictures since looking directly into the sun can be very dangerous, even it if is reflected by a spoon and a window. 

Having found no evidence of 2 mm glass window panes, I decided to measure the thickness again, subtracting the inside and outside relief of glass to frame from the width of the frame. It was 11 or 12 mm. I measured this several times to check there was no mistake, but it was definitely not 8 mm, as I had believed for the past year. The windows are likely the industry minimum standard of 3-6-3. Three mm glass panes with a 6 mm air gap.

I have no idea why I didn't take another measurement a year ago when I came up with the highly improbable thickness of 8 mm. It is a useful reminder that everyone is wrong sometimes, and that doesn't stop us from being sure of our beliefs.

Using these values, we calculated the U value of the glass to be around 2.3 W/m²K. We also estimated the U value of the frames, which are non-thermally improved aluminium, and derive most of their benefit from the surface resistance. This means around 5.6 W/m²K.

The relative area of glazing to frame was 77:23, so the windows as a whole had a U value around 3 W/m²K. Not terribly good, and illegal in many countries, but not quite as bad as I estimated last year. 

Cloud-tracking cameras to tackle dips in solar power output

This is a nice bit of technology. Compared to conventional power generators, solar panels present something of a challenge. It's fine on a clear sunny day, when you get a predictable output, peaking sometime around noon. If it's overcast you get a predictably low output. The problem is on partially cloudy days when the output will fluctuate each time the sun goes behind a cloud. 

So according to this article in The Guardian they have installed camera technology on a solar installation in Western Australia that will give a fifteen minute prediction of clouds to come, which can help switching on back up systems when needed, and can give a better idea of prices.

Lesson 5: How do you feel?

When I started planning this lesson, it was going to be about cooling, since it's starting to get a bit cold and would be nice to talk about the summer. And I wanted a break from calculation-heavy thermodynamics. Of course, I have made it clear that if we are going to save the planet, we have to do some mathematics.

Also I wanted to try to integrate the class a bit. After initial success in my language policy of dividing the class into people who want to speak English and people who want to speak Japanese, it was rapidly turning into segregation on national lines, where all the Japanese students were on one side of the class and all the non-Japanese on the other. I thought it would be good to get mixed groups of tropical and temperate-dwellers, along with my permanent goal of getting my students to talk to as many other students as possible. While I try to promote classroom democracy and learner autonomy, as the teacher it is in my power to go around the class and tell students where to sit, so I did!

The title of the lesson was originally cooling, then cooling and heating, but in fact the best title is my first question to the class: How do you feel? I wanted them to choose an answer between Hot and Cold, which I then converted to a number between +3 and -3. 

Hot -3

Warm -2

A bit warm -1

Neutral 0

A bit cool 1

Cool 2

Cold 3

I took the average, which is called the predicted mean vote, after research by Fanger in the 1970s. The average was 0.9. There is a relationship between the predicted mean vote, and the predicted percentage dissatisfied, so if the mean is zero, you can expect fewer than 5% to feel uncomfortable. There will always be some people who are dissatisfied—an important lesson for life! If the mean vote is between plus and minus 0.5 you can expect 90% to be satisfied. At plus or minus one, 28% will be dissatisfied, so our number looks like a quarter of the class were feeling uncomfortable. This is not a terribly good figure, since uncomfortable students are less likely to learn anything, but my immediate goal is in educating about thermodynamic. Solving the effects of thermodynamics on education will take a little longer!

The next question, inevitably, was why they felt hot or cold. I wanted them to brainstorm for a list, and I also gave them the big question: heating makes us feel hotter; true or false?

They wrote down all of my prepared answers, like air temperature and clothing, and a few others such as being with people who you like, eating, and drinking hot drinks. They also mentioned snow, which actually I think makes you feel warmer, but I need to do some more research on this for a definitive answer.

There were four groups and I got one of them to explain each of radiation, humidity, air movement and activity.  

The group talking about activity had some theory about blood going through the veins more quickly and creating more friction. I asked politely whether it might not be because we are burning sugar when we exercise and if we exercise more we burn more sugar and create more heat. I even drew the chemical formula on the board: 

Sugar + O₂ -> H₂O + CO₂

And further elaborated sugar to C_xH_yO_z, which impressed upon them my chemistry inability. 

The group discussing air movement correctly observed that moving air will take away more heat from our bodies, and the humidity group noted that we lose heat when moisture evaporates from our skin, and more humidity means less evaporation so we lose less heat. I later told them that 10% extra humidity feels about 1 degree celsius warmer. 

The radiation group was talking about radiation making the air around us warmer, which I also had to question. They did appreciate that heat was being radiated from many things around us. I later showed them the relation between air temperatures, surrounding surface temperatures and the temperature we feel. For example if the air temperature and surface temperatures are both 20 degrees, it will feel as hot as the surface temperatures being 17 degrees and the air temperature 23 degrees. 

I also told them about radial symmetry, and how it will feel uncomfortable if there are different temperatures between head and feet, or from different directions. 

We all began to agree that heating does not make us hotter. We are warm-blooded, and we make ourselves hot, in fact putting out something like 100 watts. In fact, heating makes us lose less heat.  

So what about the summer? 

Does insulation make buildings hotter in the summer? 

Does insulation work the same for keeping buildings cool in hot climates?

Are there some buildings that don't need insulation?

To which my answers are no, no and probably not. 

Insulation does not make anything hotter, it just stops heat moving so fast. If it's hotter outside, then insulation will stop heat getting into a building. There are two important differences between the way insulation works for hot and cold climates.

First, many things in buildings produce heat, including people, electrical appliances, cooking and hot water. In a cold climate, these are all helping to keep the house warm. In a hot climate, these are extra things we must fight to keel the house cool.

Second, cold places are a lot colder than hot places are hot. For example Yakutsk in Russia has average winter temperatures of minus 34. Around that temperature it doesn't make much difference whether you are talking about fahrenheit or centigrade. Meanwhile the average summer temperature in Kuwait is 38 degrees C. These look strangely symmetrical around the freezing point of water. Or perhaps not so strange considering our environment is as dependent upon the temperature stabilising effect of water phase change as a glass of gin and tonic. However, when we remember that humans favour temperatures between twenty and twenty five degrees, we can see that the temperature difference we are working against is four times more in the cold climate. 

I gave the example of Australia, considered to be a hot country, where more people die of cold weather than hot weather. Additionally, more people die of cold in Australia than they do in Sweden, which is most definitely a cold country. Why is this? Insulation of course. 

There may be somewhere in the world where insulation is unnecessary, but in cold climates it will help to keep you warm, in hot climates it will help to keep you cool, and in many temperate climates it will do both at different times of year. 

If you don't like reading this blog, you probably won't want to listen to this podcast

Or maybe you will like it. It depends what you don't like about the blog.

If you think there is a shortage of practical commentary on actual projects here, then you will like House Planning Podcast.

If there isn't enough of a focus here on the UK, then there certainly is on this podcast. And if you　don't really have time to read but are looking for something to listen to, then this podcast really is for you.

I particularly enjoyed This one about the balance between renewables and a fabric-first approach with Alex Baines.

And episode 126 which looked at whether to demolish or rebuild, and talked about the carbon cycle. 

Teaching environment

I'm not counting but this is my 400th blog post. If I were counting, I'd write something special, but since I'm not, this is just a regular day in the life of a teacher trying to do something about the environment. 

The low energy building course has started up again, with more students this year, and several architects, engineers and materials scientists. In the first lesson I asked what language they wanted me to speak, and what language they wanted to speak to each other. They all seemed to be happy with me speaking English, and over half of them wanted to speak English to each other, with the rest wanting to speak Japanese. Speaking to each other is important as I need to give them time to process what I'm talking about, and it helps them to work together on exercises and calculations. Also it's an interdisciplinary, and an international class, and I want them to meet as many other people as possible, and build the kind of relationships that make universities worth going, because frankly sitting in classrooms listening to teachers is very last-millennium.

I use an instructional method that is borrowed from Management, the teaching industry's estranged sister. The original is called Management by Wandering Around, or MBWA, and I call my version Teaching by Wandering Around, or TBWA because language teachers are the only people who like acronyms as much as management consultants. MBWA is often called Management by Waving of Arms, and I find myself doing a fair bit of arm-waving in my lessons, although this one is very amicable so far. 

A completely irrelevant picture of an electricity-generating shoe

To accommodate everyone's language preferences, I have split the classroom in two, with the Japanese speakers on the right and the English speakers on the left. Hopefully this works for the students, as they will be able to communicate in their preferred language. It also makes it easier for me to know which language I should speak as I patrol the class, see how they are progressing, and offer advice and encouragement. 

There is a significant Malaysian contingent, all of whom want to speak English, although I hear a bit of Bahasa when they are sitting together. I'm encouraging students to sit with different people each week. I'd also like to leave the option open for people to cross the floor, so they are not stuck in the same language with the same people for the whole fifteen weeks. But if I do this too forcefully then I may get all the people from the Japanese side move to the English side, and everyone from the English side move to the Japanese side.

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.

LED innovations

Usually I opt out of the vendor's email lists when I buy stuff online, but for some reason I didn't for Beamtec, the shop I bought our house LEDs from.

I get really annoyed with advertisements for things I have already bought, or hotels in places I've just come back from, so it was a bit stupid to subscribe to the website where I bought LEDs for my house, most of which proudly announce that they will last for tens of thousands of hours. 

One advantage is that I have been aware of the prices of LEDs, and have a record of their downward trends over the past few years. 

I have replaced one light so far: a compact fluorescent built into the kitchen hood, which blew after a rather pathetic four years. 

there are other fluorescent lights I'd like to change if I can. I'd like to replace the strip light above the upstairs wash basin. We got the washbasin as a unit with cupboards and drawers below, mirrored cupboards above and a 20 watt fluorescent strip light along the top. 

I've been looking at the prices of LED replacement strip lights, wondering at what point it's worth switching from the fluorescent tube that still works. 

They were around

2,200 yen in December 2012

1,600 yen in May 2013

1000 yen in June 2015

700 yen in September 2016

Interestingly they boast a 300-degree radiation compared to the conventional LED strip light's paltry 180 degrees. In fact in most applications fluorescent tubes are mounted on walls or ceilings, so half of the light is going into the wall, and you only need 180 degrees, but looking at the picture, and with the knowledge that the LED inside the tube is mostly sending light out perpendicularly, the larger translucent area of the tube makes some kind of sense. 

Sending light in all directions is actually a weakness of fluorescent tubes, and not something they need to go out of their way to remedy. Anyway, here are some more ideas of retro-features that they may add to fluorescent tube replacements. 

• Why not add a circuit to LED lights to make them flicker on and off a bit when you switch them on. After all, do we really want a light that comes straight on when we turn on the switch?  
• How about adding a radiant heater to the LED bulb so that it will emit heat, just like an incandescent light. 
• Or why not change the spectrum of the light to add frequencies that are invisible to us but that will attract more insects. 

Thermodynamics of cooking sources

There is obviously a link between food and thermodynamics, and it's not hard to see eating as primarily a means of getting energy into the body. 

In What is Life (the 1944 book by Erwin Schrödinger, not the 1970 George Harrison song), the physicist and theoretical cat-tormentor turned his hand to deep biology. His view seems to have been that the meaning of life is basically beating the second law of thermodynamics by moving energy from the colder bits of the universe into hotter bodies, and beating entropy by promoting some kind of order out of the inevitably increasing chaos.

Schrödinger inspired Watson and Crick in their search for the double helix, and in turn he was standing on the shoulders of Darwin, who had brought the field of biology well into the realm of science from its previous home somewhere down the corridor from stamp collecting.

In terms of evolution, getting energy into the body has been an important part of our development, and the taming of fire was a big breakthrough. Once we applied that to food, we got a double benefit of increasing the number of things we were able to eat, and reducing their volume and the time it took us to eat them. 

Previously I suggested that Watt invented the positive feedback loop that led coal to be used to power pumps that would remove water out of mines and allow more coal to be removed. But perhaps this wasn't really an invention, but simply another application of something humans have been doing for a very long time. 

It's Interesting that calories are now more often seen as enemies, to be scanned on packages, counted, and where possible reduced. Personally I always look at the label when I'm choosing what food to buy, and usually get the food with the largest number of calories since that's what I'm paying for. While some people are desperately trying to reduce the calories in the food, we rarely look at how many calories of energy went into preparation, packaging and transport of the food.

Early attempts at cooking were not so efficient. Wood was most likely the fuel, and little of the heat will have gone into the cooking, so most of the energy was going up in smoke rather than into those hungry human stomachs. 

This discussion on Ask Historians looks at the effects of gas and electric stoves on lifestyle, with many suggesting a revolution in the twentieth century, when cooking stopped being a full time job, and kitchens were no longer dedicated to food preparation, but became integrated into dining rooms. 

Another big innovation has been the microwave oven. Although scorned by a lot of people concerned about health and nutrition, and pining for "real" cooking, microwaves may be more efficient. Of course microwaves do put out radiation, but so do all other cooking appliances. Instead of sending out a broad spectrum of radiation, microwaves focus on frequencies that will excite the water molecules, and however you wrap it up in culinary language, cooking is basically about removing water. Also, you don't need to heat up a heavy metal container to cook what is inside a microwave, so it should be more efficient, but any efficiency is likely to be marginal, and savings will be much less than the energy used to read this.

(Picture stolen from: Green Lifestyle Magazine) 

Kitchen extractor fans, and their fans

What about ventilation in the kitchen then? 

The manufacturers of Best cooker hoods recommend you exchange something like ten times the volume of your kitchen per hour, which for a regular kitchen is between three and four hundred cubic metres per hour. Passive House recommends you need to ventilate the whole house around 35 cubic metres per person per hour. So these kitchen hoods need two or three times more ventilation than the whole house. Obviously this is a peak load, and the kitchen is not going to be ventilated the whole time.

Japanese cooker hoods typically have three settings: Strong, medium and weak. It may be my Japanese web-searching inability, but numbers don't seem to jump out when I try to find them. Instead there are rather a lot of sites asking why their extractor fans don't seem to be extracting very well.

This site of notes about making your own home (in Japanese) provides a lot of data about different fuels, and some calculations giving a figure of 1,166 cubic metres per hour (assuming three gas rings), or 551 if there are only two rings. Other sites and some of Mitsubishi's extractor fans go into the thousands. 

There are probably differences in peak cooking intensity between Japan and the UK. The former has a culinary history based on wood as a fuel, which gives a strong high heat, ideal for steaming and stir frying. The latter, on the other hand, used peat or coal, which give a lower, longer heat more suited to baking or roasting. Hence the Japanese language has one work—yaku—which can translate into English bake, roast or grill, while there are various different Japanese words for fry, whether itameru (stir fry) or ageru (deep fry). But I'm supposed to be writing about ventilation here, not deep culinary thermodynamics.

The choice in Japan is typically between extractor only fans and those that will bring air into the house at the same time as they are expelling air. The latter are often recommended for houses that are airtight. In our house we got an extractor only fan, with the reasoning that it would only have one hole in the wall rather than two, and therefore make the house less leaky since extractor fan ducts are major causes of reduced airtightness. I'm not sure whether we made the right choice; w hen we switch the kitchen fan on, the front door becomes difficult to open.

In other countries, at least for passive house, another choice is recirculating hoods that will send the air through a charcoal filter to remove the oil and kitchen crap before releasing the scrubbed air back into the kitchen. The heat will then stay in the thermal envelope, and the air will sooner or later pass through the heat recovery ventilation. 

Lloyd Alter on Mother Nature Network has interesting insights into the lack of clarity on the subject. And some very nice pictures of dream kitchens. He discusses how some people rail against recirculating kitchen ducts, while the people wanting low-energy buildings see them as essential. He points out that in Ireland you're allowed to connect a kitchen duct to a heat exchanger but in Canada it's illegal. 

So what should you do? Recently I've been thinking about making a pizza oven in the garden. I know that doesn't entirely answer the question, but if you want to have a low energy house, do you want high-energy cooking inside? We then get into the question of whether low energy buildings should be enforcing low-energy lifestyles, or whether they should allow people do whatever they want while reducing the energy use. 

By the way, if you were wondering why there are so many people complaining that their extractor fans don't work well, it's because they need cleaning. 

Rechargeable batteries half the size, or double the charge

There's an interesting story here in all about circuits about new battery technology that could double the density. In a lot of applications, battery weight is critical. Remote control helicopters is one example, since the power inside the battery must be used to lift the battery itself. These first appeared in the mid 1990s with nickel-cadmium batteries, but later became popular as toys when lithium-ion polymer batteries provided sufficient current for the weight. The development in battery technology marches on, and now a solar-powered plane has flown around the world. It takes a while to find information about the batteries  on the Solar Impulse website, but without the four lithium polymer batteries, which make up a quarter of the plane's weight, it would have struggled to stay up through the nights, or get through any clouds on the way to or from the stratosphere. 

Although solar power is the biggest part of the solar impulse story in the media, the batteries may be more significant, making possible hydro-electric or nuclear-fusion powered flight. Where toys and explorers play, the industrial economy often follows, and I will not be surprised to see some commercial battery-powered flight in the next ten years. It will certainly start off expensive and short-haul, perhaps flying from airports in built-up areas where noise and pollution are bigger issues. Flexible solar panels may be used cosmetically, but the batteries will be the power source.

Anyway, one of the reasons why lithium is a more popular battery choice than nickel-cadmium is that it's lighter. Anyone who has seen the periodic table knows that lithium comes in at number three, right after hydrogen and helium. Electricity is basically stored in the outer electron of each atom, so the light weight of the lithium atom means more free electrons per weight. The first lithium batteries were made with mixtures of other metals, like iron or manganese. In lithium-ion batteries, lithium atoms freed from their out electrons float through the electrolyte from one side of the battery to the other. Once these were put in plastic cases, they started to be called lithium polymer batteries. In its more technical meaning, lithium-ion polymer batteries have a polymer electrolyte.

Image from of Business Wire.

As far as the travelling ions are concerned, batteries have an anode on one side and a cathode on the other. The first lithium batteries used the metal case as the cathode, and a large chunk of lithium as the anode. Lithium-ion batteries use graphite for the anodes. This new technology uses a thin film of lithium as the anode, which means it can hold extra charge with less weight.

These batteries are still using the ions to carry the charge rather than the electrons. Looking at the relative size of the electrons and ions, this is a bit like playing tennis where the players have to go back and forth over the net, rather than the ball. Battery technology is progressing, but still has a long way to go!

You can see an infographic of how other kinds of batteries work here.

Cross leakage and cross contamination

So the big issue with Energy Recovery Ventilation is that along with the moisture, other things are going to be transferred from the exhaust air to the incoming air, compromising its freshness.
This is also called cross leakage, or how much of the outgoing air will end up coming back in again. It even has an acronym: EATR (Exhaust Air Transfer Ratio).

Air xchange.com refers to US ASHRAE standards on cross leakage. Exhaust air is classified into four different groups: Class 1 air has low contamination, for example from office spaces, classrooms or corridors. Class 2 air has moderate contamination, for example from rest rooms, dining rooms, warehouses. Class 3 has significant contamination, for example kitchens, beauty salons, pet shops. Class 4 air has highly objectionable fumes or potentially dangerous particles, for example paint spray booths, laboratory fume exhaust or kitchen grease exhaust.

The US standard states that less than 10% cross contamination is acceptable for class 2 air. This seems like a lot, but in practice you will never get 0% contamination, even with a heat recovery system that is not trying to transfer moisture. Energy recovery systems can get as low as 1%.

Mitsubishi has a report on their Lossnay ventilation system with evidence from a test in 1999 that their membranes are fine enough to prevent bacteria from passing from exhaust to incoming air. They have more information about their systems in English here.

If the membranes are this good, then perhaps we should be using ERV after all, and they should be recommended for kitchens and bathrooms. 

Another compounding factor with kitchens in Japan is that a lot of stir frying, deep frying and grilling seems to take place in Japanese kitchens, and there is usually an extractor fan with three or four times the ventilation needed for the whole house. More about kitchens later!

Green Building Advisor has a useful comparison of ERV and HRV, with a nice aside: "...assuming, of course, that the designer or installer hasn't made any blunders. (Sadly, this can be an optimistic and risky assumption.)"

Energy efficient homes will 'boost economy'

News from the BBC here about Scottish investment in housing energy efficiency, which will pay itself off for years.

They include this stock photo to symbolise an energy efficient house.



What does the photo tell us?

On a superficial level, it's a thermograph, which tells us that houses are giving off heat, and the fact we've taken a picture of the house means that we care about heat. So, it says low energy building.

A brief analysis of the photo tells a different story. The different colours indicated different temperatures, going from black for the coldest part of the picture (deep space high in the sky) to white for the hottest part of the picture, which is the parts of the upstairs wall away from the lintels.

The windows are colder than the walls.

Does this mean that the windows are doing a better job at insulating than the walls? I guess this is possible for an old house where nice new double-glazed windows have been installed, but no effort has been made to insulate the walls. Or are we seeing through the windows into the room inside, which is colder than the outside walls and the roof?

The gable end is cooler too.

Does that mean the gable end is better insulated than the front of the house? This would be a good idea as end terraces have a lot more external surface area, and need more insulation to reach the same energy efficiency as the rest of the terrace. But I thought there was no insulation in the front wall?
The front gate looks pretty warm too. Interesting. Is it heated?

The house next door seems to be equally red along the wall, and along the roof, except for an area going up into a point on the roof. Could that be the shadow of a tree?

Just a guess, but this picture was probably taken on a sunny afternoon. All the heat it shows has come from the sun, hence the warm gate and south-facing walls. The east-facing gable end has been in the shade for a while, as has the neighbour's wall and roof in the shade of the tree. The windows are cooler because a lot of the heat is going through them into the house rather than warming them up or reflecting into the camera. The bushes and trees in the garden are cooler still, because they do an even better job at absorbing the heat. Also the trees, and probably the windows too, have lower emissivity, so even if they are hotter, they'll radiate less and the thermograph won't know about it.

A thermograph taken in the day time will tell you almost nothing about the energy efficiency of a house. You need to take the picture on a cold night, when the heating inside is turned up high. Even then it's not obvious what the picture is telling you. 

Other kinds of ventilation system

There are two more kinds of heat recovery ventilation systems beyond the heat exchange and energy exchange cross flow or counterflow systems previously mentioned.

One is the enthalpy wheel. Enthalpy is not completely sensible. It is a measure of the total energy of a system, including latent heat, so they could probably have just called this an energy wheel. It is also called a thermal wheel, or a heat wheel. The wheel rotates with the incoming air going through one half of it, and the outgoing air through the other half, parallel to the axis of the wheel. If it's hot inside and cold outside, the exhaust air will warm up the part of the wheel passing through that side, then when it passes through the other side, the wheel will warm up the incoming air.  

These wheels have the advantages of energy recovery, potentially meaning more savings than a heat recovery system, and also reducing the risk of frost in the out-going air since the moisture is taken out of the air before it leaves the building. Also, the speed of the wheel can be adjusted to change the amount of energy recovery. This may be useful in seasons when you don't need to exchange much heat, or cooler nights in hot summers when you want to bypass the heat exchanger. 

Enthalpy wheels also have the disadvantage of cross contamination, as some of the exhaust is going to get back in again. Enthalpy wheels may be suited to large buildings which need constant temperatures and humidities, with relatively low ventilation rates. For example, the Passive House-certified Hereford archive and records centre uses one.

An even simpler heat exchanger is the single room energy recovery vent, or ductless vent.

This looks a bit like a regular extractor fan, but it both inhales and exhales air, and passes it through a ceramic core that stores and releases heat. Typically these systems inhale air for something like 70 seconds, pause, then exhale air for 70 seconds. 

More than one of these ventilators can be added in different parts of a building so that while one is blowing air in, another is sucking air out. 

This system has the advantage of not needing any ducts, and being very easy to retrofit, as Guy Marsden in Maine, USA explains. As it is recovering energy there is a potentially higher efficiency, better humidity control and lower risk of frost.

Also it has a remote control. I'm inclined to see this as a disadvantage, rather than an advantage, since we already have too many remote controls in our lives, and we really shouldn't need another one to breathe. Some people do like to have buttons to press though!

Another concern is that it's difficult to be sure that air blown out of the building is not going to be sucked straight back in again. Of course there is a potential problem with any ventilation system that badly positioned exhaust and fresh air outlets and inlets will just lead to a recirculation that makes irrelevant any worries of cross contamination within the system.  

Also, with the inherent problem of cross contamination in the energy exchange system, it's difficult to see how this would work with toilets, kitchens and bathrooms, where you would really only want to remove air, but not supply it. 

It's possible to imagine a configuration where the unit is placed next to an internal wall, and incoming air goes into one room, while outgoing air is expelled from another. I have no idea whether this is possible outside my imagination, but it may be worth trying!

Thanks to Devatech for the image of the wheel, which I shamelessly downloaded from your website! 

And to Nihon Stiebel who supply a "Twin air fresh" ductless, decentralised ventilation system with energy recovery. 

Air xchange.com has more technical considerations here about energy wheels. 

Turf laid... Time to get a lawn mower

Lawns are not really a big thing in Japan, so the lawn mower culture is very different. I remember lawn mowing in England as a childhood chore. First we used an old petrol-engine Mountfield that collected the clippings in a case at the back. I have bitter memories of lugging it around the lawn, and later trying to clean all the grass crud that had accumulated in the nooks and crannies. Next we got a Flymo that cut the grass as it hoovered around the lawn.

We also had one of those manual cutters that had no engine and relied on you pushing to spin the blades around. This didn't seem to cut the grass and we never used it.

I thought these would be long obsolete, but they sell them in Japan. Not so much as a cheaper option for the lawn-owning poor (who do not exist) or the congenitally tight-fisted. The tag line is that these lawn mowers are quieter, so they won't disturb the neighbours.

They also have these:

Honda Demonstrates Robotic Lawn Mower - WSJ

I can think of many things that would hinder the robot on its path. 

Can't read the air

Building culture changes around the world. People talk about "vernacular architecture" as if buildings are all having conversations with each other, but often the languages seem to be mutually unintelligible. 

Heat recovery ventilation is one area where a lot seems to be lost in translation. And there was plenty of hot air to start with.

In Japan, ventilation systems are usually called ２４時間換気 niju-yo-jikan kanki  i.e. 24-hour ventilation. It seems like a strange name, as if you would call your refrigerator a 24-hour refrigerator, or your roof a 24-hour roof! They have been mandated in new buildings since 2003, but a lot of people switch them off. So they are not really 24-hour after all. There are plenty of reports of people who have switched off their ventilation because it makes the house cold, but if you do that, as Last resort blog (in Japanese) warns, you're going to get condensation.

顕熱交換 ken netsu koukan  is heat recovery ventilation (HRV), while 全熱交換 zen netsu koukan is energy recovery ventilation (ERV) which also recovers moisture, and is probably the more common choice in Japan when any kind of heat is being recovered. Translation aside, this may be a shock for those who read the first law of thermodynamics and thought heat and energy were the same thing. My dictionary gives Ken netsu as "sensible heat". And that's not a very sensible expression in English where "sensible" usually has a different meaning. The opposite of "sensible heat" is not "foolish heat" but is "latent heat".

The Japanese language often uses abbreviations of English words that are not commonly used in English. For example PA is used for parking area, and IC for interchange, and you will find these driving on the expressways. KY is an abbreviation of kuuki yomenai, ie cannot read the air. Reading the air means reading a situation, so KY refers to someone who is out of touch with the rest of the room.

Japanese building plans with ventilation systems will show SA for supply air, RA for return air, EA for exhaust air and OA for outside air. These abbreviations are occasionally used in English.

There is a page here that:

proposes a housing environment that has a "Flow of healthy air" and is "Clean and safe".

It should be pointed out that inverted commas are used in Japanese for emphasis, so the inverted commas around "flow of healthy air" and "clean and safe" do not mean that somebody said it was healthy, clean and safe, but they're actually being sarcastic. 

Energy Thoughts and Surprises: How much electricty does the solar hot water panel pump use?

Here's someone else blogging about energy.

https://energy-surprises.blogspot.com/

I'm not the only sane person in the asylum after all!

Forgot to boil the water

In the jumble of pros and cons for ventilation systems recovering heat and moisture, the moisture advocates point out the extra energy in the water. This Polaris site (in Japanese) tells us the different heat contained in dry and humid air: apparently air at 20 degrees centigrade has 11.9 kCal of heat at 80% humidity, but only 9.2 kCal at 30%. He doesn't say how much air contains that much heat, perhaps a kilogram, or a cubic metre, or your living room? And he doesn't give a reference point for the heat, whether it is per degree, relative to zero degrees centigrade or the total heat relative to absolute zero. And how do we understand those numbers anyway? I usually only think about calories in food, and whether it's 11.9 or 9.2 it's still only about half a jelly baby.  

Whatever the actual meaning of these numbers, humid air is going to hold more heat than dry air, since the extra water in the air is holding more heat. 

But not only does the water in the air hold more heat, it also needs to have been vaporised. Most of us are familiar with water vaporisation, as it happens when we boil a kettle. Although 100 degrees is the boiling point of water, it doesn't all suddenly turn to steam when it reaches that temperature. It takes some extra heat to turn it from one phase to another. While it takes one calorie to raise one gramme of water by one degree, it takes over five hundred calories to turn a gramme of water into steam. 

This is not just true of the water in a kettle, but of any water that is evaporating. For example the water in clothes hung out to dry inside, or water that has been poured on a plant, or water in our skin. Water evaporating from skin is our main mechanism for losing heat, and our sense of temperature depends largely on how much heat we are losing. This makes humid places feel hotter, because less moisture will evaporate into humid air than into dry air. 

According to the ever-reliable Engineering Tool Box saturated air at 20 degrees centigrade has almost three times more energy than dry air relative to dry air at freezing, so the above figures would be more like 12.1 kCal per kilogram at 80% humidity and 7.5 at 30%. That's 60% more heat. 

The consequence for ventilation is that if you have a system that is exchanging heat but not moisture (HRV), then in the winter you're going to be losing a lot of energy in the airborne water vapour you expel as you bring in dry air. And in summer you're going to be bringing in a lot of heat to the house embodied in the humid air. 

So an energy recovery system will lose less energy, and is probably a good idea if you have dry winters or humid summers.

Of course you're unlikely to be choosing between 30% and 80% humidity. In the summer you may have 80% humidity and want 30%, and in the winter you're likely to get 30% humidity, but probably wouldn't want as much as 80%.

However, as the Polaris site points out, energy recovery systems transfer moisture back into the house. They usually do this across a paper membrane. Along with that moisture you can also get some bacteria and odours, which often makes people reluctant to use energy recovery ventilation in kitchens, bathrooms and toilets, putting simple extractor fans there instead. For example Mitsubishi suggests a dedicated extractor fan for the kitchen, and offers a system with additional drying, heating and direct ventilation options for the bathroom. 

Since kitchens, bathrooms and toilets are the places you usually want to extract air from, while supplying fresh air to bedrooms and living spaces, you may end up only using heat recovery ventilation for a fraction of the house, and any efficiency gains are lost, perhaps along with improvements in interior humidity. Unless of course you can recover heat and moisture without letting anything else through.

Acknowledgment:
Special thanks to Ben Shearon for asking questions that lead me to investigate this topic.

Note from Wikipedia: In SI units, cs = 1.005 + 1.82H where 1.005 kJ/kg°C is the heat capacity of dry air, 1.82 kJ/kg°C the heat capacity of water vapor, and H is the specific humidity in kg water vapor per kg dry air in the mixture.

Solar-powered wearables

Why put solar panels on the roof, when you could wear them?

www.ecouterre.com Solar powered wearables guaranteed to give you a charge

(Apart from lack of surface area, washing, electrical storage, waterproofing, most energy being needed by buildings, and probably spending most of your time inside.)

A breath of fresh air in a sea of thermodynamics

I remember a conversation between our architect and one of the potential contractors, and the question was what kind of heat recovery ventilation system we were using. I'd only just discovered that heat recovery ventilation was possible, and didn't dwell too much on this question. The answer was that we were using heat recovery ventilation rather than moisture recovery ventilation.

To recap:

• If you want a warm house, you need insulation.
• If you have insulation, the house should also be airtight. 
• If it's airtight you need mechanical ventilation with heat recovery.

Insulation, airtightness and mechanical ventilation with heat recovery represent a holy trinity of low energy building that cannot be violated. 

Without insulation, you're going to lose a lot of heat,  and you're going to get cold spots on the thin external walls, which will lead to condensation. Cold, expensive to heat, and damp!

Without airtightness, you're going to get humid air passing through the insulation and at some point that will lead to condensation. It will probably happen in the worst possible place: where you can't see it, but your structure can.

Without ventilation, you'll eventually suffocate, but way before that the humidity is going to get so high that you'll get condensation even where there is airtight insulation. 

Mechanical ventilation is best because any kind of natural ventilation will usually lead to too much or too little exchange of air, depending on how nature is feeling at a particular time. 

If you're going to have mechanical ventilation, you should put in a heat exchanger and then you don't need to throw away all the heat in the air.

...

So five years later I'm still learning things about ventilation. I've written a bit about our problems with heat recovery ventilation, but I know even less about the other kind: energy recovery ventilation, or moisture recovery ventilation. These are abbreviated to HRV and ERV for any fans of the TLA (three-letter acronym). 

In both systems the air leaving the house passes through a heat exchanger and there is a transfer of heat to the air coming into the house across a membrane. In fact it is an array of membranes and with a well-designed arrangement of cross flow and counter flow, you can recover over 90% of the heat in the air. The transfer of heat follows the third law of thermodynamics, from hot to cold, so this will keep the house warmer in the winter, and cooler in the summer.

The difference between the systems is in moisture. Heat recovery ventilation just transfers heat, while energy recovery ventilation also allows moisture to transfer. This will also move from higher to lower humidity, so will tend to keep the humidity out in the summer, and stop the house from getting too dry in the winter. 

So which one should you get? 

As usual there are different schools of thought:
A) A is definitely better than B
B) Only a bloody idiot would use A
C) There are good and bad points of both so in the end it doesn't make a lot of difference which one you choose

It's probably more fashion than physics, and I'm going to be writing about fashion soon!

But until that link works, you can read about the different kinds of heat exchanger from Zehnder America.

It's a Passive House, not a passive solar house

Here's another thing I didn't fully appreciate until taking the Passivhaus course last summer. The windows don't need to be that big.

I guess I started off with the idea of getting all our energy from the sun, so that we wouldn't need to get any heating energy from anywhere else. This is known as passive solar design. It was a popular idea in the 1970s, but by the early 1980s it was clear that super-insulation was a better approach. Trying to meet heating needs by making the south-facing windows as big as possible was the wrong approach for two reasons: it would end up being much more expensive, and on a sunny day the south facing rooms would get far too hot.

At least this was clear to those involved in those discussions in the 1970s and 1980s, but there have since been generations of house builders clinging to the dream of putting in enough windows so that heat is free.

This doesn't mean we should live in caves. Windows in houses are a very good idea, and it's also important to put most of the windows to the South where they will get solar gain in the winter and will be easier to shade in the summer. Also it's a good idea to have few windows east and west where there will be little heat to gain in the winter when you need it, but a significant amount in the summer when you don't. 

Read more from Green Building Advisor

Getting the least out of your fridge

When we go to the local electrical store, especially to buy something, I'll often start asking questions about the design or manufacture of their products. This will usually result in blank faces or repetition of advertising dogma from the sales rep, and a kick from my better half, with a suggestion that I write to someone in the company rather than bothering the staff.

This happened when we recently went to get a new fridge. Our old fridge was thawing and on its last legs. Probably the compressor going. I suppose we could have got it fixed, but it wasn't a very good fridge to start with. They had replaced it for our old fridge, which had had problems with the ice maker, but the replacement never seemed very satisfactory. It was about ten years since we bought a fridge, and I was expecting a few quantum leaps in the technology, but the main evidence was for incremental improvements in insulation and compressor efficiency. Fridges are major domestic electricity users (10-20%), and the improved efficiency probably makes the new fridge worth it, at least in economic terms. The sales staff in the electrical shop were certainly enthusiastic to tell us this. Evidence from Kakaku.com suggests three times less energy use between 2003 and 2013 models in Japan. And here's a graph showing electricity consumption of fridges in the US rising from their mass production in 1940s to a peak in the 1970s to a return to 1940s consumption around 2002, at a much larger size and for less money. (The flat part corresponds almost exactly to Bill Clinton's presidency, which may just be a coincidence.)

I had expected fridges to get a bit more intelligent. There has been some talk of smart grids, and now many houses are loaded with solar panels, which they were trying to sell in the very same shop. I expected the noble fridge, leader of the white goods, would be rising to this challenge by making more coolth when power is available, and using less power when it is not.

Blank faces.

Another question: why is the door for the fridge the same thickness as the door for the freezer? It's colder in the freezer, so wouldn't it make sense to have a thicker door with higher insulation?

More blank faces.

My answer to that question would be that it makes manufacturing easier, and fridges cheaper.

This article from Proud Green Home has some useful information on buying and using low energy fridges. It points out that smaller fridges use less energy, and that fridges full of food, or even bottles of water, will have less air to escape when the door opens and they will be much more efficient. This is in contrast to what the people in the electrical shops say: don't fill your fridge too full or the air will not be able to circulate and it won't cool your food properly. 

Why would they say such a thing?

Perhaps because they want you to spend more money on a bigger fridge!

Not only do smaller fridges use less power, they also contain less food. A significant proportion of bought food is thrown away uneaten, so unless you are able to guarantee none of your food is wasted, a bigger fridge probably just means you are going to throw away more food.

One technical development they seemed pleased with in the shop was a sensor inside the fridge looking at how cold things were. I don't understand how much of an improvement this is over a thermostat unless you are putting hot pans in there. As long as the insulation layer around the fridge is good, and heat is being pumped out, the temperature inside is going to be uniform soon after the door closes.  I will further investigate exactly what the control circuitry of the fridge is doing and what the green light on the door means.

The article also makes some interesting comparisons between different configurations. French doors would seem to be more efficient since you only need to open one door at a time, and therefore only lose half the cold air. However people often open both doors, and the doors may in fact be open longer as you are trying to remember which side of the fridge you left whatever you're looking for.

Also they show how more doors and more complicated configurations basically mean more heat loss. This will be no surprise to anyone who has been paying attention to my posts about thermal bridges. They point out that any fridge with ice and water going through the door will be less efficient than any fridge that doesn't do that. (Compare and contrast with the world's first passive house cat flap.) So if you're choosing for energy efficiency, they recommend getting one with a freezer at the top and no cat flap for water or ice.

Of course different countries have different shapes and sizes of fridge preference. Another question I had for the long-suffering sales rep was why their shop only had Japan-made fridges. A little searching on the web reveals that about the only universal in the global fridge market is that different markets favour products from different countries.

Japan sees the future and it is zero-energy homes - Nikkei Asian Review

At least that's what this article in nikkei says!

This is great news, but the silver has a little bit of a cloudy lining.

According to the article:
"Japan's Ministry of Economy, Trade and Industry has set criteria that a house must meet before it can be dubbed zero-energy. It has to:

• Be at least 20% more energy efficient than an ordinary home.
• Be airtight and adiabatic enough to increase the efficiency of air conditioners and water heaters.
• Allow for efficient ventilation.
• Have a solar power or other renewable energy system that can keep the house from sipping electricity from the grid, or even spit some electricity back onto the grid."

Interesting definitions, but wouldn't it make more sense to determine a zero-energy house as one that uses less energy than it produces?

The article does mention insulation, but only after talking about solar panels, energy management monitors and fuel cells. That's a bit like only mentioning malaria mortality after talking about terrorist attacks and aircraft accidents. (Oh, yeah, that happens in the media all the time!)

In the definitions quoted above, I guess "adiabatic" is only possible with insulation, but that's not exactly a widely used term outside school physics lessons, and even there it is not universally understood. I don't think I've ever heard anyone say: "Japanese houses are cold in the winter and hot in the summer because they are not very adiabatic." People frequently lament the lack of insulation though.

The other really big question with "zero energy" homes is how much energy they are allowed to generate. You could balance any level of energy use if you add enough solar panels, as long as you ignore how much energy was used to make the solar panels. So it's nice that zero energy homes have to be 20% more efficient than ordinary homes. But what if ordinary homes become 20% more efficient?

I could also complain about them using the term "energy efficiency". You could fill one house with energy efficient appliances, and have another house with just one appliance that is not so efficient. The house with more appliances will use more energy. Selling energy efficient air conditioners is much more appealing to the market economy than not using air conditioners at all!

It's easy to be cynical. I'd really like to see Japan's future in zero-energy homes too! I know that's where my future is.

Or maybe we should not be worrying about storing solar energy

There's a conventional wisdom on solar power in particular, and renewables in general, that we need storage to make it work properly. According to brave new climate that will probably stop them from being effective. 

They look at the energy return on energy investment (EROEI) and cite the low score for solar. In other words, the amount of energy that will come out of solar panels is not really enough to make solar panels. This means they are not sustainable and rather than contributing energy, they are using up energy created elsewhere. He suggests we should not just talk about the actual energy used in the process of manufacturing the solar panels, but also things like food and education for the people who are making them. 

Anyway, an energy source with an EROEI of one would just produce enough energy to support itself, and would be of no use to the society. The threshold for useful energy sources is something like 7. 

I have sometimes watched fish jumping out of the river to catch a fly, and wondered whether they were using more energy to catch the fly than they got out of eating it. EROEI is a bit like that. 

He quotes an EROEI of 3.5 for solar panels in Germany. This is already marginal, and if we have to store energy from renewables, then we also need to add the battery infrastructure into considerations of the EROEI, which could make solar a net user of energy rather than supplier. 

There are two other considerations. First is that solar production costs are falling all the time, and this includes embodied energy. The other is that we may soon have batteries parked outside each house in the car. 

Is it worth it? Present value factor

Building a house is a series of decisions, and a lot of these decisions put one-off capital costs against month-on-month running costs.

For example you could add insulation somewhere that will save 10,000 yen every year in heating and cooling bills, and cost 150,000 yen.

The first thing to think about is how far into the future you are going to be making savings. Let's say it's thirty years.

So if you're going to save 10,000 yen every year for the next 30 years, how much is that worth? 

Well, at first sight you'd think it's 300,000 yen. But it's not that simple. You have to think about inflation and interest.

First, imagine you don't have the money. In that case to make the capital investment you're going to have to borrow it, probably from a bank who will charge interest. This means the capital will cost more than its face value. In other words the saving from the running cost is worth less.

Second, imagine that you do have the money. In that case, spending it means you can't invest the money somewhere else, so you lose out on the opportunity for earning interest. So again the value of the cash in hand, or wherever it is, is more than its face value, in the long run.

This can all be expressed as the present value factor, which can be calculated by this equation:

 F_pv = 1-(1+P) ^-n / P

Where P is the interest rate, and n is the number of years.

But what if you're bad at making investment decisions, and would probably have lost all the money? In that case, you will probably make the wrong decision here, too, so you can stop reading, if you haven't done so already. You probably stopped reading before the equation.

And what about inflation? If the prices are going to go up, then that 10,000 yen per year is going to be increasing. Won't that balance out the interest? Can't we just multiply the annual saving by the number of years after all? 

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!

Dripping Diary

26th January, 2016

Water started dripping from the ceiling in the pantry this morning. 

When you have water dripping out of somewhere, it's a good idea to find where it is coming from and stop it from going in there. 

The immediate suspect, like the last five times water has appeared in unwanted paces, was the ventilation system two floors above.

This is actually the second water incident in the last months, but the first one was quickly noticed from the sound of drips on the bathroom ceiling, so it never got to build up anywhere. 

There was no dripping on the bathroom roof this time. That's because it was not the ventilation system leaking, even though that's where the water was ultimately coming from.

I quickly came to a second hypothesis. Half a metre of snow outside... temperatures below freezing for a few days... the drain from the ventilation system coming out of the wall about twenty centimetres above the ground... frozen pipe! 

left: drain from ventilation system

The first evidence to support this hypothesis was the water spilling gently over the the top of the drain beneath the ventilation unit, rather than actually going down it. 

A bit of hosepipe with a loop usually goes from the ventilation system to the drain. I diverted it into a bowl to stop sending more water to the overflowing drain. 

The next evidence was outside: a large icicle coming out of the drain.

A few buckets of hot water and kettles later the icicle was gone. The visible part of the icicle went fairly quickly and was soon followed by the rod of ice from within the pipe. It took a little longer to thaw the elbow. Immediate problem solved, it was time to address the cause.

The ventilation system is going to produce condensate when it's cold outside, unless we also make it cold inside, or drop the relative humidity below about 20%. It's often going to be below freezing when it's cold outside, and that's where the water is going to be dripping. So it seems inevitable that ice is going to form and, sooner or later, the outlet pipe will freeze. It will then fill up with water and start overflowing. The only mysteries are: why has this not happened before? and why did the contractors not prevent this from happening?

I suspect this probably has happened before, but it takes a while for the pipe to fill up with water before it overflows, then it takes a while for the water to drip down, around the bath that is one level below the ventilation system, then onto the ceiling of the pantry below the bath. Some of this water will be evaporating all the time, and it could be a couple of days before enough builds up to break through the plaster boards and start dripping onto the floor. By this time, the temperature outside has always gone high enough above freezing, or a few rays of pre-noon sunshine have reached the drain and thawed it. 

I was wondering if there were any mitigating circumstances leading to this, and there are a couple of things that may have made a difference. I noticed when I was clearing away another icicle a couple of days later that I'd left a gardening stake directly underneath the drain, from which was growing a nice icy stalagmite. Perhaps such a stalagmite had helped to block the drain. I was in too much of a hurry to melt the ice before and didn't document the hydro-crystalline pathology very well. 

The other thing that we had done the night before this incident was to put on the humidifiers. It gets a bit dry in the winter since we're constantly getting rid of our humid air, and replacing it with air that's already fairly dry, and is then being heated so that the relatively humidity will fall about four times. We don't have any permanent remedy for this, but when we remember, and when it gets below about 30 percent, we switch on some of our humidifiers, usually at night time. So we are adding moisture to the warm air that we are expelling from the house over a steep temperature drop, and increasing the amount of water that will end up in condensate.  

According to my previous calculation, the amount of water that's going to drip on a cold night is up to around 450 ml per hour. One drop is 0.05 ml, so that would be about two and half drops per second. Not fast enough to represent constant flow, but perhaps slightly faster than the ideal drip rate for forming icicles, which seems to be around one or two grammes per minute according to the Icicle Atlas. The precise temperature and humidity of the air in the house will determine the dew point, which will likely be a few degrees above zero. The dew point is really the critical number since it will tell us when condensation starts. 

It's 23 degrees C and 30% humidity right now, so the dew point is 4 degrees. (According to this dew point calculator.) So if the air outside goes below about 2 degrees, it's going to drop below the dew point within the ventilation system. If we had 100% efficient heat exchange, then it would be cooling the air all the way down to 2 degrees, and the air coming in would be heated all the way up to 23 degrees. It's more like 80% so we lose a couple of degrees. Some ventilation systems will recover only 60% of the heat, so they will be less likely to reach the dew point. This is only a problem that will happen in well-ventilated houses with highly efficient heat exchange ventilation systems, so I suppose that answers the question of why the contractors hadn't thought about this happening, and why we've had so many problems with this. 

When I say we've had many problems, we haven't exactly been wading through water, just needed to use a small cloth to mop up a few drops from the floor every year or two. And hopefully the structure of the house has not been damaged by the moisture. 

The other problem ventilation systems have to deal with is freezing condensate. If the air is being cooled below freezing, it may start snowing in there as vapour in the air is precipitated. This would block the ventilation and we would no longer be able to ventilate the house, so the ventilation system does something with pressure differences to stop that. I'm not really sure what it does, but the result will probably be that it never gets as low as zero in there, and in fact there may only be a very narrow window of outside temperatures when condensate is actually being produced.

(Apologies to anyone who was hoping for a story about cooking fat from the North of England.)

Note:

The other drain in the picture is from the air conditioner, which we have hardly every used. This has a de-humidifer on it, and it would take moisture out of the hot air if we were using it. There is no chance of it freezing though. 

Read about previous escapades here.