In praise of shadows... at least if they surround light

Actually, rather than being part of some consumerist conspiracy, the dearth of LED fittings for is probably much less sinister and just a lack of a market among house builders for new lighting. The electrics seem to be the last thing that is thought about in the building process. By this time the consultation process between architect and client has probably dried up and a sketch is handed to an electrician to put fittings in the ceiling in the middle of each room so everywhere is bathed in uniform light. Eat your heart out Jun'ichiro Tanizaki 

I've been reading a translation of his essay, "In Praise of Shadows" (1933) which apparently is required reading for any student of architecture in Japan, although Tanizaki is no architect. Of course architecture contains a great deal more philosophy than anything else, and you don't need to be an architect to know how buildings and spaces work. In Praise of Shadows is a good critique of modernisation and the westernisation of Japan. Tanizaki, who was born in 1886, just after the Meiji Restoration, laments the introduction of electric light into restaurants. He goes off on a crusade to find a deeper appreciation of subtlety and cloudiness in orientals from the colour of their skin to the materials used in their soup bowls and on their sliding doors. 

He wrote that "Japan wastes more electric light than any western country except America." This was in the 1930s; goodness knows what he would have made of the country more recently. He adds that "so benumbed are we nowadays by electric light that we have become utterly insensitive to the evils of excessive illumination." He talks about establishments that are "lit far too extravagently" admitting that "some of this may be necessary to attract customers."  He talks of the waste of lighting before it is dark in the summer, "and worse than the waste is the heat . . . Outside it will be cool, but inside it will be ridiculously hot, and more often than not because of lights too strong or too numerous. Turn some of them off and in no time at all the room is refreshingly cool. Yet curiously neither the guests nor the owner seem to realise this. A room should be brighter in winter, but dimmer in summer; it is then appropriately cool, and does not attract insects. But people will light the lights, then switch on an electric fan to combat the heat. The very thought annoys me." (p 36-37)

If only he were still alive and working as an electrician in Matsumoto.

"Light is used not for reading or writing or sewing," he says later, "but for dispelling the shadows in the farthest corners, and this runs against the basic idea of the Japanese room." So when we're asking what went wrong with Japanese architecture and looking for a culprit, we can add electric lights to aluminium windows in the line up of usual suspects. And I suppose the Japanese obsession with imitating the West. 

Joshua Sowin writes more about Tanizaki's essay here . I've been reading a 1977 translation by Thomas J Harper and Edward G Seidensticker, published by Leete's Island Books of Stony Creek, CT. 

No LEDs on display, but what is on display is being lit by LED...

We went to a few showrooms the other day to look at stuff for the house. We're interested in LEDs, for reasons explained here. One problem is knowing how bright the LEDs will actually be. Everybody used to know what a 60 Watt bulb was like, but to compare incandescents, fluorescents and LEDs, wattage has little meaning, and it's not so helpful to compare different LEDs. Light manufacturers have now started putting lumen values on their products, rather than just wattage, so there is some way of comparing, but the angle at which the light comes out can also be an issue in terms of how bright it is. 

We saw lots of LEDs in the Bathroom shop, Takara, where they have recently changed all their display lights into 60-watt halogen-style bulbs (around 7 watts) in lighting rails for the displays. They even have extra LED spotlights inside the bathrooms on display, to supplement the standard light fittings inside their bathrooms, which puts aside previous concerns that LEDs aren't bright enough.

We asked them to switch off the fitted lights in one bathroom, and just switch on the two LED spotlights to get an idea of how bright they were. They were certainly bright enough, especially under the relatively large area under the spot, but it was definitely less bright on the ceiling and higher up on the walls. Not very good, for example, if we invite a vampire round for a bath, and they turn into a bat and hang from the ceiling. Or perhaps they would prefer to be in the dark, and even for our vampire friends LEDs may be better. Anyway, as a whole the room seemed less bright, as it contained darkness, but it was bright enough where needed.

They are putting LEDs in one of their display bathrooms next week, and the bathroom we're getting has LED downlights as an option to the standard bracket-lights. This will cost us 39,000 yen extra. Obviously they're charging over the odds for this, but the design is superior, with down-lights rather than bracket lights, and it will claw back some of the cost in electricity bills in the next few decades, and should reduce some extra heat in the summer. It's best to write it off as an early adopter tax. 

In the tile shop they had several larger LED display units on the ceiling, like these from Toshiba. Much bigger units.

We asked about LEDs in the home fittings showroom of Panasonic, the electrical manufacturer, and got a rather blank look. They were using some for lighting their own displays of other fixed furnishings, but it obviously hasn't seriously crossed their minds to try to get people to put them in new houses. 

It seems in these, and many other shops that putting LEDs in makes a great deal of financial sense as they can get the same light output for a lower running cost, both in terms of electricity and bulb replacement. There seems to be much less effort getting them into new builds, although they are probably still working on the loss-leader concept that Gillette developed with their razor blades. Buy an LED fitting and you will have light for the rest of your life.  Buy a normal fitting and you'll be buying light bulbs for the rest of your life. Why get people to buy one thing when you can get them to buy two?

LED light bulb... this should be a contradiction in terms.

Just read is-this-the-ultimate-green-led-light-bulb. And it makes me wonder what's going on. It talks about "solving the problem of uni-directionality in older LED bulbs". I wonder whether Edison was concerned with the "problem" of his lightbulb not having an open flame...

Another thing that doesn't make sense is the idea of a replacable LED bulb.  LEDs have rated lifespans of over 40,000 hours. That's three hours a day for forty years. Form most domestic uses, the only reason for replacing the bulb would be if you wanted to change the fitting and keep the bulb. 

This guy at My LED lighting guide gives a list of eight reasons why LEDs are better than compact fluorescants, and Eternaleds asks if LEDs are brighter than CFLs and finds that no, they aren't really brighter. 

The point is that the light all comes out in the same direction, so if you know what you want to be bright, and can point the light there, then the LED is going to use a lot less power, not because it's producing light more efficiently, which it isn't, but because it's going to the right place.

If there's a chance that you're going to be doing something behind the lightbulb, in that bit of the wall where small dead insects accumulate, and you want to make sure it's not dark there, then CFLs or incandescants are for you. If you don't even want a space there, you should probably consider LEDS. If a light is not going to be used very much, and if you're not sure which part of a large area you're going to be using, then fluorescents will probably do as good a job as LEDs, and currently cost less to buy and fit, although LEDs use less resources and as they work out how to manufacture them in bulk, and once they pay back the retooling costs, LEDs will be cheaper.

A practical example in the house is a store room that may be used a few minutes a day. Rather than putting LEDs all around, we'll just put one fluorescent tube in the middle. This will brighten up the whole room in one go, and should still last a few decades. The other low-energy option would be to have a couple of head torches left on a hook at the entrance and turn a trip to the basement into a caving expedition!

But anyway, I wish people would stop talking about LED light bulbs. The whole point of a light bulb is that Edison's elements needed a vacuum, or an inert gas, so that they wouldn't burn away. Rather sensibly, with glass being transparent and easy to blow or suck into bulbs, he put them into a glass bulb. LEDs are semiconductors, typically produced on a flat wafer. They don't need a bulb. It may be a good idea to put a lens in front of them.

Putting LEDs into bulbs is like using a keyboard designed for typewriters over a hundred years ago when you're inputting words into a computer...

Slits in the envelope

In most places we have walls interrupted by occasional windows. The wall is a more-or-less uniform structure with three layers of insulation. Although the middle layer has a lot of wood in it, the first degree estimate (10% wood, 90% insulation) is near enough. We have data for the windows of the U values of glass and frame, and the thermal bridge "psi" value between glass and frame, and between frame and structure. U values come in W/m2K, in other words the heat flow per area per temperature difference. The psi value is in W/mK, so gives the heat flow along a line. A square window with one metre for each side will have an area of one square metre, but for the thermal bridge, the length is 4 metres. As window get smaller and less square, the relative effect of the thermal bridge gets bigger. 

A rather wonderful piece of software called Therm can answer the question of how much heat is going to be lost from an actual wall structure, so we can see how close the actual U factor is of a wall with a wooden pillar running down it, compared to the prediction from the U values of 10% wood and 90% insulation.

You start by drawing the structure and setting each polygon to the appropriate material from the library of data the system has. In this picture, you can see the three layers of glass wool insulation in blue, a wooden pillar in the middle in orange, and a couple of layers of structural board in the other colour. Is that puce?

Next you set the boundary conditions. You can tell the software whether each surface is inside or outside, or whether to ignore it. You can consider a surface it adiabatic, in other words that heat is not going to flow through it at all. It would be very time consuming, and not particularly helpful, to model the whole house, and you usually want to find out about a particular bit of wall, or a boundary between roof and wall, or some kind of junction. 

To model a wall, you can slice it in two places and put in an adiabatic surface in each, so you can get some meaningful estimation of what's going on. The main concern is heat flowing from inside the house out, so once you get far enough away from the part you're interested in, you can ignore any heat flowing along the walls. 

In this case, the left side is outside, the right side is inside, and the top and bottom are adiabatic, so we're just looking at heat flowing from inside (where the temperature is assumed to be 20 degrees C) to outside (where it's assumed to be very cold - 18 degrees below zero). Of course the temperature will be changing all the time, as will the humiditiy, but this is just looking at a steady state in the worst case. Another piece of software called Wufi http://www.wufi.de/index_e.html will simulate the humidity conditions over a year or two, and show where moisture could build up in a wall or roof structure. That's not avaiable as a free download though!

To find out the thermal bridge effect of the wooden pillar running through an insulated wall, I compared three different structures. First, I made an ideal wall with a 50mm insulation on the inside, 120 mm in the middle, 12 mm of structural board, then 100 mm of insulation on the outside (1). Ideal, but of course it would not hold up very well! This has a U value of about 0.131 W/m2K. 

Next I made a wall with the 120 mm middle layer completely made of wood (2). This has a U value of  0.187 W/m2K. In both cases 1 and 2, the U factor can be calculated directly from the U values of each component part. To do this you have to add up the R values (the reciprocals of the U values) which measure thermal resistance. There are also surface effect factors to account for convection, inside and outside, and factors to account for radiation. When you get to the surface, convection is the biggest cause of heat loss, but across the wall the heat is conducting. 

Next, I made a wall with a 120x240 wooden beam in the middle. This is close to the real situation. As there is 240 mm of wood and 760mm of insulation, we would assume that the U factor of this bit of wall is 0.24 x  U1 + 0.76 x U2, or 0.145 W/m2K. The Passive house spreadsheet also assumes this. In fact, the wall is conducting 0.147 W/m2K. This represents a difference of 0.002W/m2K. This corresponds to 0.002 W/mK along the length of the beam, and is the thermal bridge effect. This is small enough that we need not worry about it. Larger thermal bridge effects need to be added to the passive house spreadsheet. You can see the isotherms on this picture, showing how the temperature is distributed. 

This picture, much more pretty, shows the temperature by colour, as you'd see from an infrared camera. 

The next picture, perhaps even prettier still, shows the heat flux, with white representing the highest flux. So we can see which parts of the wall the heat is rushing through. 

This software uses what's called a finite element grid, which I can remember hearing about in my lectures at university. I think I nodded off shortly after them, only to wake up just before my finals, but along with the thermodynamics, I realise now that at least something stuck from those days, and at least in some tiny way I can call myself an engineer. I'm not sure whether it was the result of my university study, or whether it was instilled in me from earlier by my father. Perhaps the essence of engineer goes further back, and courses through my veins from generations living in the harsh and unyielding environment of the North of England, with nothing but their ingenuity, which the word engineer probably came from before they ever got around to making engines. I digress.

Calculating heat flow over complex shapes with different materials is tricky, but if we imagine a small rectangle or triangle with a constant temperature along each side, we can easily work out how temperature is going to flow through it. Therm breaks any structure up into such polygons, then goes from one end to the other working out how much heat is going through each part until it reaches some kind of equilibrium. 

Therm can be downloaded for free from here. http://windows.lbl.gov/software/therm/6/index.html

A big batsu for Japanese architecture?

Batsu is the Japanese word for a cross, and it means that something is wrong or not allowed.  I noticed a few of them on the pillars and beams of the house as it was going up. Perhaps I'm reading too much into it, but I can't help seeing it as someone putting red crosses where something is wrong.  And it seems to be a little critical of Japanese architecture.

I learnt in first-year engineering classes that squares and rectangles are not a good idea for a structure, as they create a mechanism. The top can swing from side to side, turning from a rectangle into a parallelogram. If it keeps swinging, as it well might in a strong earthquake, the parallelogram turns into a horizontal straight line with the ceiling meeting the floor. To stop this, you need triangles. 

Our first-year engineering project, as I remember, was to design a structure--basically a bridge-- that would hold one tonne across a span of one metre. Most people built a square-based pyramid, with a hook at the top to hold the weight, and a beam diagonally across the square base to turn the square into two triangles and avoid the mechanism. My group made a tetrahedron: a triangular-based pyramid, so there were no squares to start with. This is the basis of the geodesic dome, which is a very light structure. Our "bridge" weighed a little over half the next heaviest design, fulfilling the goal of the engineer to build something that will do the job using the least necessary resources.

Anyone can build a bridge, we were told, but an engineer will build a bridge that is strong enough for its purpose, using as few resources as possible. 

I really don't know very much beyond first-year engineering, but I can't help feeling that there's just far too much wood in the structure of the house, and it's all in mechanisms. When we're talking about shelves and internal woodwork, I'm constantly being told that solid wood is really expensive, and we need to use laminated wood, or fibreboard. Then I see huge chunks like this being used where the roof meets the walls: 

The lateral strength is coming from kenaf board, imported from Malaysia and made from a baste fibre. A package was left on the balcony the other day, which alarmed me somewhat as it has a "No wet" sign and an umbrella. The architect assured me that this just meant the contents should not get wet, and it would be fine to leave the palate out in the rain.

The kenaf board is being put around the outside of the pillar and beam structure, then the batsu can all be removed. It doesn't look very rigid, but according to this paper it seems to be strong along its length. 

Passive? Or massive assive?

So, this is a passive house, but what is a passive house, and who really cares? Aren't houses all passive? I mean, they don't run around do they! And if this is passive, why does it have an active ventilation system? Pumping air in and out twenty four hours a day doesn't sound very passive!

And why do people say 無暖房住宅 (mudanbou jutaku - literally no-heating house)?

The Passive House, or Passivhaus if you prefer the German name, is a standard based on the idea that, if a house has sufficiently low thermal losses, then you don't need a central heating system. In the long-term, any extra initial cost will be saved a few times over in lower heating bills. In fact, if there is no need to make a central heating system, there may be no extra initial cost. 

Hence mudanbou jutaku. The problem with this term is that it doesn't really mean there is no heating, just that there is no central heating, so you don't need a radiator in every room. It's possible to add a little heat to the ventilation system, so the air coming in is a degree or two warmer. The window manufacturer suggested that if we were cold we could just switch on a 100 watt bulb for a few minutes and the room would be warm enough.

Japanese building is at a stage where there has never been a radiator in each room, and central heating is something that is new and seen a desirable thing to put in your house. At the same time it seems that cutting-edge European building is trying to get away from central heating.

I can't help feeling that I'm paying over the odds for this in Japan, where a lot of the building concepts are alien, building materials are sourced from local cartels, energy standards are lax and voluntary, people who can do the necessary insulation and draft-proofing work are few, far between and charge a premium.

So what is the Passive House standard?

Low thermal losses means three things: 

* high insulation, which will stop heat being conducted and convected away from the walls, windows and doors

* zealous draft-proofing, which means that, in the winter, warm air is not going to be lost

* a heat exchanger on the ventilation system. Thermal efficiency without suffocation!

Thermal gains are also important, so in the winter as much of the winter sun should get in through the windows as possible, which is known as passive solar design. The sun is higher in the summer, so careful placing of fixed shading, and the judicious use of movable shading can stop the house getting too hot when the outside temperature is above the comfort zone around 20 degrees centigrade. Energy efficient appliances within the house are also important, otherwise the house will get too hot in the summer.

The standard states three things:

1. The energy loss from the house should be under 15 kWh/m²; 15 kilowatt hours of energy per square metre of floor space per year. 

2. The total primary energy use of the house should be under 120 kWh/m²a. This is referring to the original fossil fuel, so if the house uses electricity, you need to multiply the electricity consumption by 2.7 to account for inefficiencies in the power stations and getting the electricity from them to your house.

3. The house should leak less than 60% of its volume of air each hour. This sounds like a lot, but houses in Japan generally leak about ten times this, and old houses in the UK are worse, although leaky houses are a good idea when a coal fire is burning in each room!

They also recommend:

a heating load less than 10W/m²

windows with U value less than 0.8 W/m²K, (although see here for localisation).

a ventilation system which recovers over 75% of the outgoing heat

thermal bridge-free construction

See more on Wikipedia and at Passive House US.

Can't you just use metric?

I mean, what kind of unit is this?
Watts/ft/hr/100°F

Watts are SI; feet and farenheit are imperial, also known as US customary units in the country which is ironically about the last bastion of these units based on the size of royal body parts and the temperature of sheep's blood, over three hundred years after the idea of a unified, decimal system was proposed. I've heard the metric has yet to be adopted in Burma or Myanmar (depending on what you want to call the country), and Liberia is the only other country that has not officially adopted the system.

There is another website here that has different pipe diameters in inches, surrounded by recommended insulation in millimetres:

http://www.engineeringtoolbox.com/heat-loss-insulated-pipes-d_1151.html

I suppose motorists in Britain can only relate their fuel efficiency in miles per litre, as they drive along the roads in the former, but put the latter in their tanks. It almost seems as if someone is trying to stop them from thinking about fuel efficiency.

Anyway, there are several different units for measuring energy.

The joule gets its name from the 19th century Manchester brewer who started to use very accurate thermometers in his vats of mash, and discovered that the work of the paddles stirring his proto-beer resulted in a rise in temperature. This brought on the first law of thermodynamics. Although Joule's beer was served in good old pints, one joule is the energy required to work against a force of one Newton by one metre. One newton is roughly the gravitational force on a 100 gramme object, such as an apple. In electrical terms, a joule is the work done to get one amp of current through one ohm of resistance. 

Joules are pretty tiny. Apparently the human body gives off 60 joules in heat every second. The kilowatt hour is much more tangible. Watts measure power (Watt was the name of the person who invented the steam engine, as I like to ask people). James Watt invented the idea of horsepower, but the eponymous SI unit was named after him. It is customary among units to spell them out in lower case, to avoid confusion between the power of Mr. Watt and a watt of power, but capitalise them when initialed, so in Nm or W/mK, the initials of newtons, watts and kelvins are capitalised in honour of Newton, Watt and Kelvin, but the m is small as the metre is not named after anyone.

One watt is equivalent to one joule per second. One watt hour is therefore 3,600 joules, and a kilowatt hour is 3.6 million joules. You'll find the kilowatt hour on your electricity bill. Switch on a 100W bulb for ten hours, and you'll use one. Ovens run at around a kilowatt, so leaving an oven on for an hour will use one kWh. One litre of kerosene contains about 10 kWh. This may be a practical conversion in Japan where kerosene is the heating fuel of choice for those who don't have any choice.

The calorie is another unit of energy. It is not an SI measurement, but it is metric: based on the amount of energy needed to raise one gramme of water by one degree centigrade. According to wikipedia, its use in most fields is archaic, although in my experience, heating engineers in Japan still seem to like it. It is still used for representing energy in food, where a food calorie is actually a kilocalorie, the amount of energy needed to raise one kilogramme of water by one degree centigrade. Water can carry a lot of heat for its weight, with a specific heat capacity of 4.2 kJ/kg^oC, which makes it very useful for heating and cooling. That's why it flows around radiators in cars and houses. One calorie is around 4.2 joules, although the amount of energy required to raise water temperature varies with temperature, so a literal calorie is not an exact unit,and some averaging and standardising has gone on, and in fact it is defined in joules, which go back to the precision of metres, kilogrammes and seconds. 

The British thermal unit is the amount of energy required to raise one pound of water by one degree farenheit. This is the same idea as the calorie, although in imperial units. I don't wish to waste any of my energy discussing this unit, or giving a translation to the other units. Nor can I be bothered to talk about tonnes of TNT, or barrels of oil.

I will add that the sun hits the earth at roughly one watt per square metre, and photovoltaic solar panels produce about 190 watts of electricity per square metre.

To add some hot water to the hot air, if you have 860 litres of water it'll take one kWh to heat it by one degree, or looking at it the other way around, it will give out a kWh of heat if it drops by one degree.

My favourite unit must be the beard-second. In contrast to the light-year--the distance light travels in a year, used for very large distances--the beard-second indicates how much a beard grows in one second, and corresponds to roughly 5 nanometres, or 5 millionths of a millimetre.

The temperature is being logged

Some data loggers have just arrived for the thermometers we put into the slab at a couple of levels. The recording all started back in the middle of winter at the bottom of the foundation, when we added sensors into the rebar.

Then we had all these sensor plugs growing like flowers from the wet concrete.

Most of them survived the layer of aggregate, then another sensor was added in the metal grid for the screed floor. I tried to get them to move the sensors as far as possible from the underfloor heating pipes, outlined in red.

Hopefully the sensor in the middle is around this position, although it may have moved when the concrete was poured.

After the screed floor, there's a few centimetres of wire to the plug. This is at the back of the house where the store room floor is a few centimetres lower and the slab a few centimetres thinner.

To avoid another decapitation, the carpenters very quickly made little boxes to cover the protruding sockets.

Tsukanaka-san arrived from T&D, and fixed the one we broke when the aggregate was poured in. I had tried to fix it, and stripped back the cover of the wire only to find three identical wires inside. I tried to fix them together, hoping for the best, but when Tsukanaka-san and the company president Morizumi-san plugged in the sensor, there was no reading. The president pulled my work apart, and reconnected two of the wires. One is apparently a dummy. He got the right two wires first time!

When the data loggers arrived they had to make bigger boxes.

You can see from the readings that there's already over 2 degrees difference between the temperature at the top of the slab to the bottom. There was also a difference from the west side of the slab, which gets some sunlight in the evening, while the other parts are in the shade. We can track the temperature over the next few months and get some idea of its reaction time, which should help when we start operating the underfloor heating. I'm hoping to some extent we can build up heat at the end of summer, and then release it over the winter so the slab is as cool as possible when summer hits. Probably not enough thermal inertia though. 

Each logger has an index number from 1 to 10, so we have started in the middle of the house with number 1 at the bottom of the foundation, inside the insulation, and number 2 in the concrete floor. Each logger can store 16,000 readings, or around 110 days' worth of data. The batteries last six months, so we need to fix the loggers where we can get to them. They have extension cables, but three pairs are positioned in or under cupboards, one is under the stairs and the other is in the storeroom. Maybe the cupboards should have removable floors or something. The data can be collected by a radio collector, which can then put the information into a computer.

There are fifteen channels, so we can record the room temperature and humidity in a few places, possibly outside as well. Also I was wondering about recording the temperature in the air channel under the solar panels, which I think is going to get quite hot and impair the power generation.

Tower of Babel

Just interesting to note four different writing systems used in four characters on each pillar. "1F" combines arabic numerals and roman letters to indicate the first floor. The house is divided into a grid where Chinese numbers indicate the position from north to south, and Japanese hiragana indicate the position east to west. For the carpenter, the zero point is the north-east corner. The architect, on the other hand, starts with X0 and Y0 in the bottom left hand corner of the drawing: the south-west corner.

The order of the hiragana is not the phonetic order usually used in teaching (a i u e o ka ki ku ke ko...あいうえおかきくけこ) but the older order, i-ro-ha order (i ro ha ni ho he to chi ri nu wo... いろはにほへとちりぬを). This order came from a poem written around a thousand years ago, that contained each syllable only once. Read more on wikipedia. they changed to the new order, based on Sanskrit, apparently, in the Meiji reforms in the latter 19th century. Iroha is still alive and well in house building.  

Less bare pipes... and some bare facts

We met the architect again and he provided some information on the pipe insulation. There was some information on standard polybutene pipe from the suppliers, showing how low their pipes' thermal conductivity was compared with stainless steel or copper pipes (k = 0.17 W/mK cf 16 or 330). This is rather like boasting how tasty your coffee is compared with muddy water.

He also brought a sample of 10mm thick insulating tube that goes around 13mm pipe, and some composite insulated pipe. The advantage of the former is that the inside pipe could be changed without needing to change the insulation. These insulators had a conductivity of 0.043, probably made of polyethylene. They're usually used here for external pipes, which have electric heating elements along the inner pipes to stop them freezing in the winter. The insulated pipes cost about 800 yen per metre. He also talked about some super-high insulated piping that cost 30,000 yen per metre. 

The idea of insulating hot water pipes still seems an alien concept, but to put it into perspective, running hot water in houses is a very new idea in Japan. In the usual mixture of very high and very low efficiency, until recently hot water has been created at or very near the source. Above the kitchen sink is a gas geezer, which produces hot water, up to near boiling. It has a pipe all of twenty centimetres long. The bath water is heated directly by a kerosene recirculating heater which is on the other side of the wall, again pipes very short. the longest pipes are perhaps from the gas heater to the shower, which is on the other external wall of the bathroom. Even then, the pipe may be a little over a metre in length.  In terms of layout, houses are designed by adding rooms onto each other, rather than rooms being filled into an overall structure. Bathrooms, and even kitchens, are not traditionally considered as part of the house; there's a sense in which they are separate rooms that have been added onto it, although kitchen-living-dining rooms have become quite common. In houses, Japanese lavatories always have a pair of slippers in them, and I believe this is because toilets are traditionally considered to be outside, so you need to put shoes on to go there. (I have to confess that most Japanese people think this idea is rather strange, but they have probably never stopped to consider the humble toilet slipper, any more than people in England have stopped to wonder why they put milk in tea.)

Until recently Japanese buildings have avoided the inherent inefficiency of central heating and hot water being generated in one place and distributed far and wide, but the recent propagation of the Eco cute atmospheric heat pump boilers means that hot water pipes are getting longer and longer, and awareness of the issue needs to increase if the Eco is going to reach the house-owner and environment rather than just staying as money in the bank for the manufacturers and electricity companies. At the moment heat loss in hot water pipes seems to be off the radar, languishing in the zone of apathy and ignorance.

Anyway, I did some calculations, and using the 13 mm polybutene pipes under the floor will mean a heat loss of 100 Watts per metre. In other words, whenever we are using hot water, it's like switching on a 100 Watt light bulb for each metre length of the pipe. To the kitchen, the pipe drops about three metres from the boiler upstairs, then meanders three metres under the floor, and climbs another metre to the sink. If we assume a very minimal ten minutes' hot water use per day, and ignore losses from what's left in the pipes each time it is turned on or off, then we will lose 42 kiloWatt hours per year. Similar calculations for 30 minutes' hot water per day going to the washing machine lead to 126 kWh per annum. 

Pipes with 10mm insulation will lose around 7.5 W/m. If we ignore the pipe space under the floor and save two metres on each length by sending the pipes across the ceiling and down the wall, and use higher insulated pipes, we get the losses from the kitchen down to 2 kWh/a and the washing machine to 5.4 kWh/a. Seems worth it. 

For these calculations, I'm assuming hot water at 45 degrees centigrade, and a temperature difference of 25 degrees to the 20-degree room temperature. I think 45-degree water should be hot enough. It's usually set much hotter, which just results in more waste. Thankfully, no hot water pipes have been installed for the basins by the lavatories, perhaps unthinkable in Europe, but another plus for Japan's eco-credentials. 

The architect had brought another sheet of paper with a list of insulated pipe materials and thicknesses, the thermal conductivity (熱伝導率 netsu-den-do-ritsu) in W/mK and what it called 熱貫流率 (netsu-kan-ryu-ritsu), the coefficient of overall heat transmission, which it gave in mK/W. Generally speaking, any given material has a thermal conductivity, which is some indication of how good it is at conducting. When it gets below 0.05 it's insulating fairly well, although there is no magic number at which something becomes an insulator and stops being a conductor. Wood is around 0.17 W/mK, and anyone in a log house will tell you that it's quite warm, if the walls are thick enough. Of course, even insulators conduct--just not very well. There are no perfect insulators (except a perfect vacuum) any more than there are perfect conductors.

Once a material is made into a wall, a pipe, a fur coat or some kind of structure, that combination then has a coefficient of heat transmission. For flat surfaces, this is usually given in W/m2K and called a U value or U factor. It shows how much heat will flow through the surface for each square metre, for each temperature difference of one degree. For pipes, this is given in W/mK, as we're not so interested in the area of the pipe, just its length. Rather confusingly, the units for thermal conductivity of materials, W/mK, are the same as those for pipes.

Whoever had produced the sheet of paper with the figures for pipe insulations had evidently not appreciated this, and for a start had got the units for coefficient of heat transmission upside down, mK/W. They had put a note at the bottom saying that it was a measure of how easily heat passed through the pipe which was correct. Whoever had made it had simply divided the thermal conductivity by the thickness of insulation, and come up with a number with scant regard for the units, dividing W/mK by metres, and getting mk/W. Obviously never heard of dimensional analysis.

Newton worked out that heat flow was proportional to surface area and temperature difference, and inversely proportional to thickness of material, and thermal conductivity is the heat flow per area, per temperature difference for a unit of thickness. To get to the heat transfer coefficient (U value or U factor) for a flat surface, you just have to divide the thermal conductivity by the thickness. (So if you had a wall of polyethylene one metre thick, it would conduct heat at 0.043 W/m2. The best natural insulators are around this level, so if you're aiming for 0.15 W/m2, your wall needs to be about 30 cm thick.)

For pipes, the picture is a bit more complicated as the surface area gets bigger the wider the pipe is. We have to use calculus, another of Mr. Newton's tricks, which should also be credited to Leibniz, and take the integral--the last recourse of the mathematical scoundrel. This gives us the equation:

Q = 2 pi k L (T1-T2) / ln(r2/r1)

Or U value for the pipe (in W/mK) = 2 pi k/ln(r2/r1)

Where:

k is the conductivity of the pipe material,

r2 is the external radius (half the diameter)

r1 is the internal radius

T1 is the internal temperature

T2 is the external temperature

ln is the natural logarithm. 

pi is π the ratio of the circumference to the diameter of a circle.

You can use Google as a calculator and put in something like (2 * pi * 0.17 /ln (0.0085/0.0065)) and it will understand and know what to do. Isn't technology wonderful!

Bare pipes

I did ask where the insulation around the hot water pipes was, before the pipes were buried and sealed under the concrete screed floor. The cold water comes into the house on the north side, running under the store room, then shoots up the pipe space in the middle of the house to the boiler. The blue pipes have cold water pipes in them, already plumbed in, and the red are for hot water pipes to be sent through later. 

This is the utility room looking East. The cold blue pipes are coming from the storeroom to the left. Five red hot water pipes are coming down the pipe space on the left. One is going to the sink, which you'll be able to see on the left against the far wall. To the right of the sink is the washing machine, which is fed by one hot water pipe from the boiler, and another carrying bath water, which in Japan is usually used in part of the clothes-washing cycle. Another pipe heads off south to the kitchen.

This is the view from the utility room, standing on the left of the last photo looking to the right. You can see two blue cold pipes coming to the dish washer and the kitchen sink, and a red pipe for hot water to the kitchen sink. The drain (grey) runs in a lovely straight line, which is a jolly good idea. The hot and cold water pipes meander about a metre to the left, adding to their length and heat loss, which doesn't seem such a good idea.

Hot water pipes loose heat in two ways. First, as hot water is flowing through them, it conducts out of the pipe. This increases as the pipe gets bigger and longer as there is more surface area, and decreases with more insulation around the pipe. I can remember doing a maths problem at school to work out the optimum width of insulation, which showed that there is a point after which more heat is lost than gained because more insulation is increasing the external width of the pipe, and this has a greater effect than the reduced heat loss through extra insulation.

The other way heat is lost is because hot water is left in the pipes after the tap is switched off. The longer the pipe, and the greater the diameter, the more hot water is left inside. This hot water will likely cool down to room temperature before the tap is turned on again, so all the heat in it is lost. This will also mean that when you turn the tap on, cold water will come out at the beginning, and, depending also on the level of insulation, it will take a while to get to the desired temperature. So generally short, narrow, insulated pipes are a good idea. There's an excel file here that can calculate all of this for different pipe lengths, widths, amounts of insulation and temperature differences.

Anyway, this all seems to be a digression from what's happening in my house. I asked the architect at least twice about the insulation, a week or two before the screed went down, then more urgently a couple of days before. I also sent him an email on 15th May, which has yet to be replied to. He told me that the actual hot water pipes would be sent through the red tubes and that they would be insulated. I've since asked for details of the insulation on these hot water pipes, and he's told me each time that he'll find out and get back to me.

I asked the site manager yesterday and he told me that there wasn't going to be any insulation on the hot water pipes. Evidently we share different notions of energy efficiency, and the importance of keeping hot water pipes short and well insulated that I've been talking to the architect about for two years now has not registered. Maybe this is just a Japanese architecture thing, where stuff like electricity and water should not really be in a house in the first place, so are not really part of the equation and should just be quietly ignored or hidden as best they can. Most of this theory goes back to Newton's law of cooling, so it is not particularly revolutionary, new-fangled or controversial.

Anyway, I'll be encouraging them not to use the underfloor pipes, and save about three metres of pipe length by going across the ceiling and down the wall, rather than down one wall, under the floor, then up another wall. Rather than two separate hot water pipes going to the sink and the washing machine next to it, the same pipe can take hot water to both. This may result in lower pressure, but usually both are not going to be used at the same time, so that is not a major issue.

To be honest, I would have been happier to see some insulation around the cold water pipes. In the winter we're going to be sending hot water through the floor to heat it up, and the cold water pipes are going to be doing exactly the opposite. With the hot water pipes, as well as the simple question of efficiency and the fact that any heat loss means less hot water coming out for each kWh of electricity we put in, a bigger problem is in the summer when this heat loss is going to be warming up the floor slab that we'd rather stays cool. 

The final piece goes into the puzzle

As jigsaw puzzles go, our roof was probably not the most complicated, with it's 48 identical pieces. As I said before it didn't identically match the picture on the box, but it was pretty close. It still took them a couple of days. I saw them put the last piece in around 10am on the second day, and they then put the cosmetic panels around the edges, and were away around tea time. This was the biggest array they had assembled. They had put up another 48-panel array, but with these panels rated at 190 watts each, rather than 180, it's the most powerful. Apparently it's the most efficient format, under 10 kiloWatts, as panels need to be 6 in a series to get the voltage high enough. If you go over 10 kW they consider it a power station and you loose a lot of the benefits. While the steep angle had been a real headache for the carpenters, 31 degrees is pretty much ideal for solar panels, so they were very happy.

So now we have our very own 9.12 kW generator. Unfortunately it doesn't look like it's going to be plugged in until October, when the house is ready, so those electrons will just be sitting in the panels, all revved up but no circuit to go around. It will be dormant over a summer with peak air-conditioning demands and nuclear power stations that have been put off line now that they realise they were being kept to the same safety specifications as the ones in Fukushima.

I was trying to convince the site manager that they should at least try to use it for the onsite electrics, rather than paying for the power through the temporary sockets they've installed. He seemed to think it was impossible, as they can't use it until the contract with the electric company. I have a lot of trouble understanding this. As far as I know, the electric company does not own the sun, and I own the panels and the power conditioner, which converts the direct current of the panels to alternating current. So anything that comes out of them is mine, and should be possible to use on site, providing the sockets are connected by a competent electrician. And I sincerely hope that our electrician is competent. 

There may be some subtlety of a power conditioner that I don't understand, or it may be that it needs to be connected to someone on the main grid to tell it when to switch on and off, although that leads me to wonder what would happen in the future if there is a power cut. I'm hoping that having our own power generation will mean that in a power cut we'd still have power, at least in the day time unless it's very overcast or there's a few inches of snow on the roof.

I mean, it's not like it's going to explode from a build up of electrons, or the electrons are going to start pouring out and getting into the sea or anything. Electrons don't do that.

Roof going solar

Forty-two of the 48 solar panels went on the roof today, making up most of the 9.12 kiloWatt array. Three companies were on site this morning, although the architect didn't make it until later as he'd been out of town, and nobody from the builders came all day, as far as I can tell.  The three companies were the manufacturer of the solar panels, Caname; Rooftech, a company from Yamanashi who install solar panels; and Yamazaki, the roof-workers, who work for Rooftech. The electrician also came in at some point to discuss the connections, although the last I saw this won't happen until October when the house is ready.  I'm sure, at the very least, they could connect the power conditioner up so that everyone working on the house can use the free electricity rather than having to pay for it.

The eight people working on the roof seemed to spend a few man hours at first working out what to do as the top of the roof was 13 mm wider than on the plan, and it was about 5 mm longer from the top North ridge to the bottom South edge. They seemed to work out what to do eventually, and they started sending materials up to the roof just as I had to set off from work. I got back in the evening to see them install twelve panels and send the remaining six up to the roof ready to install tomorrow. 

I saw the carpenters working on the tricky west side of the roof a couple of days ago, as they laboriously trimmed all the rafters sticking out the side of the roof, only to find that the eaves weren't straight when they put them on. They hammered away to take the eaves off, then knocked off for their lunch. If I'd known how much trouble the west wall was going to be, we may have gone for a square house, but every time I look at it, I'm convinced it was the right decision.

Those numbers, 42 and 48 have another significance.  We reckon on around 100 kWh/Kw month. In other words, we have 9.12 kW of panel, so we can expect 912 kWh of power each month. KiloWatts represent the power, and one kiloWatt for one hour amounts to one kWh of energy. Electricity companies sell their electricity by the kWh. Manufacturers of devices that produce or consume electricity rate their products in Watts or kiloWatts.

Now, in their attempts to encourage solar power, the government has been obliging power generators to pay people with solar panels over the normal electricity rates for their electricity. There's a ten year contract and the price last year was 48 yen per kWh. Electricity companies usually charge around 24 yen per kWh. If we could sell all our solar electricity, and only use cheap offpeak night time electricity, at 9 yen per hour, then we'd get an income of over 40,000 yen per month. 

The prices drop to 42 yen this year, which represents a loss of over 5,000 yen per month. With all the delays, it was looking like we'd missed the boat for 48 yen, but I just heard that, because of the recent earthquake and disruption to the building trade, they have extended the 48 yen contracts. I don't think our delays had anything whatsoever to do with the disaster. There does seem to be an invigorated interest in solar power as a result of Japan's recent nuclear problems, and it seems likely that the government will continue or even increase their subsidies and benefits. To be honest, until now they seem to have been more interested in increasing sales for their friends in the big electric manufacturers, who happen to hold large chunks of the world share in solar, and the "eco" has been more -nomic than -logical.

Post-Promethian Society

Burning stuff has been a pretty important part of humanity for a while now. Fire has been around in nature a long time, and we have to say that it was discovered and harnessed by humans rather than invented. According to Greek myth, Prometheus stole it from the gods to give to man. Other mythologies share this theme of theft

Perhaps in the distant future there will be myths of how the god Watt stole coal from the ground and turned it into thick air, or how divine Einstein found electricity in rays of sunlight. Wikipedia mentions the hero Mātariśvan in the Rig Veda (3:9.5), recovering fire, which had been hidden from mankind. In Cherokee myths and those of some Pacific Northwest tribes, fire was variously stolen, or almost stolen but ultimately handed over to humans by Possum, Buzzard, Grandmother Spider with her web, Coyote, Beaver or Dog while among some Yukon First Nations people, Crow stole fire from a volcano in the middle of the water. According to the Creek Indians, Rabbit stole fire from the Weasels.

It sounds far-fetched, but remember the ancient four elements—fire, air, water, earth—are in fact four states. Plasma, gas, liquid and solid, liquid.

I watched the Day After Tomorrow the day before yesterday. The basic plot is that drastic climate change happens, but not by a couple of degrees over a few score years, but by scores of degrees over a couple of days. The science is hardly that rigid. It seems that changes in ocean currents cause a massive hurricane-like storm system over the northern hemisphere. I suppose that much is possible, although it's unlikely as hurricanes hardly ever happen high in the arctic, possibly
due to the Coriolis effect, which is largest in the tropics and sub-tropics.

The eyes of these storms brought down cold air from the troposphere, where the temperatures are very low, and froze everything in sight. I think the problem with this is that temperatures are very low in the troposphere because pressures are very low. We'll find out more of this when we consider how heat pumps work, but basically as the pressure drops, the temperature drops and as the pressure rises the temperature rises. You can feel this with a bicycle pump. Generally a rise of 100 metres will lead to a drop of one degree (although less if the air is humid) and a fall of 100 metres will lead to an increase of one degree. This causes the Foehn effect in alpine climates, where humid wind blows up one side of an alp, dropping in temperature slowly and shedding its humidity as rain. It then heads down the other side of the alp dry, gaining temperature as it falls leading to a very hot day in the valley on the other side.

If the eyes of these storms were making holes in the atmosphere where there was no air at all, then there would have been no pressure either, and rather than freeaing, people would probably have boiled, and their eyes popped out. However, I digress from Prometheus. That's sounding more like Tantalus.

I suppose the movie was trying to advocate action against global warming, although a lot of the time it felt like it was just nostalgia for those disaster movies of the 80's. The biggest problem was the reaction to this storm, which was for them to burn as much as they could. The hero was holed up in a library with his septicemic girlfriend, an aging gentleman of the road and a couple of librarians,
and their solution was to start burning books. It would have been much more sensible for them to line the books around the walls for more insulation and to reduce the size of the room, and start burning the furniture and shelves, or the guy who was clutching the bible. The only allusion to this was the gentleman of the road tearing bits out of a book and stuffing them in his clothes. The hero, his two sidekicks and the romantic adversary were all supposed to be academic decathletes, but the bum seemed to know more about thermodynamics than they did, and more than the people who made the movie for that matter.

So the moral of the story was... global warming's coming but you'll be OK if you burn lots of stuff.

Thermal bridges and nekkyo

There seems to be some confusion over thermal bridges. The concept in English, or in fact German where it arose, is connected with multidimensional heatflow.  Insulation is not really rocket science. All materials conduct heat, the better at conducting, and the thinner the layers, the more heat is conducted. The worse at conducting and the thicker, the less heat is conducted. Everyone knows this, so we'll put on a thick down jacket in the winter rather than a thin cotton shirt, and put a pile of newspapers rather than some aluminium foil on the table underneath a hot baking tray. It's very easy to calculate heat flow in one dimension. If there is an infinitely large wall, a uniform thickness of a uniform material with one temperature on one side, and another temperature on the other, then heat is going to flow in a straight line, in proportion to the conductivity of the material and the temperature difference, and in inverse proportion to its thickness.

Unfortunately, buildings are not made up of infinitely large walls of uniform materials. Or we may consider this to be fortunate if we appreciate having our own buildings, and the luxury of doors, floors and roofs. When the wall hits a window, or hits a corner, of if the wall is made up of different materials and contains pillars and beams, then the calculations change. The walls we are using in our house are basically made from a wooden frame of 120x120 mm pillars and beams, with the gaps between filled with insulation, then one layer of 50 mm insulation on the inside, and 100 mm of insulation on the outside, held in place by plastic brackets. If we forget about the internal and external layer for a moment, and just consider the 120x120 mm beams and pillars, filled with insulation, then we can do a simple calculation of the insulation performance by assuming that around 10% of the wall is wood, which has a conductivity of about 0.17 W/mK, and 90% glass wool, with a conductivity of about 0.04 W/mK.  Average them out and you get about 0.05 W/mK.  

This is not really a thermal bridge in English, but is often referred to as Nekkyo (literally heat bridge) in Japanese. In one sense the wood is acting as a bridge for heat to get through the insulation. The same effect could happen with nails or various other heat conductors that find their way into buildings, innocently going about their business of stopping the buildings from falling down. The thermal bridge effect is usually considered a secondary effect to this. Once you start introducing different materials of non-uniform shapes and varying conductivities, heat does not simply travel in one direction. It will take the easiest path, and more heat is going to rush through the higher conductors, so the wall will lose more than the simple average suggests. As the amount of insulation goes up, the significance of this error becomes greater, and care must be taken within wall and roof structures and at the boundaries between walls, and between walls and floors, ceilings, doors or windows. Windows and doors should be designed and constructed so that the thermal bridge effects are as small as possible between glass and frame, between moving frame and stationary frame, and between the stationary frame and the wall. 

There's a great piece of software called Therm that can calculate all this. http://windows.lbl.gov/software/therm/6/index.html

It'll look nicer when we get the wallpaper up...

... and the walls.



This is the upstairs.


Here's the view from the south-west corner.

All in a day's work

Yesterday there was blue tarp, filled with puddles, and today it looks like a house.

When I got there a little after 8am, most of the pillars for the first floor were in place. When they knocked off a little before six, they had reached the roof. Tomorrow they should get the rafters and the bottom of the roof on, and it will be ready for the solar panels, which arrive on Tuesday.

It's impressive what seven men with tabi on their feet and tools belts around their waists can do with a crane and seven truckloads of wood. 

The wood was all ready cut and in many places it looked like a giant puzzle that had been set for the carpenters by the architect, who was standing watching from the edge of the site for a lot of the time.

It's amazing how quickly this has turned from a stagnant pool of concrete into something that really resembles the house that we've been planning for the past two years. It's a bit like a sumo bout where they spend half an hour position themselves and eyeing each other up, then the action is over in about three seconds.

Yesterday I was looking at puddles in tarpaulin, and today I was walking around upstairs. A link has finally been made between the building in my head and a solid and substantial house we can live in!

Four corners

This works better than the stereo vision. Soon there'll be pillars sticking up from each of these corners.

The shape of things to come

For a while it felt more like funeral than a christening. There was a great sense of loss as the concrete was being poured and the plans that have been living, breathing and growing for years were set in stone. Gravel to gravel. Cement to cement.

Now that the first pieces of wood have gone down and the scaffolding has gone up, it really seems like we have a house. You can see the scaffolding from across the bridge, where in a few days there will be a roof, and in a few months a whole house. From the shape of the scaffolding, you can see roughly how the house is going to look. I've been taking pictures from strategic spots around the plot, with a view to charting the progress of the building and ultimately creating a movie from all the stills. It's a relief, now that the scaffolding is up and the shape of the building is clearer, to see that it will fit into the frame that I have been taking the pictures within. 

Now I have to work out exactly where to take pictures inside the house, so that the same effect can be created with the interior, as it turns from empty space surrounded by scaffolding to furnished space. I need a good idea of where we'll be able to take pictures from when it's all ready. I'm sure there is somewhere from the scaffolding that will correspond to a good interior shot of the house, but it's tricky to work out exactly where it will be.