Wednesday 30 December 2015

Lesson 10: generating power

First I asked how power could be generated, which elicited a long list, including the methods below that I had prepared earlier.

The first electric power was probably generated by water, just as water mills were probably the first regular power sources to be harnessed, long before the discovery of electricity or the scientific understanding of energy and power. In 1868 a hydroelectric power station was built at Cragside, a country house in Northumberland, UK. The first modern power station was built at Niagara Falls, 1895, producing alternating current that was sent over power lines to a town several miles away. Coal was first used to generate power in 1882, in Pearl Street, Manhattan. The first electricity was generated from wind in 1887 in Glasgow. The first commercial wind farm was commissioned in 1980 in Crotched Mountain, New Hampshire. Geothermal power began on a small scale in 1904 in Lardello, Italy, and was commercialised in 1911. Oil and gas are also used to generated electricity, using similar steam turbines to coal power stations.

More recently,  nuclear power was first generated in 1954 in Obninsk USSR. Silicon solar cells were first made in the same year, and the first large-scale solar power station was built in the Mojave desert, California, in 1984. Other forms of generation include biomass, tide and wave.

Which of these is zero carbon?

None of them!

Why not?

In each case, fossil fuels are used, and carbon is emitted at some stage in the construction process. Once solar cells have been installed or hydroelectric dams have been built, electricity can be produced without carbon cost, but we need to take account of the whole lifecycle when estimating carbon footprint. Radioactive decay does not produce any carbon, but the mining, transportation and purification of nuclear fuel do, and these must be taken into consideration. 
The more pertinent questions are: which is lowest carbon? which is cheapest? and which is best? I gave this question a little bit more depth by asking which is the best way to make energy if you're an electricity company; if you're a government; if you're a city; if you're a business or if you're a home owner.

There are at least three factors to take into consideration when we're looking at cost analysis. First is $ per kWh. Second is kilograms of carbon per kWh. Third is energy return on energy invested (EROI, or EROEI), kWh out per kWh in. You can see some comparisons in the table below from two different studies.

Murphy and Hall
(2010)
Scientific American
(2015)
Hydroelectric
100
40+
Wind
18
20
Coal
80
18
Natural gas
10
7
Solar
7
6
Nuclear
10
5
Oil 1970
35
Oil 2007
12

If you are a homeowner, you would not want to live under a coal power station or a nuclear reactor, and most locations would not suit hydroelectric turbines or windmills, but living under solar panels seems like a good idea in most places.

The current economics of solar power  see costs falling, year on year, and the cost of the competition rising. Fossil fuels are finite, and the situation can be likened to hiding ten thousand yen in hundred yen coins around the room. The first few coins will be really easy to find, but as more are found, the time and effort taken to find each one will increase. You can see in Murphy and Hall's data above that oil in 2007 takes almost three times more energy to extract than it did in 1970.

Grid parity is the point at which solar power costs the same as other electricity available on the grid. Of course this will be different at the point of production to the point of use. If you are an electricity company considering building a new power station, the cost of solar electricity will need to be cheaper than other options such as nuclear, coal or hydroelectric. If you are a homeowner, then you are comparing the generation cost with the market value of the electricity, which includes the transmission costs as well as other overheads and profits of the electricity companies. In many places grid parity has been reached at the point of use. This depends greatly on the local cost of electricity, and local sunlight conditions, as well as local cost of solar panels and fees for installation. Conditions are skewed by grants and feed-in tariffs.

The advantages of solar power generation include no fuel, no pollution, no noise and a long lifetime. Solar power is modular so an array can be any size from a few watts to a few megawatts, to meet supply or demand, while other forms of electricity generation need to be on a large scale. The disadvantages and challenges include the high cost and relatively large area. Orientation must be carefully considered. Solar power is unreliable and varying: nothing will be generated at night time and clouds and weather make a difference. Sunny days produce a predictably high level. Overcast days produce a predictably low level. The worst days are partly cloudy, when generation will go up and down with each passing shadow.

This is a particular challenge for the electricity companies, who have long been working on the balance between electricity supply and demand. Unlike other areas of supply and demand, electricity must be immediately available when people turn the switch on. Usually the various users in the grid will average out, but George Monbiot, in his book Heat, writes about the FA cup final. When this is on, most TVs in England are tuned to the game. This is not such a big problem, but when half time comes, somebody sitting in front of each of those TVs gets up, goes into the kitchen and puts on the kettle. This creates a surge in demand bigger than the largest power station in the country. To cope with fluctuations in demand, there are hydroelectric facilities which pump water up the hill when there is too much electricity on the grid, and send it down again when more is needed.

I have an image of guy somewhere in Wales in front of a portable TV, glued to the first half of the game and ready to flick a switch as soon as the ref reaches for his whistle.

Storage may be needed to cover the unreliability of solar, but the extra cost of the storage, especially in terms of energy, may make an already marginal source of power unsustainable.

Will solar panels save us? Are they good for the environment? Until now more energy has gone in to making solar panels than has been generated from them, but that changed around this year, and as production becomes cheaper, the return on energy invested will improve. They may save us in the future.

I didn't properly have time to cover the installation of solar panels, the best orientation, angle to the horizontal and other conditions such as the avoidance of obstacles.

Also I didn't have time to talk about solar thermal collectors, which can make a difference to the energy use of a building. There are flat plate collectors and vacuum tubes, circuits and drain back systems. Challenges include overheating, freezing, hygiene, and once again we face unreliability and the need for backup

I also didn't have time to talk about PV-T hybrid systems that combine electricity generation and collection. In the process of collecting heat, the photovoltaic elements are cooled, which makes generation more efficient, and overall these kinds of panels can reach efficiencies of something like 80%.

References
Murphy, D.J. & Hall, C.A.S. (2010). "Year in review EROI or energy return on (energy) invested". Annals of the New York Academy of Sciences 1185: 102–118.

Monday 28 December 2015

Lesson 9. Windows 2.0

Back to the windows again.

We started with the same question: how could you improve the windows in the classroom? And got a fairly good range of answers, which I covered for the rest of the class. 

I gave them a short history of double glazing, from the probable invention in Victorian Scotland to commercialisation in 1930s US. Coal was cheap and windows expensive in the UK until the oil shock of the 1970s, which gave birth to the predatory double glazing salesman. I found an Everest TV advert to show them with Ted Molt on top of the Pennines. Nostalgia for me. Alien historical relic for them!

The double glazing wars continued and thicknesses began to increase. At first windows had a 6 mm gap. This went up to 8, bringing up to 50% improvement in window performance and giving the salesmen a number to show customers that their products were better than others. This went up to 12 mm, which showed a slight performance improvement and allowed people to say: "The neighbours have 8 mm double glazing, be we have 12!" They then wanted to go up to 16, but in fact this does not improve the windows, and as they get thicker, the performance starts to get worse. This is because of convection. Air can circulate within the window gap, letting heat from the inside surface rise, then drop down the cold surface on the other side. 

Capitalism and competition are not always a bad thing, and in the case of windows they have brought great improvements in performance, which have certainly improved comfort and probably reduced energy use. With extra thickness shut off as an avenue for improvement, the manufacturers had to look to other tricks, such as low-e coatings, triple panes and noble gas fillings.

After this history lesson, I wanted to give them an exercise in choosing windows, and I'd spent a long time trying to find realistic costs of windows and U values. I wondered whether something like Heisenberg's uncertainty principle was taking place, and it was impossible to know both the cost and U values of a window at the same time. 

I put "double glass" in Japanese into google shopping and it came up with some rather nice looking Bodum drinking glasses. It certainly looks like insulation is a bigger priority in Japan for beer drinking than house building. There is also a semantic element. Japanese has two words for glass: garasu and gurasuGurasu comes from English and refers to drinking glasses. Garasu comes from Dutch, and refers to the material. Even a search for garasu seemed to yeild more drinking glasses than windows.

I had previously spent ages trying to find a U value for the double glazed windows in the classroom, which are basically single-pane frames with two bits of glass forced in there. I started trying to find the worst double glazed windows in the world. Australian wers.com has a useful searchable database. Their worst double-glazed windows have a u-value of 6.4. That's the same as a poor single-glazed window. 

I had time in this lesson to properly introduce the surface resistance, which is an extra R value applied on each side of an insulation unit. If you imagine a thin piece of paper in the middle of a wall, it's going to have some effect keeping you warm, just because it's stopping the air from moving. The surface resistance on the outside is 0.04 m2K/W, and on the inside it's 0.13 m2K/W. The surface resistance on the outside is less than on the inside because it's more windy and the heat will be taken away more easily. 

I asked them to calculate the U value for a piece of paper by adding up the R values and ignoring the R value of the paper. This gives a U value of 5.9.

Somebody asked how the windows could have a lower U value than a piece of paper. 

I know, it's impressive isn't it. That's the power of aluminium!

They did quite a good job comparing the different kinds of windows, working out how much heat each one would lose over a year, translating that into heating costs and working out how many years it would take for the heating savings to pay for the windows. 

References
An interesting article here on homes.co.jp (in Japanese). Title roughly translates to "Japanese windows: More interested in convenience for manufacturers than benefits for consumers"

Friday 18 December 2015

Eight ultra low energy passive buildings around the world

The internet is as replete with exotic buildings of exemplary design as the real world is filled with concrete contortions and architectural afterthoughts. 

Here's a list of eight ultra-low-energy passive buildings from around the world. It says they are passive houses, but they may not all be certified, or even meet the standard. They are all at least based on PH principles. 

One of them is particularly interesting as it's a dome. As far as I know there are no certified passive house domes, which is a bit surprising. I'd love to find out more about the halo dome in China, but searching for it on Google mostly arrived at a vape pipe. I wonder if they left any cookies.

Domes are very energy efficient shapes, with a lower surface area to volume than any other. The only way to get a better form factor is to start turning it into a sphere and bringing it out of the ground. You sometimes see water tanks of that design. Even then, you may be better off with a hemisphere since the ground tends to be warmer than the air in the winter, so less heat will be conducted than into the air. On the other hand, heat is often more convected than conducted to air, so the conduction to the ground may be higher. Also, there would be less radiation and less convection from the parts of a protruding sphere pointing downwards. I probably need to investigate this more.

Looking at the geometry of form factors, a single storey dome of any size has the same form factor as a completely square two storey standalone building. If the dome has many storeys inside, it will have a better form factor than anything. The only problem is building without straight lines and right angles. A trivial problem when you're sketching ideas on paper, but a huge problem when you're procuring building parts and giving instructions to builders.

Wednesday 16 December 2015

Lesson 8: Standards

There are several reasons to build a low energy building. It may save you money through cheaper bills over the lifetime of the building. It may reduce your carbon footprint and reduce damage to the environment. It may be eligible for grants or tax breaks that could make building or financing cheaper. 

Another reason, in some places, is that there are building standards that require you to build a low energy building. The earliest of these was probably the Danish BR77 standard, introduced in 1977 and obligatory a couple of years later. The 1980 Swedish SBN-80 (Svensk Bygg Norm) also set demanding energy efficiency requirements early on. Around the same time the R-2000 standard came out in Canada, although that was voluntary.

At the risk of coming out with a lesson dryer than the one on humidity, I started off putting my students into a couple of groups, telling them to imagine they were governments and getting them to come up with some standards to reduce energy use in buildings.


First they were to brainstorm a list of ideas. Later they would be able to use judgement and discussion to choose the best. They had various ideas, from banning aluminium windows and setting limits on carbon emissions to setting up bodies to reduce energy use and prohibiting air conditioners.
There are basically three different kinds of standards: prescriptive, performance based and outcomes based.

Prescriptive standards tell builders and designers what they must do, for example that walls must have U values of 0.13 W/m2K. The advantage of prescriptive standards is that they are clear and definitive. The disadvantage is that they may may be too conservative, leading to buildings that are over-engineered, or they may not take into account how prescribed building elements are used, for example the orientation of the windows.

Performance-based standards require calculations to predict how much energy a building will use. For example heating energy of less than 15 kWh/m2a. This gives designers more freedom in how to use building elements in optimal ways, and to make sensible compromises with the over picture in mind. They do mean that designers have to make those calculations. Performance-based standards may also help in the introduction and use of non-traditional features and techniques.

Outcome-based codes mean that the actual performance of buildings is measured and reported, to ensure that standards have been met. If it turns out they don't, it's too late!

I gave a brief history of building standards around the world, starting in the 1970's. I briefly mentioned the US's flirtation with energy conservation in that short era of energy democracy, before the energy republic of Reagan took over.

The main story was in Denmark and Sweden, where standards in 1980 were only reached in the UK in 2006. Meanwhile over here in Japan, the standards today in Matsumoto are roughly equivalent to those in 1985 in the UK.

Of course it is very difficult to compare building standards in different countries, and normalising for weather is one issue. Another is how many buildings comply to the standards. Not only are Japan's standards something like thirty years behind the UK and fifty years behind Sweden, they are also applied to well under half of newly built small homes.

Here are some links if you want to read more:
Global energy efficiency measures could save €410 billion by 2030
Map of global standards

Friday 11 December 2015

15 quid a year Passive House in Wirral wins award

On the BBC here.
And more details from architects John McCall here.

It's similar to our house in many ways:
  • Roof integrated solar panels, although I think we about have twice as many
  • Atmospheric heat pump, so electricity is the only energy source
  • Underfloor heating
  • The same foundation structure
  • Similar annual heating load where we are and the Wirral 
The construction is completely different. Ours is wood but theirs is concrete block. It looks to have better insulation and better windows, and is more airtight.

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

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

Tuesday 8 December 2015

2015: Hottest year on record

Yes, 2015 is the hottest year on record. It's official! Admittedly my records only go back three years. But this year is definitely the hottest!

Usually we switch on the heating 1st December. This year it's already a week later and we haven't thought about switching it on yet. It doesn't feel like we need it, but maybe that's just us getting hardy? 

With sixteen thermometers built into the the house, recording data for the past four years, it's possible to actually check the data. Numbers don't have feelings!

I looked at just three temperatures: the centre of the slab, the south-west corner of the slab, and the north-west corner of the slab. The slab is something like seventy centimetres deep, so there is a big different in the fluctuation of temperature from top to bottom, and up to a couple of degrees difference in actual temperature. The temperature at the top of the slab can vary by up to half a degree in a day, while at the bottom it's more like half a degree a week. 

As of 8th December, the middle of the slab is warmest, currently around 23 degrees. The South West corner is a couple of degrees cooler, around 21 degrees, and the North West corner is a few degrees cooler still, around 17 degrees. This is near the front door, and that's another story. 

As the temperature outside rises and falls, the temperatures inside slowly follows, heat making it's unassailable journey from hotter to cooler. The North East corner of the house gets cooler quicker, less affected by the sun, and more affected by outside air. The centre of the house is slowest to cool, surrounded by all the thermal mass of the concrete. In the summer it is the slowest to warm up.

Looking back over data for the last three years, the house was at the same temperature on 16th November 2014, 13th November 2013, and 20th November 2012. That's around three weeks earlier. 

The threat of global warming threatens increased flooding, extreme weather conditions and climate disruption. A reduction in my already very small heating bill may offer a silver lining, admittedly a pathetically thin one that may not help people who have to cross their living room by dinghy. I may be able to buy a new paddle for my dinghy. 

Wednesday 2 December 2015

Lesson 7: Ventilation

The first attempt at teaching a course is always a much bigger lesson for the teacher than the students. As in warfare, the first victim of a lesson is often the battle plan. 

Three times I've found that a single lesson has turned into two, and the course feels like it is being resized and re-dimensioned. I thought we were almost half way through the time, but only a quarter of the way through the plan, but checking back with the plan I now realise that the lesson I had prepared on insulation included thermal bridges, and the lesson on air and water included ventilation, which were four lessons on the original plan, and I'm more or less where I thought I would be. 

The ventilation lesson began at the realisation that houses must be both insulated and airtight to have low energy loss. If an insulated building is not airtight, three things will happen: you will get condensation within the walls, you'll lose heat with the leaking air, and you'll get fresh air in the house. The last one doesn't sound so bad, and in fact you need fresh air in a building. I asked the class why, and how much we need. 

The most obvious is to provide oxygen. Although the most obvious it is not the most serious. We need around one litre of air per second per person to avoid a build up of carbon dioxide. Relatively low levels of carbon dioxide can lead to lack of concentration. 

You need about three litres per second to remove nitrous oxides given off while cooking, and 3.5 litres per second do remove unpleasant odours from the house. Then you need about 6.5 litres per second to be safe from the volatile organic compounds that are used in paints, varnishes, glues and other chemicals in building and its furniture. The biggest need for ventilation is to stop a build up of moisture, for which we need about seven litres per second per person. The air we exhale is close to 100% relative humidity, since we are mostly water, and close to body temperature, since we are warm-blooded, so we're putting out a lot of moisture. 

This means a design ventilation of 8 litres per second, or 30 cubic metres per hour per person. Taking an average of 35 square metres per person this means about one complete air change every three hours, or 0.34 air changes per hour. 

Air can be changed by opening windows, using air vents, using extractor fans or mechanical ventilation systems. 

Natural ventilation, whether by windows or vents, is cheap and easy. It works either on pressure difference or temperature difference. Opening windows on the north and south of a building will create a through draft. Opening windows upstairs and downstairs causes air flow through the stack effect. This can be calculated, but not in my lesson! 

Natural ventilation will usually provide too much or too little ventilation. There is also a risk that someone will get in and steal your telly if you leave the windows open. And it may not be a good idea if it's raining outside. Extractor fans are relatively cheap and will provide a more steady rate of ventilation. Mechanical ventilation systems are more expensive to install but will provide steady ventilation, and also allow heat recovery. 

So how much heat will be lost by ventilation? Using a few assumption, on a winter's day when it's freezing outside and 20 degrees inside, we lose heat at a rate of almost 200 watts per person. At first this doesn't sound like so much. 

We looked at heating degree days. For example, the graph below shows in blue how hot it was outside and how many degrees each hour we have to heat up the air by. 


As far as heating energy is concerned, a temperature difference of one degree for ten hours is the same as a temperature difference of ten degrees for one hour. 

You can add these up over the year, and for Matsumoto it's a total of 80,000 kelvin hours per year, or 80 kilo kelvin hours per year. Incidentally this is about the same as for Manchester. So you can work out that ventilation for a year is going to lose 768 kWh. This is about a month's electricity bill, so it looks like quite a lot. 

Finally I explained mechanical ventilation with heat recovery (MVHR), which turns out to be a very cheap way to heat your house, as long as you have gone through the expense of making it airtight and well insulated.



Also in today's lesson I gave out some questionnaires, which the school hands out in the middle of the term. Everyone seemed happy with the course the way it is, except one person who wanted me to make the calculations easier! I'm doing my best.

Friday 27 November 2015

Five great ideas for boring house gifts

Your friends just moved into a new house, and they invited you round. It would be nice to take them a present, for the house, but what should you get? Here are some house gifts that seem pretty dull, but in fact may be highly appreciated by the homeowners.


1. A wheelbarrow
Maybe not such a good idea if they don't have a garden. More of a garden gift than a house gift. A very useful garden gift.


2. Extension cables
There are never enough sockets in a house, and they are often in the wrong place. Especially useful are extensions with multiple sockets, each with a switch. Sockets with timers can also be useful.

3. A bucket
The chances are that nobody else got one for them. Buckets always come in handy, for example when your friends have their first flood. You could get a really nice stainless steel one. Or you could get a plastic bucket that look like metal, if they have a sense of humour.


4. Shelf brackets
Houses never have enough shelves. Don't buy the actual shelves as they will probably be the wrong size.

5. A snow shovel
Good for areas where it snows, obviously. They may already have one, but it may not be a very good one and low quality snow shovels break fairly quickly. Snow is a lot heavier than it looks. Even if they already have a good one, another one could come in handy since shovelling snow is much faster and more fun in company.

And even if it doesn't snow in your area now, it may do soon! Global warming means higher temperatures and more extreme weather. Since most of the world's surface is water, that higher temperature is going to mean more evaporation, and more moisture in the atmosphere. When that moisture hits extreme cold, you're going to get snow. 



Tuesday 24 November 2015

Thermodynamics of the bathtub

We got a cover for the bath tub. It already has a lid, but there's a sizeable air gap between the water and the lid, and the lid is not exactly airtight. As the water is going to be reheated most days, it makes sense to keep it as warm as possible. Putting the lid on makes a big difference, but the heat from the bath is still evaporating away into the air, which is going to be humid and capable of carrying more heat away. They sell bath covers in hardware shops and supermarkets that you can cut to the shape of the bath. They are usually about 4 mm thick plastic foam with one side silvered. I just used a camping mat, essentially the same thing but thicker and presumably better at insulating.

The big question is, of course, do you put the silver side up or down? My initial feeling, probably like yours, is that the silver side should go down, so it is reflecting heat back into the bath. One problem with this, as we experienced in our old house, is that the silver foil can come away from the plastic foam. This was exacerbated when we forgot to take the bath cover off when heating the bath. The bath heater, which was on the outside wall next to the bathroom, sent very hot water back into the bath tub, often bubbling and steaming. The system we now have sends in water at a much more modest temperature.

So here is a plan for finding out, experimentally. After bath time, leave lids and covers in various combinations, for example: lid with no cover; cover, shiny side up with no lid; cover, shiny side down with no lid. Put a thermometer with a data logger into the bath. Repeat a few times to get statistical significance. Observe results and rate of temperature drop, from which we can deduce the heat loss.

For the reliability of the experiment, we need to take a few things into consideration. The volume of water in the bath should be the same, so we may need to add or take out water. The temperature of the bathroom should be the same, so we should be having baths around the same time each day. We should also be measuring the temperature of the bath water in the same place. We have some data loggers attached to thermometers, so it would be easy to put one of these in the bath, but perhaps we need to fix up a rig that can be lowered into the bath when we're not in it. For example a PET bottle with a weight in the bottom, and a thermometer fixed onto its side somewhere.

In the summer we were taking showers rather than running the bath, and also when we did run a bath we wanted to keep the heat in the bath rather than letting it escape into the house, so winter is going too be the best time to carry out this experiment.

We may of course find that any difference is marginal, and that even where there is a difference it is in the steepness of initial temperature drop, and not in the difference of temperatures twenty three hours later when we want to heat up the bath again.

I think we'll find that pointing the shiny side upwards is more effective than pointing it downwards. The shiny side stops radiation, but will have little effect on conduction. Since the bottom of the cover is in contact with the water, heat is mostly going to be conducting, and radiation will make very little difference. At the interface between the top of the cover and the air, there will be less conduction since air can carry something like four thousand times less heat than water. So the radiation is going to make a difference.

The counter-intuitive part is that when it comes to heat, the reflective part is just as good at reflecting heat in as it is as reflecting heat out. Our vision is impairing out judgement.  

Friday 20 November 2015

Affordable housing project wins Passive House Institute Awards

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

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

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

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



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

Tuesday 17 November 2015

Lesson 6: A lesson in humidity

A week after my lesson in humility.

Once again I got about half way through my lesson plan by the time the bell went. This time it was a good thing as I reached a fairly neat cut-off point.

The title of the lesson was Air and Water, and after explaining humidity, I had planned to go on to talk about ventilation, but that will wait for another day. I hope nobody is holding their breath!

I started by asking why my glasses steam up when I come in from the cold, why mirrors mist up when you breathe on them, and what this has got to do with low energy buildings. The answer of course is humidity.

I next asked them to estimate how much air was in the room, and how much water was in the room. Their estimates for the amount of air in the room ranged from 150 to 600 cubic metres. I had a tape measure which allowed a more precise calculation, of around 190. Their estimates of the amount of water in the room were just as varied, although one group was also taking into account the human beings in the room, who are 70% water. I managed to steer us onto the water in the air, or more precisely water vapour.

Next I asked what you would do with water if you wanted to dissolve a lot of sugar in it. One of the students had brought to class a thermos flask with sugar water, which provided a nice link to this question.

In just the same was as you heat up water to dissolve more sugar in it, heating up air allows it to hold more water vapour. In fact the amount of water it holds doubles every ten degrees or so. Very roughly a kilogram of air at freezing will hold almost 4 grammes of water. At 10 degrees it will hold almost 8 grammes. At 20 degrees 15 grammes and at 30 degrees 28 grammes.

The trickier part to understand is relative humidity. This is the amount of water in the air as a percentage of the maximum moisture the air can hold. So for a given body of air, as the temperature goes up, the relative humidity will go down. As the temperature goes down, the relative humidity will go up.

I tried to explain this by talking about the class, which had a total of nine students, of whom three were Japanese. So the class was around 30% Japanese. If three of the non-Japanese people left the class, there would still be three Japanese, but they would now be 50% of the class.

Back to the moisture in the air, if the temperature continued to go down, at some point it would become saturated and the water would start precipitating or condensing. That's called the dew point.

Next we considered what would happen if air were able to pass through insulation. In winter it's going to be something like 20 degrees inside and freezing outside. As the air passes through the insulation and the temperature drops, it's going to hit dew point and you'll get condensation forming in the wall.

This left me with my top two suggestions if you want condensation in your house: make it airtight with no insulation, or make it well insulated but not airtight. The moral of the story, in fact the moral of the course so far, a little insulation is a dangerous thing.

===
Temperature and humidity chart from sustainabilityworkshop.autodesk.com

Friday 13 November 2015

Early adopters

You may already be familiar with Bernal's ladder, which refers to the way new ideas are received. According to the twentieth century crystallographer, as reported in Nigel Calder's Magic Universe: A Grand Tour of Modern Science, each new idea goes through four stages. First, it can't be right. Then, it might be right but it's not important. Next, it might be important but it's not original. Finally it is what people have thought all along.

At a slight tangent to this, here is a look at the people who adopt a new technology. We are familiar with labels such as "early adopter" and "late adopter". Here are the kinds of people who may adopt a technology, with a tentative order:
  • Nutters
  • Idealists
  • People who can do maths
  • Big businesses
  • The majority of the population
  • Stubborn reactionaries

The first people to use technology are the mad scientists. For example Alexander Graham Bell made the first phone call and Albert Hofmann took the first dose of LSD. Hot on their tails you get people who have irrational and idealistic reasons for using technology. 

Sooner or later, if an idea is to succeed, it will be for economic reasons. Edison's bulbs took over from candles because they produced more light and less incendiary damage per unit of cost. Generators and electric wiring cost more than chandeliers and ladders, but in the longer term candles cost a lot more than coal. People who are good at mathematics would realise this sooner than others. Some people are not good at mathematics, and many more believe they are not good at mathematics. Initially this was because most people could not go to school and did not have the opportunity to study maths. More recently it is because maths is used in schools to discriminate between different students, and a majority are persuaded that they are no good at the subject so that education systems can devote their limited resources to a smaller group. 

In addition, political biases can influence mathematical ability, as reported here. As Upton Sinclair said, "It is difficult to get a man to understand something, when his salary depends on his not understanding it." There may be two competing mathematical calculations; if the first one is somebody else's money, the one in your pay packet will probably take precedence.

Big businesses often have few people who can do mathematics. Promotion to positions of power more likely depends on interpersonal skills and verbal skills. But once the mathematicians have won their case over the politicians who are in charge, these businesses will take advantage of new technology. Once they have done this, and their own media activities kick in, the masses will adopt the technology. They may have not choice. Whether or not people have adopted LEDs for their homes, they will likely have them in their fridges and cars if they have bought a recent model.

Finally all that are left are the stubborn reactionaries.

Wednesday 11 November 2015

Lesson 4. How to slow down heat

Some questions for starters:
How do you stop heat flow?
What is a "thermal envelope"?
What is "heat loss form factor"?
What can nature tell us about building a low-energy house?
Are there are situations when you don't want high insulation and low form-factor?

The first four were revising what happened the previous week. This was especially helpful for two of the students who had missed the last lesson. After reminding them of fourier's law, I started making things a bit more complicated. What if there are two different insulators? You know, like in the real world. Because you can't just make a building out of glass wool. I guess you could try to make one out of polystyrene, but it would probably break. Or blow away. 

First of all, and with the lobster fresh in our minds, I put a layer of glass wool on top of a layer of wood. I should have brought some actual insulation materials to the class to show the students what I was talking about, but I don't have any handy. I saw some bits of foam insulation on a building site yesterday, ready to go under the floor I think. If I go today, there may be some offcuts in their skip. I can probably work out better ways than prowling around builders' rubbish, but maybe not much better! And I wouldn't really want to bring glass wool to the class.

Anyway, absent of real materials, I used a powerpoint slide.
I told them about the R value, which is the inverse of the U value. This is resistance, and works just like resistance in an electrical circuit. This seemed to be familiar to most of them, not just the electrical engineer and the IT engineer in the class. In the same way as adding the resistors together, you can add up the resistances.

In terms of U value, it looks a bit more complicated: 1/U = 1/U1 + 1/U2 + ...

We have to remember it's upside down. This made one of the students laugh, as he remembered a scene in Pirates of the Caribbean. This equation is a bit like that. First you have to turn each of the maps (U values) upside down, then you have to turn the whole boat, I mean ship, upside down. 

Next I showed them some insulation in parallel. We used the same amount of insulation, but instead of a 100mm layer of wood on top of a 100mm layer of insulation, we had 200 mm of wood next to 200 mm of insulation.

Before starting the calculation, I got them to guess whether this would be better or worse than the last case, and they guessed it would be worse, so the U value should be higher. Sure enough, when they did the calculation it came out worse. 


Next, we delved further into the real world with a mixture of serial and parallel elements. 

There are two ways you can work this out. The serial method is to break it up into layers, calculate the R value for each layer, then add the R values. The middle element has 90% insulation and 10% wood, so you need to work out the U value of that by adding 9/10 of the insulation U value and 1/10 of the wood U value. 
The parallel method is to break it up into different bits of wall, work out their U values, then average those. 

I got half the class to work this out with the serial method, and the other half to work it out with the parallel method. I had hoped they would come up with their answers at more or less the same time, so I could then compare them. The two methods produce two different answers, and I was hoping for an argument to ensue, in which both sides would recheck their numbers, and insist they were correct.

In practice what happened was that the highly numerate students finished working out the first calculation, I suggested they try using the other method, which they also worked out, realised the two answers were different, and the less numerate students were still struggling with the first calculation. By this stage of the course, I should really have worked out which students were which, and paired the mathematical with the non-mathematical, so they would help each other, then go and help other pairs when both of them had finished. I did regroup them to some extent at the beginning of the lesson, but need to work a bit harder next time.  

So we established that the two methods produced different results. Here was another of those important lesson that has relevance way beyond low energy building. If you do two calculations and get two different answers, there are three possible reasons: one of the answers is correct and you made a mistake in the other one; you made a mistake both times; or you are using two different methods that produce different answers. Getting calculations right is a good idea, since you could be paying for the wrong answer in heating or cooling bills for the rest of your life. A few minutes checking the calculations is worth it!

So, the two methods gave different answers, and I wondered, in a rhetorical sort way, whether the formula for serial or the formula for parallel insulation was incorrect. One student suggested the parallel calculation was wrong because this wouldn't happen in the real world. Why on earth would anyone put insulation between bits of wooden structure? 

I had to tell him that alas, this was often the way insulation was used. Building structures are frequently made up of pillars, and builders see insulation as a magical ingredient that can be added at random to reduce the heat loss. Although this was the wrong answer, I was quite pleased that this student had learnt more about insulation in a couple of lessons than some architects seem to have in their whole careers.  

The parallel calculation is incorrect, not because it doesn't happen, but because there will be some lateral heat flow between the two kinds of insulation, so the heat is moving in two dimensions. For the serial insulation, heat is basically flowing in one direction, so fourier's law holds true. 

To work out what is really going on within complex structures, you need to use finite element analysis, and software like Therm. The computer makes a grid of squares and triangles, it calculates heat flow between each element, and repeats the process for every element several times until the numbers stop changing. Then it can tell you what the temperature and heat flux will be throughout the wall. You can see more details in my previous blog post slits in the envelope.

Then I got to the last question from the beginning of the lesson. In preparation for the lesson I'd been looking for a climate where you don't need any insulation. This would have to be between 20 and 30 degrees pretty much every day. The climate in the Caribbean is fairly constant and not too hot, but the best I found was in Ecuador and Columbia.

Everywhere else either gets hot or cold, or both.

40% of power in Mumbai is used for air conditioning, and it has been estimated that by 2060 the energy used worldwide for cooling will exceed the energy used for heating. The US, original home of the air conditioner, and country of vast wealth uses more electricity for cooling than Africa uses for everything. If I had invented an air conditioner and was wondering which continent needed it, I would have made a different choice!

Air conditioning may seem like a great idea for individuals with a bit more cash in their pocket who want a bit more cool in their lives, but it's a bit of a disaster for global warming. As well as the energy used by the air conditioners, often from coal-fired power stations, the refrigerants used in the air conditioners are often 4,000 times worse than CO2 as a greenhouse gas. 

And of course more energy use and more refrigerants leaking into the air will lead to hotter temperatures and more need for air conditioners. 

People often think that insulation will make buildings hotter in the summer, but insulation does not make anything hotter. It just slows down heat flow. So if it's cooler inside and hotter outside, then less of the heat will get in. Of course there are differences. Many things in a house create heat, such as electrical appliances, hot water and people. If you are in a heating situation, these are all on your side and will reduce the amount of heating you need. In a cooling situation these are all enemies for which you need extra cooling. 

Also, colder places are a lot colder than hotter places are hot. The average winter temperature in Yakutsk, probably the coldest city in the world, is -34°C. The average summer temperature in Kuwait is 38°C. There seems to be some symmetry to these numbers, but remember the temperature we want to live in is around 25°C, so Yakutsk is four or five times further away. Also cold weather seems to be more deadly than hot weather. 

We tend to think of Australia as a hot country, but cold weather kills more people in Australia than hot weather does. However, we should also note that more people die of cold in Australia than in Sweden. Almost twice as many. Sweden is not a hot country, but Swedish houses are insulated. If Australia insulated its houses less people would die. People who aren't paying with their lives would pay less on their heating bills. If Mumbai used more insulation they would use less energy for their cooling. 

I didn't have time but was hoping to talk a bit about thermal mass, and whether that can be used instead of insulation. The short answer is that it can't. 

So far we've got to the following implications for the basic design decisions: keep form factor low, put insulation on the outside, and beware of thermal bridges.

References and further reading:

Friday 6 November 2015

Lesson 5. Windows

It had been a busy week with not enough hours to properly get ready for this lesson, and a few unfortunate decisions. The biggest of which was probably attempting to work out the U values of the windows in our classroom. 

This has left me wondering (like many pc users) why windows? My students probably think the same thing, and I hope I haven't lost them!

I started with a story of a concrete breeze block that had been filled with insulation, with the claim that it would reduce heat loss. Actually a true story, although I couldn't locate a picture of the actual product. The problem with this is that the insulation is just in the middle of the breeze block, and the heat will all escape through the concrete around the edges. The insulation won't make a lot of difference. It's like having a really good down jacket with no buttons to keep it together at the front. 

I did have an hour or so in the morning preparing for the lesson, but a lot of that seemed to be sucked up by a desire to find some actual U values for Japanese windows, and the internet connection not working very well.  

This image came up in my search, which is similar to the insulation-filled breeze block, and a symptom of the idea that just adding insulation will improve performance. In reality, the important point is where you add insulation.


This website zissil.com - efficient on the truth, though probably not energy - states "Standard aluminum, fiberglass and vinyl window frames have hollow channels inside them which offer higher insulating capabilities when they are filled with foam."

This is kind of true. The hollow channels will insulate better if they are filled with foam. But if the frames are made of aluminium, so much heat is going to choose that route rather than embarking on a perilous voyage of conduction and convection through an air gap, that filling with foam will not make a difference. If you eat peanuts with beer, changing the peanuts is not going to make a difference to how drunk you get. 

Being worried whether I'd prepared enough for the lesson, the idea of estimating the window U values in class seemed quite attractive. In preparation I'd made some preliminary measurements and found that the width of the glazing was 8mm. That would even be a reasonably poor air gap, but 8mm was the width of the whole glazing. It seems unlikely that the panes are each 4mm thick and there is zero mm of air between. I guess each is 2mm thick, with 4mm of air between. 

4mm of air. 

Is that some kind of joke? I've been talking about down jackets, but that's like putting on a couple of t-shirts. It's as if they are trying to make it as thin as possible. As if they are trying to fool someone that the windows really only have one pane of glass. Maybe they are.

Surely they could make the gap bigger. It's not as if the air costs anything!

I'm still searching for information on these windows, which have no name, serial number or stars on them, except the YKK logo. 

Finding information on these is difficult. Putting in a search for YKK and U values will find their high-quality export windows. I'm not sure whether thermodynamics applies to internet searches, but it seems that information on low-energy windows is conducting much better, while there is high resistance to the U values of poor-quality windows seeing the light of day. 

It's as clear as mud. 

If their windows were this clear, they would be walls. 

There is a YKK database here, but I can't find any 2 mm glass, so these windows probably have 3mm glass with a 2mm air gap. One t-shirt. 

For the calculation in class, we assumed the aluminium frames were square boxes, and the aluminium was 1mm thick. The high U values came out even higher because we were ignoring the surface resistance. I had thought about teaching this first, but decided not to as it would have complicated things. Another dodgy decision! So we finished the class with an inconclusive decision on the U values of the windows in class, and without going through in detail what makes good windows good. 

We had at least spent a few minutes discussing windows, walking around the well-appointed classroom and comparing those bathing in the sun on the South side with those in the cold to the West. 

At the end of the lesson one of the students asked me whether people building houses had to make all these calculations. I told him they usually didn't, but they should!




Stirling engines, hydrogen energy storage and other perpetual motion engines

The Stirling engine was invented in 1816. It produces power from heat. Since there is heat everywhere, it should be the answer to all of our problems. It doesn't seem to exist in any practical applications on any significant scale, with the possible exception of Swedish submarines. And that is only if you think that eight is a significant number of submarines. Wikipedia has several applications, each hedged by "may", "could", or recording historical experiments. Cryocoolers are cited as a use of stirling engines, but this doesn't really count as they are not being used as engines to convert heat into power, but are using power to create extreme cold. The largest use of Stirling engines is probably in classrooms, to demonstrate how Stirling engines work. This sounds a bit like perpetual motion.

We've all had ideas for generating energy that amount to engines connected to generators. They all fail before we start as we are bound by the second law of thermodynamics, and rather than the energy generating itself, it will fall short as some is sapped away by entropy. There are many ideas that aren't actually perpetual motion, but they are so impractical that they might as well be.

Hydrogen is one of the components of water. There are gazillions* of hydrogen atoms literally floating around in the ocean. They come in pairs bonded with oxygen atoms, so all you need to do to get the hydrogen out is pass a bit of electricity through the water. Wouldn't it be easy to store extra electricity by just converting it to hydrogen?

I used to do this when I was a kid, with a transformer and a couple of carbon electrodes. Hydrogen gas would bubble up from the anode, and oxygen gas from the cathode. A little bit of salt helped the process by making the water more conductive. The build-up of hydrochloric acid was only very slight, but the electrodes deteriorated and discoloured pretty quickly.

I may have been trying to produce enough gas to fill a model airship, but that project was plagued by lack of materials, equipment, knowledge, experienced personnel and time. Without effective storage technology, all of my hydrogen was destined to leak away, or vanish with squeaky pops. 

You can try this as home, but it's not a very practical way of storing electricity. Very little of the electricity going into electrolysis actually liberates hydrogen atoms. Once they have been liberated, the hydrogen molecules need to be stored, probably via a compressor which will use more power. When you have the compressed hydrogen, you need a special engine to use it as a fuel, unless you are just content with a squeaky-pop machine, or an explosion hazard.

The R100 airship started to develop engines that could run on either hydrogen or kerosene. (That was the airship that didn't explode in Picardy, Northern France.) It used hydrogen for buoyancy; the tanks of kerosene would get lighter as the journey went on, and they could then switch to hydrogen, which would make the ship heavier. In the end they didn't have enough time to develop the engines.

If electrolysis were a good way of producing hydrogen, they would be using that to produce hydrogen on a commercial scale. In fact 95% of hydrogen gas is produced by passing high-temperature steam through natural gas.

So don't hold your breath for hydrogen as a way to store all that excess solar energy.

* a million is one with six zeros, a billion has nine zeros, a trillion has twelve. A gazillion has more than that. The word is often used colloquially to describe large numbers that would more accurately be described as trillions, billions, millions, thousand, or even hundreds. 

Monday 2 November 2015

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

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

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

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

Visits to our house by reservation only. 

Friday 30 October 2015

What if we were talking about cocaine, rather than coal?

Australian prime minister Malcolm seems-like-Jesus-after-the-last-guy Turnbull has just decided to keep shipping coal, and ignore suggestions to stop digging any new mines. (World's largest coal exporter) Australia takes over 400 million tonnes of coal out of the ground each year, exporting over 300 billion tonnes and earning AS$37 billion last year.  

Let's pretend this was the president of Columbia talking about cocaine and re-analyse his arguments. 

You may think it's flippant to compare coal to cocaine but there are a few important similarities. First, they are both addictive. Coal creates dependencies. Once you build those power stations, you need to feed the habit. You can try putting other stuff in there instead, but it just doesn't give the same kick. Switch it off, and all those connections down stream will hit serious lows, and you'll get cravings and yearnings. Actually this is sounding more like heroin. 

Second, coal, like cocaine, will increase your productivity. It will give you extra power.

Third, coal, like cocaine, is a highly profitable item that can only be produced in certain parts of the world.

So let's translate a few of Turnbull's arguments and see how they sound. Words with an asterisk have been change.

***

"If *Columbia stopped exporting *cocaine, the countries to which we export it would buy it from somewhere else ... there is absolutely quite a lot of *cocaine around ... so if *Columbia were to stop all of its *cocaine exports it would not reduce *drug use one iota. In fact, arguably it would increase ... because our *cocaine, by and large, is cleaner than the *cocaine in many other countries."

He points out: "*Cocaine is a very important part...the largest single part of the global *drug mix and likely to remain that way for a very long time. "

He also uses the moral argument, which basically goes along the lines that we have been using *cocaine, it has helped us get where we are, so it would be unfair to deprive the rest of the world. As his predecessor said, *cocaine is "good for humanity".

"You have to remember that *drug poverty is one of the big limits on global development in terms of achieving all of the development goals, alleviating hunger and promoting prosperity right around the world – *drugs are an absolute critical ingredient. So *cocaine will play a big part in that."

He goes on that it's "important to take the ideology out - just approach it in a very clear-eyed, cool-headed, rational way".

*Farmers, *cartel bosses and other people involved in the *cocaine industry are applauding his decision.

Reading what he says, I don't think Turnbull even really believes this. He's just being pressured by people in the right wing of his party, and the billions of dollars income from exports. 

He'd much rather see people just surviving on sunlight. And I'm sure people in Australia would be able to help show them how to do that!

***

Read more
in the Guardian

Notes:
Cocaine is not actually the same as coal in a couple of crucial ways:
1. Cocaine comes from plants, and is therefore a renewable source. Exporting a lump of cocaine this year does not stop you from exporting it next year.
2. Using cocaine has impacts on the users, but these are mostly confined to the user, and perhaps those in the immediate vicinity. As well as producing local pollution, coal leads to global warming, so has global consequences. You can safely export cocaine, and if you're not doing any of it yourself, there will be few ill effects. Coal, on the other hand, will affect your climate, wherever in the world it is burnt, and if you export it, people will burn it. I mean, they're not using it for rock gardens, are they!
3. It's difficult to get precise figures, but Columbia probably earns around US$4 billion from cocaine exports. Around a tenth of what Australia gets for coal. Somewhere around 200 tonnes is exported, although it's very difficult to know how much, because it seems to fall off the boat. This is less than a millionth of Australia's coal exports. Something the Australian government should seriously consider. Or start exporting whatever drugs they're taking!

Monday 26 October 2015

Lesson 3. How to stop heat - Form factor

We now know from the first law that energy is heat, so the first step in low energy building is to lose less heat. So how do you stop heat?

The opening question has a very simple answer: You can't. The second law states that the heat will move from hotter to cooler, so sooner or later the heat will get through.

The universe is a casino, its currency is energy, and sooner or later we're going to lose it all.

You can't stop heat flow, but you can slow it down, and that is the basis of insulation. Intuitively we can guess that the amount of heat flowing through a wall is going to bigger if the wall is bigger. It's logical that doubling the area will double the heat flow. Also that doubling the thickness of the wall will halve the heat flow. Or at least it will take the heat twice as long to get through, since it has twice as far to go.  

It's also intuitive that a higher temperature difference between the two sides will increase the heat flow, and easy to imagine that twice the temperature difference will double the heat flow.

And then the material the wall is made of is going to make a difference.

These are all bound by Fourier's law. If you want to see the equation, you can google it. I'm not going to add it here since every equation added to a piece of text halves the audience. Luckily that is not holding true in my class, and so far the number of students seems to be holding steady, but there is always a chance that students will lose their energy over the course, and stop coming to class.

Fourier was also an accomplished mathematician and he apparently was into dimensional analysis. Applying dimensional analysis to his equation tells us that the units we need for thermal conductivity, the constant applying to materials, is Watts per metre Kelvin. You can see a long list of thermal conductivites here on engineering toolbox. The lower they are, the better they are at insulating.

Jumping straight in to our goal of low energy building, I decided we should try to build a house. This was just on paper, and we made a few assumptions. It was a cube with five-metre sides, insulated with 100mm of glass wool all around. It was going to be in Matsumoto in the winter, where it's zero degrees centigrade outside, and we want it to be 20 degrees inside. The building has no doors and windows, is completely airtight and is floating in air, so it's losing heat equally from all six sides. We worked out that this will lose heat at a rate of 1.2 kW.


This number has two significant implications. First, to keep the house at 20 degrees centigrade, we're going to need 1.2 kW of heating inside. Second, 100mm of glass wool is not going to be enough for a low energy building.

In the process of this, I told them about the U value, which is the heat loss per unit area, or the conductivity divided by the thickness of insulator.

Next, we went on to a couple more buildings, one a single-storied rectangle, the other single-storied and L-shaped. The rectangle lost more heat than the cube, and the L more still. 



This led me to form factor, which is the ratio of surface area to floor area. The most important area, as far as heat is concerned, is the surface area, since this is how it escapes from the building. Or if it is a hot climate, this is how it gets in. As far as the inhabitants of the building are concerned, the floor area is the important part.

For a given insulating material, and with the same desired heat loss, the thickness of insulation goes up with form factor.


We looked at form factors for a few more buildings, noticing that as the building get squarer and bigger, the form factor goes down.
Generally, the form factor goes down as buildings get larger, since larger buildings generally have more storeys, so the floor area is going up faster than the surface area. Below is a graph for an idealised cubic building with storeys two and half metres high. You can see it gets very difficult when you get very small buildings.



We looked at a few real buildings to consider their form factors.




The modern Tokyo mini-house and classic modular capsule block are not very impressive.

Nor is the typical Japanese apartment block with its balconies, rooms bulging out of a sensible thermal envelope and random sticky-outy bits of wall. Flying butresses can be excused on medieval cathedrals. Do we still need them now?




The Dome house in Miyazaki looks a bit better, but more about domes in another post.


My house is not too bad.

I also pointed out that the balcony on my house is separate to the structure, as you can see from the picture below before it was put on.




I'd hoped to say more about insulation, and what happens when we start using different materials together, but I was running out of time and that will end up in the next lesson.

There was time to show a picture of a lobster and a person and elicit some differences. The critical ones for our discussion are that Lobsters are cold-blooded and have their skeletons on the outside, while humans are warm blooded and have their skeletons on the inside. Not all cold-blooded animals have skeletons on the outside, but I think all warm blooded animals have theirs on the inside. There is no "list of warm-blooded animals with exoskeletons" on wikipedia, which I take to be conclusive proof.

The point is that evolution, with the wisdom of millions of years to try out designs, has decided this is the best strategy. Life is essentially a temporary defeat of the second law of thermodynamics, so when we're aiming at  low energy building we are wise to follow the lessons in biology and put the structure on the inside, and the insulation on the outside.

=== 

The calculations above are all done with idealised pencil drawings as walls, and relatively simple physics. Real buildings are going to make most of these effects worse, since walls of finite thickness are going to reduce the floor area, and details in and around windows and doors are all going to increase the surface area.

Things will generally only get worse. Entropy is also at work in the design process. So it's a good idea to start a building with as small a form factor as possible

Thank you to Nick Grant for great lessons and some great shared slides on slideshare.net/ecominimalnick.

And to Elrond Burrell, bloggin here: elrondburrell.com