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. 

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.  

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. 

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.

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Temperature and humidity chart from sustainabilityworkshop.autodesk.com

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.

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:

World set to use more energy for cooling than heating
Guardian, 26th October, 2015

Artificial cooling makes hot places bearable—but at a worryingly high cost
Economist, 5th Jan, 2013

Australian houses are just glorified tents in winter
The Age, 11th June 2015

Passipedia: Insulation vs Thermal mass

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. 

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.