The pursuit of ambience

It's going to take us a year or two to work out exactly what to do with the cooling and heating of the house. It will probably boil down to three different strategies: cooling, passive heating and active heating. There may be some gaps in between where we don't have to worry, but I suspect at any given time we should either be cooling the house in anticipation of impending heat or heating it in anticipation of impending cold. The weather and climate are changing but the seasons are here for a while.

We switched off the active heating April 10th, and the house has not been cold since. The last night below zero outside was 8th April, when it was minus 2, according to tenki.jp, although it was down to 3 degrees above freezing in the wee hours of 13th May and this year it didn't start getting really hot until the middle of July. 

We're now in cooling mode and have begun a routine of opening up the windows when it drops below about 25, which is often at 7 pm, and closing them when the temperature outside rises above 25, which is around 7 am. July 21st was cool and rainy, in the low 20s all day, so the house was cooled a little more.

The bypass system on the ventilation is now working, so it will be pumping cooler air into the house throughout each night, exchanging all the air every two-and-a-half hours. Opening the windows substantially increases the air flow and cooling. In an ideal world they would open and close automatically, like the heat-exchanger bypass switches on and off automatically, depending on temperature difference.

The daily indoor temperature variation is bigger than I expected, probably due to the size of the windows on the south wall, and the lack of a decent awning to keep the heat off the terrace. At the moment we just have a little camping tarp over it.

UK Best in energy efficiency - apparently - Japanese buildings lag behind

The UK has Beaten the Germans, Italians and Japanese, and is ahead of the USA and Brazil, and well ahead of the Canadians and Russians, according to the US ACEEE,  the American Council for an Energy-Efficient Economy. France, Australia, the EU  and China come in the middle of the pack, which consists of the twelve biggest economies in the world. I will leave the strange fact that it includes the EU as well as four of its constituent countries, but does not include California, part of the US, that would be the world's 8th biggest economy, were it a separate state. California would probably do much better than the US as a whole, just as the UK, Germany, Italy and France usually do better than the EU as a whole.

I found out about if from proudgreenhome, who have a more succinct take on it than the original 100 page pdf, although you really have to read that to find what's going on.

The ratings are worked out by looking at four areas each with a different number of possible points: buildings (28), national efforts (25), industry (24) and transport (23). Each area is broken down into different factors with a different weighting.  

The ratings depend on both actual results and policies or frameworks that will presumably lead to results in the future. For example, the UK does better on results than on policies, while Germany does better on policies than results. Both countries do well though.

There are obvious difficulties in comparing these twelve economies fairly. The report demonstrates this by comparing two tables of oil consumption among the twelve economies. One is per capita, in which China come second from the top, with the US and Canada at the bottom, consuming around five times more. The other is per billion dollars of GDP, in which China comes second from the bottom, below the US and Canada, using about twice as much oil to generate each dollar of its GDP. Should we measure the efficiency of an economy by the number of people it supports or the number of dollars it makes? Perhaps the answer would be different depending on whether you're asking in the US or in China.

In energy efficiency of buildings, China does the best, by a long way. Japan comes near the bottom, beating only Brazil, Canada and Russia. 

Energy use of residential buildings gets five points, and of commercial buildings also gets five points. The unit is British thermal units per square foot (a unit that I'm sure they even had to convert into from Britain's data, as well as those more recent parts of the British Empire: Canada and Australia) so once again we could question how efficient the buildings in different countries are, as there are radical differences in average area per dwelling and average area per inhabitant. This is weighted in some way to take account of different climates. I suspect it does not take account of the temperature inside, and how efficient the buildings are at delivering a comfortable temperature.

China gets full points for both. Australia gets full points for residential buildings, but its commercial buildings are not so energy efficient. Japan almost gets full points for residential buildings, but scores badly for commercial buildings, which will surprise nobody who has been into a Japanese shop. Germany scores badly for its residential buildings, but very well for its commercial buildings. 

Energy use makes up 10 of the 28 points. Another three points each are given for residential and commercial building codes. This seems a good idea as codes will presumably determine the efficiency of new building stock. For residential buildings, they looked at insulation in walls and ceilings, window U-factors, shading and solar heat gain coefficients, lighting efficiency requirements, heating and cooling requirements, and air sealing. Many countries scored full marks, Japan lost a point for having no air sealing codes. Japan did get full points for commercial building codes, for which air sealing is not considered.

The report admits that they "did not evaluate the effectiveness, stringency or enforcement of these requirements", which would be a major challenge. At the moment, each score is just a "yes" or "no". The appendix for Japan notes that while compliance is high at 88% among commercial buildings, "at least in the design stage", only 39% of residential buildings comply to building codes. My impression, at least for the house I built, is that there are no mandatory energy efficiency codes, and that the design stage is not faithfully reflected in the building stage. 

The number of standards for appliances gets up to 6 points, and the US gets a full six. Once again, this does not include the level of compliance to these standards, how stringent they are, or the percentage of consumption that these standardised appliances consume, which makes me wonder why such a large score was given.

Building energy labelling gets another 3 points, of which Japan gets only one point as labelling is voluntary. The local electrical shop labels the energy efficiency of each appliance, and presumably at least some people look at that when choosing an appliance, so once again the challenge of comparing these different economies is highlighted. 

To quote the report on the prospects for Japan: "In the longer term, the most important opportunity for energy efficiency for Japan exists in the building sector." I hope somebody over here is reading that. It goes on, "Energy consumption in residential and commercial buildings almost doubled from 1990-2009".

Looking at a map of the twelve economies, it looks like the main factor in the efficiency of the economy is the area of the country, with the only country seriously out of step being Brazil, so they may just have found an elaborate way of showing that the UK is smaller than Japan, and Russia is bigger than the US.

The report is a good effort that should raise awareness of energy efficiency, and as they frequently note it is a first effort that will be refined and built upon. Look forward to next year's!

Adding insult to insulation

While browsing the Weird Wired World for shades to hang over our terrace, I came across a few that claimed to be insulation. Like this one on amazon. At least they claim to be 断熱 dannetsu, which I've always translated as insulation. Maybe this is just a bit of a false friend and the meaning of the Japanese word is wider, but I think it's just another example of thermal ignorance, which transcends linguistic, as well as national and cultural borders.

The shades--bits of fabric to stretch out in front of windows or over terraces--are certainly going to be stopping radiation and cutting ultra violet. To put it more precisely, I should just say that they will stop radiation, as UV is a kind of radiation. That's what the websites were saying, though. 遮熱 shanetsu is the Japanese word for thermal shielding, but I'm not completely sure  if that is the English word for it.

Hanging a piece of fabric in front of your window is going to have very little insulation effect. For a start it's not really thick enough to insulate. You don't see many people heading out on a cold winters day holding a plastic sheet next to them to keep the heat in, although of course it would be better than nothing. Even if it were insulating, the fact that it's hanging a few centimetres away from the window, or stretched out at 60 degrees to the window, means that any insulation effect will be severely compromised by the hot air sneaking around the sides. 

Beating the heat

Just because we live in a low energy house, it doesn't mean we can completely ignore the summer. In fact there are lots of things we can do to keep the house cool, now that it's going to get over 30 degrees centigrade oustide pretty much every day for the next two months. Some of these you may be able to try at home. Some of them rely on infrastructure such as high insulation, airtightness and good windows. Having a low energy house is one thing, but being a low energy person is another. Some try to tread lightly on the planet and make their carbon footprint small, but attempts are thwarted because they are surrounded by energy inefficiency. Others have all the low energy tools at their disposal, but they have so many of them, and use them so much that their energy consumption is even higher. The goal of low energy design is to make it both impossible and undesirable to consume energy copiously.

1. Shut the blinds in the morning. Tempting though it is to shut them at night and open them in the day time, as the sun starts getting higher and further south, we really don't want it's rays to reach into the house. After the summer solstice in June, the sun starts getting lower, so as summer builds up pace, the solar gain is also increasing. External blinds are more effective at keeping heat out.

2. Shut the windows when it gets hotter outside than it is inside. Also counterintuitive, but this will keep the heat out. There is an argument that opening the windows will get some breeze going through the house, and that breeze will take the heat away from us and cool us down. This is true if the breeze is blowing past us, but in terms of temperature, a breeze of hot air is going to heat up the house. If you have an air conditioner on, it will work much better with the windows shut, just like a heater works better with the windows shut, and a fridge works better with the door shut.

3. Open the windows when it gets cool in the evening, or early in the morning.This will let some of the heat out and let cool air in.

4. Use cold water. If you have to use hot water, use as little as you can, and turn it off as quickly as you can. Hot water is going to heat up the house, and the more airtight and well insulated you are, the more it will heat your thermal envelope. If you have a smart boiler, which I think we do but it's too smart to give itself away, a secondary effect of this is that using more hot water will encourage the boiler to make more hot water, in other words keeping its water at a higher temperature. This will mean that more heat leaks into the house.

5. Switch electrics off. They're all giving out heat too. Don't use them unless you have to. Switch them off as soon as you've finished.

6. Cook at night or early in the morning, especially if you're using an oven. If you boil a kettle it should just have as much water as you need in it. Any more means more heat in the house. I get really annoyed when I see a kettle or pan of water being kept on the boil with the cooker on low. Much better to boil the water when you need it, and switch off the heat and use it as soon as it's ready. If you don't use it as soon as it's ready it could be there putting out heat for half an hour, and in fact it often is.

7. Stop using ice. It may cool you down, but the fridge puts out a lot of heat to make it. Iced tea is probably the worst as it involves boiling water then adding ice. To be honest ice makes less of a difference than the things above, and a couple of lumps is not going to make a big difference to the heating effect of your fridge, but I'm with the Chinese that you should drink hot drinks when it's hot. Cold drinks just confuse your body. I grudgingly confess that ice improves gin and tonic.

8. There's a whole load of really obvious stuff like wearing light clothes and not doing much exercise, and slightly less obvious things like not eating so much, and eating food that will cool you down rather than heat you up. Cucumbers and bananas are good. Meat and potatoes are not. 

9. Also there's probably a lot of subliminal stuff that will make you feel cooler starting with the colours, patterns and textures you can see around you. Having an electric fan in the room, even if it's not switched on, may make a psychological difference. 

10. Use LEDs. The above are all about using or not using what you have. LEDs make sense for two reasons. First, they are more efficient so they add less heat to the thermal envelope. Second, while incandescent and fluorescent lights give of heat in their radiation, LEDs just radiate light, so you won't get hot standing under an LED. Also, LED light does not attract insects, in stark contrast to incandescent and fluorescent light, so there is less threat leaving windows open at night time. It's a good idea to get other low-energy appliances too.

Tiles and heat

So far the tiles on the ground floor have been great. They feel warm on cold days, and cool on warm days. Six months after moving in, the extremities of the slab have warmed up, and it will now hopefully work as a passive heat sink.

The only thing that seems to have been a waste of time is the active system for pumping heat around the slab. I had over-ambitious hopes for the tiles to absorb direct sunlight and help bring the heat of the sun into the thermal mass of the concrete slab.

I think this was also tied up with earlier ideas using solar thermal collectors and pumping excess heat into lower levels of the slab, from where it would keep everything warm. The pumping system we have for the underfloor heating is not wasted, of course, as it still works with the heating system, which would have strained to pump hot water around the floor area we have, and would have been sending it at far too high a temperature. 

When we were choosing tiles I was interested in how much of the sun's heat they would absorb, but asking the supplier about this was like asking the fishmonger how many microgrammes of mercury are in his salmon. Perhaps something they should know, but certainly not something they do know.

The answer from the Passive House lady was more than nothing, but less than you think. This seems to have been accurate.

From a thermal point of view we should probably have got darker tiles with a matt finish. I don't know how this would have affected the aesthetics of the room though.