Different thermal aesthetics

The basic idea behind our house is that heat is insulated, so the temperature stays within a comfortable range throughout the year. A little can be added in the winter. A little could be taken away in the summer.

Japan is hot in the summer, and cold in the winter, so measures often need to be taken to both heat and cool. This is the case in many places. In the UK and northern climates, overheating is usually not a problem, but heating is needed for much of the year. In tropical climates, heating is never really needed, but the temperature is too high for much of the year.

So a number of different thermal aesthetics are possible.

One approach is to design for the summer, aim to reduce excessive temperatures, then provide extra heating available for the winter.

Another approach is to design for the winter, aim to keep temperatures high, then provide extra cooling for the winter.

Commonly in Japan, buildings are designed for spring and autumn, so heat needs to be added in the winter, and cooling needs to be provided for the summer.

Ideally, a building should be designed for the whole year, so that it will not get too hot in the summer, and not get too cold in the winter. This is possible, but needs thermal insulation and thermal mass. Insulation and thermal mass both cost money, and calculations of the cost and benefit seem to be highly skewed against high capital costs and towards high running costs. In fact calculations are usually not even made, and capital costs are kept as low as possible without even considering running costs.

Heaters in Japan are often portable kerosene stoves, which can be moved into place and cleared away when the seasons change. Heating is not part of the building itself, but something that can be added later. This makes the buildings much more simple. Since the fuel is kerosene, filled from a tank, there is no need for fuel lines into the building. Just electric cables to pump in fuel and keep the fans running. This approach can lead to much lower fuel consumption, if heat is just provided where and when it is needed. Although fuel efficiency in modern western buildings is much higher, fuel consumption can also be much higher since the whole building is kept at a high temperature the whole time, while there may only be a couple of people in one or two rooms some of the time.

The traditional wisdom in Japan is that windows can be opened in the summer. As everyone knows, or soon finds out, opening windows doesn't work when it's in the thirties outside. Especially with some of the modern building techniques and their emphasis on cosmetics and cost cutting. So air conditioners are usually also installed.

The air conditioner is an effective device in the scenario of low-cost high-turnover buildings. They are usually wall or ceiling mounted so they take up little or no floor space. As a heat pump, they can cool buildings in the winter as well as heating them in the summer. In addition they can remove humidity from the air. This seems to me to be an example where the electronics industry is making up for deficiencies in the building industry. 

Fans for power conditioners

You really have to read the small print. 

The rating of the Power conditioners is 4 kW, but this is at a temperature of 30 degrees. It drops to 3.2 kW when the temperature goes up to 40 degrees. 

This is a big deal if we have two power conditioners, which we do, and the panels are producing over 8 kW, which they will on many sunny days. 

I don't have much solid data at hand on the hourly generation. I started off copying it from the display panel, but gave up after about three weeks and have just been recording the daily figures since then. The 22 days of recorded data, of which 16 were sunny, and what I see when I walk past the display panel, show that it's rare for the power conditioners to be producing more than 7kW. Of the hours we'd expect maximum output, we got 7.2 kWh per hour once, but the normal maximum is about 6.9 kW.  

Since the temperature of the power conditioners mostly depends on the heat they put out, and the heat they put out is a percentage of the electrical power going through them, they are unlikely to deliver 4kW. 

If they could be cooled, we may get an extra half kilowatt out of each power conditioner when it is generating a lot. That could be for four or five hours on a good day. Maybe an average of two hours a day. 2 kWh, 100 yen in the bank every day. 

Cooling them is easy. You can put a fan in front of them. The room with the power conditioners gets hot, and the thermometer in there shows that it's over 30 between about 10:30 and 16:30, but circulating the air is going to cool the machines down. 

I put a fan in there the other day and watched the numbers on the power conditioners go up from 3.2 to 3.99 while they were blown on. 

The fan is going to use electricity, of course, but probably only around 20 Watts. Fixing it to a timer to run between 11:00 and 16:00 each day would cost us 100 Wh, but this is only 5% of the extra 2 kWh we could make, so we'd be winning. 

Of course we have to offset these financial savings with the capital investment. We may need to get another fan since the time we want to cool down the power conditioners coincides with it being hot downstairs when we want to circulate air in the house. 

It would be really good to have a fan connected to the DC output of the panels, that would start working when it got to around 4kW. This is part of a broader desire to take power straight off the panels without sending it through the power conditioner, for example in running a heat pump for hot water. I don't think it would be very difficult technically, but I'm really not sure whether I'll be able to find anyone interested in doing 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!

Passive? Or massive assive?

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

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

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

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

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

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

So what is the Passive House standard?

Low thermal losses means three things: 

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

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

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

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

The standard states three things:

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

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

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

They also recommend:

a heating load less than 10W/m²

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

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

thermal bridge-free construction

See more on Wikipedia and at Passive House US.

Windows and "Eco Glass"

Can you tell which is which of these pictures?

Exhibit 1

Exhibit 2

One of them is a set of radiator fins designed to take heat away from
electrical devices. The other is part of a window frame, designed to... keep heat in? I've certainly always thought the job of windows is to keep it
warm inside when it's cold outside, and I suppose to keep it cool
inside when it's hot outside. Could you tell which picture was which?
Pretty tricky, eh!

It has been said that aluminium window frames destroyed Japanese
architecture. Apparently when aluminium was discovered, people made
jewellery out of it. It must have seemed like a great option to wood,
when it came to be used in windows. It must have been very cheap. But
when it comes to heat conduction, aluminium conducts about 1500 times
more than wood. Obviously, you can get away with using less aluminium,
but the surface area is likely to be similar, and heat conduction
depends a lot on the surface area.

Japan currently has ratings for window performance, based on their
heat conductivity. There is a star system, going from one star to four
stars. Four stars is the highest rating! This sounds really good,
until you look at what the stars are and are not measuring.
Read more about it here, and hear the annoying jingle! but no actually
meaningful numbers.

First of all, one star means more than 4 W/m2K. That means that at least 4
Watts of heat will flow through each square metre, for every degree of
temperature difference. One star just means that there is glass. A
single pane.

From 4 to 2.7 W/m2K gets 2 stars. This generally means double glazing.
2.7 to 2.33 W/m2K gets 3 stars. To get two stars, you need low-e
glass. This means low emissivity. I don't completely understand this,
but I think it's the opposite of reflectivity, so they could call it
"highly reflective" glass, and people would be able to understand
easily, but in their wisdom they don't. They add a thin film of metal
onto one of the sheets, so more heat is reflected back into the house,
or indeed reflected out of the house, if it's summer.

Less than 2.33 W/m2K gets 4 stars, the highest possible level.
Two-star glass is double glazed, with a 6 mm gap between. In the
example I've got, 4-star glass has a vacuum between the pains.

This is called Eco glass, where once again we have that feel-good
green feeling, but we're not sure whether it's the green trees
swishing in the breeze, or some green notes floating into our wallets,
or not floating out. In fact I think the motivation maybe neither and
the concern to keep the economy of the domestic window industry going.

In the grand scheme of glass thermal efficiency, 2.33 is far from the
highest possible level. I'm not sure how they arrived at the numbers
4, 2.7 and 2.33, but I imagine a few aging window makers got together
over a few beers and discussed the best windows they could remember
making. Anyway, let's say the next logical place for a mythical
5-star window would be around 2. To get to this performance of glass,
you need to start making a bigger gap between the panes. If the gap is
too big, the air in the gap starts circulating, so the convection
starts transferring more heat. The optimum thickness is something like
16 mm, but 12 mm with one low e pain will get under 2 W/m2K. Of
course once you start getting such a huge gap as that, the frame might
start to get bigger than the standard sizes of window frames.

Oh yes. What about window frames? Won't it make a huge difference what
the frame is made of? If you have an aluminium frame, the aluminium
will be conducting heat to its heart's content with something like 60
W/m2K, and condensation will be flowing like the Niagara falls. Since
April 2011, the window rating includes the frame, so it will make a
difference whether it's made of a thin sheet of aluminium, or wood
with a sandwich layer of insulation. The numbers have changed so the
whole window and frame assembly gets two stars if it's less than 4.65
W/m2K, three stars for 3.49 W/m2K and four stars for less than 2.33.
Until you get to the magical figure of 2.33, it seems they are
expecting the frame to conduct more than the glass. This contrasts
intriguingly with European manufacturers who consider that the frame
will conduct less than the glass until you get to triple panes.

It's great that they're taking account of the frames, even if they are
giving them more leeway than they give to the transparent bits that
are pretty much limited to glass. But they still haven't taken account
of how airtight the whole thing is. The window can have as many stars
as you like, but it won't help as much if cold air is blowing in. And
that's not even mentioning thermal bridges. I think we may have to
talk about those another time.

Stars	Eco Glass(old)	Eco Glass Windows (new!)	Notes
****	<2.33	<2.33	Double glazed, 6mm gap between pains, low e
***	<2.7	<3.49	Double glazed
**	<4	<4.65</td>	Double glazed. Wait a minute, why are they allowing the frame to let more heat through than the glass?(1)
*	>4	>4.65	Credit where it's due, one star for not being a hole in the wall!

Note 1. They probably have shares in aluminium manufacturing.

Getting back to the glass, if you start using noble gases instead of
air, there are two advantages. First, the noble gase, usual Argon, Krypton
or Xenon, has single-atom molecules, while air is mostly made up of
double-atom nitrogen and oxygen, so the noble gases hold a lot less
heat. Because they hold less heat, they transfer less heat. Also they
are more viscous, so they don't start moving around until the gap gets
close to 20mm, and a thicker gap means a warmer house. The noble gases
are also inert, colourless and odourless, so they don't go off. Argon
is the cheapest and conducts one third less heat than air. Krypton is
more expensive but conducts half of Argon, so it is only used for high
performance, or extra-thin multi-paned windows. These gases will get
the glass down to 1.5 W/m2K, which should surely be worth 6 stars, and
we haven't even looked at triple glazing yet.

Let's give seven stars for glass under 1 W/m2K, even though we got an
extra star for an improvement of a little over 10% from 2.7 to 2.33.
If we were following the same progression, there would be so many
stars on the glass by now, you wouldn't be able to see through the
window! It's a good thing that 2.33 is the highest level! To get our
hypothetical seven stars, you need three layers of glass, two of them
should be low-e so they are reflecting back the reflected heat too,
and you need argon filling them.

Southwall Technologies are talking about U values under 0.5 W/m2K. They seem to be from the US, where the units are imperial--British thermal units per square foot degree farehneit--and different to metric by a factor
of six. It can be confusing as the units are usually missing when U
values are quoted.

The answer, by the way: Exhibit 1 is a set of radiator fins for cooling electrical devices. Exhibit 2 is an aluminium window frame.