Blind faith

Originally we were going to get strips of fabric running vertically where the strings hold the blinds up. These were sold to us quite agressively as covering the holes in the blinds, stopping pinpoints of light getting through, and the pictures in the brochures made it look like they were some fancy design feature, embellishing the beauty of the blinds. 

We were struggling to decide what colour these fabric strips should be, worrying that with time the colour would fade in a different way to the blinds themselves, and I made an executive decision and said we didn't want any. Without them, the blinds look like blinds. They have fine strings attached, but we're used to that. That's what blinds look like. With the fabric, they look like blinds with bits of fabric coming down them. What made the decision for me was that they insist on having them at about 30 cm intervals, which seems to be massively over-engineered. I can see with thin flexible blinds, some extra support would help, but these slats are wooden, so there is no bending. They really only need strings at each end, and perhaps in the middle for extra stability. They're made of wood, not lead, and are not that heavy.

When they recalculated the price without the strips of fabric, it went down by over 10%. They were trying to rob us blind! I suppose that's just business. Tell your customers they're getting a massive discount. Try to add as many extras to your products as possible. Tell the customer how much they need them. Charge extra for each one.

We had to choose colours for the slats themselves, and the choice was white, matching  the walls, and window frames, or dark brown, matching the shelves and cupboards. Actually there was a wider range of choices than this, but within our colour scheme, those were the two choices. We chose white, which looks good, but I have that nagging feeling we should have chosen dark brown. The ideal would have been white on one side, and dark brown on the other. We suggested this, and tried to make the blind man see, but it was impossible. They don't make them. We'll have to just paint one side of them!

White reflects better, so it may prevent heat getting in in the summer. I'm not sure exactly how effective this will be as the three window pains do their fair share of reflecting. The G value of the windows is 50%, so half of the radiation gets through, and the other half is reflected. This will also happen on the way out, so once the radiation gets into the house, half of it will stay. Actually, a certain amount is going to be heating up the middle pain, but keeping it simple, drawing the blinds on a hot day is going to stop direct radiation getting into the room, and it will feel less hot, although it will only halve the amount of heat getting into the house. It'd be nice to have a radiation meter so that we can tell exactly how much radiation is coming in. 

Another advantage is that white is lighter, so the room will be less dark. Brown, on the other hand, absorbs more heat and radiates more heat. In the winter brown would be better if we ever have the blinds down in the day time, as it will get the heat into the house, but not the radiation. Also brown will probably feel warmer when we have the blinds down at night. Anyway, the white blinds will be a lot warmer than nothing. We'll have to give it a year.

Perhaps we'll look back and think we were colour blind, but we had to choose something!

At the moment every time I go past the blinds, I put them up so I can see outside, and every time my better half goes past, she puts them down, worried about the neighbours looking in. We need to work more on the garden.

But what about all the energy used to make the house?

"Toilet seats from the UK, 250 kg of window from Germany, special visits from foreign manufacturers... are you going for some kind of embodied carbon record?" PJ just wrote.

I remember talking to someone from the Green Party a few years ago about environmental costs, and saying how great it would be if there was some measure of how bad things were for the environment, so we could make the right decisions.

"There is," he said. "It's called money."

And to a large extent he was right.

Recently, Japan has introduced Eco points, whereby you get points for buying energy efficient products. You can then spend these points on... anything you like really. Beer even. Not sure how energy efficient beer is, but that is not the point.

A student said he'd just bought a new TV, and got lots of Eco points for it. Apparently, the bigger the TV, the more Eco points you get. A bigger TV means more energy consumption, so really you should be getting less Eco points for a bigger TV and more for a smaller one, and in this case the money you spend may be a better indication of ecological strain. If you're comparing TVs of the same size, of course the Eco points will help.

Even with a Passive House, the units are all measured per unit area of floor space, so a palatial one-person passive house could use a lot more energy than a one-room home for a family of seven. 

But money doesn't always count.

I remember being told that cars consume ten times more energy in their manufacture than in their normal lifetime, so buying a new car, however energy efficient it is, is likely to be worse than carrying on using an old car. What Car claimed that 80% of the life-cycle energy of a car comes out in its use, with 15% in manufacture and 5% in its scrapping. But perhaps What Car have a vested interest in people buying new cars. According to an article by Mike Berners-Lee in the Guardian, the amount of energy used in manufacture and use is around equal, half and half, but perhaps he has a vested interest in people buying his book on carbon footprints.

Anyway, embodied carbon is an important issue, and the University of Bath has produced an inventory of carbon and energy per kilogramme of various materials, which they will email you if you ask nicely. As well as looking at Carbon Dioxide emissions, they look at other greenhouse gases and convert them to CO2 equivalents. A lot of research and thought has gone into their work, and they even have a special excel file that will calculate the carbon footprint of concrete depending on the mix used. 

For example, it gives the following figures in kg of carbon dioxide per kg of various different kinds of insulation:

polyurethane (flexible) 4.06

polystyrene (high impact) 2.76

glass wool 1.35

rock wool 1.05

wood wool (board) 0.98

cork: 0.19 

But you'd have to drink a lot of wine for the last one, and it's not as good an insulator as the others. After all the wine it may not matter. 

It also gives figures for timber framed and aluminium framed windows at 12-25 kg CO2/kg and 279 respectively. So aluminium frames are not only going to consume a lot more energy in their lifetime, they also consume a lot more in their manufacture. In a lot of cases, though, you have to look at the weight of materials used. For example, aluminum is lighter than wood, although not ten times lighter.

With a little more energy of the human kind on my part and a little more support, it would have been great to balance the embodied carbon in the building with the energy use of the building's lifetime, but the main focus has been on consuming as little energy as possible over the house's lifetime. This is perhaps a foolish thing to do in Japan, where the life expectancy of a building is less than a quarter of a century. On the other hand, if what we are doing can make a difference to the way people build in Japan, then it may be a good thing. 

It may of course backfire, as people copy the mistakes and collateral details rather than the main points. I've heard that the Nara local government are sending their wood to Germany to be built into windows there, as Japan does not have the window manufacturing technology, then sent back to Japan so that they can have windows made of Japanese wood. Not sure how that comes out on the carbon calculator. Also not sure whether trees have a sense of national identity, but that is another issue.

In many cases back in our house, we looked at choices where there is a clear increase in cost which results in a clear decrease in energy use, and the payback period can be calculated.The pay back on the solar panels is around 8 years. There was one issue with the windows that meant a pay back of around 50 years, which is around the lifetime of the windows and, on financial terms, not worth it. In terms of carbon, the choice was between paying for cuttting edge technology and expertise against paying people to pump fossil fuels into fires for the next 50 years, so the carbon calculator gives a clearer answer.

Even if you are just looking in financial terms, the budget of the project will affect how much you can actually spend now, because saving money in the future is no use if you don't have enough to spend now. Reality bites.

I think we looked at reducing the amount of heat we would lose by raising the window frame specs to "Passive House Certified", which sandwich insulation in the frame, but the pay back would have been more than their life time. Increasing the amount of heat coming in by changing the glass in the south-facing windows to high-g led to an extra cost with a much quick payback.

What we have tried to do, anyway, is to optimise the building for lifetime energy efficiency, but work needs to be done in both areas, and our understanding of the carbon footprint is deepening the whole time. This should show what is possible, and where we want to go. The bigger question is how we get there.

Give me sunshine

The insolation for January here in Matsumoto is over four times what it is in Germany, according to the data we have from the Passive House institute. Insolation is the amount of energy you get from the sun. This is pretty important. With about 20 square metres of windows on our south-facing walls, a bit of space to the south before the next house, which is a bungaloo, and having taken care not to design anything that will block the sun out, we stand to gain about 970 kilowatt hours in the month of January. We're using triple windows with special clear glass that will let through more heat.

Usually triple windows let through about 50% of the sun's heat, while double glazing lets through 70%. Of course double glazing will let out more heat than triple glazing because the insulation is much better. In Europe, or at least central Europe, where winters are cold and the sun doesn't make much of an appearance, using triple glass is a no-brainer. Windows are basically a liability when it comes to the thermal performance of the house.

Here, where winters are cold but the sun is above the horizon for much more of the day, and hiding behind clouds much less, south-facing windows will bring heat into the building. They are our heater. They'll bring in over 5,000 kWh in the cold part of the year, and lose less than 1,500. The gain is around 3,750, according to the Passive house software PHPP. As we've put almost half our windows on the south side, it looks like the windows are going to net over 3,000 kWhs of heat in the cold part of the year. That's about 60 gallons of heating oil. Or 290 litres of kerosene, the fuel of choice for heating in Japan for people who have no choice.

Interestingly, if the south-facing windows were double glazed, they would lose a lot more--over 2,000 kWh per year--but they would also gain a lot more--over 6,000. In fact double glazed may even have a slightly higher net gain. There would also be less cost.

Of course curtains aren't so nice when it's snowing outside, and double glazing would allow more of a temperature drop over night, and probably encourage cold drafts and condensation. We would want curtains to improve the insulation of the double glazing. According to the man who makes them, you can sit comfortably up against triple-glazed windows in the middle of winter. This will make the part of the room we can use bigger.

The decision was largely made when we applied for the grant from NEDO, the new energy development organisation.