Defrosting the ventilation system

Apparently a heating element is standard with the ventilation system when it is supplied in Germany.

Exhaust air below freezing within the ventilation system is bad news, since it's going to be increasingly humid as the temperature drops and this will form frost when it drops below freezing, and could block the passage of air. This is not going to happen on the incoming air, since the temperature is rising and relative humidity falling, but it will very likely happen on the outgoing air.

Our system avoids this by blowing out more air than it sucks in. This makes the heat exchanger less efficient, so the outgoing air temperature drops less. It also drops the pressure in the house as a whole, and cold air is sucked in at two or three weak points in the airtight membrane. These points are the extractor fan in the kitchen, the gap at the bottom corner of the second and third leaves of our concertina door, and the front door.

In terms of a thermal system, a pressure imbalance is not a bad approach, if it is not used for long periods.

It's better having the house slightly under-pressure in the winter than over-pressure. Firstly, sucking cold air in probably means less heat loss than blowing hot air out, although every time I think about this, my head starts hurting. The cold air coming into the house will make the temperature drop a little, but the heat loss can be calculated by the lower efficiency of the heat exchanger. Secondly, an over-pressure house could lead to humidity building up in the wall structure, as air flows out and condensation occurs somewhere on the falling temperature gradient.

The alternative is heating the air coming into the heat exchanger so that it is closer to freezing and so that the air going out will not drop below the frost-point.

In this case, the temperature in the house will not drop much, and the heat loss can more directly be measured as the energy going into the heating element. This is likely to be electrical, and electrical heating is expensive. The main advantage is that it would stop the genkan area just inside the front door from getting so cold. 

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. 

More shelves

We have rather a lot of shelves in the house, but apparently not enough. In many places we have metal rails up each side, so the shelves can be moved up and down and added to.

In a couple of places we may have too many shelves, but that is not such a serious problem any more. One problem is that each shelf alcove is a different width, so we can't simply move a shelf from where there are too many to where there are not enough, and we couldn't have ordered an extra few shelves from the carpenter, in the knowledge that we would certainly need shelves, since we were uncertain exactly where we would need them.

In one place, above the laundry shoot in the bathroom upstairs, we have extra shelves since we changed our minds about the colour. In most places we have two colours: white and dark brown. Our original order was for white shelves but we later revised it to brown since the shelves were liable to get dirty and white would show this dirt much better. In the meantime the first shelves had already been painted, so we got another three.  And those three shelves have been waiting for something to happen. Specifically, waiting for us to get the small brackets that slot into the metal rails running up and down each side. The site foreman showed us where we could get them the last time he visited, which is a few months back now. It's not particularly far away, but not somewhere we usually pass, except on weekends, and then it's closed.

We made it today and the shop, Okano, is a real treasure trove of building stuff, with whole rows of drill bits, and rooms full of aluminium rods. It's the kind of place that would sell left-handed screwdrivers and bottomless buckets of sparks. They had the brackets and asked how many I wanted. I asked how many were in a box, assuming they would be cheaper that way. There were 200 in a box, and they cost 68 yen each. This seemed a lot for a little bit of metal with some rubber on it, until I got back and tried to find it on the internet, armed as I now was with a part number from the receipt. The cheapest I could find them on the internet was 84 yen, so in this case the bricks and mortar shop with the friendly people worked out cheaper. I bought fifty brackets off them, so since there are four brackets to each shelf and when I can find the other one that's left in a safe place in the house, we'll be able to put up 13 more shelves.

So next we went to the DIY shop looking at bits of wood we could use for more shelving, and were quite shocked how cheap it all was. Several pieces were available off the peg in shelf-like shapes and sizes. Actually they were often on shelves.

I'm sure with a little bit of effort all the shelves in our house could have been designed in these predetermined widths and saved the carpenter a lot of work and materials, and knocked thousands of yen off our bill.

The old, the random and the ugly

I walked to work on one of those those beautiful spring days where it's summer in the sun and winter in the shade. It's four kilometres each way, which gives me plenty of opportunity to look at walls and fences. We need one for the boundary along one side of our house with the new neighbours and their new house.

The words "wall" and "fence" have slightly different meanings between Englsih and Japanese, being defined more by material in the former and function in the latter. Kabe is a wall of a house or building, while hei is a standalone fence or wall. The English words seem to be distinguished depending on whether they are made of wood or stone, although of course you can have a wooden wall. The Great Wall of China is called the ten-thousand-mile castle in Japanese, and probably Chinese too, but I digress.

I live to the West of the city centre, and work to the North, and walked two different routes through residential areas. The whole time I was looking out for inspiration and fences or walls that would look good for us.

I found none. 

The walls I saw break down into three groups: traditional, random and ugly. A lot of the traditional walls and fences looked really good, but would not suit our house. There were walls of beautiful stone, and fences of dark wood with tiled roofs running along the top. 

Actually most of the traditional walls didn't look that great. They would better fit into the random or ugly categories. A lot of them were all three. There seems to be a tendency to throw up anything without worrying about those details like function or appearance, or even cost. Some of them looked really expensive, but they would stop short of whole perimeters or even sensible spans. Walls with posts at the end but no gates between making you wonder whether they are there to actually do anything, or just look like a large receipt for materials and building services.

Many of the old wooden fences were rotting or splintering and in need of repair. Even when they were new, you could see that in a few years they are going to look terrible. Short-term cosmetic additions to a short-term and cosmetic building.

In many cases walls and fences had been patched together, not matching the building behind or anything on either side whether on the same plot or next door. Where a low wall had a fence fitted on top of it, the fence had often been replaced by something entirely incongruous with the surroundings. I guessed that a wooden fence had been neglected for years, then replaced with aluminium.

There was a lot of aluminium. Maybe it's a sensible thing to make fences from, as it's relatively cheap, strong and light, and allows gaps where wind could blow through rather than adding pressure to the wall. In several places I saw louvred aluminium, which I'm sure must have some useful function, but I can't really imagine it. Perhaps it lets in light and heat in the winter but not the summer. At least it would do that if aligned in the right direction, but it didn't seem to be very often.

And there was even more wire mesh. I suppose there's nothing wrong with wire mesh, if you have a car park or a tennis court, or if you keep fierce dogs. 

Once I saw a wall made of concrete blocks that had been painted in a thick red paint that was peeling off in several places. 

The most annoying materials for me were imitation brick walls, obviously imitation because the bricks are cut off at the edge of each block so the natural pattern of overlapping bricks is broken. 

The most pleasing boundaries were hedges and a few had tasteful herbaceous borders.

I suppose, following Edison's philosophy, it was worthwhile as I now know a couple of thousand things that I don't want.

Batteries

One of the running costs for the house is batteries for the thermometers. There are 16 thermometers around the house with data loggers collecting their temperature all the time. Each one has a battery in. They are lithium, not sure of the original serial number but I've been replacing them with CR2s, since they sell them at the local electrical shop. Two for a thousand yen.

The thermometers are not essential to the running of the house, but useful in seeing how heat is flowing around it.

The batteries seem to last around six months, but I had to change a lot of them recently and I wondered, why not rechargables? I should have thought of it much earlier, but they didn't sell them at the electrical shop so I hadn't pursued it. 

I found two types on the net. One was selling with a charger, so I got that. Unfortunatlely the batteries didn't seem to work very well. The data loggers came on when I put them in, but were still flashing "low battery". Not wanting to give up straight away, I ordered a couple of the other type, Ultrafire, that did not come with a charger. These were a little over half the price of the CR2s from the elctrical shop.

The Ultrafire batteries are 800 mAh, while the other ones were only 250. Not necessarily bad batteries but just smaller capacity. The voltage of batteries drops steadily as they loose charge, so a high capacity 3 volt battery may start at about 3.6 while a low capacity one just around 3. The data loggers, like many other semi-sentient electronic devices, judge the battery life by measuring its voltage.

The Ultrafire CR2s are still working a couple of months later, and I just ordered another four, in anticipation of having to change some batteries when I did my monthly data download. In the event, none of the batteries ran out this time, so I still have four ready for next time, and over the next six months I'll need to get 10 more so I can replace all of them.

The site I bought them from on Rakuten only ever says they have one or two packs of two in stock, although this may be because people usually only want one or two for their camera and a spare, so I'll have to ask them to let me order 5 packs.

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.