Gratuitous post about the eclipse

Eclipses don't really have much to do with house building, even if if it is an annular eclipse. Annular eclipses are are far from annual. Unless you travel around looking for them, they are a once-in-a-lifeime experience. Like building a house? Still gratuitous.

So, I set up my tried and tested eclipse-projecting technology, which puts the sunlight through a pin-hole, then uses a mirror to reflect the image onto a wall in the house. The tricky part is working out where the sun is being projected in the house, as it's much fainter than anywhere in the sun, so you have to close all the other curtains anyway, and actually go back into the house to find where it is projecting, then go out again to adjust it. You always think you can just look in the window and see where it is, but usually you can't. If you have somebody inside helpfully directing you left or right, up or down, that helps, but usually people just look at you with utter confusion. 

Anyway, here are some projections.

Sure enough, the eclipse started around 6:15 and reached it's peak around half past seven. Our house is about a mile away from the line with an annular eclipse. It was close enough to see that the moon's shadow is smaller than the sun. Just a little further South East and we would have seen a complete ring. This information was all made available on a website, into which you could put your location and it would give you precise times, to the second, when the eclipse would start, when totality would start, if at all, when it would peak, and so on. Next to each time was a percentage of eclipse. This time something like 94%. Although the light was very thin and eerie at only 6% of the sun's full power, it was still very bright. There was no way you would look straight at it. This shows how very bright the sun is, which I suppose is something relevant to house building. 

We had the blinds down and the house was darker than it usually is, although probably not as dark as the old house we were in. This goes to show how quickly people get used to living conditions. 

Here's an interesting effect with crescent shadows from my hands.

The other thing that does have a profound bearing on housebuilding is the exact predictability of the position of celestial objects. The local castle has a moon viewing room, clearly designed and placed to view the moon, which is as reliable in its movements as the mountains around are in their staticity. In fact the moon is probably a lot more reliable than the mountains, which are constantly being eroded and have their tops blown off from time to time. The sun is also absolutely predictable, so there is absolutely no excuse for not positioning the house and its windows in such a way that you will optimise all the heat and light that it produces.

The next one to pass this way is due in thirty years. Or was it three hundred? I can't remember, but someone somewhere knows the exact time and place.

Defrosting the ventilation

The Passive House lady was talking about defrosting inside the ventilation system, and this seems like it could be a problem on cold winter days. So far it hasn't actually been a problem, but I'm not sure why.

The problem relates to humidity. As we all know the capacity of air to hold water decreases with temperature. We can see this in the condensation on low spec windows and on glasses of beer as the cooling air deposits its moisture. We can see the opposite effect in hair dryers, as the hot air carries water away.

So in the heat-exchanging ventilation system, on a cold day, the air leaving the house drops from room temperature towards outside temperature, and the humidity will go from 50%, or whatever it is in the house, up to 100% if it drops 10 degrees. As the temperature continues to drop, with 100% relative humidity, the moisture will start to precipitate. Back in December, when the airtightness expert came to show us how the ventilation system worked, we could hear a gurgling sound as the air flow in the ventilation system was turned up, evidencing this jettisoned moisture.

It stopped gurgling when we put a loop in the hose, as it suggests in the Steibel manual, which the expert had apparently not read very carefully.

Anyway, what was worrying the Passive House lady was what happens when it's really cold outside, and the heat exchanger is taking the outgoing air below freezing. In this situation, the precipitating moisture is going to be ice, or perhaps snow, or is going to form icicles inside the pipes. Ice is a crystalline structure, and once it starts, it will keep growing. This could spread to take over the ventilation system, block the exhaust ducts and lead to a lack of fresh air within the building.

To try to get an idea of the size of this problem, we need to think about the amount of water that the air can hold, which goes up exponentially with temperature. Very roughly, the capacity of air to contain moisture is 4 grammes per kg of air at freezing. This halves or doubles with each 10 degree change, so is 2 grammes at -10, 1 gramme at -20. Going the other way, it's 8 grammes at +10, and 16 grammes at +20.

When it's cold outside, it's going to be cold inside the heat exchanger and the air could be precipitating moisture below freezing and ice could form. This may start to happen around -4 degrees (water needs to be below freezing to actually freeze). If it's 20 degrees inside, and the heat exchanger is 80% efficient, that's going to start happening at outside temperature around -8 degrees or something. Even if it's very dry inside, say 25% humidity, by the time the air temperature has dropped 20 degrees, the relative humidity will have doubled to 100%.

The total amount of moisture that air can contain at that -4 C is something like 3 grammes per kilogramme. As it was probably saturated (100% humidity) at 0 C, it was holding 4 grammes and will have precipitated 1 gramme. A kg of air is about 0.8 cubic metres, so if the pump is set to 120 cubic metres per hour, that's 150 grammes of water per hour. If the outside air gets colder, it's going to precipitate more.

Of course the air is moving. If the cross-sectional area is 100 square centimetres, or 0.01 square metres, that's moving at 12 km/h, so some of the precipitation is going to be carried away. That's not a very fast wind, and we've all seen icicles form in windier situations. 

http://lilt.ilstu.edu/jrcarter/geo211/webpage-211/mod5-p4.htm
I've been monitoring the outside temperature, and it's been below -8 only half a dozen days, and then for an hour or so in the morning. It doesn't stay that cold here for very long.

In Central and Northern Europe, where this technology comes from, it does get that cold, and does stay that cold, so there are electric heaters within the system to keep the air above the dew point.

Counter-intuitively, the more efficient the heat exchanger, the bigger the problem, which reduces their efficiency as electrical heating consumes a lot of energy. Perhaps our ventilation system also has one, although there was no evidence of excessive electricity usage on those cold mornings.

The airtightness expert seems to have been completely unconcerned with this problem, perhaps because it is not an issue in the Japanese climate. It may be that he's just not very good with numbers, unless they have yen signs next to them.

No more left over water left over

When you have a house, you know that sooner or later you are going to find a large pool of water somewhere. It may be dripping through the ceiling, trickling down the wall, or being sucked up by some cardboard boxes on a linoleum floor. Ours came rushing out of the washing machine, onto the tiled floor of the utility room, and then into the storeroom next to it, which has been cleverly placed a step lower down.

Washing machines are not supposed to let you open the door when they have water in them, and are not supposed to have water in them when they let you open the door, so we called the washing machine man in. Luckily the washing machine is still under guarantee, although we have had it a few years and brought it from our old house. The washing machine man came and declared that it was the fault of the plumbing. He demonstrated this by taking one of the pipes out of the top of the washing machine, and showing that water was dripping from this when the tap was switched off.

As in many cases, Japanese plumbing demonstrates both extravagance and frugality, making up this country's confused position as a home of both energy efficiency and resource squandering. Japanese baths, sweeping generalisation notwithstanding, are very large, using a lot of water and heat. On the other hand, they are not filled every day: the washing takes place outside the tub, so just a little topping up and reheating is necessary. Also, it is normal practice for the water from the tub to be used in the early cycles by the washing machine, recycling both the heat and water. Traditionally, I suppose, a bucket was used, then electric pumps and washing machines with built-in pumps.

In the old house, we had to put a hose into the bath tub, which would suck water into the washing machine when needed. As is customary, the washing machine was in the room next to the bathroom. This is very sensible architecturally, thermodynamically and ergonomically, but not ideal in our case as the room next to the bathroom was the kitchen.

The new house has a further development, taking the water from the bath directly from the plumbing to a tap in the wall next to the washing machine. This is much easier than a hose to be put into the bath. In our new house, the bath and washing machine are still relatively close to each other, only vertically rather than horizontally: the bathroom, as is customary in England, is upstairs. This still meets the criteria above, keeping all the water pipes in the same part of the house, shortening hot water pipes. We have a laundry shoot so clothes can be sent down from the bathroom to the utility room.

Many people here suggested, or assumed, that it was impossible for the building to take the weight of an upstairs bathroom, but we reminded them that there are plenty of aparment blocks with upstairs bathrooms.

Anyway, we have been having trouble using the bathwater for washing. The flood on the floor when we opened the door was the worst case, but when we did try to use the bath water, the washing machine was using up the entire content of the bath--over 100 litres--in one wash.

In the end, after the plumber coming to fix the tap, which he admitted was a new and untried model, and the washing machine man coming back again, we have heard, once again, that there is nothing they can do. The pump is designed to get bathwater from the same level, not to work as a tap. Because of the height difference and water pressure, once it gets the water going from the bath, the syphon effect will take over and it doesn't stop until all the water has gone. 

The washing machine man shook his head. Nothing can be done. All washing machines are the same. They're not made for upstairs baths. It's impossible to change the pump to one that actually stops water when it's off.

It seems that it would at least be possible to have an electric tap on the wall, activated via a relay when the washing machine switches its pump on, but he didn't seem terrible interested in solving the problem, content to tell us that it couldn't be done. 

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.

Getting certification and thinking about solar gain

The passive house lady visited in April and told us what we need to do to get passive house certification.

Basically we need to send in the PHPP excel file, which contains all the calculations, then send any drawings and data we have to justify the numbers we have put in.

We need cross-sections of the house showing where the vapour barriers are, and showing the wall sections to satisfy the insulation calculations and the airtightness requirements.

We need some kind of plan of the ventilation system, and ideally projected and measured values of the flow of air into, out of and through each room in the house.

We talked a bit about solar gain from the windows, which I'll go into more detail on later. When I started playing around with the PHPP file, I noticed very quickly what a massive difference was made by tiny changes around the windows. For example moving the south-facing windows a few centimetres further out could be the difference between meeting or not meeting the passive house criteria. I've tended to think of solar gain in a rather bow-and arrow way, that the sun is directly radiating into the house, in a straight line. In fact in Europe they estimate that 50% of solar radiation will come directly from the sun (in a straight line) and the other half will be reflected, and come from all different directions. In Japan, on the other hand, about 75% of the sun's radiation is coming direct, and 25% is reflected because there is less cloud cover. This means the PHPP calculations could be a bit pessimistic for our South-facing windows, which will actually bring more heat into the house. 

An interesting and counter-intuitive consequence of this notion of reflected radiation is that in the summer we could get more solar gain on cloudy days, when the geometrical shading blocking out the direct sun will be less effective at stopping dispersed and reflected radiation. On sunny days, though likely to be much hotter, we should be able to cut out most of the direct radiation, and very little is going to come from the blue sky. This is the opposite of the way that the most solar gain is coming into the house in the coldest months of the year.