Using more electricity

Another record electricity bill came through. 9,000 yen. Almost 2,000 yen higher than any bill since last February. Deja vu. And we haven't put the heating on yet. Once again, this inspires me to look through the numbers and work out exactly what they are charging us for. The electricity bill doesn't say what the rate per kWh is, which I eventually found on the electricity company's website. 

Day time: 31.43 yen/kWh

At-home time: 21.23 yen/kWh

Night time: 9.33 yen/kWh

Then there is a fuel surcharge. This started the year at 1.3 yen/kWh and crept up to 1.8 in August, then dropped a little. It's going to be 1.64 in December. How careless of the electricity company to forget about the cost of fuel when deciding their tariff. I blame the airline companies for this practice, and I'm worried how far it will go. Perhaps the next time I go to the cinema they will charge extra for the film, or the next time I buy a carton of milk they will charge me extra for the milk.

Even so, this only makes at most  700 yen of the bill, and the difference between the higher rate and the lower rate is a less than 200 yen. 

Then there is a solar surcharge, which lets the electricity companies pass on the burden of paying people like me with solar panels for our electricity. This is only a tenth of a yen. 

Since August, they've added a renewable energy generation surcharge. Not sure why they need to do this as well as the solar surcharge. I thought solar was renewable, at least in the long-range future, if not aeonic future. This similarly makes a difference of tens of yen. Writing this paragraph probably cost me considerably more.

So we're no nearer explaining the 2,000 yen hike and it must be down to consumption. I can't compare with the previous year yet, but compared with the previous few months, the at-home consumption went up about 150 watts, night time 300 watts. That's a 40% an 45% increase.

Part of the reason is probably the humidifier, which I'll go into more later. We got a cheap humidifier at a second hand shop in preparation for the dry winter. If that accounts for the 150 watts at-home time, and some of the night time increase, then it was an expensive bargain!

I don't know if we're using more hot water, but heat pumps are less efficient at lower temperatures, so the drop in night time temperatures may account for the higher usage of night time electricity. 

Passive House Days

Our house was one of six houses in Japan that were listed in the worldwide Passive House Days. Low energy buildings around the world were open to visitors.

I'd been waiting for almost two years to get our house certified as a Passive House, spending many hours of discussion with the Passive House lady about the certification process. In the end, I registered it myself on the database held by the Passive House Institute in Darmstadt. Perhaps we will get certification in another year or two.

People didn't exactly beat a path to our door for the Passive House Days, although that was probably because we only opened the house on Friday, not the weekend, and we didn't do any publicity. I suspect they are a bit more organised in Europe, especially in Germany, and possibly less factional and cliquey. Having said that, cliques and factions are probably not limited to Japanese architecture, and probably apply in all areas of alternative technology and architecture in any country. Also, I was adding the building as a home owner, not an architect or a builder with an agenda of increasing my customer base.

I did ask Passive House in Germany about publicity for Passive House Days in Japan, and they told be about a person who I know indirectly, and have spoken to on the telephone who I'm going to call Mini Me. They said Mini Me knew me, so I assumed would be in touch. Mini Me had prepared a webpage announcing all the Passive House Days buildings in Japan, and I guessed that our house may be added to it, with it being on the Passive House database, and one of the houses open for Passive House Days. I think the list was not so much of Passive House buildings in Japan as Mini Me Passive House buildings in Japan. Not houses meeting an international standard, but buildings that Mini Me had been involved with the construction of, advertising Mini Me's services.

The list of "Passive Houses" in Japan on Mini Me's website page about Passive House Days had nine houses, although if you read carefully, and had some insider knowledge of the Passive House database, you could work out that only three of them were actually part of Passive House days, while they other six had "Passive House" in their names and claims that they had applied for certification, or planned to apply. Among them, this one looks similar to ours, at least in southern profile.


Actually, I didn't really expect to hear anything at all from Mini Me. I keep wondering whether I've been talking to the wrong people, or whether the world of Passive House is filled with unhelpful people. Being of a scientific disposition, I have not yet made a decision on this, and am waiting for more evidence to come in.

Not enough humidity in the winter

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 very roughly, and to keep the numbers simple, is 4 grammes per kg of air at freezing. This halves each time it gets 10 degrees colder, so is 2 grammes at -10, 1 gramme at -20. It doubles each time it gets 10 degrees hotter: 8 grammes at +10, and 16 grammes at +20. There are some more precise figures at the bottom for anyone needing to do exact calculations.

The volume of the house, again in the roughest of ballparks, is 500 cubic metres. A kg of air takes up about 0.8 cubic metres, so let's over-compensate for our overestimation of the amount of water that the air can hold, and say that a cubic metre of air can hold 4 grammes of water at freezing, 8 grammes at +10 and 16 grammes at +20. In a house we're not really interested in the weight of air, and the volume is going to be pretty constant.

If we start with 50% humidity at 20 degrees inside the house, that means there are 500 * 0.5 * 16g = 4kg = 4 litres of water in the air. If we imagine it's a steady zero degrees outside, also 50% humidity, and we switch on the ventilation system to shift 120 cubic metres in and out per hour, that's going to bring in 120 * .5 * 4g = 240 grammes per hour, and expel 120 * .5 * 16g = 960 grammes. A net loss of 720 grammes.

The humidity outside is going to make a difference, but even if the air is dripping with mist and it's 100% humid, we're still going to be losing twice as much water as we gain, around half a litre per hour. If it's bone dry, we lose almost a litre. Britain tends to be dryer in the summer and wetter in the winter, while Japan is the opposite, with humid summers and dry winters. In the summer, the opposite effect happens, so if it's 35° C outside, even if there's only 50% humidity when the temperature drops to the 25° C inside temperature, it will be saturated.

To maintain the humidity in the cold winter, then, we need to be emptying something like one wine bottle of water into the air in the house every hour. Of course, there are some sources of humidity within the house, for example bathing, washing clothes and cooking. If we use a tumble dryer, or hang out washing inside, this will help keep the humidity up. As humans respire and perspire, we're giving out water too. The air we breathe out from our moist lungs is saturated and above room temperature. That's why mirrors and spectacles steam up when we breathe on them. House plants can also keep the humidity up as the water we give them evaporates. This is all good, but I'm not really sure how big the effect is.

Burning fossil fuels gives off moisture, as the hydrogen atoms within the hydrocarbons combine with oxygen in the air. Our cookers are electric, so they don't help us.

The other place humidity is going to come from is the building materials. This is not such good news, if the building is drying out.

At the moment we have one small humidifier which gurgles away noisily and empties its 2 litre tank in about six hours, which is not going to keep up with the ventilation system's dehumidifying effect.

One option when we were choosing a ventilation systems was whether they maintain humidity going in and out, or ignore humidity. We chose one that ignores humidity, probably for reasons of hygiene as the moisture that it's passing from the outgoing air to the incoming air could contain bacteria. Legionnaires' disease has been known to thrive when moisture is circulated in a ventilation system. We usually just hear about this from hotels, rather than private houses. This may be because hotels have bigger systems, or maybe because it affects more people and is bigger news. Since this disease kills one in ten healthy people it affects, the stakes are high and caution is warranted.

The US Department of Labor offers some useful tips on designing HVAC systems to avoid legionnaires' disease. Very simply, if a system avoids bodies of water, especially any between 25 and 45° C, and only allows clean air in, it should be OK. Perhaps we could have followed these to make a built-in system to regulate the humidity safely. Getting another humidifier is probably much easier and cheaper though.

More precision (than you probably need or want)

Temperature	Maximum possible water vapour grammes per kg of air
-10° C	1.79
0° C	3.84
10° C	7.76
20° C	14.95
30° C	27.69

Too much humidity in the summer

Some of the thermometers in the house have been dutifully recording humidity for over a year now, but for the first few months I was largely ignoring that, much more interested in the temperature. Humidity is, of course, important for the health of the building and of the people in it. If the humidity is too high, there will be condensation. Condensation provides an ideal habitat for molds and mildews. Dust mites also like humidity, so high humidity means more dust mites, which in turn cause more allergies and asthma for people.

If the humidity is too low, the wood in the building can dry out and shrivel up. This may not have huge structural consequences, but can lead to warped plaster board and cracks in the paint work.

The comfort level for humidity is between 30 and 50%, apparently. Or between 40 and 50% or between 35 and 45% depending on which website you're reading. Our house was usually in that range in the first winter, but over July and August was in the 50 to 70% range. 

The human body generates heat at around 100 watts, and has to lose it somehow to avoid overheating. The main method of heat loss is evaporation, and the more humidity is in the air, the less effective this is. This means that if air is very humid, it feels a few degrees hotter because we judge temperature by the amount of heat we lose. If the air is very dry, it can feel cooler, but this can also lead to dry skin and respiratory problems.

Humidity is not presented as an absolute quantity of moisture in the air, but the amount of moisture relative to the maximum the air can hold. As air gets hotter, it can hold more moisture, just as hotter tea can hold more sugar, although technically speaking the humidity is not dissolved in the air as the sugar is in the water. So as the temperature goes up, we can expect the relative humidity to go down, and vice versa, as we can see on this graph of the temperature and humidity inside and outside on a couple of days in the summer. The total amount of moisture in the air, both inside and outside, is not changing very much.

Drip drip drip

I already mentioned pools of water and houses and the question not being if it will happen, but when. It seems a bit soon to get another one, and a little inconvenient that it was on a Sunday when I had to work.

When I was making breakfast I saw the small puddle and the drips coming from the ceiling in the utility room. The utility room is directly under the bathroom, so that's where any water is going to end up. Although it doesn't have much respect for a house free of fungi, water does at least obey the laws of gravity.

The first reaction was to call the plumber. Actually the first reaction was to get a bucket for the drips and a cloth for the puddle as it still hadn't got very far. Also, since it was dripping quite slowly, I thought we should let the plumber finish his breakfast.

I finished my work early enough that the plumber was still working, searching for the source of the leak. When I spoke to him on the phone, he hadn't found it, and was about to give up and go home. He said the water was not coming from the bath or any leaks in pipes there, but from the wall between the bath and the boiler.

Thinking about the mystery on my way home, like a Poirot of plumbing, it increasingly seemed that the ventilation system was the problem. In the process of exchanging heat, the ventilation system takes a lot of water out of the air, which must find its way through a drain out of the house. This seemed the most likely source of the water.

The night before had been the first below freezing, and I wondered whether the outside drain from the ventilation system had frozen over, stopping the water from escaping. Of course the temperature had only just dipped below freezing, so it wasn't cold enough for pipes to freeze, and there had not been enough time for a dam of water to build up and get through the ceiling.

When I got home, the first thing I did was look at the drain as it leaves the house on the East side. There was no ice there. In fact the drain pipe itself was dry.

The plumber showed my the pipes above the utility room when I got into the house, and the one that water was dripping down the outside of. We went upstairs to the boiler, which was installed by different tradesmen and was not really his responsibility. There were pipes coming in from the external heat exchange units for the boiler, and the air conditioner that we don't use. There were just two pipes for each: a supply and return for the coolant. No drains.

I then suggested the room upstairs, which he had had nothing to do with, and was unaware of. Above the bath is the machine room with the solar power conditioners and the ventilation system.
And there was the smoking gun. Or at least the dripping pipe, and a pool of water underneath the ventilation system.

The pipe coming out of the ventilation system had come out of the drain in the floor. It had not been fixed in there, but was just pushed in, the ventilation "experts" no doubt hoping for the best. I go into that room about once a month, and it could well have been knocked out when I was vacuuming the floor last time I was in there a month before. Water had been slowly dripping onto the floor, gradually increasing in flow as the outside temperature dropped. As it found its way down past the bath, following the pipe, it would gradually have evaporated back into the house. For the last couple of nights, as the temperature dropped to around zero and the amount of moisture coming out of the air in the house increased accordingly, more or the moisture got to the puddle above the ceiling of the utility room, and in the morning it finally got through the drywall. In fact the dry wall was now a wet ceiling.

It's a good thing we'd just used drywall for this room rather than a plastered and painted ceiling. A screw driver is enough to take a panel off, and it can easily be replaced without needing to call in a procession of tradesmen. The drywall panel is now propped against the wall to let the ceiling dry out, and I can put it back again in a couple of days without having to call the plumber out again.