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.
Thursday, 9 September 2010
The window
We had a nice open space on the south facing wall, about 2.7m wide, or a ken and a half. A ken is a Japanese building unit, 6 shaku, two tatami mats long, that corresponds to one beam. A shaku is almost exactly one foot, 30 cm.
Outside the room is a terrace, and we'd like to link the inside space with the outside space, and be able to open up the gap in the wall. The problem is what happens to the windows when they open. They cannot just vanish. A sliding window would be all very well, and wouldn't take up much room space, but it would have to slide somewhere. This would only leave us half the window width to walk through.
Swinging doors would work, but two doors would have to be 1.3 m wide, and would swing into rather a lot of the room.
French windows seem like a good idea, but unfortunately the window construction doesn't last so well for windows that open outwards. This is perhaps something they need to work on.
Another problem with swinging doors is that there is a counter to one side of the window, and a gap through which to reach the kitchen. A swing door would block off this gap.
The solution we found was a concertina door, so there are three window panes, which open onto each other and slide up neatly to the other side from the counter. I say "neatly" but each window is over 10 cm thick, and when they pile up they will be 45 cm wide, and sticking into the room around 90 cm. This will still give us over two metres of gap, so for example we can sit around a table half inside and half outside.
So many decisions to make. We have to convince ourselves that each one was the right one!
Outside the room is a terrace, and we'd like to link the inside space with the outside space, and be able to open up the gap in the wall. The problem is what happens to the windows when they open. They cannot just vanish. A sliding window would be all very well, and wouldn't take up much room space, but it would have to slide somewhere. This would only leave us half the window width to walk through.
Swinging doors would work, but two doors would have to be 1.3 m wide, and would swing into rather a lot of the room.
French windows seem like a good idea, but unfortunately the window construction doesn't last so well for windows that open outwards. This is perhaps something they need to work on.
Another problem with swinging doors is that there is a counter to one side of the window, and a gap through which to reach the kitchen. A swing door would block off this gap.
The solution we found was a concertina door, so there are three window panes, which open onto each other and slide up neatly to the other side from the counter. I say "neatly" but each window is over 10 cm thick, and when they pile up they will be 45 cm wide, and sticking into the room around 90 cm. This will still give us over two metres of gap, so for example we can sit around a table half inside and half outside.
So many decisions to make. We have to convince ourselves that each one was the right one!
Sunday, 4 April 2010
Heat - Units
I probably learnt most of my basic thermodynamics from a song by Flanders and Swan called the second law of thermodynamics. This states "Heat won't pass from a cooler to a hotter" and the song has the refrain "You can try it if you like, but you'd far better notter"! They also mention the first law, heat is work and work is heat. I think this was proven by a brewer in Manchester called Joule, who gives his name to the unit of energy required to raise one kilogram of water by one degree.
Joules are tiny units and a more tangible figure for energy is the kilowatt hour. Watt spent some time with steam engines, and his unit measures power. Power is simply the exertion of energy, so if you're exerting one joule every second, that's one Watt. Use a thousand watts for an hour and you have a kilowatt hour. Bringing it home, if you leave a hundred-watt lightbulb on for ten hours, that will use a kilowatt hour. An electric oven uses about a kilowatt, so leaving that on for an hour will use a kilowatt hour.
The sun also gives out about a kilowatt of heat every square metre of earth. We can't use all of this as a bit gets lost in the atmosphere, and the square metre may not be at the same angle as our square metre of window or of solar panel. Even with south facing windows, the sun is always going to hit them at an angle, unless they are tilted inwards. The solar thermal panels are likely to produce 2.3 kWhours in hot water for each square metre every day in the winter. The question of how many we need is tricky. The hot water needs of the house will probably be 12 kWhours per day. This will not change much throughout the year. The heating needs on a very cold day in the winter could be 36 kWhours. Even in the middle of winter, on a sunny day, plenty of heat will get into the house and there will be days when we don't need any heating.
The panels are PVT, which means photovoltaic thermal, so they produce both heat and electricity. They are rated at a little over 30 volts, so we need three to make 100, which is a usable voltage. We probably need some multiple of three panels, although I'm sure it would be possible to put them in parallel and series. Anyway, 6 panels would produce enough hot water for most of the year, but not enough heat for a few cold days in the winter.
We can store some heat, but there's a limit to how much and for how long.
Whatever happens, we need some backup heating system. For example, it may snow for a week, and solar panels will definitely not work if they are covered in snow. As we are connected to the electricity grid, and if we can use off-peak electricity, which should compensate for us adding to the grid at peak summer times, then electricity seems a reasonable backup heat source. We may need to think of an alternative if the economy collapses, but I think we'll be OK for now! Electricity is not that efficient for producing heat, which is not a big problem if we don't use a lot of it.
My car is not so efficient but it averages only about 30 km per week, so probably has the lowest emissions of any in the neighbourhood.
The cheapest heating system is a heating element, like you get in an electric kettle. One of these could be put into the hot water tank that the solar panels supply and switched on at night when the water's too cold.
A more efficient way of using electricity for heat is a heat pump. A heat pump uses slightly more advanced thermodynamics than in the song. Basically it is like an inside-out fridge. A fridge pumps heat from inside the fridge to make it cooler. Somewhere on the outside of the fridge it is hotter. Heat pumps are also used in air conditioning, where they take heat from a cooler room and pump it into the heat outside. In the case of heating, the heat pump takes heat from outside, where it is cold, and brings it inside, where it is hot.
This is in blatant defiance of the second law of thermodynamics, "heat won't pass from a cooler to a hotter". The way they cheat is basically by a compressor. Going back to the first law: heat is work and work is heat, so at a molecular level, heat just means that all the little bits of matter are moving around. If it's hotter, they move around more. If it has less heat, they move around less. This seems to be the opposite of people...
One difficulty in explaining this is the confusion between heat and temperature. For a given object at a given size, adding temperature will increase the heat, and increasing the heat will raise the temperature. However, if you take a gas and compress it to half the volume, the same amount of heat will now be contained in a much smaller size, and the temperature will correspondingly rise. Back in the heat pump, this can then be passed through the warm place you want to get hotter. Next it passes through a valve, then drops in temperature, and can now pass through the cool place that it will be colder than, and so will absorb heat from. And so the cycle goes around again.
Producing heat in this way, or rather sucking in heat from thin air, uses much less energy than making the heat directly from energy. With a kilowatt of electricity, you can bring in heat at up to five kilowatts.
Commercially available systems in Japan are called eco cute. "Kyuto" means water heater, and sounds like "cute". "Eco" is a reprehensible advertising prefix, that I feel refers more to economics than to ecology. The greek root of both words is the same. These water heating systems use off-peak electricity to run heat pumps that suck heat from the air outside. Although it makes economic sense to do this, as electricity is cheap at night when nobody is using it, it makes less sense from an energy point of view. Heat pumps run less efficiently the lower the temperature gets, although they will still be able to suck some heat out of the air when it gets down to ten or fifteen below zero. In our case, the time we're going to need the extra heat is on cold days in winter, when the heat pump will be at its least efficient. The coldest days are sunny, so actually it will not quite be the coldest days, but the days we need extra heat will certainly not be warm.
It may still be that as a product eco cute turns out cheaper than patching together our own system for delivering hot water and underfloor heating, although we need to find a way of feeding the water from the solar panels into it as they are usually supplied from the water main. This system would cycle water from the panels through one tank, than take hot water from this tank into the eco cute. The eco cute would then use its mass produced control system to send this hot water where it is needed, and to switch on the heat pump when it's getting too cold. It might be upset that it is not using its heat pump very often, although that's tough!
The other system would simply use one tank, heated by the solar panels, backed up when there is not enough heat by a heating element, feeding hot water to the house, and heating either a pipe for underfloor heating or heating the air that is sent under the floor.
The control systems we'd need would be:
1. when to pump water from the solar panels, which we're on our own for with or without an eco cute
2. when to add extra heat, which we wouldn't want to do other than at off peak
3. when to send heat into the underfloor heating.
4. I'm becoming less and less convinced we need this, but if we are going to reheat the bath water, then we need it decide when to do that.
Joules are tiny units and a more tangible figure for energy is the kilowatt hour. Watt spent some time with steam engines, and his unit measures power. Power is simply the exertion of energy, so if you're exerting one joule every second, that's one Watt. Use a thousand watts for an hour and you have a kilowatt hour. Bringing it home, if you leave a hundred-watt lightbulb on for ten hours, that will use a kilowatt hour. An electric oven uses about a kilowatt, so leaving that on for an hour will use a kilowatt hour.
The sun also gives out about a kilowatt of heat every square metre of earth. We can't use all of this as a bit gets lost in the atmosphere, and the square metre may not be at the same angle as our square metre of window or of solar panel. Even with south facing windows, the sun is always going to hit them at an angle, unless they are tilted inwards. The solar thermal panels are likely to produce 2.3 kWhours in hot water for each square metre every day in the winter. The question of how many we need is tricky. The hot water needs of the house will probably be 12 kWhours per day. This will not change much throughout the year. The heating needs on a very cold day in the winter could be 36 kWhours. Even in the middle of winter, on a sunny day, plenty of heat will get into the house and there will be days when we don't need any heating.
The panels are PVT, which means photovoltaic thermal, so they produce both heat and electricity. They are rated at a little over 30 volts, so we need three to make 100, which is a usable voltage. We probably need some multiple of three panels, although I'm sure it would be possible to put them in parallel and series. Anyway, 6 panels would produce enough hot water for most of the year, but not enough heat for a few cold days in the winter.
We can store some heat, but there's a limit to how much and for how long.
Whatever happens, we need some backup heating system. For example, it may snow for a week, and solar panels will definitely not work if they are covered in snow. As we are connected to the electricity grid, and if we can use off-peak electricity, which should compensate for us adding to the grid at peak summer times, then electricity seems a reasonable backup heat source. We may need to think of an alternative if the economy collapses, but I think we'll be OK for now! Electricity is not that efficient for producing heat, which is not a big problem if we don't use a lot of it.
My car is not so efficient but it averages only about 30 km per week, so probably has the lowest emissions of any in the neighbourhood.
The cheapest heating system is a heating element, like you get in an electric kettle. One of these could be put into the hot water tank that the solar panels supply and switched on at night when the water's too cold.
A more efficient way of using electricity for heat is a heat pump. A heat pump uses slightly more advanced thermodynamics than in the song. Basically it is like an inside-out fridge. A fridge pumps heat from inside the fridge to make it cooler. Somewhere on the outside of the fridge it is hotter. Heat pumps are also used in air conditioning, where they take heat from a cooler room and pump it into the heat outside. In the case of heating, the heat pump takes heat from outside, where it is cold, and brings it inside, where it is hot.
This is in blatant defiance of the second law of thermodynamics, "heat won't pass from a cooler to a hotter". The way they cheat is basically by a compressor. Going back to the first law: heat is work and work is heat, so at a molecular level, heat just means that all the little bits of matter are moving around. If it's hotter, they move around more. If it has less heat, they move around less. This seems to be the opposite of people...
One difficulty in explaining this is the confusion between heat and temperature. For a given object at a given size, adding temperature will increase the heat, and increasing the heat will raise the temperature. However, if you take a gas and compress it to half the volume, the same amount of heat will now be contained in a much smaller size, and the temperature will correspondingly rise. Back in the heat pump, this can then be passed through the warm place you want to get hotter. Next it passes through a valve, then drops in temperature, and can now pass through the cool place that it will be colder than, and so will absorb heat from. And so the cycle goes around again.
Producing heat in this way, or rather sucking in heat from thin air, uses much less energy than making the heat directly from energy. With a kilowatt of electricity, you can bring in heat at up to five kilowatts.
Commercially available systems in Japan are called eco cute. "Kyuto" means water heater, and sounds like "cute". "Eco" is a reprehensible advertising prefix, that I feel refers more to economics than to ecology. The greek root of both words is the same. These water heating systems use off-peak electricity to run heat pumps that suck heat from the air outside. Although it makes economic sense to do this, as electricity is cheap at night when nobody is using it, it makes less sense from an energy point of view. Heat pumps run less efficiently the lower the temperature gets, although they will still be able to suck some heat out of the air when it gets down to ten or fifteen below zero. In our case, the time we're going to need the extra heat is on cold days in winter, when the heat pump will be at its least efficient. The coldest days are sunny, so actually it will not quite be the coldest days, but the days we need extra heat will certainly not be warm.
It may still be that as a product eco cute turns out cheaper than patching together our own system for delivering hot water and underfloor heating, although we need to find a way of feeding the water from the solar panels into it as they are usually supplied from the water main. This system would cycle water from the panels through one tank, than take hot water from this tank into the eco cute. The eco cute would then use its mass produced control system to send this hot water where it is needed, and to switch on the heat pump when it's getting too cold. It might be upset that it is not using its heat pump very often, although that's tough!
The other system would simply use one tank, heated by the solar panels, backed up when there is not enough heat by a heating element, feeding hot water to the house, and heating either a pipe for underfloor heating or heating the air that is sent under the floor.
The control systems we'd need would be:
1. when to pump water from the solar panels, which we're on our own for with or without an eco cute
2. when to add extra heat, which we wouldn't want to do other than at off peak
3. when to send heat into the underfloor heating.
4. I'm becoming less and less convinced we need this, but if we are going to reheat the bath water, then we need it decide when to do that.
West Wall
Here is a difficult dilemma. Should the west wall be perpendicular to the north and south walls, or should it be parallel with the western perimeter of the land?
The land slightly tapers towards the south, the eastern perimeter running more or less due north south, while the western perimeter veers a little east of south. To maximise solar gain, both for the south facing windows and solar roof, we need the south wall to run due east west, so squaring the box brings the east wall parallel to the east perimeter, and brings the north wall parallel to the south wall and the west wall parallel to the east wall. This will leave a narrow space between the south west corner of the house and the perimeter.
In terms of construction, four right angles makes everything easier. Building with right angles is straightforward, the parts are all there, spans are all uniform and there are no left over bits.
In the end, the West wall runs parallel to the plot, so the building is slightly tapered north to south, perhaps around 7 degrees off the right angle.
The land slightly tapers towards the south, the eastern perimeter running more or less due north south, while the western perimeter veers a little east of south. To maximise solar gain, both for the south facing windows and solar roof, we need the south wall to run due east west, so squaring the box brings the east wall parallel to the east perimeter, and brings the north wall parallel to the south wall and the west wall parallel to the east wall. This will leave a narrow space between the south west corner of the house and the perimeter.
In terms of construction, four right angles makes everything easier. Building with right angles is straightforward, the parts are all there, spans are all uniform and there are no left over bits.
In the end, the West wall runs parallel to the plot, so the building is slightly tapered north to south, perhaps around 7 degrees off the right angle.
Wednesday, 17 February 2010
International Standards
It's now about three months later, and things seem to have been very busy, but I'm not sure how fast they have been moving.
We've decided to make a Passive House. This means it must follow strict standards for insulation and airtightness. It will need some kind of mechanical ventilation system that will transfer the heat leaving the building to the heat coming in, so it will maintain ambient temperature.
Whenever I talk about insulation, people seem to automatically say how hot it's going to be in the summer. This seems intuitive but not completely logical. After all, thermos flasks can keep cold things cold, and fridges and freezers are insulated too.
There's also a very strong sense in Japan that this country is completely different and what happens in Germany cannot be applied here. As far as I can tell the same laws of thermodynamics apply, and water and air have more or less the same chemical composition in both places. The climate is certainly a bit different though.
Summer temperature is about five or ten degrees warmer in Matsumoto than in Germany, and five or ten degrees colder in the winter. Also there is a difference between average monthly highs and lows of over ten degrees every month, with August having average highs of 30.5 and lows of 19.8. January swings from 4.9 to -5.5. As well as looking at averages, the extremes are also interesting. In 1987 there were two days when nighttime temperatures went above 25 degrees. This was a record. In other words, on pretty much every day of every year, opening the windows at night is going to let in air below 25 degrees.
1943 saw 155 days where the temperature fell below zero. This makes me think that the cold is a more serious problem than the heat!
There are places in Austria with a similar temperature range, for example Eisenstadt or Baden. Searching for "passive house" on the internet in English, you find lots of people making them in the US and talking about making them in the UK. Searching for Passivhaus in Eisenstadt, I found most of the hits were estate agents selling those that have been built over the past twenty years!
We've decided to make a Passive House. This means it must follow strict standards for insulation and airtightness. It will need some kind of mechanical ventilation system that will transfer the heat leaving the building to the heat coming in, so it will maintain ambient temperature.
Whenever I talk about insulation, people seem to automatically say how hot it's going to be in the summer. This seems intuitive but not completely logical. After all, thermos flasks can keep cold things cold, and fridges and freezers are insulated too.
There's also a very strong sense in Japan that this country is completely different and what happens in Germany cannot be applied here. As far as I can tell the same laws of thermodynamics apply, and water and air have more or less the same chemical composition in both places. The climate is certainly a bit different though.
Summer temperature is about five or ten degrees warmer in Matsumoto than in Germany, and five or ten degrees colder in the winter. Also there is a difference between average monthly highs and lows of over ten degrees every month, with August having average highs of 30.5 and lows of 19.8. January swings from 4.9 to -5.5. As well as looking at averages, the extremes are also interesting. In 1987 there were two days when nighttime temperatures went above 25 degrees. This was a record. In other words, on pretty much every day of every year, opening the windows at night is going to let in air below 25 degrees.
1943 saw 155 days where the temperature fell below zero. This makes me think that the cold is a more serious problem than the heat!
There are places in Austria with a similar temperature range, for example Eisenstadt or Baden. Searching for "passive house" on the internet in English, you find lots of people making them in the US and talking about making them in the UK. Searching for Passivhaus in Eisenstadt, I found most of the hits were estate agents selling those that have been built over the past twenty years!
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