Japan sees the future and it is zero-energy homes - Nikkei Asian Review

At least that's what this article in nikkei says!

This is great news, but the silver has a little bit of a cloudy lining.

According to the article:
"Japan's Ministry of Economy, Trade and Industry has set criteria that a house must meet before it can be dubbed zero-energy. It has to:

• Be at least 20% more energy efficient than an ordinary home.
• Be airtight and adiabatic enough to increase the efficiency of air conditioners and water heaters.
• Allow for efficient ventilation.
• Have a solar power or other renewable energy system that can keep the house from sipping electricity from the grid, or even spit some electricity back onto the grid."

Interesting definitions, but wouldn't it make more sense to determine a zero-energy house as one that uses less energy than it produces?

The article does mention insulation, but only after talking about solar panels, energy management monitors and fuel cells. That's a bit like only mentioning malaria mortality after talking about terrorist attacks and aircraft accidents. (Oh, yeah, that happens in the media all the time!)

In the definitions quoted above, I guess "adiabatic" is only possible with insulation, but that's not exactly a widely used term outside school physics lessons, and even there it is not universally understood. I don't think I've ever heard anyone say: "Japanese houses are cold in the winter and hot in the summer because they are not very adiabatic." People frequently lament the lack of insulation though.

The other really big question with "zero energy" homes is how much energy they are allowed to generate. You could balance any level of energy use if you add enough solar panels, as long as you ignore how much energy was used to make the solar panels. So it's nice that zero energy homes have to be 20% more efficient than ordinary homes. But what if ordinary homes become 20% more efficient?

I could also complain about them using the term "energy efficiency". You could fill one house with energy efficient appliances, and have another house with just one appliance that is not so efficient. The house with more appliances will use more energy. Selling energy efficient air conditioners is much more appealing to the market economy than not using air conditioners at all!

It's easy to be cynical. I'd really like to see Japan's future in zero-energy homes too! I know that's where my future is.

Or maybe we should not be worrying about storing solar energy

There's a conventional wisdom on solar power in particular, and renewables in general, that we need storage to make it work properly. According to brave new climate that will probably stop them from being effective. 

They look at the energy return on energy investment (EROEI) and cite the low score for solar. In other words, the amount of energy that will come out of solar panels is not really enough to make solar panels. This means they are not sustainable and rather than contributing energy, they are using up energy created elsewhere. He suggests we should not just talk about the actual energy used in the process of manufacturing the solar panels, but also things like food and education for the people who are making them. 

Anyway, an energy source with an EROEI of one would just produce enough energy to support itself, and would be of no use to the society. The threshold for useful energy sources is something like 7. 

I have sometimes watched fish jumping out of the river to catch a fly, and wondered whether they were using more energy to catch the fly than they got out of eating it. EROEI is a bit like that. 

He quotes an EROEI of 3.5 for solar panels in Germany. This is already marginal, and if we have to store energy from renewables, then we also need to add the battery infrastructure into considerations of the EROEI, which could make solar a net user of energy rather than supplier. 

There are two other considerations. First is that solar production costs are falling all the time, and this includes embodied energy. The other is that we may soon have batteries parked outside each house in the car. 

Is it worth it? Present value factor

Building a house is a series of decisions, and a lot of these decisions put one-off capital costs against month-on-month running costs.

For example you could add insulation somewhere that will save 10,000 yen every year in heating and cooling bills, and cost 150,000 yen.

The first thing to think about is how far into the future you are going to be making savings. Let's say it's thirty years.

So if you're going to save 10,000 yen every year for the next 30 years, how much is that worth? 

Well, at first sight you'd think it's 300,000 yen. But it's not that simple. You have to think about inflation and interest.

First, imagine you don't have the money. In that case to make the capital investment you're going to have to borrow it, probably from a bank who will charge interest. This means the capital will cost more than its face value. In other words the saving from the running cost is worth less.

Second, imagine that you do have the money. In that case, spending it means you can't invest the money somewhere else, so you lose out on the opportunity for earning interest. So again the value of the cash in hand, or wherever it is, is more than its face value, in the long run.

This can all be expressed as the present value factor, which can be calculated by this equation:

 F_pv = 1-(1+P) ^-n / P

Where P is the interest rate, and n is the number of years.

But what if you're bad at making investment decisions, and would probably have lost all the money? In that case, you will probably make the wrong decision here, too, so you can stop reading, if you haven't done so already. You probably stopped reading before the equation.

And what about inflation? If the prices are going to go up, then that 10,000 yen per year is going to be increasing. Won't that balance out the interest? Can't we just multiply the annual saving by the number of years after all? 

Certified Passivhaus Consultant

Passive House Institute sent me a letter saying I passed the exam, and can now call myself a Certified Passive House Consultant. 

Passive House (or Passivhaus) is a standard that ensures buildings provide a comfortable environment, all year, with a very low energy cost. The Passivhaus Institute is based in Darmstadt, Germany. 

There are over a thousand certified Passivhaus consultants and designers in Germany, hundreds in the UK, over a hundred in South Korea, and three of us in Japan.

This qualification means:

• I can advise house builders and architects on Passive House building, and low-energy building in general. 
• I can work with builders and architects to calculate the energy performance of a building.
• I can determine whether a building meets the standard and help apply for Passive House certification.
• I can calculate the impact of changes in construction details, and estimate the longer-term energy costs. 
• I should be writing here more regularly!

Here's some free advice: if you are going to make a low-energy building, that should be one of the first decisions you make. Adding low-energy features is a bit like starting to make a boat, and only deciding later that you're going to be using it in water.

Note:

Above it says Passivhaus Berater. I think this is the German word for "consultant" although I am always happy to berate people who build to waste energy!

Dripping Diary

26th January, 2016

Water started dripping from the ceiling in the pantry this morning. 

When you have water dripping out of somewhere, it's a good idea to find where it is coming from and stop it from going in there. 

The immediate suspect, like the last five times water has appeared in unwanted paces, was the ventilation system two floors above.

This is actually the second water incident in the last months, but the first one was quickly noticed from the sound of drips on the bathroom ceiling, so it never got to build up anywhere. 

There was no dripping on the bathroom roof this time. That's because it was not the ventilation system leaking, even though that's where the water was ultimately coming from.

I quickly came to a second hypothesis. Half a metre of snow outside... temperatures below freezing for a few days... the drain from the ventilation system coming out of the wall about twenty centimetres above the ground... frozen pipe! 

left: drain from ventilation system

The first evidence to support this hypothesis was the water spilling gently over the the top of the drain beneath the ventilation unit, rather than actually going down it. 

A bit of hosepipe with a loop usually goes from the ventilation system to the drain. I diverted it into a bowl to stop sending more water to the overflowing drain. 

The next evidence was outside: a large icicle coming out of the drain.

A few buckets of hot water and kettles later the icicle was gone. The visible part of the icicle went fairly quickly and was soon followed by the rod of ice from within the pipe. It took a little longer to thaw the elbow. Immediate problem solved, it was time to address the cause.

The ventilation system is going to produce condensate when it's cold outside, unless we also make it cold inside, or drop the relative humidity below about 20%. It's often going to be below freezing when it's cold outside, and that's where the water is going to be dripping. So it seems inevitable that ice is going to form and, sooner or later, the outlet pipe will freeze. It will then fill up with water and start overflowing. The only mysteries are: why has this not happened before? and why did the contractors not prevent this from happening?

I suspect this probably has happened before, but it takes a while for the pipe to fill up with water before it overflows, then it takes a while for the water to drip down, around the bath that is one level below the ventilation system, then onto the ceiling of the pantry below the bath. Some of this water will be evaporating all the time, and it could be a couple of days before enough builds up to break through the plaster boards and start dripping onto the floor. By this time, the temperature outside has always gone high enough above freezing, or a few rays of pre-noon sunshine have reached the drain and thawed it. 

I was wondering if there were any mitigating circumstances leading to this, and there are a couple of things that may have made a difference. I noticed when I was clearing away another icicle a couple of days later that I'd left a gardening stake directly underneath the drain, from which was growing a nice icy stalagmite. Perhaps such a stalagmite had helped to block the drain. I was in too much of a hurry to melt the ice before and didn't document the hydro-crystalline pathology very well. 

The other thing that we had done the night before this incident was to put on the humidifiers. It gets a bit dry in the winter since we're constantly getting rid of our humid air, and replacing it with air that's already fairly dry, and is then being heated so that the relatively humidity will fall about four times. We don't have any permanent remedy for this, but when we remember, and when it gets below about 30 percent, we switch on some of our humidifiers, usually at night time. So we are adding moisture to the warm air that we are expelling from the house over a steep temperature drop, and increasing the amount of water that will end up in condensate.  

According to my previous calculation, the amount of water that's going to drip on a cold night is up to around 450 ml per hour. One drop is 0.05 ml, so that would be about two and half drops per second. Not fast enough to represent constant flow, but perhaps slightly faster than the ideal drip rate for forming icicles, which seems to be around one or two grammes per minute according to the Icicle Atlas. The precise temperature and humidity of the air in the house will determine the dew point, which will likely be a few degrees above zero. The dew point is really the critical number since it will tell us when condensation starts. 

It's 23 degrees C and 30% humidity right now, so the dew point is 4 degrees. (According to this dew point calculator.) So if the air outside goes below about 2 degrees, it's going to drop below the dew point within the ventilation system. If we had 100% efficient heat exchange, then it would be cooling the air all the way down to 2 degrees, and the air coming in would be heated all the way up to 23 degrees. It's more like 80% so we lose a couple of degrees. Some ventilation systems will recover only 60% of the heat, so they will be less likely to reach the dew point. This is only a problem that will happen in well-ventilated houses with highly efficient heat exchange ventilation systems, so I suppose that answers the question of why the contractors hadn't thought about this happening, and why we've had so many problems with this. 

When I say we've had many problems, we haven't exactly been wading through water, just needed to use a small cloth to mop up a few drops from the floor every year or two. And hopefully the structure of the house has not been damaged by the moisture. 

The other problem ventilation systems have to deal with is freezing condensate. If the air is being cooled below freezing, it may start snowing in there as vapour in the air is precipitated. This would block the ventilation and we would no longer be able to ventilate the house, so the ventilation system does something with pressure differences to stop that. I'm not really sure what it does, but the result will probably be that it never gets as low as zero in there, and in fact there may only be a very narrow window of outside temperatures when condensate is actually being produced.

(Apologies to anyone who was hoping for a story about cooking fat from the North of England.)

Note:

The other drain in the picture is from the air conditioner, which we have hardly every used. This has a de-humidifer on it, and it would take moisture out of the hot air if we were using it. There is no chance of it freezing though. 

Read about previous escapades here.