Friday, 15 January 2016

Lesson 12, part IV: Life cycle analysis

So you have to look at the whole lifecycle, like we did with power generation. We need to look at positive and negative impacts during manufacture, installation, use, decommissioning and disposal.
Let's look at some glass wool insulation. You can get a roll 11 metres long, 910 mm wide and 100 mm thick for around 6,000 yen. For the same price you could get around 90 litres of paraffin. So which should you get?

You need to keep warm, and you can either wrap your house in the glass wool, or burn the paraffin. How long would it take for the insulation to save the energy in the fossil fuel?

The glass wool has a U value around 0.44 W/m2K, and we can assume 80 thousand kelvin hours per year heating demand. There's about ten square metres of it, so putting it on a wall will stop something like 352 kWh of heat per year.

A litre of paraffin has around 9.8 kWh of energy, so the 90 litres have 880 kWh.

Therefore, it will take about two and half years of heating bills to pay back the insulation costs.

We're forgetting a few things in our calculations. Of course we need a heater to burn the paraffin, and we need to install the insulation. It's not going to make us any warmer just by buying it and putting it in the corner.

We're probably not starting from zero insulation, but adding that insulation on top of existing walls. If we already have a U value of 0.44, this extra layer will only save half the heat. The more insulation we have, the less heat there is for extra insulation to stop.

We also need to remember the Jevons paradox. If a house is poorly insulated, and paraffin needs to be bought and burnt every time we want to heat it, it is probably not going to be at that ideal inside temperature all the time.

If we have a traditional building with very little or no insulation, the temperature will be low a lot of the time, and the heating bills will be moderate.

We could put more heating in to get the building to a comfortable temperature, but the heating bills will be very high.

Adding a little insulation will mean the temperature is higher, but we are probably going to be using the same amount of heat we started with to keep it comfortable for longer. This is the Jevons Paradox.

If we get enough insulation, then the temperature can be kept comfortable the whole time, with much lower heating bills.

A little insulation is a dangerous thing!

Back to the insulation and heating oil, we can also look at the carbon costs. While the financial costs were similar, in terms of CO2 emissions, burning the paraffin will emit two hundred times more carbon than manufacturing the glass wool. This puts the carbon return on investment around five days.

In all these calculations we need to look at the trade-off between running costs and lifetime, since the total cost of the house includes initial costs plus running costs multiplied by the lifetime. The length of the lifetime makes a difference to these calculations. If you have a building component with a pay back of twenty-five years, that makes sense in a house that will last a hundred years, but not in one that will last fifteen years. But who would build a house that only lasts fifteen years?

So we have a vicious cycle here where houses are worth nothing after less than twenty years. This means banks give small loans, buildings are built cheaply, they are not maintained and are often knocked down within twenty years.

This short lifetime means that return on investment calculations will prevent investment in long-term energy saving technology.

More serious, short lifetime of building means massively more energy is spent on the buildings. Low energy investments are usually tiny percentages of the total building cost. A building that uses half the energy over its lifetime does not use twice as much energy to make. It may use ten percent more. Often low energy buildings are high technology and while the costs may increase, in carbon accountancy there is no difference.

So if buildings have a lifetime of twenty years, they could be using four or five times more energy than in another country where their life expectancy is a hundred years. This is obvious. The reasons why Japan has a disposable building culture are a little more complicated. How Japan can get out of this situation is the trillion yen question!

Ito, Akiko (2013). Policy and programs for energy efficient houses and buildings
Further reading
Further listening
Freakonomics: Why are Japanese homes disposable?