Water harvesting and conservation

As part minimising the impact of our house and lifestyle, conserving water is just as important as conserving energy. Indeed, if we consider that it takes energy to clean, move (pump), and then dispose of water, saving water goes hand in hand with saving energy.

Features we have to minimise our water use are:

  • using a wetland-pond area for recycling household greywater (subject of a future blog)
  • water-saving shower and tap fittings
  • a compost toilet (previous blog entry)
  • green (living) rooves (previous blog entry)
  • rainwater collectors (rainwater harvesting)

For a full list of the house features you can visit this previous blog entry

Although Japan has plenty of rainfall (on average, about double that of the UK), from a gardener’s point of view, there are often long tough periods without rain. May of this year (2015) for example was particularly dry, and after the June rainy season, will probably be as usual; very hot, humid, and dry.

It is during these times that one really appreciates how much water is needed to grow food, something that consumers  are often not aware of when they buy imported greens or meat from relatively dry countries – Australia, Africa etc. The consequence is that we can accumulate very large hidden water footprints – embedded or virtual water. In the worse cases, we may be contributing indirectly to water stress in other countries that are exporting food and other consumables with large amounts of embedded water.

A good site to get an idea of the water footprints of different products you can visit sites such as:

Returning to the water saving features. To help save water consumption in the garden, we collect as much rainwater as possible. During very dry spells, I use up to 80 litres per day watering. A more sophisticated way to tackle this problem however is to use more efficient watering methods than the simple watering can. These include drip feed irrigation or clay pot irrigation that have the potential to cut water use by up to 70%.

Happy rainy season.

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Green (living) roof

A quick update and review of the main green (living) roof on our property. The attached photo gallery shows the 5 main layers needed to make a successful green roof, and how well the sedum has established itself and matured over the past two years. Sedums are ideal for green rooves as their root systems are shallow but dense and the plants themselves need very little water or weeding.

The 5 layers are:

  • Waterproof layer (pond liner)
  • Drainage layer (small stones)
  • A layer to help hold moisture (old carpets)
  • Root barrier
  • Soil (sand and leaf mould)

The benefits of any living roof are:

  • supports biodiversity
  • helps clean the air – absorbs CO2, gives of O2
  • helps retain water and runoff -soaks up large amounts of rain and releases it slowly
  • is a natural insulation – keeping building below cool in summer, warm in winter
  • can lengthen the life of a roof

Please feel free to contact me with any questions or comments.

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TV appearance

tv slotLast December our house and family were featured in a programme here in Japan. The series is about the lifestyles of families that, for one reason or another, they consider interesting or different.

Here is the link to a copy of the program. I have split it into Parts 1, 2, 3

We saw this as an opportunity to get wider exposure that would help in changing peoples’ perceptions that building an eco house and having an green lifestyle requires huge compromise, sacrifice, and expense. Indeed, in building the house we have always been keen to highlight the many aspects of the house and our lifestyle which enhance quality of life and comfort, and which are invariably simpler and cheaper, and of course, have a lower inpact on the environment.

Unfortunately, we were informed that we could not talk about the energy-saving features of our house:

  • insulation,
  • triple glazing,
  • wood stove,
  • absence of air condition

The reason: the programme series was sponsored by an energy company. Incredulous!

Anyway, we hope you find the programme interesting, even though it is in Japanese.

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Insulation – 1st year’s performance

The insulation of this house was given top priority (see previous blogs #1 #2) so in this post gives an update on how this insulation has performed.


In December 2014 I starting recording temperatures inside and outside the house to measure the effects of the insulation during the winter. As can be seen from the graph (click for full size), average temperature inside the house during the 18 hours when we don’t have any heating on in the house, is 16c, whereas the average temperature outside over the same period has been 4c.

temperature data

temperature data

Hira eco house snowWe only have the wood stove for heating and almost without exception, the fire only needs to be on in the evening, after six or seven o’clock. The house then remains warm until the following evening.

To show this in more concrete terms, I recorded temperatures in the early morning, and again in the early evening, before the fire was lit again.

The lowest temperatures in the house are in the evening Hira eco house snow viewand after days that are particularly cold, windy or cloudy. Results are from recorded readings made are over a 3 or 4 week period, but on random days, depending on when I was around and/or remembered to make them.


During our first summer in 2014, while temperatures outside reached as high as 37c, inside rarely went above 28c. And while the windows were open most of the time, the reflective properties of the insulation still helped to keep the house cool by preventing the heat of the sun penetrating the roof and walls of the house. As a result, we only needed the moderate use of fans, mostly at night, and kept windows open to encourage air flow through the house.

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Solar PV – 1st Year’s data

Our 4.9kW solar system has performed well we think. Based on 1 year’s data the average figures per day are:

Produced 17.51 kWh

Used 8.26kWh

Sold 15.47kWh

Monthly data can be seen in the following graph.

2014 solar data

January and December figures are high because of Christmas and New Year family social gatherings and entertainment – additional cooking (all electric) and hot water usage.

I will also need to try an identify why in October, so much electricity was used.

As mentioned in a post last year entitled energy use, according to  Strinkthatfootprint.com the avarage household electricity use in Japan (so excluding gas energy use) is around 15kWh.

To help in getting our average down to 8.26kWh, the most electricity hungry activities (washing machine and the air-source heat pump for the hot water) are set to work only at night. All other heating is from the wood stove, and cooling in the summer simply by the house insulation (earlier post insulation for more details), and natural air flow.

To help improve the figures for 2015, I hope to work out how to use the hot water system better (all the instructions are in Japanese) to control more closely when and how much water is produced.

Any comments or questions on these results most welcome.

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Milk & Goats

Part of any sustainable project must consider energy and if the same project involves the home and everyday living, then inevitably, the type and source of the food you consume needs to be considered.

Basically, the more local the food, the more control you should have over it in terms of being able to know where it is sourced. In addition, there will be less embodied energy through lower transportation (food miles) , storage, and packaging.

The goal then is to source food that is safe, healthy, and has a minimum environmental footprint. In general, protein rich foods; particularly meats and dairy products carry the highest environmental costs. A quick google search of food, water and  footprints striking comparisons of different food stuffs can easily be found.

Two good sites include  Water Footprint.org and Foodmiles.com

With my house project, securing a large enough piece of land to grow vegetables and have a variety of fruit trees, nut trees, vines, and other perennials.

For main sources of protein, we have seven chickens for eggs and on occasion, meat, and in the summer of 2014 we got two female Sannen goats from which we hope to secure a safe and healthy source of milk and cheese – without the hormones or antibiotics that are often used in commercial dairies.

This commitment however is not without problems that need to be overcome. In short these are:

#1 Noise: Both goats when we first got them, were extremely vocal. However, after a week they had settled in, and noise is now no longer a problem – BIG relief.

#2 Land: We need more grazing land to which we can take and leave them during the day We have found a couple of empty rice fields near our house which we have permission to use. In addition there is a lot of other unused land near our house where we can leave them.

#3 Feed: There are very few farm animals in Japan compared with 30 years ago, and certainly compared to my home town in Devon, UK. As such, hay is a rare and expensive commodity here.

#4 Trees: I now have the dilemma every time I want to plant another tree – should I leave the land tree free and usable by my goats or continue tree planting, so reducing the land available for grazing by goats? Goats love to eat trees and tree bark, which quickly kills the trees. As problem #2 has mostly been overcome, this dilemma has all but disappeared.

In the spring 2016, we would hope to have the arrival of our first baby goat(s) from which time, the supply of milk and then cheese would hopefully start.

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Recycling, upcycling and repurposing

In this post,  some of the things we recycled, upcycled, reclaimed, reused or repurposed.

A good article how these terms differ or are interchangeable is at greenlivingtips.com. And as it rightly points out “not all the “cycling’s” are created equal”.

Throughout the building project – from the design stage, to all the sourcing of the materials –  efforts were made to minimise the amount of new resources committed to the completion of the project. In the design for example, the foundations had gaps included to minimise the amount of concrete used. In addition, the open design of the house itself, while ensuring the most efficient heating, cooling and natural lighting, also meant less walls – so less wood, drywall, and paint.

A big part of this effort also involved finding discarded and unused materials that could be used instead of new materials. Wood, stone, bathroom fixtures and fittings are all examples.

Notes on the gallery: The first stage of the project was to demolish an old guest house (see demolition stage for a detailed photo gallery of the demolition) and the wood from the building, was all kept for use in and around the new house. The photo gallery includes some shots of frame of the main deck which was all made from this wood. Car tyres were used for creating a network of natural drainage around the house, and also for landscaping. Other items were reclaimed from other building sites in and around Kyoto city.



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Compost toilet – now online

Because the winter temperatures had receded, it was time to hook up and start the composting process of our compost toilet. Ironically it was the first item we got for the house (purchased in February 2012) yet one of the last of the houses main features to be installed and running.

The toilet is a Sun Mar 2000 AF NE. This model is a central system which means the holding compartment is separate from the toilet unit. From the attached photo gallery you can see the unit under the house. It is also non-electric using a natural ventilation system and without no electric heating, and flush free, that minimises the amount of water needed.

Fixing the air vent chimney was the hardest job. It has to survive the strong winds we get off the mountains and the yearly typhoons that could hit our area (2 last year) and I also needed to make many of the brackets and pipe joints. To start up the process just needed to add fibre (hemp), microbes (power and spray), and water. Then add waste as and when desired.

So far, so good, but will need to wait a month or more before the composting process is in full swing and compost output starts to appear in the collection tray. Will update the situation when needed.

Final point worth noting is that although we have bags of hemp fibre to keep the system in balance, wood shavings or rice husks are equally as good. When our hemp fibre runs out we will be using rice husks.

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Energy use and production

We’ve  now had the solar PV system working since August. We were lucky to get it installed early on in the building process, so could therefore start producing energy as soon as was possible. And because we weren’t living in the house, most of the energy we were producing at that time was being sold. As a result, our first energy bill after installation, was not a bill but a rebate – for ¥19,500 (about $190).

Winter's day performance of our 5kw solar PV system

Winter’s day performance of our 5kw solar PV system

The best conditions are of course bright, cloudless days, but also the cooler days of autumn and spring, due to the fact that solar PV efficiency is reduced by high temperatures. On a good day the system will make on average about 25kwh.

In the example pictured above the total made so far that day was 19.93kwh, we had used a total of 5.15kwh but as most of this was needed at night most of the energy we were billed for that day (4.42kwh) was not home produced energy. As a result, most of the energy made we were able to sell at the premium rate which is about double the regular electricity rate.

With this in mind, in order to mazimise the amount we get back (energy sold), we reduce our energy use during the day when the system is producing energy. Except the wood stove, the whole house runs on electricity and the hot water system, washing machine etc are all set to work at night. This also means rather than paying ¥22 per kWh, we are being charged at an off-peak rate of ¥11. This minimised any charges and therefore gives us a greater net rebate.

So in addition to having a carbon positive househould in terms of the energy we use/produce, the solar system also helps us track our energy use more carefully (currently around 7kwh per day). According to  Strinkthatfootprint.com the avarage household electricity use in Japan (so excluding gas energy use) is around 15kwh.

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Time to reflect … almost

Although still busy decorating etc we are slowly starting to find some time to relax and enjoy our new living environment. My spring holiday will be starting soon, at which point I will be able to finally catch up and add some feedback on how the house design and building process have worked out so far.

Outlining some of the more obvious benefits so far offered by the house, are almost constant warm indoor temperatures, absolutely no condensation on any windows, and it seems – regular monthly energy payments rather than energy bills.

And at this time of year we are being blessed with some wonderful clear sunny winter days which deserve an attached photo …

clear winters day

clear winters day

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