2012 - January 2013
Reaping the Rewards?
Back in May 2012 the diary entry ended with the unfinished rainwater harvesting system. We were still using
a temporary mains water supply then, fed into the house from a standpipe in the garden via a hosepipe, backwards
through the outside tap. This obviously wasn't satisfactory in the long term, and we also knew we were due to lose
our mains water supply, so in May, Mike got started on the rainwater system.
The rainwater is stored in redundant bulk orange juice transport containers known as Rotoplas tanks.
They hold 1500 Litres each, and we have twelve of them ten store untreated rainwater, another houses a slow sand filter,
and the twelfth is a store of filtered clean water. Connecting that lot together is no small undertaking.
After drilling holes for the interconnections, the next job was to tap threads for the pipe connectors. The polypropylene
which these tanks are made from is pretty tough, as they're built to withstand a sea journey from Israel, full of
a tonne and a half of orange juice concentrate. So with a little care, threads can be tapped directly into them.
The fittings are all standard items used in water supply and irrigation systems, and they all push and screw together
rather like chunky plastic children's toys. If you're lucky, they don't leak.
Water from the slow sand filter system feeds into the clean water store by gravity, meaning it needs to be raised above it,
by way of this dais. Built from left over scaffolding planks, it needs to support around 2 tonnes
the weight of the Rotoplas tank plus the sand, gravel and water contained inside.
A simple sight-glass, fashioned from clear polypropylene pipe. Mike is pointing to it in case you're not sure.
This will allow us to keep an eye on our stored water levels, and ease off consumption if we experience long spells
without rain. Remember we have no mains backup it's up to us to manage the natural resources on which we rely.
As has been the case so often during this project, small pieces of specialist equipment have had to be constructed,
as there's nothing available off-the-shelf. This multiply-perforated pipe will collect the water from the gravel layer
at the bottom of the slow sand filter, without allowing the gravel to get out.
Installing this was a little uncomfortable, but once it was in place, and with the rest of the tanks plumbed together,
we were able to begin construction of the slow sand filter.
We've had a lot of valuable assistance from Dr. Tim Pettitt at The Eden Project an expert on filtration systems.
On one of the hottest days of the year, we took delivery of a tonne of one of Tim's 'favourite sands', and a similar
amount of gravel.
The soaring temperatures made the transfer of these materials to the basement a decidedly uncomfortable task,
but half a tonne of gravel, and the entire tonne of sand, were carried down a couple of buckets at a time.
The filter system was built in a Rotoplas tank with the top cut off, to allow for easier construction and maintenance.
The gravel in the bottom of the tank allows the filtered water to collect as it drains through the sand layer above.
Here it is with the perforated 'collection tube' just beginning to disappear.
Once the gravel layer has been built up, in goes the sand......
....a whole tonne of it on top of the gravel, after which the system can be filled with water.
As the filter 'matures', organisms which are naturally present in the rainwater form a biofilm on the surface of
the sand particles. It's the organisms in the biofilm which clean the water, as it percolates through from top to bottom.
When the system is first set up there's no biofilm, so the water coming out isn't really any cleaner than the water going in.
Here's the clean water store on the left, with the slow sand filter, all completed, on the right. While waiting for the
filter to mature, we continued to use mains water for drinking purposes, but harvested rainwater for everything else.
The water is fairly clean now, and Mike has drunk lots of it, with no ill-effects at all, although it tastes a bit musty.
The sand filter and clean water tanks are fitted with float valves......
...which control small 12-volt pumps, running from our battery system which also supplies the low voltage lighting.
These are commonly available components the small recirculating pump on the left is used in backpack sprayers,
and the larger high pressure pump is the type often used in motor homes and narrow boats.
So here it is the completed system, which has been supplying our water since May. We've since had to fit a pH correction
unit, because the harvested rain water was so soft (i.e. acidic) that it began to attack the copper pipes in the plumbing,
so it had to be made 'harder'. The main reason for the low pH of rain water is carbonic acid, caused by dissolved atmospheric
CO2, which is at a higher level now than it's been for 800,000 years. Can you guess who's fault that might be, children?
One final job in the basement insulating the composting toilet chutes. We reclaim the heat carried down them from the house
and that generated within the compost pile, so applying this insulation was important. The toilet system has genuinely been a
success. The constant airflow down the pedestals means no smells in the house, and with two occupants, who've now lived
here for 18 months, using the toilet (an impressive) 12 times each per day, we've saved at least 8000 gallons of flushing water.
Of course some people will have reservations about having to 'maintain' a composting toilet system,
although those same people would probably be quite happy to change babies' nappies, or clear up after their dog.
But composting toilet maintenance is less unpleasant than either of those tasks, and when you see a barrow-load of
the rich, odourless, high quality garden compost which you've produced yourself, you can't help but feel a sense of pride.
After removal from the toilet chamber, the compost spends a few more weeks in an ordinary garden compost bin,
after which it can be put straight on the garden. Here's Matt Wallin, our garden helper, spreading some of our s***.
After the initial drought the tremendous amounts of rain really spurred on growth in the garden this year, as well as
keeping the rainwater harvesting tanks permanently full. Our natural pond is very popular with the local birdlife...
...... as is our perimeter hedge large sections of which are now dense enough for nesting.
Possibly less successful has been the rammed earth turf wall the very steep sides seem to be making it difficult for the
grass to grow. Matt Wallin's dad Peter, who helped with our garden planning, came back with
some additional plants, which we hope will spread out and help to protect the rammed earth structure.
Whether the strategy is a success or not, it looks as though we all had a good time.....
.....and Mike took the opportunity to offer Matt's dog Diesel some ideas for a makeover.
Work on the house slowed significantly around July, partly because it was sufficiently complete not to notice the few
sections which weren't, but also because Mike ran out of enthusiasm, and couldn't face another screwdriver,
hammer or spanner for a while. But there were a number of diversions, including a couple of magazine articles to write, and
presentations at Ecobuild in London, and the Big Green Homes Show at the National Self-Build and Renovation Centre.
It's always good to have (another) professional photographer around the place, and here's Steve Taylor,
who came to do a major photoshoot for Self Build and Design magazine. If you didn't see the article
when it was published, you can download a pdf of it by clicking this link.
Seeing our main staircase as it is now it's remarkable to look back....
...to the day it arrived here all 2½ tonnes of it lowered into position by an enormous crane.
This took place just three years ago, but so much has happened since then it feels like much longer.
The scene which Steve Taylor was photographing for the magazine article has also changed considerably....
.....as this shot, taken shortly after the staircase arrived, shows.
Fortunately it's s lot warmer than this in the house now, despite not having any kind of heating system.
Regular followers of the project will know that we had a bit of a cock-up in the front door department. The first custom-built,
super-insulated door arrived from the manufacturer with the hinges on the wrong side, meaning it was completely useless.
We had to order a replacement immediately, and, as you can probably guess, doors like this aren't particularly cheap.
Meanwhile the original 'mirror-image' version cluttered up an already very full garage, while we tried to find a buyer for it.
(It's on the right, with the garden gate leaning against it). But one day in September an enquiry came out of the blue,
and just a couple of days later, the door was on its way to be built into an experimental 'eco-pod' at Nottingham University.
Nottingham University is where Prof. Brenda and Dr. Robert Vale worked, before emigrating to New Zealand. While still in the
UK they built the Southwell autonomous house, which provided Mike's inspiration. One of the eco-pods has been built, like the
Cropthorne house, to the exacting German Passivhaus standard; the second to ordinary UK building regulations. Students are
monitoring their performance, including comfort levels and energy requirements. Early results suggest a dramatic difference.
A mirror image (almost). On the left, our original door, now installed in the experimental Nottingham University
Passivhaus eco-pod. On the right, our own front door at Cropthorne. It couldn't have worked out better, really.
The combination of a good few weeks' break, and the freeing-up of space where the front door had been, spurred Mike
to get back to work and finish the electrical installation in the garage at last. This is how to light a garage low-energy
style with small lights on either side, mounted on a white background. The more common central fluorescent tube lights
the roof of your car brilliantly, leaving everywhere else in partial darkness, meaning you need more watts of lighting.
Removing the spare front door from here also meant we could have a jolly good sort-out and tidy-up.
So we turned this.....
.....into this with a place for everything. On the left our low-energy transport bicycles and tandem, plus the Vectrix
electric motorcycle, which we can use in the summer, recharging when possible with electricity from the photovoltaic array.
Our car's rather embarrassing, environmentally speaking, so it's been left outside. But incredibly, it does actually fit in the garage.
It was back at the end of 2010 that LeBrun construction were on site tidying the ground after the structural part of the build,
and also putting in an 80 metre cable run for our 'Narnia lamp', to be installed more than halfway down the garden.
Almost two years on, Mike had taken advantage of space in the newly tidy garage to restore the lamp, which we'd spotted in a
salvage yard while shopping for reclaimed bricks. With the cable and the base already in place, and the painting completed,
installation was relatively simple. Illumination is provided by a tiny 1.2 watt LED cluster lamp, running from our 12-volt batteries.
This is in effect a 'folly'. It's 80 metres down the garden, and doesn't serve any purpose, but there's something wonderful about it.
Within days of the installation of the Narnia lamp we had a dramatic cold snap, which turned everything white.
Ice formed on the pond, and the photovoltaic array was covered in a layer of frost.
Condensation formed on the windows, which then froze. But in the Autonomous House the frozen condensation is on the outside,
not the inside. The reason is that the triple-glazed windows lose so little heat that the outer surface is cold enough for
condensation to form. Less efficient windows are warmed by heat leaking out of the house, so this doesn't happen.
This seems like an excellent opportunity to look at our temperature data from April to December 2012. The internal temperature
(red trace) follows the external, but much more slowly than in a conventional building. Short-term highs and lows don't
really register at all, and the internal temperature hasn't ever dropped below 17.5°, despite some long periods with little sun.
If you'd like to see more detailed data, click here for a larger graph (pop-up window) or download the source spreadsheet.
So with a minimum temperature of 17.5° the interior has never really been cold, but you do need an extra layer or two of clothing.
Dispensing with a heating system altogether was a calculated risk, but it seems to have paid off so far, needing only minor
adjustments. We can add a bio-ethanol stove in future if we feel the need a tiny amount of heat input will raise the temperature to
a more 'normal' level. So the zero-heat strategy has worked, at least so far. In other areas there's more work to be done....
Despite all our attempts to encourage growth on the rammed earth wall, there are more and more bare patches. A good covering
of plants is essential to protect the outer surface and prevent it being eroded, which will threaten the structure itself.
To paraphrase an old adage, the grass is always greener on the other side, they say. Unfortunately it isn't.
Here at the northern end of the wall the grass has died off completely, and the recent heavy rain has washed away some
of the rammed earth. The cracks look ominous too. We need to find a solution to this as an urgent priority.
Covering with sedum matting, as used on 'green' roofs, is one possibility we're considering.
Inside the conservatory the presence of old sheets, and staining on the staircase, indicate that it's still leaking.
It's particularly bad in conditions of wind-driven rain something we've had plenty of lately.
Mike spent some time earlier in the year filling external gaps with sealant, but to no avail.....
......it now looks as though we'll have to strip all the external oak cladding off and see what lies beneath.
Finally, the shower room remains the only unfinished room in the entire house.
It really does seem like a very long time since 2006 when we stood, still with a slight sense of disbelief, on the building site
which we'd just bought. With a reasonably good idea of what we wanted to achieve, but little idea how to actually do it,
the journey ahead felt both exciting and daunting. Mike was also well aware he was about to sink most of his life savings
into what was, essentially, an experiment.
Today, aside from one or two unresolved problems we're pretty much there. Zero-heat, warmed by the sun, water supplied
by rain falling on the roof, and our waste turned into clean odour-free compost for the garden all of these have succeeded.
The house is now as close to complete as any house ever is in that they all require attention throughout their
operational lives. But we can relax a little more now, and reflect on this extraordinary project, and enjoy the house and
the beautiful sunsets which we regularly see from our west-facing windows.
And as the sun sets on the Cropthorne Autonomous House, one can also reflect on whether or not it will make any difference.
It's made a massive difference for us the experience, the worry, the hard work and the triumph of a largely successful outcome,
with an exceptional house to live in. But in the broader context of the significant environmental problems which humanity faces,
and in that context the need for every single new property to be built to the same standards as this one will it make a difference?
Of course it won't. But at least we tried.