2011 - April 2012
The First Winter
As spring arrives the Autonomous House doesn't look dramatically different from the outside a little tidier perhaps?
But in the preceding months, a great deal has been going on inside one of Britain's few houses with no heating system.
With a seemingly overwhelming number of jobs still to complete, the decision was made to press on with
the main upstairs room, so at least we would have a civilised living space. Remaining areas, such as bedrooms,
could be completed when time allowed, and with minimum disruption. So the main lights were installed....
.....yet another floor painstakingly cleaned....
...and given a final polish with beeswax a very tough hard-wearing finish which is entirely natural. Unfortunately
it takes several days to harden, so to give it some initial drying time without being trampled on, we finished the polishing
then left the house and stayed in a pub for the night, where we had some very nice food and a jolly good bottle of wine.
As we moved into winter and temperatures began to fall, uncompleted insulation jobs became more pressing. Our solar water
system was designed to extract the maximum possible heat from the sun, and store it in this giant 500 Litre tank. This can hold
enough hot water to see us through a week or more without any sunshine, but with only the original 'sprayed on' insulation,
it was losing heat fast. The answer was to add a 50mm layer of Knauf Dritherm the same insulation used in the house walls...
.....followed by a further layer of reflective insulation so around 100mm in total. The results were immediately
noticeable, with heat loss down to around 2 degrees per day. meaning we only used the immersion heater
four times over the entire winter. Once was before the insulation was added, and on two subsequent occasions,
being very low power, the immersion heater was entirely fed by the output of the photovoltaic array.
In December we were visited by Andrew Farr of the Green Building Store. Andrew was responsible for the design
of our mechanical ventilation system, and supply of all the components. On this occasion, he came to commission the
entire system, which means measuring air flows, as seen above, and balancing the system for best performance.
A check of the filters in the main heat exchanger unit revealed no problems. Interestingly hay fever sufferers can install special
pollen filters into the system, which, in an airtight house with no leaks, means no hay fever symptoms.
Finally with Mike acting as assistant / logger, all the data was saved, and a certificate issued,
which also satisfies building regulations requirements for ventilation.
Looking at a section of the graph of internal and external temperatures from our data loggers reveals a gradual
downward trend in internal temperatures as we moved into winter, although the brief cold snap around January 14th has
little effect on a house as well insulated as this.
Scientists may click here to view (or right-click to download) a higher definition graphic of the entire winter's temperature log. Unfortunately one of the
data loggers failed at the beginning of the year, so some of the graph had to be made up, so should only be regarded as a rough guide.
Part of the reason for the downward trend in temperatures was that we hadn't had time to finish insulating the mechanical
ventilation system ductwork, which runs along the basement ceiling. As a result, air coming out of
the house was losing its heat to the cold basement, before it could be extracted in the heat exchanger.
So the incoming air wasn't being warmed properly resulting in an estimated 2 degree temperature loss inside the house.
We still survived the winter, but with very occasional use of a one-bar electric fire late in the evening.
As soon as time allowed, we got on with this important insulation job.
It actually didn't take that long to complete there had just been more pressing matters to deal with first.
Once completed, the difference in temperature inside the house was obvious, meaning the possibility of
living without a heating system through subsequent winters looks very promising.
One of the more pressing matters had been to complete all of the electrical wiring, which actually meant
finishing most of the 12-volt system. We'd extended our deadline for clearing building control once already,
and didn't want to do so again, as every extension costs money.
Just like the standard mains electrical system, the independent 12-volt system needed a distribution and fuse unit.
The problem is, you can't just go to an electrical wholesaler and buy one, so Mike had to build one from scratch.
It took a couple of days of intensive metalworking and wiring, but it was completed successfully and installed in the basement.
For the moment it supplies all of the low voltage lighting, and the broadband router, but more low-voltage devices will be transferred
to this system as time allows, to avoid the energy wasted in the many small power supplies which are used these days.
Measuring our smoke alarm current consumption revealed each one was consuming 7 to 8 watts from the mains
around 30 watts in total, wasted in inefficient mains power supplies. Smoke alarms are required by building regulations so
we couldn't leave them out, so Mike built a system where the alarms are fed from the low voltage supply, using their
backup battery terminals. This has reduced a potential 30 watts of consumption to around 2 milliwatts.
So here's our 12-volt distribution board all complete and working....
...and connected to a pair of ex-BT backup batteries, which provide all of our 12-volt power.
They're charged by very efficient switched-mode chargers, but only during daylight hours, when the photovoltaic array
is producing electricity. So although available 24 hours per day, the electricity is all solar-generated.
Paul Jennings is a UK authority on air leakage testing, having been one of the first people in the country to buy
the equipment to do it. This consists of a large 'blower door', containing a huge fan, which is used to suck air out of the house.
This essential test aims to locate any leaks within the building, which would lead to heat loss.
The initial test revealed plenty of leaks some in the composting toilet chamber, which were temporarily sealed
with tape, pending the fitting of better door seals.
Having returned to witness the tests, project manager Mike Neate set to and sealed another major leak around
the lid of the chamber. This was quite unexpected as considerable attention had been paid to sealing this up during
construction. But it did explain the rather strange smell we'd sometimes encountered in the basement.
The most difficult leak to deal with was inside the house, in an inaccessible area of the mezzanine, where
the airtight membrane which seals the roof area had become detached from the wall.
This was another job which involved considerable grovelling around in awkward spaces we managed to manoeuvre a layer
of special airtightness tape into position, using pieces of string, and some rags taped to the end of a paint roller handle.
When Paul Jennings returned a few days later with his big blower door, we obtained a creditable Passivhaus air
test result of 0.36 (q50), so all the remedial grovelling had paid off. This test, along with the sign-off of the electrical installation,
meant we could finally complete building control - another significant obstacle cleared.
After an imperceptibly brief break, the decision was made to decorate the spare bedroom, on the grounds that it was
quite small, so it wouldn't be too difficult, and that when it was finished, people would be able to come and stay here.
Mike built a plastic enclosure while he did the sanding, to keep the dust out of the rest of the (now fairly clean) house.
And so yet more painting....
...and a very satisfactory 'before-and-after' picture. This room had been a tool and junk store for so long,
it was really satisfying to turn it into a usable guest bedroom.
A brief diversion here building a shoe rack for the front porch, using pieces of scaffold plank left over from the build.
A good bit of recycling which, along with some coat hooks mounted on oak left over from the conservatory, makes
the front porch look rather welcoming to visitors......
...who, on entering the house, can then ascend our tiled staircase, now fully cleaned and waxed.....
...and which leads to the upstairs living area. This is now largely complete, despite there being a few boxes to unpack.
At some point we may treat ourselves to a new dining table, although making one from old scaffold planks is a
possibility, if Mike can be bothered to do it.
Looking towards the east, again things are now relatively complete. One as yet unresolved problem is the ladder for access to
the mezzanine. Few ready-made loft ladders are suitable for this job, and those that are don't look very nice.
This is one of the many small jobs still waiting to be completed. Added together, they represent quite a lot of work.
Regular readers may remember our composting toilet shed. Built in the garden at the very beginning of the project,
it was used throughout construction by the building team, and was environmentally less damaging, and far cheaper,
than those strange blue plastic sheds which you usually see on building sites, and which stink of industrial chemicals.
Now redundant, and looking a little weathered and untidy, we decided it was time for it to go.
Advertising it on the local Freecycle network brought in a huge number of enquiries from would-be re-users, seemingly
unconcerned about its former role. The lucky new owners soon had it dismantled and reassembled, freshly painted,
on their allotment by the next day.
Having not been used for almost a year, the 'contents' had rotted away to virtually nothing, although curiously we found
two pairs of underpants among the waste. We didn't re-use those, but piled some wood cuttings over the hole.
This will now be left to naturally rot away to nothing, enriching the garden as it does so.
Making good use of the last of our leftover rubble, our landscaping helper
Matt Wallin prepared the foundations for a path to the washing line.
Mike helped by preparing some of the bricks the very last of the ones we dug out of the ground before the project started.
Soon we had a completed path. Like the green driveway, this uses no concrete, and will rely on the roots of the grasses
which will grow between the bricks to bind it all together.
Finally other areas are becoming tidy, and the basement stairwell, which for ages was filled with
insulation offcuts, now contains some smart new shelves.
This has freed up space in the basement itself, and for the first time we now have some reasonably organised storage.
But turning in the opposite direction brings a stark reminder that there is still one major project to be tackled.
With the increasing incidence of drought in Britain, we'd very much like to sever our temporary mains water connection,
and finally allow the house to become fully autonomous, by having its own independent water supply.
Despite the range of work needing to be finished upstairs, the rainwater harvesting system, still far from completed, is calling.
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