This site not been updated since 2006.
There is a new and improved website in
preparation at http://homepages.phonecoop.coop/eno-swales
If you want to know when the site
is significantly updated send an email to edenhope@riseup.net
with ‘Update’ in the subject line.
EDENHOPE DESIGN AND SELF
BUILD
AN ENVIRONMENTALLY AND FINANCIALLY
AFFORDABLE HOUSE IN
The site, which we bought in March 2001,
lies in the Scottish Borders, on the north slopes of the Yarrow Water and six
miles west of Selkirk.
The half acre site is set in a remnant of
plantation woodland, faces south and lies on glacial moraine composed of a very
free draining mix of boulders, gravels, sands and clays.
Across the valley to the south we face Black
Andrew Wood, with views west and east along the Yarrow valley. Sheltering us
from the north are the mixed woodlands of Hangingshaw
and above this is the Southern Upland Way, a long distance route running from
the Irish Sea to the North Sea.
View of plot and its setting from the
opposite side of the Yarrow valley (January 2001)
It’s a lovely position but there are a
number of practical constraints to building here. The site lies c. 1km down the
beech lined
The wooded site slopes steeply to the south
and east so that there is a 6-7 metre difference in
level from the track at the bottom to the top of the site. There is no room for
a large level storage area, there is no water on site, the track to the site is
narrow and there is no turning room for delivery trucks.
To solve the immediate water supply
requirements, we set up a shed with roof rainwater collection into 1500 litre drums. We are able occasionally to use a neighbour’s otherwise closed access from the west thus
avoiding the bridge, deliveries, however, have to be very carefully arranged,
taking account of weight, wagon size, nature of the materials and method of
unloading and we were very lucky to be able to store materials in another neighbour’s barn..
The house design is based on a concept
developed by Gokai Deveci
(Robert Gordon University) in the late 90’s and the then Scottish Homes, to be
a financially and environmentally affordable house with low running costs and
built of commodity materials.
Drawing 1. Very simple rectangular one and half storey design,
facing due south, with central glazed area, clad in wood and slated.
Several similar houses have already been
built in Aberdeenshire. We need a cheap house to run
and maintain because our pensions will be minuscule! It will be off-grid and no
mains services. We have ended up with a design which is better than carbon
neutral in construction and occupation. And if it was already available, we
would not be building it ourselves!
Environmentally affordable is a good area for
discussion. As the TV series, Grand Designs has shown – there are different
interpretations. Probably the best of the designs was Ben’s house built from
the woods materials around him. If only!
For us, environmental affordability includes
using sustainable, recycled and local materials, minimising
the energy capital (amount of energy used in cradle to grave analysis of the
materials); minimising health threatening toxins
(e.g. formaldehyde glue in manufactured boards) etc. We are also using
materials which ‘carbon bank’ thus contributing towards offsetting the carbon
used in any manufacturing energy.
However, there are inevitably trade-offs and
compromises, not least because we are working within a society which places a
low value on these concepts at present. This makes it quite difficult, for
example, to source the most appropriate building components because often
no-one in the
***********
Edenhope is a zero-heating design which means it doesn’t have
to have a dedicated space heating system. Instead it is designed to retain all
its heat by being super-insulated and airtight (i.e
no draughts!). There will be a very small junk mail-burning stove however. The
main heating comes from passive solar (south-facing glazing), people (400w
each), lighting and running domestic appliances. In summer, there is more
likely to be a problem with over-heating. A heat recovery ventilation system
helps regulate the internal environment.
With no mains water nearby and a borehole
supply estimated to cost about £7000 we have gone for roof collected rainwater
with a series of filters and UV steriliser for
potable water and provision for using re-cycled cleaned up (with wee reed beds)
water for toilet flushing, etc. This was one of several matters which caused
Building Control and us some challenges. Eventually they agreed providing we
install a 25,000 litre tank. We demonstrated that if
it had been in use for the last 30 yrs it would never have run out.
Electricity connection would be at least
£3000. Instead of paying Powergen, we will build-in
off-grid photovoltaic generation.
The house is about 200 sq m floor space (100
sq m per storey) and sits on a cellar (or undercroft) of c. 100sq m cut into
the slope of the land. This gives us the space for the water storage, battery
storage and a workshop.
The construction stages are:
- Decide where on the site the house is going, dig out a hole in the
sloping site, c. 14m x 12m, level it and peg out for foundations
- Make the foundations and on them, build the undercroft.
- Pre-assemble the walls and roof elements on the floored undercroft
- Erect the house, make wind and water tight
- Install electricity, water and sewerage.
- Finish internal and ground works
Stage 1. Looking down into the undercroft
hole, foundation trenches laid out and piles of sieved and washed gravel won
from the site spoil.
Devichi’s design is based on a timber frame building system
called Masonite. It uses engineered timber I-beams
which are commonly used in floor joists because they have a very good strength
to weight ratio.
Masonite ‘I’ beams make good use of small timber and the
waste wood generated from milling processes.
View looking up into roof and showing a
close-up of timber I beam structure - wall studs, rafters and floor joists.
The beams come in standard lengths so we
dimensioned the house to fit the 9m and 12m lengths although we did have to cut
about 500 shorter pieces for dwangs, rafters, wall
studs etc. The beams are so light that even the 12m beams are easy for 2 people
to carry.
The walls and roof are of a fairly standard
breathable design, i.e. vapour resistance decreases
from inside to the outside. This means that moisture can move out without
condensing on any cold surfaces thus avoiding the potential for causing rotting
of any materials.
The frame is sheathed outside with 10mm Panelvent and 6mm Paneline
inside. Both are compressed fibre boards similar to
hardboard but thicker and glueless. The fibres are compressed and the heat and pressure bind the fibres by using the natural resins.
The foundations (reinforced concrete) and
undercroft (walls of concrete blocks) are the only elements which use a fairly
high embodied energy. This was minimised by using
1200mm x 500mm deep trenches rather than a full span concrete raft for the
foundation and sifting and washing by hand, about 25 tonnes
of sand and aggregate from the site.
Stage 3. Undercroft walls with row of pillars about 1/3rd
way from back wall. These will support the roof ridge beam. Ground level at top
right is at cellar floor level, and bottom left corner is at ground floor level
of the house.
Once the undercroft was built and the joists
laid and floored we had the large level area or "table" which we
needed for the next construction stage – flat assembly of the front and back
walls and gable ends.
Nearly at end of Stage
3. Undercroft finshed and ‘I’ beam ground floor joists placed on the
walls. Once temporarily floored we had the "table" for Stage 4, the
wall assembly.
The undercroft was floored by May 2004.
The next 5 months were spent convincing Building
Control that our waste water disposal methods were acceptable, and preparing
the next stage of the house.
This stage was the painstaking final cutting
and pre-assembly of the 500+ I beam wall and rafter pieces which were each
individually labelled according to drawings and the
cutting plan and stacked in the undercroft.
Stage 4. Assembled back and front walls
lying on the "table". All the gable ends had been cut,
temporarily assembled, taken apart and re-stacked in the undercroft.
All that sort of handling takes so much
time, but care in preparation pays off later!
By November 2004, we got our second stage
building warrant which meant we could have a house raising!
Stage 4. The house raising! Starting with
the back wall – raised by ropes, pulley and five chaps.
View from west showing front and back
frames erected and some gable studs in place
Stage 4 continued….all but the apex of the
gable end sheathed with Panel vent.
The house frame was completely erected,
sheathed and the roof membrane was on by the end of December 2004. It looked
like a giant cardboard box!
However, it was not fully nailed together
and the gable ends were only secured by nylon ropes to handy birch trees! The
January 2005 gales were a worrying time because we feared the house would turn
back into a pile of boards and beams. Thankfully, it survived, though the roof
membrane was re-fitted a few times.
Most of 2005 has been concerned with
finishing Stage 4, making the house wind and water tight.
The roof was slated (local reclaimed
slates). All the flashings, soakers, window sills and gable end dry-verges have
been made on site from 0.4mm stainless steel to avoid any heavy metal
contamination of the rainwater because we will be drinking it eventually. Steel
roofing is common on mainland
Initial cutting of the steel, folding to
strengthen edges and get the basic shapes were done by a local firm. Here, Andy
is doing the final bends and soldering corners for a flashing round a roof
light.
Fakro rooflight showing
stainless steel soakers and flashings
The roof lights are made by Fakro rather than Velux. They
were a better price but also the handles are on the bottom edge meaning short people
can reach to open them! The windows, external doors and sun room glazing are
made by Vrogum in
Early stage for the cladding –larch logs
at the mill
The walls are externally clad in larch which
has been sourced and milled locally. Sadly, the mill didn’t get the hang of our
instructions – which was to mill to boards from the heartwood and avoid the
soft sapwood. We have therefore had to chuck a lot of the boards (chicken sheds
perhaps…).
Putting the cladding on is an exacting
business to make it function properly as a rain screen and also look good. We
are paying considerable attention to the detailing at the corners and round
openings – it’s where many wood clad buildings are let down. But its worth it –
it looks great. Although pinkish at the moment, it will weather naturally
silver and be a nice fit to the woodland setting.
West end view - vertical
larch board-on-batten over the sheathing shown above, to give appearance of a
flush surface. The rough
sawn boards are machined to give a smarter finish – more suited to a dwelling
house. Under the gable it will be horizontally clad to give some variation to
the design
Its difficult to show the inside but the first floor
joists are in place, a sub-floor is down and the insulation has been blown in
the roof and upstairs walls. The upstairs space is wonderful.
Front view December 2005. Shows the
glazed area or bay window (covered in polythene), the black external membrane (Solitex) and some larch cladding stacked in front and
against the wall…The black area in the roof is not slated but is corrugated Onduline, on which some of the PV will sit.
This is now January 2006 and the house is
close to finishing stage 4. There have inevitably been hitches, mistakes and
difficulties. Some of the material sourcing has been very time consuming and
frustrating. - the
13 March 2006: At last the ‘bay-window’ and
glazed roof are in place, still a bit of fine tuning needed and the sills
fitting but no more drips inside. Completion of the Warmcell
installation also done so at last a cosy place to work.
And costings ? Well, so far we are within budget on materials, but well
over on labour! The next job is to source and buy all
the photovoltaic kit which will be the third biggest expense, estimated at
about £5000. This should mean a pay-back time of about 15 years, although with
fuel prices rising this may be even less!
Watch this space….updates and more technical
information (hopefully) to follow…...
Edenhope’s Affordability Background
As Sarah says in the build story – if we
could just go out and buy one of these houses we wouldn’t be building it. We’ll
try to give an idea of what ‘one of these houses’ means.
Our starting point was that we wanted to
live in a house consistent with being environmentally affordable as well as
financially affordable, an idea given form following Gokay
Deveci’s model for affordable rural housing. Our
solution is a design which is not only affordable in both respects but is
easily replicable without needing specialised skills
or hard to source materials – in many respects a commoditised
solution.
One of our requirements is that we want our
miniscule pensions to go a long way. Having an interesting life doesn’t lead to
a big pension so minimising bills is of great
interest. Making its own power using photovoltaic panels, collecting its own
water from the roof and treating its effluent make their contributions as do
the zero-heating design low or zero maintenance finishes and the ‘healthy
building’ materials.
The most unaffordable element of the whole
project is the very high price we would have had to have paid if we had not
been able to research and design it ourselves. We have kept the fee load to
relatively low levels largely by limiting consultants to inspection and
certification (neither of us has a relevant qualification). Consultants,
like architects and engineers, in general aren’t used to working this way in
the