The design process
In this section:
Four-stage design process
What to change? Dreams and fantasies
What to work with? Orientation and site
Existing energy consumption and heat loss
We followed a four-stage design process:.
It started by discussing
how we wanted the house to feel and what we needed it to do. Like
permaculture, environmental architecture should start with solutions
to peoples needs that save them energy in their lives.
The second stage was looking
at what we already had to work with- existing structures and materials,
the opportunities provided by the site and orientation to the sun.
The third stage was to make
our own audit of the existing performance of the house, obtain a
full set of energy readings, and look carefully at the main areas
for heat loss. That way we could prioritise changes to bring the
Finally- the design stage;
seeking ways to meet these needs, using the opportunities of the
existing property, in ways that respect the environment, but also
met the conservative standards of building inspectors.
PROCESS: 1. WHAT TO CHANGE?
- DREAMS AND FANTASIES
The Yellow House had been cheap to buy because of four main areas
in urgent need of renovation. These could no longer be put off:
replacing the kitchen
which was falling apart, filthy and a flourishing rat habitat
replacing the extension
which was rotting through, infested with wasps, and due to collapse
renovating the water and
heating system which was old and inefficient
fully renovating the bathroom
which had ugly stained fittings and mold on the walls
We wrote these down first then
talked freely about our dreams and wrote down ideas as they came
to us. Many ideas started with feelings- Annie wanted a house that
felt fresh and bright and healthy, which didnt feel cluttered
where we could clean in the corners. She wanted a higher degree
of privacy and hated the downstairs bathroom (filthy, damp and unprivate).
I wanted a house that felt different from other peoples and felt
exciting to live in. After years of environmental campaigning, I
wanted to feel proud of a house that entailed as few environmental
compromises as possible. As we spoke through what we wanted from
our life in the house and how we would live in it, five main needs
came into focus:
a well lit workspace for
Annie's art projects, so she could spread out her work things
without having to constantly tidy them up
enough space for one or
a spare bedroom for visitors
a warm, dry, pleasant,
lots of storage space
We only had three rooms upstairs.
Including a bedroom for ourselves, this list required between five
and six upstairs rooms. Even if we forgot about one of the hypothetical
children, we still needed to find two additional rooms. Whilst we
continued to consider our options, I read widely on environmental
design and studied how the existing house functioned.
PROCESS: 2. WHAT
TO WORK WITH? ORIENTATION AND SITE
The front of the house faces south west, which, though not ideal,
is within the bounds of viability for capturing solar energy in
winter (more on orientation
and solar energy...)
The house overlooks open fields to the southwest, and the house
receives the full winter sun until sunset.
An ideal house would face due south
with no obstacles of any kind between south East and South West.
South facing houses are rare to come by, and it is even rarer to
have open vistas in any direction. All in all, the Yellow House
is reasonably well orientated; what it loses in sun from not facing
due south is partly compensated by the open aspect to the South
The house is located at the bottom
of the shallow Thames valley, so is partly sheltered. Nonetheless,
the house faces the cold winter winds which come directly across
the open fields to the South West. In this respect the open aspect
to the South West is a disadvantage. When the front door is opened
in winter, cold air can force its way deep into the house.
PROCESS: 3. EXISTING
ENERGY CONSUMPTION AND HEAT LOSS
We made a thorough inventory of the existing energy consumption.
We found that the heat loss through the extension was truly appalling.
Neither walls nor floor were insulated. The ceiling of the extension
was a sheet of 5 mm hardboard. There was a 100mm square hole in
one corner through which one could see the tiles. The rear wall
of the extension had single glazing in leaking frames on one concrete
block thick walls. Cold air could enter through the holes and through
a large air vent in the door required by law to provide ventilation
for the gas boiler. All in all, a well sealed tent could have had
superior heat retention.
The other main sources for heat
loss were the wall of the rear bedroom and office, the bathroom,
the front door, the living room floor and the roof. The bathroom
and toilet were built of single block concrete. There was no insulation
of floor, walls or roof. The front door was aluminium and glass,
both poor insulators. Because it faces south west, cold air is always
trying to find an entry and there were constant draughts around
the base and sides and through the letter box. The living room floor
was not insulated and cold damp air freely circulated underneath
it and infiltrated the house through gaps in the floor, the skirting,
and the cupboard under the stairs.
There was already some fibre glass
insulation in the attic but it did not cover the joists, and did
not extend under the eaves. The 10% of the first floor ceiling which
was under the eaves was not insulated at all. The hatch to the attic
was not insulated or draught proofed.
PROCESS: HEATING SYSTEMS
The boiler was well maintained for its 15 years, but far less efficient
than a newer condensing boiler and approaching the end of its designed
lifespan. It fed five radiators. Hot water was stored in a tiny
poorly lagged copper tank, which predated the rest of the heating
system. The plumber had no idea of how old it was other than "bloody
PROCESS: ENERGY CONSUMPTION
I obtained gas bills for the house dating back to March 1997, and
electric bills dating back to November 1997 from the power supply
companies. I disregarded all estimated meter readings- they can
often be wildly inaccurate. I crunched the numbers and came up with
the best average I could. During the summer, the only gas consumption
was for hot water, so from this I could calculate how much of the
houses energy was going into water heating, and how much was
going into space heating.
Annual gas consumption: 554 units
Each gas unit is 100 ft2. There are approximately
3m3 in each of these units.
Hot water consumption: 240 units @20 units per month
Annual space heating: 314 units
Annual electricity consumption: 3,100 kWh
PROCESS: 4. DESIGNING
In each decision, the first stage was to develop options of how
to get the best use of a limited space within the restraints of
cost and convenience. Each option was then examined in the light
of the principles of environmental design and a final decision reached
that seemed like a reasonable compromise. (for
more on the environmental
Moving the bathroom upstairs turned out to be the demand from which
all other aspects of the design followed. There were three options:
The simplest and cheapest
option was to convert one of the rear bedrooms to a bathroom.
Alternatively we could
build the rear extension up to two storeys, and put the bathroom
(and maybe even an extra room) in the first floor of the extension.
The third option was to
keep three bedrooms, but somehow to carve out a bathroom between
The first option was immediately
ruled out. We needed to add two rooms in all, and this would have
replaced one existing room with another, still leaving us two rooms
short. It would also have reduced the number of bedrooms to two
with a ruinous effect on the value of the house.
The second option was more viable.
The problem this created, though, was how to gain independent access
to the additional room- vital for both convenience and building
regulations. The only possibilities were stairs from below or a
corridor to the back. Both cases entailed a waste of precious space
and great expense. What is more, to avoid blocking light and air
to the back rooms, the extension would have had to stick out from
the rear of the house. This is a clumsy configuration, though common
in Victorian houses.
The third option made the maximum
use of the available space, but sacrificed some room in the bedrooms.
The main environmental consideration concerned thermal
zoning. Good thermal zoning avoids placing warm rooms, such
as bathrooms, on the north side of a building. A central location
is the optimum for thermal zoning.
The final decision was therefore informed by practical and environmental
considerations. Option one was ruled out for practical reasons,
but, even if viable, would have led to poor thermal zoning. Option
two was difficult and costly, and would have greatly increased the
area of wall and window on the north side. Option three was the
best option for meeting both practical and environmental criteria,
and the ideal location for thermal zoning was between the front
and rear bedrooms. Here the bathroom was in the core of the house
and could be as hot as we wanted.
PROCESS: THE ADDITIONAL WORK SPACE
The obvious place to look for the additional space for Annies
work space was in the loft. The only viable place to insert a new
set of stairs was starting in the corner of the bedroom and running
directly above the existing stairs. Although, it was fine with us
if we had to cross the bedroom to get to the stairs, building regulations
require that any new room above the first floor must have independent
access to the main stairs. A standard loft conversion would have
required carving a needless corridor off the bedroom to provide
The solution, suggested by Annie and planned by our
creative builder, Bill Frizell, who can quote
building regs from memory, was to knock out the ceiling of the bedroom
and turning the loft space into a mezzanine balcony overlooking
the bedroom below. Providing that the floor area of the loft/balcony/mezzanine
floor was less than half the area of the bedroom, we could argue
that the loft space was an extension to the bedroom, rather than
a new room, and therefore did not need an independent escape. To
keep within this limited area, the mezzanine area was less than
2m across which, given the low head height of the roof, was close
to the maximum useable space in any case. The remaining loft space
behind the mezzanine could then be walled up with access doors so
that it could be used for storage without being included in the
By a nice coincidence, this meant
that the mezzanine was directly over the bathroom. By lowering the
ceiling of the bathroom, we could gain an extra 30 cm in head height
to the mezzanine.
It was an ingenious solution which
building control was forced reluctantly to approve. Given my growing
awareness that building regulations exist to confound creative and
innovative design, I was not surprised that one month later an amendment
banned mezzanine floors above the first floor.
In this case, the design had been forced by practical and legal
restrictions with no chance to consider environmental performance.
The result was a design which posed problems for heating and insulation.
Double height rooms are attractive soaring spaces but also increase
heating demands. To make matters worse, the removal of the bedroom
ceiling would allow all the hot air in the house to collect at the
apex of the roof. The result could be a baking hot loft space that
sucked heat from the rest of the house.
A double height room also creates
a powerful stack
effect. In summer this would be desirable, drawing air
through the house. However, in winter, the stack effect would make
any leakage of hot air from the roof above the mezzanine a major
source of heat loss.
Finally, any loft conversion expands
the outer "skin" of the house. Depending on the pitch of the roof,
the area at the top of the house requiring insulation is increased
by between 10% and 50%. In the Yellow House, the mezzanine increased
the area of the external skin at the top of the house by 15%.
Several changes were made to the design in response to these weaknesses.
We decided to install a fan and ducting to pump the warm air from
the apex of the roof into the rear extension where it was most needed
on the fan ducting...).
Once the decision was made to install
the fan, it seemed that any additional heat we could obtain was
all to the good. We specified two large skylights for the south
west side to increase solar heating. One was placed in the middle
of the roof to allow a view from a sitting position on the mezzanine.
The second was placed high in the roof as close to the apex as possible
so that in summer it could function to best effect as a solar chimney.
There were no windows on the north facing roof. The insulation all
around the loft space was to the maximum specifications possible
within the available space (more on loft
PROCESS: EXTENSION, UTILITIES ROOM AND
After these other confusing decisions, the design of the extension
was relatively straightforward. Foundations had already been dug
by the previous owner one metre beyond the existing rear wall. A
one storey extension of this size would have a volume of 47m3, just
within the 50m3 allowed without planning permission. We therefore
decided to build a low one storey extension on these new foundations.
Within a small house every decision
creates a series of new problems. The decision to move the bathroom
upstairs created the problem of what to do with the old bathroom
space. We decided to keep the toilet, but to reconfigure the space.
The old extension had housed the washing machine and freezer and
had provided a space for drying clothes in winter. Our desire to
use the new extension as a dining and living area meant that we
would have to find a new home for these services.
Looking at the orientation of the house, the extension would be
on the north east facing side of the house. Most of the sun in the
winter is crossing the back of the house from the south east. Even
in summer trees block much of the easterly sun.
Clearly this was a poor place to
put a warm zone living room or a one storey extension with windows.
As we were not willing to reconsider our decision to use the extension
for warm zone living, we gave careful thought to energy conservation
The reconfiguration of the rear
of the house posed new environmental opportunities as well as problems.
The relocation of the bathroom created the opportunity of creating
a hot zone utilities and drying space where it had previously stood.
Moving the bath upstairs created an interesting opportunity to capture
and use the waste bath water.
The shape of the new extension was simple and regular, to add as
little as possible to the area of the outer wall of the house. The
insulation of the roof and walls was specified to high standards.
The windows were kept to the minimum possible area that would still
allow a view over the garden, with most light provided through two
Large skylights with low heat loss
were specified to bring light into the kitchen.
We decided to utilise the rising heat in the rear upstairs rooms.
Two vents were placed at the top of the mezzanine leading through
to just above floor level in the rear rooms. These could then be
adjusted to control the flow of warm air from the kitchen and mezzanine
into the top of the house. In summer these vents would facilitate
effect and draw cooler air from the rear of the house
through the rear rooms.
We included a range of energy conservation
features to minimise the heat loss from the extension. The windows
had low heat loss glass. Insulation standards were two to three
times that required by building regulations. Soil was "bermed" to
the height of the windowsills and a specialist contractor installed
a high insulation turf
The old bathroom had been poorly
constructed so we demolished it and walled in a new toilet/drying/utility
room alongside the kitchen. Along with the bathroom, this meant
that the three hottest rooms in the house were placed at the core
of the building.
The washing machine and clothes
drying racks were installed in the utility room. A laundry shoot
led down from the bathroom directly above, and allowed the warm
damp air to rise through the bathroom and out through the extractor
fan. Reluctantly, in the interests of saving space, we had to put
the freezer in the hot zone utility room, the least desirable location
for refrigeration. To compensate, we reinsulated
We re-used the old copper hot
water tank, destined for the scrap yard, to store the
waste bath and shower water for flushing the downstairs toilet.
The tank was positioned directly above the toilet and slowly radiated
the heat from the waste bath and shower water into the drying/utility
We decided to add a porch to the
extension to reduce the heat loss through the garden doors. A solid
wall on one side is orientated to pick up the south east sun. During
the months of November to February the porch is mainly a draught
lobby, preventing air from entering the house when we open the door.
At this time it also doubles as a storage space for foodstuffs.
During spring and autumn, it captures
and holds the low sun coming from the south east and open vents
allow the warmed air to enter the house. During the summer one or
both sets of doors are removed to allow the free flow of space and
air between house and garden.
As well as providing storage for
garden implements, the sun porch also doubles as a potting shed
in spring and a greenhouse in summer, providing tomatoes late into
the autumn. All in all, a very satisfactory addition to our original